【Flume】【源码分析】深入flume-ng的三大组件——source，channel，sink

朴灿烈づ我的快乐病毒、 2022-08-04 09:26 205阅读 0赞

转载：http://blog.csdn.net/simonchi/article/details/43308677

# 概览 #

flume-ng中最重要的核心三大组件就是source,channel,sink

source负责从源端收集数据，产出event

channel负责暂存event，以备下游取走消费

sink负责消费通道中的event，写到最终的输出端上

![Center][]

以上是总体的一个简单结构图，下面我们来深入每一个组件的内部看看：

# 1、Source #

source接口的定义如下：

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1.  @InterfaceAudience.Public  
2.  @InterfaceStability.Stable  
3.  **public** **interface** Source **extends** LifecycleAware, NamedComponent \{  
4.    /\*\* 
5.     \* Specifies which channel processor will handle this source's events. 
6.     \* 
7.     \* @param channelProcessor 
8.     \*/  
9.    **public** **void** setChannelProcessor(ChannelProcessor channelProcessor);  
10.   /\*\* 
11.    \* Returns the channel processor that will handle this source's events. 
12.    \*/  
13.   **public** ChannelProcessor getChannelProcessor();  
14. \}

source生成event并且调用配置的channelprocessor的相关方法，持续的将events存入配置的channel里

channelProcessor中有通道选择器和拦截器链，该过程处在source端收到数据和放入通道直接

看一个source的具体工作流程：[ExecSource][]

## 该source继承了两个类 ##

### 1、NamedComponent  ###

负责给每一个组件取一个唯一标识，就是名字，这个名字来源于我们的配置

### 2、LifecycleAware ###

负责组件的启停和状态维护

## Source接口的直接实现类是AbstractSource抽象类 ##

该类中就定义了通道处理器

还有一个生命状态周期的枚举类型

**\[java\]**  [view plain][] [copy][view plain] [print][view plain] [?][view plain] [![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **enum** LifecycleState \{  
2.    IDLE, START, STOP, ERROR;  
3.    **public** **static** **final** LifecycleState\[\] START\_OR\_ERROR = **new** LifecycleState\[\] \{  
4.        START, ERROR \};  
5.    **public** **static** **final** LifecycleState\[\] STOP\_OR\_ERROR = **new** LifecycleState\[\] \{  
6.        STOP, ERROR \};  
7.  \}

这里就定义了一个组件会有的4种状态

实现接口的启停组件方法，方法体中只有一个状态的赋值，具体实现，我们来看一个具体的Source——ExecSource

读取配置方面很简单，这里就不说了，看下start方法

**\[java\]**  [view plain][] [copy][view plain] [print][view plain] [?][view plain] [![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  **public** **void** start() \{  
2.      logger.info("Exec source starting with command:\{\}", command);  
3.      executor = Executors.newSingleThreadExecutor();  
4.      runner = **new** ExecRunnable(shell, command, getChannelProcessor(), sourceCounter,  
5.          restart, restartThrottle, logStderr, bufferCount, batchTimeout, charset);  
6.      // FIXME: Use a callback-like executor / future to signal us upon failure.  
7.      runnerFuture = executor.submit(runner);  
8.      /\* 
9.       \* NB: This comes at the end rather than the beginning of the method because 
10.      \* it sets our state to running. We want to make sure the executor is alive 
11.      \* and well first. 
12.      \*/  
13.     sourceCounter.start();  
14.     **super**.start();  
15.     logger.debug("Exec source started");  
16.   \}

该方法内部就是启动了一个线程去执行我们配置的终端命令

前面一篇文章也说过从入口分析如何调用到该start方法，以及调用频率：[http://blog.csdn.net/simonchi/article/details/42970373][http_blog.csdn.net_simonchi_article_details_42970373]

#    2、channel #

对于通道来说，最重要的就是event的维护，flume的核心就是要中转这些event，所以event一定不能出事

## Channel接口定义如下： ##

通道中的event全部都在事务的管理之中

先来看看这个事务的定义

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 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &lt;pre&nbsp;code_snippet_id="593798"&nbsp;snippet_file_name="blog_20150130_5_6226220"&nbsp;name="code"&nbsp;class="java"&gt;public&nbsp;interface&nbsp;Transaction&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> public&nbsp;enum&nbsp;TransactionState&nbsp;{Started,&nbsp;Committed,&nbsp;RolledBack,&nbsp;Closed&nbsp;};&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;/**&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;p&gt;Starts&nbsp;a&nbsp;transaction&nbsp;boundary&nbsp;for&nbsp;the&nbsp;current&nbsp;channel&nbsp;operation.&nbsp;If&nbsp;a&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;transaction&nbsp;is&nbsp;already&nbsp;in&nbsp;progress,&nbsp;this&nbsp;method&nbsp;will&nbsp;join&nbsp;that&nbsp;transaction&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;using&nbsp;reference&nbsp;counting.&lt;/p&gt;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt;:&nbsp;For&nbsp;every&nbsp;invocation&nbsp;of&nbsp;this&nbsp;method&nbsp;there&nbsp;must&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;be&nbsp;a&nbsp;corresponding&nbsp;invocation&nbsp;of&nbsp;{@linkplain&nbsp;#close()}&nbsp;method.&nbsp;Failure&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;to&nbsp;ensure&nbsp;this&nbsp;can&nbsp;lead&nbsp;to&nbsp;dangling&nbsp;transactions&nbsp;and&nbsp;unpredictable&nbsp;results.&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;/p&gt;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*/&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;public&nbsp;void&nbsp;begin();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;/**&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;Indicates&nbsp;that&nbsp;the&nbsp;transaction&nbsp;can&nbsp;be&nbsp;successfully&nbsp;committed.&nbsp;It&nbsp;is&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;required&nbsp;that&nbsp;a&nbsp;transaction&nbsp;be&nbsp;in&nbsp;progress&nbsp;when&nbsp;this&nbsp;method&nbsp;is&nbsp;invoked.&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*/&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;public&nbsp;void&nbsp;commit();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;/**&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;Indicates&nbsp;that&nbsp;the&nbsp;transaction&nbsp;can&nbsp;must&nbsp;be&nbsp;aborted.&nbsp;It&nbsp;is&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;required&nbsp;that&nbsp;a&nbsp;transaction&nbsp;be&nbsp;in&nbsp;progress&nbsp;when&nbsp;this&nbsp;method&nbsp;is&nbsp;invoked.&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*/&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;public&nbsp;void&nbsp;rollback();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;/**&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;p&gt;Ends&nbsp;a&nbsp;transaction&nbsp;boundary&nbsp;for&nbsp;the&nbsp;current&nbsp;channel&nbsp;operation.&nbsp;If&nbsp;a&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;transaction&nbsp;is&nbsp;already&nbsp;in&nbsp;progress,&nbsp;this&nbsp;method&nbsp;will&nbsp;join&nbsp;that&nbsp;transaction&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;using&nbsp;reference&nbsp;counting.&nbsp;The&nbsp;transaction&nbsp;is&nbsp;completed&nbsp;only&nbsp;if&nbsp;there&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;are&nbsp;no&nbsp;more&nbsp;references&nbsp;left&nbsp;for&nbsp;this&nbsp;transaction.&lt;/p&gt;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;p&gt;&lt;strong&gt;Note&lt;/strong&gt;:&nbsp;For&nbsp;every&nbsp;invocation&nbsp;of&nbsp;this&nbsp;method&nbsp;there&nbsp;must&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;be&nbsp;a&nbsp;corresponding&nbsp;invocation&nbsp;of&nbsp;{@linkplain&nbsp;#begin()}&nbsp;method.&nbsp;Failure&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*&nbsp;to&nbsp;ensure&nbsp;this&nbsp;can&nbsp;lead&nbsp;to&nbsp;dangling&nbsp;transactions&nbsp;and&nbsp;unpredictable&nbsp;results.&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;*&nbsp;&lt;/p&gt;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;*/&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;public&nbsp;void&nbsp;close();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> }&nbsp;&nbsp;&nbsp;&nbsp;</li> 
 </ol> 
 </div> 
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 </div> </td> 
 </tr> 
 </tbody> 
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和我们想想中的一样，也就是一些标准的事务方法的定义，和一个事务状态的枚举类型的定义

## 基本事务语义抽象类是对它的实现BasicTransactionSemantics ##

该类定义了两个属性

state状态和initialThreadId，id是唯一的，用来标识事务

构造方法中会赋值为NEW状态，并获取当前事务的一个ID值

重点来看下如下几个方法的具体实现：

## 1、doBegin ##

没什么好说的，就是检查状态是否NEW，ID是否匹配，没有问题后，将状态修改为OPEN，表示事务打开

## 2、doPut ##

takeList和putList维护的是希望取出成功和放入成功的event队列

检查ID是否匹配，状态是否打开，event是否为空，为空当然这个put就没意义了

关键看具体是怎么put的？

在FileChannel中有个内部静态类

static class FileBackedTransaction extends BasicTransactionSemantics

这分别定义了两个双向队列，用于拿和放

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 </div> 
 <ol style="padding:0px; border:none; list-style-position:initial; color:rgb(92,92,92); margin:0px 0px 1px 45px!important; background-color:rgb(255,255,255)"> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> protected&nbsp;void&nbsp;doPut(Event&nbsp;event)&nbsp;throws&nbsp;InterruptedException&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;channelCounter.incrementEventPutAttemptCount();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(putList.remainingCapacity()&nbsp;==&nbsp;0)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Put&nbsp;queue&nbsp;for&nbsp;FileBackedTransaction&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"of&nbsp;capacity&nbsp;"&nbsp;+&nbsp;putList.size()&nbsp;+&nbsp;"&nbsp;full,&nbsp;consider&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"committing&nbsp;more&nbsp;frequently,&nbsp;increasing&nbsp;capacity&nbsp;or&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"increasing&nbsp;thread&nbsp;count.&nbsp;"&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;this&nbsp;does&nbsp;not&nbsp;need&nbsp;to&nbsp;be&nbsp;in&nbsp;the&nbsp;critical&nbsp;section&nbsp;as&nbsp;it&nbsp;does&nbsp;not&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;modify&nbsp;the&nbsp;structure&nbsp;of&nbsp;the&nbsp;log&nbsp;or&nbsp;queue.&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(!queueRemaining.tryAcquire(keepAlive,&nbsp;TimeUnit.SECONDS))&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelFullException("The&nbsp;channel&nbsp;has&nbsp;reached&nbsp;it's&nbsp;capacity.&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;"This&nbsp;might&nbsp;be&nbsp;the&nbsp;result&nbsp;of&nbsp;a&nbsp;sink&nbsp;on&nbsp;the&nbsp;channel&nbsp;having&nbsp;too&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;"low&nbsp;of&nbsp;batch&nbsp;size,&nbsp;a&nbsp;downstream&nbsp;system&nbsp;running&nbsp;slower&nbsp;than&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;"normal,&nbsp;or&nbsp;that&nbsp;the&nbsp;channel&nbsp;capacity&nbsp;is&nbsp;just&nbsp;too&nbsp;low.&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;boolean&nbsp;success&nbsp;=&nbsp;false;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.lockShared();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;FlumeEventPointer&nbsp;ptr&nbsp;=&nbsp;log.put(transactionID,&nbsp;event);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Preconditions.checkState(putList.offer(ptr),&nbsp;"putList&nbsp;offer&nbsp;failed&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;queue.addWithoutCommit(ptr,&nbsp;transactionID);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;success&nbsp;=&nbsp;true;&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(IOException&nbsp;e)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Put&nbsp;failed&nbsp;due&nbsp;to&nbsp;IO&nbsp;error&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor,&nbsp;e);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;finally&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.unlockShared();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(!success)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;release&nbsp;slot&nbsp;obtained&nbsp;in&nbsp;the&nbsp;case&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;the&nbsp;put&nbsp;fails&nbsp;for&nbsp;any&nbsp;reason&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;queueRemaining.release();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 </ol> 
 </div> 
 </div> </td> 
 </tr> 
 </tbody> 
</table>

第一行，跟监控的度量信息有关，表示即将放入通道的event数量+1，监控度量请参考：[http://blog.csdn.net/simonchi/article/details/43270461][http_blog.csdn.net_simonchi_article_details_43270461]

### 1、检查队列的剩余空间 ###

### 2、keepAlive秒时间内获取一个共享信号量，说明put的过程是互斥的 ###

如果该时间内没有成功获取该信号量，那么event放入失败

### 3、FlumeEventPointer是用来做检查点机制的，因为这是文件通道，会用日志记录的 ###

1、将event和事务id绑定到Pointer上

2、将pointer放入队列尾部

3、通道中的事件队列FlumeEventQueue添加一个未提交的事件，绑定了事务ID

### 4、释放共享信号量 ###

## 3、doTake ##

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 <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; width:579px; background-color:inherit"> 
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 [java]&nbsp; 
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 <div style="position:absolute; left:509px; top:6222px; width:29px; height:14px; z-index:99"> 
 </div> 
 </div> 
 </div> 
 <ol style="padding:0px; border:none; list-style-position:initial; color:rgb(92,92,92); margin:0px 0px 1px 45px!important; background-color:rgb(255,255,255)"> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> protected&nbsp;Event&nbsp;doTake()&nbsp;throws&nbsp;InterruptedException&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;channelCounter.incrementEventTakeAttemptCount();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(takeList.remainingCapacity()&nbsp;==&nbsp;0)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Take&nbsp;list&nbsp;for&nbsp;FileBackedTransaction,&nbsp;capacity&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;takeList.size()&nbsp;+&nbsp;"&nbsp;full,&nbsp;consider&nbsp;committing&nbsp;more&nbsp;frequently,&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"increasing&nbsp;capacity,&nbsp;or&nbsp;increasing&nbsp;thread&nbsp;count.&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.lockShared();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/*&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;1.&nbsp;Take&nbsp;an&nbsp;event&nbsp;which&nbsp;is&nbsp;in&nbsp;the&nbsp;queue.&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;2.&nbsp;If&nbsp;getting&nbsp;that&nbsp;event&nbsp;does&nbsp;not&nbsp;throw&nbsp;NoopRecordException,&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;then&nbsp;return&nbsp;it.&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;3.&nbsp;Else&nbsp;try&nbsp;to&nbsp;retrieve&nbsp;the&nbsp;next&nbsp;event&nbsp;from&nbsp;the&nbsp;queue&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;4.&nbsp;Repeat&nbsp;2&nbsp;and&nbsp;3&nbsp;until&nbsp;queue&nbsp;is&nbsp;empty&nbsp;or&nbsp;an&nbsp;event&nbsp;is&nbsp;returned.&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*/&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;while&nbsp;(true)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;FlumeEventPointer&nbsp;ptr&nbsp;=&nbsp;queue.removeHead(transactionID);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(ptr&nbsp;==&nbsp;null)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;null;&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;else&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;first&nbsp;add&nbsp;to&nbsp;takeList&nbsp;so&nbsp;that&nbsp;if&nbsp;write&nbsp;to&nbsp;disk&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;fails&nbsp;rollback&nbsp;actually&nbsp;does&nbsp;it's&nbsp;work&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Preconditions.checkState(takeList.offer(ptr),&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"takeList&nbsp;offer&nbsp;failed&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.take(transactionID,&nbsp;ptr);&nbsp;//&nbsp;write&nbsp;take&nbsp;to&nbsp;disk&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Event&nbsp;event&nbsp;=&nbsp;log.get(ptr);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;event;&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(IOException&nbsp;e)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Take&nbsp;failed&nbsp;due&nbsp;to&nbsp;IO&nbsp;error&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor,&nbsp;e);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(NoopRecordException&nbsp;e)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;LOG.warn("Corrupt&nbsp;record&nbsp;replaced&nbsp;by&nbsp;File&nbsp;Channel&nbsp;Integrity&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"tool&nbsp;found.&nbsp;Will&nbsp;retrieve&nbsp;next&nbsp;event",&nbsp;e);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;takeList.remove(ptr);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(CorruptEventException&nbsp;ex)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(fsyncPerTransaction)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException(ex);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;LOG.warn("Corrupt&nbsp;record&nbsp;found.&nbsp;Event&nbsp;will&nbsp;be&nbsp;"&nbsp;+&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"skipped,&nbsp;and&nbsp;next&nbsp;event&nbsp;will&nbsp;be&nbsp;read.",&nbsp;ex);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;takeList.remove(ptr);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;finally&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.unlockShared();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 </ol> 
 </div> 
 
 
 </div> </td> 
 </tr> 
 </tbody> 
</table>

### 1、剩余容量检查 ###

### 2、检查点机制，日志记录操作，从头部取event ###

### 3、从takeList中删除该event ###

## 4、doCommit ##

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 [java]&nbsp; 
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 <ol style="padding:0px; border:none; list-style-position:initial; color:rgb(92,92,92); margin:0px 0px 1px 45px!important; background-color:rgb(255,255,255)"> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> protected&nbsp;void&nbsp;doCommit()&nbsp;throws&nbsp;InterruptedException&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;puts&nbsp;=&nbsp;putList.size();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;takes&nbsp;=&nbsp;takeList.size();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(puts&nbsp;&gt;&nbsp;0)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Preconditions.checkState(takes&nbsp;==&nbsp;0,&nbsp;"nonzero&nbsp;puts&nbsp;and&nbsp;takes&nbsp;"&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.lockShared();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.commitPut(transactionID);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;channelCounter.addToEventPutSuccessCount(puts);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;synchronized&nbsp;(queue)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;while(!putList.isEmpty())&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(!queue.addTail(putList.removeFirst()))&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;StringBuilder&nbsp;msg&nbsp;=&nbsp;new&nbsp;StringBuilder();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append("Queue&nbsp;add&nbsp;failed,&nbsp;this&nbsp;shouldn't&nbsp;be&nbsp;able&nbsp;to&nbsp;");&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append("happen.&nbsp;A&nbsp;portion&nbsp;of&nbsp;the&nbsp;transaction&nbsp;has&nbsp;been&nbsp;");&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append("added&nbsp;to&nbsp;the&nbsp;queue&nbsp;but&nbsp;the&nbsp;remaining&nbsp;portion&nbsp;");&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append("cannot&nbsp;be&nbsp;added.&nbsp;Those&nbsp;messages&nbsp;will&nbsp;be&nbsp;consumed&nbsp;");&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append("despite&nbsp;this&nbsp;transaction&nbsp;failing.&nbsp;Please&nbsp;report.");&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;msg.append(channelNameDescriptor);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;LOG.error(msg.toString());&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Preconditions.checkState(false,&nbsp;msg.toString());&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;queue.completeTransaction(transactionID);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(IOException&nbsp;e)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Commit&nbsp;failed&nbsp;due&nbsp;to&nbsp;IO&nbsp;error&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor,&nbsp;e);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;finally&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.unlockShared();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;else&nbsp;if&nbsp;(takes&nbsp;&gt;&nbsp;0)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.lockShared();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.commitTake(transactionID);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;queue.completeTransaction(transactionID);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;channelCounter.addToEventTakeSuccessCount(takes);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;catch&nbsp;(IOException&nbsp;e)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw&nbsp;new&nbsp;ChannelException("Commit&nbsp;failed&nbsp;due&nbsp;to&nbsp;IO&nbsp;error&nbsp;"&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;+&nbsp;channelNameDescriptor,&nbsp;e);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;finally&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.unlockShared();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;queueRemaining.release(takes);&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;putList.clear();&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;takeList.clear();&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;channelCounter.setChannelSize(queue.getSize());&nbsp;&nbsp;</li> 
 <li style="margin:0px!important; padding:0px 3px 0px 10px!important; border-style:none none none solid; border-left-width:3px; border-left-color:rgb(153,153,153); list-style:decimal-leading-zero outside; color:rgb(119,119,119); line-height:18px; background-color:rgb(249,249,249)"> &nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;&nbsp;</li> 
 </ol> 
 </div> 
 
 
 </div> </td> 
 </tr> 
 </tbody> 
</table>

### 1、如果putList不为空，提交的是放入通道的事件数量 ###

### 2、如果takeList不为空，提交的是从通道拿走的事件数量 ###

## 5、doRollback ##

在此之前，putList,takeList都没有clear，所以这里可以对着两个双向队列回滚操作

以上是文件通道的实现，如果是内存通道，就没有log的检查点记录了，简单多了，不需要维护状态了。

# 3、sink #

sink的接口定义如下：

sink与一个通道连接，并消费通道中的events，把它们发送到一个配置的目的地

其实和source的原理大部分相同，同样有一个AbstractSink

我们同样看一个具体实现吧，HDFSEventSink

看它的process方法

这里可以看到，flume-ng在sink端是有事务控制的

事务从 从通道中取event开始，到sink到下一个目的地结束

在这个过程中，任意的失败都会导致事务的回滚，这就保证数据了一致性。

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[http_blog.csdn.net_simonchi_article_details_43270461]: http://blog.csdn.net/simonchi/article/details/43270461