【kafka】使用Kafka Connect API创建Apache Kafka连接器的4个步骤

待我称王封你为后i 2022-12-22 04:38 198阅读 0赞

### 文章目录 ###

*  一. Kafka Connect简介
 *  二. 使用Kafka自带的File连接器
 *   *  图例
     *  配置
     *  运行
 *  三、 自定义连接器
 *   *  参考
     *  Task
     *  SourceTask
     *  SinkTask
     *  Connect

# 一. Kafka Connect简介 #

Kafka是一个使用越来越广的消息系统，尤其是在大数据开发中（实时数据处理和分析）。为何集成其他系统和解耦应用，经常使用Producer来发送消息到Broker，并使用Consumer来消费Broker中的消息。Kafka Connect是到0.9版本才提供的并极大的简化了其他系统与Kafka的集成。Kafka Connect运用用户快速定义并实现各种Connector(File,Jdbc,Hdfs等)，这些功能让大批量数据导入/导出Kafka很方便。

# 二. 使用Kafka自带的File连接器 #

## 图例 ##

![在这里插入图片描述][20201120091953763.png_pic_center]

## 配置 ##

本例使用到了两个Connector:

> FileStreamSource：从test.txt中读取并发布到Broker中  
> FileStreamSink：从Broker中读取数据并写入到test.sink.txt文件中 其中的Source使用到的配置文件是$/config/connect-file-source.properties

name=local-file-source
    connector.class=FileStreamSource
    tasks.max=1
    file=test.txt
    topic=connect-test

其中的Sink使用到的配置文件是$/config/connect-file-sink.properties

name=local-file-sink
    connector.class=FileStreamSink
    tasks.max=1
    file=test.sink.txt
    topics=connect-test

Broker使用到的配置文件是$/config/connect-standalone.properties

bootstrap.servers=localhost:9092
    key.converter=org.apache.kafka.connect.json.JsonConverter
    value.converter=org.apache.kafka.connect.json.JsonConverter
    key.converter.schemas.enable=true
    value.converter.schemas.enable=trueinternal.key.converter=org.apache.kafka.connect.json.JsonConverter
    internal.value.converter=org.apache.kafka.connect.json.JsonConverter
    internal.key.converter.schemas.enable=false
    internal.value.converter.schemas.enable=false
    offset.storage.file.filename=/tmp/connect.offsets
    offset.flush.interval.ms=10000

## 运行 ##

启动Kafka Broker
    先运行zookeeper
    [root@localhost kafka_2.11-0.11.0.0]# ./bin/zookeeper-server-start.sh ./config/zookeeper.properties &
    再运行kafka
    [root@localhost kafka_2.11-0.11.0.0]# ./bin/kafka-server-start.sh ./config/server.properties &
    
    [root@localhost kafka_2.11-0.11.0.0]# ./bin/connect-standalone.sh config/connect-standalone.properties config/connect-file-source.properties config/connect-file-sink.properties
    
    消费观察输出数据
    ./kafka-console-consumer.sh --bootstrap-server 192.168.137.121:9092 --topic connect-test  --from-beginning
    
    kafka根目录添加输入源，观察输出数据
    [root@Server4 kafka_2.12-0.11.0.0]# echo 'firest line' >> test.txt
    [root@Server4 kafka_2.12-0.11.0.0]# echo 'second line' >> test.txt
    
    输出数据
    { "schema":{ "type":"string","optional":false},"payload":"firest line"}
    { "schema":{ "type":"string","optional":false},"payload":"second line"}
    
    查看test.sink.txt
    [root@Server4 kafka_2.12-0.11.0.0]# cat test.sink.txt 
    firest line
    second line

# 三、 自定义连接器 #

## 参考 ##

http://kafka.apache.org/documentation/#connect
    
    https://docs.confluent.io/current/connect/index.html
    
    https://www.confluent.io/blog/create-dynamic-kafka-connect-source-connectors/
    
    https://github.com/apache/kafka/tree/trunk/connect
    
    http://www.itrensheng.com/archives/apache-kafka-kafka-connectfileconnector
    
    https://github.com/apache/kafka/tree/trunk/connect/file/src/main/java/org/apache/kafka/connect/file
    
    // 开发自己的connect
    https://www.jdon.com/54527
    https://www.cnblogs.com/laoqing/p/11927958.html
    https://www.orchome.com/345
    // debezium 开源实现比较好的
    https://github.com/debezium/debezium

maven

<dependency>
 <groupId>org.apache.kafka</groupId>
 <artifactId>connect-api</artifactId>
 <version>2.6.0</version>
 </dependency>

## Task ##

## SourceTask ##

/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
 package org.apache.kafka.connect.source;
 
 import org.apache.kafka.connect.connector.Task;
 import org.apache.kafka.clients.producer.RecordMetadata;
 
 import java.util.List;
 import java.util.Map;
 
 /** * SourceTask is a Task that pulls records from another system for storage in Kafka. */
 public abstract class SourceTask implements Task { 
 
 protected SourceTaskContext context;
 
 /** * Initialize this SourceTask with the specified context object. */
 public void initialize(SourceTaskContext context) { 
 this.context = context;
 }
 
 /** * Start the Task. This should handle any configuration parsing and one-time setup of the task. * @param props initial configuration */
 @Override
 public abstract void start(Map<String, String> props);
 
 /** * * Poll this source task for new records. If no data is currently available, this method * should block but return control to the caller regularly (by returning {@code null}) in * order for the task to transition to the {@code PAUSED} state if requested to do so. * * * The task will be {@link #stop() stopped} on a separate thread, and when that happens * this method is expected to unblock, quickly finish up any remaining processing, and * return. * * * @return a list of source records */
 public abstract List<SourceRecord> poll() throws InterruptedException;
 
 /** * * Commit the offsets, up to the offsets that have been returned by {@link #poll()}. This * method should block until the commit is complete. * * * SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. * */
 public void commit() throws InterruptedException { 
 // This space intentionally left blank.
 }
 
 /** * Signal this SourceTask to stop. In SourceTasks, this method only needs to signal to the task that it should stop * trying to poll for new data and interrupt any outstanding poll() requests. It is not required that the task has * fully stopped. Note that this method necessarily may be invoked from a different thread than {@link #poll()} and * {@link #commit()}. * * For example, if a task uses a {@link java.nio.channels.Selector} to receive data over the network, this method * could set a flag that will force {@link #poll()} to exit immediately and invoke * {@link java.nio.channels.Selector#wakeup() wakeup()} to interrupt any ongoing requests. */
 @Override
 public abstract void stop();
 
 /** * * Commit an individual {@link SourceRecord} when the callback from the producer client is received. This method is * also called when a record is filtered by a transformation, and thus will never be ACK'd by a broker. * * * This is an alias for {@link #commitRecord(SourceRecord, RecordMetadata)} for backwards compatibility. The default * implementation of {@link #commitRecord(SourceRecord, RecordMetadata)} just calls this method. It is not necessary * to override both methods. * * * SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. * * * @param record {@link SourceRecord} that was successfully sent via the producer or filtered by a transformation * @throws InterruptedException * @deprecated Use {@link #commitRecord(SourceRecord, RecordMetadata)} instead. */
 @Deprecated
 public void commitRecord(SourceRecord record) throws InterruptedException { 
 // This space intentionally left blank.
 }
 
 /** * * Commit an individual {@link SourceRecord} when the callback from the producer client is received. This method is * also called when a record is filtered by a transformation, and thus will never be ACK'd by a broker. In this case * {@code metadata} will be null. * * * SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. * * * The default implementation just calls {@link #commitRecord(SourceRecord)}, which is a nop by default. It is * not necessary to implement both methods. * * * @param record {@link SourceRecord} that was successfully sent via the producer or filtered by a transformation * @param metadata {@link RecordMetadata} record metadata returned from the broker, or null if the record was filtered * @throws InterruptedException */
 public void commitRecord(SourceRecord record, RecordMetadata metadata)
 throws InterruptedException { 
 // by default, just call other method for backwards compatibility
 commitRecord(record);
 }
 }

## SinkTask ##

/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
 package org.apache.kafka.connect.sink;
 
 import org.apache.kafka.clients.consumer.OffsetAndMetadata;
 import org.apache.kafka.common.TopicPartition;
 import org.apache.kafka.connect.connector.Task;
 
 import java.util.Collection;
 import java.util.Map;
 
 /** * SinkTask is a Task that takes records loaded from Kafka and sends them to another system. Each task * instance is assigned a set of partitions by the Connect framework and will handle all records received * from those partitions. As records are fetched from Kafka, they will be passed to the sink task using the * {@link #put(Collection)} API, which should either write them to the downstream system or batch them for * later writing. Periodically, Connect will call {@link #flush(Map)} to ensure that batched records are * actually pushed to the downstream system.. * * Below we describe the lifecycle of a SinkTask. * * <ol> * <li>Initialization: SinkTasks are first initialized using {@link #initialize(SinkTaskContext)} * to prepare the task's context and {@link #start(Map)} to accept configuration and start any services * needed for processing.</li> * <li>Partition Assignment: After initialization, Connect will assign the task a set of partitions * using {@link #open(Collection)}. These partitions are owned exclusively by this task until they * have been closed with {@link #close(Collection)}.</li> * <li>Record Processing: Once partitions have been opened for writing, Connect will begin forwarding * records from Kafka using the {@link #put(Collection)} API. Periodically, Connect will ask the task * to flush records using {@link #flush(Map)} as described above.</li> * <li>Partition Rebalancing: Occasionally, Connect will need to change the assignment of this task. * When this happens, the currently assigned partitions will be closed with {@link #close(Collection)} and * the new assignment will be opened using {@link #open(Collection)}.</li> * <li>Shutdown: When the task needs to be shutdown, Connect will close active partitions (if there * are any) and stop the task using {@link #stop()}</li> * </ol> * */
 public abstract class SinkTask implements Task { 
 
 /** * * The configuration key that provides the list of topics that are inputs for this * SinkTask. * */
 public static final String TOPICS_CONFIG = "topics";
 
 /** * * The configuration key that provides a regex specifying which topics to include as inputs * for this SinkTask. * */
 public static final String TOPICS_REGEX_CONFIG = "topics.regex";
 
 protected SinkTaskContext context;
 
 /** * Initialize the context of this task. Note that the partition assignment will be empty until * Connect has opened the partitions for writing with {@link #open(Collection)}. * @param context The sink task's context */
 public void initialize(SinkTaskContext context) { 
 this.context = context;
 }
 
 /** * Start the Task. This should handle any configuration parsing and one-time setup of the task. * @param props initial configuration */
 @Override
 public abstract void start(Map<String, String> props);
 
 /** * Put the records in the sink. Usually this should send the records to the sink asynchronously * and immediately return. * * If this operation fails, the SinkTask may throw a {@link org.apache.kafka.connect.errors.RetriableException} to * indicate that the framework should attempt to retry the same call again. Other exceptions will cause the task to * be stopped immediately. {@link SinkTaskContext#timeout(long)} can be used to set the maximum time before the * batch will be retried. * * @param records the set of records to send */
 public abstract void put(Collection<SinkRecord> records);
 
 /** * Flush all records that have been {@link #put(Collection)} for the specified topic-partitions. * * @param currentOffsets the current offset state as of the last call to {@link #put(Collection)}}, * provided for convenience but could also be determined by tracking all offsets included in the {@link SinkRecord}s * passed to {@link #put}. */
 public void flush(Map<TopicPartition, OffsetAndMetadata> currentOffsets) { 
 }
 
 /** * Pre-commit hook invoked prior to an offset commit. * * The default implementation simply invokes {@link #flush(Map)} and is thus able to assume all {@code currentOffsets} are safe to commit. * * @param currentOffsets the current offset state as of the last call to {@link #put(Collection)}}, * provided for convenience but could also be determined by tracking all offsets included in the {@link SinkRecord}s * passed to {@link #put}. * * @return an empty map if Connect-managed offset commit is not desired, otherwise a map of offsets by topic-partition that are safe to commit. */
 public Map<TopicPartition, OffsetAndMetadata> preCommit(Map<TopicPartition, OffsetAndMetadata> currentOffsets) { 
 flush(currentOffsets);
 return currentOffsets;
 }
 
 /** * The SinkTask use this method to create writers for newly assigned partitions in case of partition * rebalance. This method will be called after partition re-assignment completes and before the SinkTask starts * fetching data. Note that any errors raised from this method will cause the task to stop. * @param partitions The list of partitions that are now assigned to the task (may include * partitions previously assigned to the task) */
 public void open(Collection<TopicPartition> partitions) { 
 this.onPartitionsAssigned(partitions);
 }
 
 /** * @deprecated Use {@link #open(Collection)} for partition initialization. */
 @Deprecated
 public void onPartitionsAssigned(Collection<TopicPartition> partitions) { 
 }
 
 /** * The SinkTask use this method to close writers for partitions that are no * longer assigned to the SinkTask. This method will be called before a rebalance operation starts * and after the SinkTask stops fetching data. After being closed, Connect will not write * any records to the task until a new set of partitions has been opened. Note that any errors raised * from this method will cause the task to stop. * @param partitions The list of partitions that should be closed */
 public void close(Collection<TopicPartition> partitions) { 
 this.onPartitionsRevoked(partitions);
 }
 
 /** * @deprecated Use {@link #close(Collection)} instead for partition cleanup. */
 @Deprecated
 public void onPartitionsRevoked(Collection<TopicPartition> partitions) { 
 }
 
 /** * Perform any cleanup to stop this task. In SinkTasks, this method is invoked only once outstanding calls to other * methods have completed (e.g., {@link #put(Collection)} has returned) and a final {@link #flush(Map)} and offset * commit has completed. Implementations of this method should only need to perform final cleanup operations, such * as closing network connections to the sink system. */
 @Override
 public abstract void stop();
 }

## Connect ##

/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
 package org.apache.kafka.connect.connector;
 
 import org.apache.kafka.common.config.Config;
 import org.apache.kafka.common.config.ConfigDef;
 import org.apache.kafka.common.config.ConfigValue;
 import org.apache.kafka.connect.errors.ConnectException;
 import org.apache.kafka.connect.components.Versioned;
 
 import java.util.List;
 import java.util.Map;
 
 /** * * Connectors manage integration of Kafka Connect with another system, either as an input that ingests * data into Kafka or an output that passes data to an external system. Implementations should * not use this class directly; they should inherit from {@link org.apache.kafka.connect.source.SourceConnector SourceConnector} * or {@link org.apache.kafka.connect.sink.SinkConnector SinkConnector}. * * * Connectors have two primary tasks. First, given some configuration, they are responsible for * creating configurations for a set of {@link Task}s that split up the data processing. For * example, a database Connector might create Tasks by dividing the set of tables evenly among * tasks. Second, they are responsible for monitoring inputs for changes that require * reconfiguration and notifying the Kafka Connect runtime via the {@link ConnectorContext}. Continuing the * previous example, the connector might periodically check for new tables and notify Kafka Connect of * additions and deletions. Kafka Connect will then request new configurations and update the running * Tasks. * */
 public abstract class Connector implements Versioned { 
 
 protected ConnectorContext context;
 
 
 /** * Initialize this connector, using the provided ConnectorContext to notify the runtime of * input configuration changes. * @param ctx context object used to interact with the Kafka Connect runtime */
 public void initialize(ConnectorContext ctx) { 
 context = ctx;
 }
 
 /** * * Initialize this connector, using the provided ConnectorContext to notify the runtime of * input configuration changes and using the provided set of Task configurations. * This version is only used to recover from failures. * * * The default implementation ignores the provided Task configurations. During recovery, Kafka Connect will request * an updated set of configurations and update the running Tasks appropriately. However, Connectors should * implement special handling of this case if it will avoid unnecessary changes to running Tasks. * * * @param ctx context object used to interact with the Kafka Connect runtime * @param taskConfigs existing task configurations, which may be used when generating new task configs to avoid * churn in partition to task assignments */
 public void initialize(ConnectorContext ctx, List<Map<String, String>> taskConfigs) { 
 context = ctx;
 // Ignore taskConfigs. May result in more churn of tasks during recovery if updated configs
 // are very different, but reduces the difficulty of implementing a Connector
 }
 
 /** * Returns the context object used to interact with the Kafka Connect runtime. * * @return the context for this Connector. */
 protected ConnectorContext context() { 
 return context;
 }
 
 /** * Start this Connector. This method will only be called on a clean Connector, i.e. it has * either just been instantiated and initialized or {@link #stop()} has been invoked. * * @param props configuration settings */
 public abstract void start(Map<String, String> props);
 
 /** * Reconfigure this Connector. Most implementations will not override this, using the default * implementation that calls {@link #stop()} followed by {@link #start(Map)}. * Implementations only need to override this if they want to handle this process more * efficiently, e.g. without shutting down network connections to the external system. * * @param props new configuration settings */
 public void reconfigure(Map<String, String> props) { 
 stop();
 start(props);
 }
 
 /** * Returns the Task implementation for this Connector. */
 public abstract Class<? extends Task> taskClass();
 
 /** * Returns a set of configurations for Tasks based on the current configuration, * producing at most count configurations. * * @param maxTasks maximum number of configurations to generate * @return configurations for Tasks */
 public abstract List<Map<String, String>> taskConfigs(int maxTasks);
 
 /** * Stop this connector. */
 public abstract void stop();
 
 /** * Validate the connector configuration values against configuration definitions. * @param connectorConfigs the provided configuration values * @return List of Config, each Config contains the updated configuration information given * the current configuration values. */
 public Config validate(Map<String, String> connectorConfigs) { 
 ConfigDef configDef = config();
 if (null == configDef) { 
 throw new ConnectException(
 String.format("%s.config() must return a ConfigDef that is not null.", this.getClass().getName())
 );
 }
 List<ConfigValue> configValues = configDef.validate(connectorConfigs);
 return new Config(configValues);
 }
 
 /** * Define the configuration for the connector. * @return The ConfigDef for this connector; may not be null. */
 public abstract ConfigDef config();
 }

[20201120091953763.png_pic_center]: /images/20221120/9c2941eedfd34f809964ec03574254b5.png