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本文主要研究一下flink的ActorGateway
ActorGateway
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/instance/ActorGateway.java
public interface ActorGateway extends Serializable {
/**
* Sends a message asynchronously and returns its response. The response to the message is
* returned as a future.
*
* @param message Message to be sent
* @param timeout Timeout until the Future is completed with an AskTimeoutException
* @return Future which contains the response to the sent message
*/
Future- ActorGateway接口定义了ask、tell、forward、retry、path、actor、leaderSessionID方法；它有一个实现类为AkkaActorGateway
AkkaActorGateway
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/instance/AkkaActorGateway.java
public class AkkaActorGateway implements ActorGateway, Serializable {
private static final long serialVersionUID = 42L;
// ActorRef of the remote instance
private final ActorRef actor;
// Associated leader session ID, which is used for RequiresLeaderSessionID messages
private final UUID leaderSessionID;
// Decorator for messages
private final MessageDecorator decorator;
public AkkaActorGateway(ActorRef actor, UUID leaderSessionID) {
this.actor = Preconditions.checkNotNull(actor);
this.leaderSessionID = Preconditions.checkNotNull(leaderSessionID);
// we want to wrap RequiresLeaderSessionID messages in a LeaderSessionMessage
this.decorator = new LeaderSessionMessageDecorator(leaderSessionID);
}
/**
* Sends a message asynchronously and returns its response. The response to the message is
* returned as a future.
*
* @param message Message to be sent
* @param timeout Timeout until the Future is completed with an AskTimeoutException
* @return Future which contains the response to the sent message
*/
@Override
public Future- AkkaActorGateway实现了ActorGateway接口，它的构造器要求输入ActorRef及leaderSessionID，同时基于leaderSessionID创建了LeaderSessionMessageDecorator；ask、tell、forward、retry方法均首先调用LeaderSessionMessageDecorator.decorate方法包装message参数，然后再去调用ActorRef的相应方法
MessageDecorator
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/messages/MessageDecorator.java
public interface MessageDecorator extends java.io.Serializable {
/**
* Decorates a message
*
* @param message Message to decorate
* @return Decorated message
*/
Object decorate(Object message);
}- MessageDecorator接口定义了decorate方法用于包装message，它有一个实现类为LeaderSessionMessageDecorator
LeaderSessionMessageDecorator
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/messages/LeaderSessionMessageDecorator.java
public class LeaderSessionMessageDecorator implements MessageDecorator {
private static final long serialVersionUID = 5359618147408392706L;
/** Leader session ID with which the RequiresLeaderSessionID messages will be decorated */
private final UUID leaderSessionID;
/**
* Sets the leader session ID with which the messages will be decorated.
*
* @param leaderSessionID Leader session ID to be used for decoration
*/
public LeaderSessionMessageDecorator(UUID leaderSessionID) {
this.leaderSessionID = leaderSessionID;
}
@Override
public Object decorate(Object message) {
if (message instanceof RequiresLeaderSessionID) {
return new JobManagerMessages.LeaderSessionMessage(leaderSessionID, message);
} else {
return message;
}
}
}- LeaderSessionMessageDecorator实现了MessageDecorator接口，其decorate方法判断message是RequiresLeaderSessionID类型的话，则返回JobManagerMessages.LeaderSessionMessage，否则返回原始的message
JobManagerMessages.LeaderSessionMessage
flink-1.7.2/flink-runtime/src/main/scala/org/apache/flink/runtime/messages/JobManagerMessages.scala
object JobManagerMessages {
/** Wrapper class for leader session messages. Leader session messages implement the
* [[RequiresLeaderSessionID]] interface and have to be wrapped in a [[LeaderSessionMessage]],
* which also contains the current leader session ID.
*
* @param leaderSessionID Current leader session ID
* @param message [[RequiresLeaderSessionID]] message to be wrapped in a [[LeaderSessionMessage]]
*/
case class LeaderSessionMessage(leaderSessionID: UUID, message: Any)
//......
}- JobManagerMessages.LeaderSessionMessage是一个case class，它有两个属性，分别是leaderSessionID及message
小结
- ActorGateway接口定义了ask、tell、forward、retry、path、actor、leaderSessionID方法；它有一个实现类为AkkaActorGateway
- AkkaActorGateway实现了ActorGateway接口，它的构造器要求输入ActorRef及leaderSessionID，同时基于leaderSessionID创建了LeaderSessionMessageDecorator；ask、tell、forward、retry方法均首先调用LeaderSessionMessageDecorator.decorate方法包装message参数，然后再去调用ActorRef的相应方法
- MessageDecorator接口定义了decorate方法用于包装message，它有一个实现类为LeaderSessionMessageDecorator；LeaderSessionMessageDecorator实现了MessageDecorator接口，其decorate方法判断message是RequiresLeaderSessionID类型的话，则返回JobManagerMessages.LeaderSessionMessage，否则返回原始的message；JobManagerMessages.LeaderSessionMessage是一个case class，它有两个属性，分别是leaderSessionID及message
doc
- ActorGateway