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本文主要研究一下flink的FencedAkkaInvocationHandler
FencedRpcGateway
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/FencedRpcGateway.java
public interface FencedRpcGateway extends RpcGateway {
/**
* Get the current fencing token.
*
* @return current fencing token
*/
F getFencingToken();
} - FencedRpcGateway接口继承了RpcGateway接口，它定义一个泛型F，即为fencing token的泛型
FencedMainThreadExecutable
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/FencedMainThreadExecutable.java
public interface FencedMainThreadExecutable extends MainThreadExecutable {
/**
* Run the given runnable in the main thread without attaching a fencing token.
*
* @param runnable to run in the main thread without validating the fencing token.
*/
void runAsyncWithoutFencing(Runnable runnable);
/**
* Run the given callable in the main thread without attaching a fencing token.
*
* @param callable to run in the main thread without validating the fencing token.
* @param timeout for the operation
* @param type of the callable result
* @return Future containing the callable result
*/
CompletableFuture callAsyncWithoutFencing(Callable callable, Time timeout);
} - FencedMainThreadExecutable接口继承了MainThreadExecutable，它定义了runAsyncWithoutFencing、callAsyncWithoutFencing方法用于运行unfenced runnable或者unfenced callable，之所以这样定义主要是因为FencedMainThreadExecutable继承了MainThreadExecutable，因而MainThreadExecutable里头定义的runAsync、callAsync、scheduleRunAsync方法的语义就变成是Fenced
FencedAkkaInvocationHandler
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/akka/FencedAkkaInvocationHandler.java
public class FencedAkkaInvocationHandler extends AkkaInvocationHandler implements FencedMainThreadExecutable, FencedRpcGateway {
private final Supplier fencingTokenSupplier;
public FencedAkkaInvocationHandler(
String address,
String hostname,
ActorRef rpcEndpoint,
Time timeout,
long maximumFramesize,
@Nullable CompletableFuture terminationFuture,
Supplier fencingTokenSupplier) {
super(address, hostname, rpcEndpoint, timeout, maximumFramesize, terminationFuture);
this.fencingTokenSupplier = Preconditions.checkNotNull(fencingTokenSupplier);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Class declaringClass = method.getDeclaringClass();
if (declaringClass.equals(FencedMainThreadExecutable.class) ||
declaringClass.equals(FencedRpcGateway.class)) {
return method.invoke(this, args);
} else {
return super.invoke(proxy, method, args);
}
}
@Override
public void runAsyncWithoutFencing(Runnable runnable) {
checkNotNull(runnable, "runnable");
if (isLocal) {
getActorRef().tell(
new UnfencedMessage<>(new RunAsync(runnable, 0L)), ActorRef.noSender());
} else {
throw new RuntimeException("Trying to send a Runnable to a remote actor at " +
getActorRef().path() + ". This is not supported.");
}
}
@Override
public CompletableFuture callAsyncWithoutFencing(Callable callable, Time timeout) {
checkNotNull(callable, "callable");
checkNotNull(timeout, "timeout");
if (isLocal) {
@SuppressWarnings("unchecked")
CompletableFuture resultFuture = (CompletableFuture) FutureUtils.toJava(
Patterns.ask(
getActorRef(),
new UnfencedMessage<>(new CallAsync(callable)),
timeout.toMilliseconds()));
return resultFuture;
} else {
throw new RuntimeException("Trying to send a Runnable to a remote actor at " +
getActorRef().path() + ". This is not supported.");
}
}
@Override
public void tell(Object message) {
super.tell(fenceMessage(message));
}
@Override
public CompletableFuture ask(Object message, Time timeout) {
return super.ask(fenceMessage(message), timeout);
}
@Override
public F getFencingToken() {
return fencingTokenSupplier.get();
}
private FencedMessage fenceMessage(P message) {
if (isLocal) {
return new LocalFencedMessage<>(fencingTokenSupplier.get(), message);
} else {
if (message instanceof Serializable) {
@SuppressWarnings("unchecked")
FencedMessage result = (FencedMessage) new RemoteFencedMessage<>(fencingTokenSupplier.get(), (Serializable) message);
return result;
} else {
throw new RuntimeException("Trying to send a non-serializable message " + message + " to a remote " +
"RpcEndpoint. Please make sure that the message implements java.io.Serializable.");
}
}
}
}
- FencedAkkaInvocationHandler继承了AkkaInvocationHandler，实现了FencedMainThreadExecutable、FencedRpcGateway接口；runAsyncWithoutFencing、callAsyncWithoutFencing发送的均为UnfencedMessage
- FencedAkkaInvocationHandler的invoke方法针对FencedRpcGateway、FencedMainThreadExecutable的方法则对当前对象进行对应方法调用，其他的就转为调用父类的invoke方法
- 父类的runAsync、scheduleRunAsync、callAsync最后调用的是tell或者ask方法，而FencedAkkaInvocationHandler覆盖了父类的tell及ask方法，将runAsync、scheduleRunAsync、callAsync方法的语义变为Fenced；这里的tell及ask方法通过fenceMessage方法构造FencedMessage，而fenceMessage方法通过getFencingToken方法获取fencing token；getFencingToken方法调用的是fencingTokenSupplier.get()，fencingTokenSupplier由构造器传入
UnfencedMessage
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/messages/UnfencedMessage.java
public class UnfencedMessage {
private final P payload;
public UnfencedMessage(P payload) {
this.payload = Preconditions.checkNotNull(payload);
}
public P getPayload() {
return payload;
}
@Override
public String toString() {
return "UnfencedMessage(" + payload + ')';
}
}
- UnfencedMessage即不需要fencing token的message
FencedMessage
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/messages/FencedMessage.java
public interface FencedMessage {
F getFencingToken();
P getPayload();
} - FencedMessage接口定义了getFencingToken及getPayload方法；它有两个子类，分别是LocalFencedMessage及RemoteFencedMessage
LocalFencedMessage
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/messages/LocalFencedMessage.java
public class LocalFencedMessage implements FencedMessage {
private final F fencingToken;
private final P payload;
public LocalFencedMessage(@Nullable F fencingToken, P payload) {
this.fencingToken = fencingToken;
this.payload = Preconditions.checkNotNull(payload);
}
@Override
public F getFencingToken() {
return fencingToken;
}
@Override
public P getPayload() {
return payload;
}
@Override
public String toString() {
return "LocalFencedMessage(" + fencingToken + ", " + payload + ')';
}
} - LocalFencedMessage实现了FencedMessage接口，其中fencingToken的类型要求实现Serializable接口，它有fencingToken及payload两个属性
RemoteFencedMessage
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/messages/RemoteFencedMessage.java
public class RemoteFencedMessage implements FencedMessage, Serializable {
private static final long serialVersionUID = 4043136067468477742L;
private final F fencingToken;
private final P payload;
public RemoteFencedMessage(@Nullable F fencingToken, P payload) {
this.fencingToken = fencingToken;
this.payload = Preconditions.checkNotNull(payload);
}
@Override
public F getFencingToken() {
return fencingToken;
}
@Override
public P getPayload() {
return payload;
}
@Override
public String toString() {
return "RemoteFencedMessage(" + fencingToken + ", " + payload + ')';
}
} - RemoteFencedMessage实现了FencedMessage及Serializable接口，同时payload的类型也要求实现Serializable接口，它有fencingToken及payload两个属性
小结
- FencedRpcGateway接口继承了RpcGateway接口，它定义一个泛型F，即为fencing token的泛型；FencedMainThreadExecutable接口继承了MainThreadExecutable，它定义了runAsyncWithoutFencing、callAsyncWithoutFencing方法用于运行unfenced runnable或者unfenced callable
- FencedAkkaInvocationHandler继承了AkkaInvocationHandler，实现了FencedMainThreadExecutable、FencedRpcGateway接口；runAsyncWithoutFencing、callAsyncWithoutFencing发送的均为UnfencedMessage；父类的runAsync、scheduleRunAsync、callAsync最后调用的是tell或者ask方法，而FencedAkkaInvocationHandler覆盖了父类的tell及ask方法，将runAsync、scheduleRunAsync、callAsync方法的语义变为Fenced；这里的tell及ask方法通过fenceMessage方法构造FencedMessage
- UnfencedMessage即不需要fencing token的message；FencedMessage接口定义了getFencingToken及getPayload方法；它有两个子类，分别是LocalFencedMessage及RemoteFencedMessage；LocalFencedMessage与RemoteFencedMessage的区别在于RemoteFencedMessage实现了Serializable接口，同时payload的类型也要求实现Serializable接口
doc
- FencedAkkaInvocationHandler