org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever Maven / Gradle / Ivy
/*
* 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.flink.runtime.webmonitor.retriever;
import org.apache.flink.runtime.rpc.RpcGateway;
import org.apache.flink.util.FlinkRuntimeException;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
/**
* Generic retriever interface for {@link RpcGateway}.
*
* @param type of the object to retrieve
*/
public interface GatewayRetriever {
/**
* Get future of object to retrieve.
*
* @return Future object to retrieve
*/
CompletableFuture getFuture();
/**
* Returns the currently retrieved gateway if there is such an object. Otherwise
* it returns an empty optional.
*
* @return Optional object to retrieve
*/
default Optional getNow() {
CompletableFuture leaderFuture = getFuture();
if (leaderFuture != null) {
if (leaderFuture.isCompletedExceptionally() || leaderFuture.isCancelled()) {
return Optional.empty();
} else if (leaderFuture.isDone()) {
try {
return Optional.of(leaderFuture.get());
} catch (Exception e) {
// this should never happen
throw new FlinkRuntimeException("Unexpected error while accessing the retrieved gateway.", e);
}
} else {
return Optional.empty();
}
} else {
return Optional.empty();
}
}
}