io.helidon.grpc.core.SafeStreamObserver Maven / Gradle / Ivy
/*
* Copyright (c) 2019, 2024 Oracle and/or its affiliates.
*
* Licensed 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 io.helidon.grpc.core;
import java.lang.System.Logger.Level;
import io.grpc.Status;
import io.grpc.stub.StreamObserver;
/**
* A {@link StreamObserver} that handles exceptions correctly.
*
* @param the type of response expected
*/
public class SafeStreamObserver implements StreamObserver {
/**
* Create a {@link SafeStreamObserver} that wraps
* another {@link StreamObserver}.
*
* @param streamObserver the {@link StreamObserver} to wrap
*/
private SafeStreamObserver(StreamObserver streamObserver) {
delegate = streamObserver;
}
@Override
public void onNext(T t) {
if (done) {
return;
}
if (t == null) {
onError(Status.INVALID_ARGUMENT
.withDescription("onNext called with null. Null values are generally not allowed.")
.asRuntimeException());
} else {
try {
delegate.onNext(t);
} catch (Throwable thrown) {
throwIfFatal(thrown);
onError(thrown);
}
}
}
@Override
public void onError(Throwable thrown) {
try {
if (done) {
LOGGER.log(Level.ERROR, () -> "OnError called after StreamObserver was closed");
} else {
done = true;
delegate.onError(checkNotNull(thrown));
}
} catch (Throwable t) {
throwIfFatal(t);
LOGGER.log(Level.ERROR, () -> "Caught exception handling onError", t);
}
}
@Override
public void onCompleted() {
if (done) {
LOGGER.log(Level.WARNING, "onComplete called after StreamObserver was closed");
} else {
try {
done = true;
delegate.onCompleted();
} catch (Throwable thrown) {
throwIfFatal(thrown);
LOGGER.log(Level.ERROR, () -> "Caught exception handling onComplete", thrown);
}
}
}
/**
* Obtain the wrapped {@link StreamObserver}.
* @return the wrapped {@link StreamObserver}
*/
public StreamObserver delegate() {
return delegate;
}
private Throwable checkNotNull(Throwable thrown) {
if (thrown == null) {
thrown = Status.INVALID_ARGUMENT
.withDescription("onError called with null Throwable. Null exceptions are generally not allowed.")
.asRuntimeException();
}
return thrown;
}
/**
* Throws a particular {@code Throwable} only if it belongs to a set of "fatal" error varieties. These varieties are
* as follows:
*
* - {@code VirtualMachineError}
* - {@code ThreadDeath}
* - {@code LinkageError}
*
*
* @param thrown the {@code Throwable} to test and perhaps throw
*/
private static void throwIfFatal(Throwable thrown) {
if (thrown instanceof VirtualMachineError) {
throw (VirtualMachineError) thrown;
} else if (thrown instanceof ThreadDeath) {
throw (ThreadDeath) thrown;
} else if (thrown instanceof LinkageError) {
throw (LinkageError) thrown;
}
}
/**
* Ensure that the specified {@link StreamObserver} is a safe observer.
*
* If the specified observer is not an instance of {@link SafeStreamObserver} then wrap
* it in a {@link SafeStreamObserver}.
*
* @param observer the {@link StreamObserver} to test
* @param the response type expected by the observer
*
* @return a safe {@link StreamObserver}
*/
public static StreamObserver ensureSafeObserver(StreamObserver observer) {
if (observer instanceof SafeStreamObserver) {
return observer;
}
return new SafeStreamObserver<>(observer);
}
// ----- constants ------------------------------------------------------
/**
* The {2link Logger} to use.
*/
private static final System.Logger LOGGER = System.getLogger(SafeStreamObserver.class.getName());
// ----- data members ---------------------------------------------------
/**
* The actual StreamObserver.
*/
private final StreamObserver delegate;
/**
* Indicates a terminal state.
*/
private boolean done;
}