com.datastax.oss.driver.internal.core.util.concurrent.BlockingOperation 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 com.datastax.oss.driver.internal.core.util.concurrent;
import edu.umd.cs.findbugs.annotations.NonNull;
import io.netty.util.concurrent.FastThreadLocalThread;
import java.util.concurrent.ThreadFactory;
/**
* Safeguards against bad usage patterns in client code that could introduce deadlocks in the
* driver.
*
* The driver internals are fully asynchronous, nothing should ever block. On the other hand, our
* API exposes synchronous wrappers, that call async methods and wait on the result (as a
* convenience for clients that don't want to do async). These methods should never be called on a
* driver thread, because this can lead to deadlocks. This can happen from client code if it uses
* callbacks.
*/
public class BlockingOperation {
/**
* This method is invoked from each synchronous driver method, and checks that we are not on a
* driver thread.
*
*
For this to work, all driver threads must be created by {@link SafeThreadFactory} (which is
* the case by default).
*
* @throws IllegalStateException if a driver thread is executing this.
*/
public static void checkNotDriverThread() {
if (Thread.currentThread() instanceof InternalThread) {
throw new IllegalStateException(
"Detected a synchronous API call on a driver thread, "
+ "failing because this can cause deadlocks.");
}
}
/**
* Marks threads as driver threads, so that they will be detected by {@link
* #checkNotDriverThread()}
*/
public static class SafeThreadFactory implements ThreadFactory {
@Override
public Thread newThread(@NonNull Runnable r) {
return new InternalThread(r);
}
}
static class InternalThread extends FastThreadLocalThread {
private InternalThread(Runnable runnable) {
super(runnable);
}
}
}