/*
 * 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.rpc;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nullable;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * This utility exists to bridge between the visibility of the
 * {@code currentMainThread} field in the {@link RpcEndpoint}.
 * 
 * The {@code currentMainThread} can be hidden from {@code RpcEndpoint} implementations
 * and only be accessed via this utility from other packages.
 */
public final class MainThreadValidatorUtil {

	private static final Logger log = LoggerFactory.getLogger(MainThreadValidatorUtil.class);

	private final RpcEndpoint endpoint;

	public MainThreadValidatorUtil(RpcEndpoint endpoint) {
		this.endpoint = checkNotNull(endpoint);
	}

	public void enterMainThread() {
		assert(endpoint.currentMainThread.compareAndSet(null, Thread.currentThread())) : 
				"The RpcEndpoint has concurrent access from " + endpoint.currentMainThread.get();
	}
	
	public void exitMainThread() {
		assert(endpoint.currentMainThread.compareAndSet(Thread.currentThread(), null)) :
				"The RpcEndpoint has concurrent access from " + endpoint.currentMainThread.get();
	}

	/**
	 * Returns true iff the current thread is equals to the provided expected thread and logs violations.
	 *
	 * @param expected the expected main thread.
	 * @return true iff the current thread is equals to the provided expected thread.
	 */
	public static boolean isRunningInExpectedThread(@Nullable Thread expected) {
		Thread actual = Thread.currentThread();
		if (expected != actual) {

			String violationMsg = "Violation of main thread constraint detected: expected <"
				+ expected + "> but running in <" + actual + ">.";

			log.warn(violationMsg, new Exception(violationMsg));

			return false;
		}

		return true;
	}
}

/*
 * 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.rpc;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nullable;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * This utility exists to bridge between the visibility of the
 * {@code currentMainThread} field in the {@link RpcEndpoint}.
 * 
 * The {@code currentMainThread} can be hidden from {@code RpcEndpoint} implementations
 * and only be accessed via this utility from other packages.
 */
public final class MainThreadValidatorUtil {

	private static final Logger LOG = LoggerFactory.getLogger(MainThreadValidatorUtil.class);

	private final RpcEndpoint endpoint;

	public MainThreadValidatorUtil(RpcEndpoint endpoint) {
		this.endpoint = checkNotNull(endpoint);
	}

	public void enterMainThread() {
		assert(endpoint.currentMainThread.compareAndSet(null, Thread.currentThread())) : 
				"The RpcEndpoint has concurrent access from " + endpoint.currentMainThread.get();
	}
	
	public void exitMainThread() {
		assert(endpoint.currentMainThread.compareAndSet(Thread.currentThread(), null)) :
				"The RpcEndpoint has concurrent access from " + endpoint.currentMainThread.get();
	}

	/**
	 * Returns true iff the current thread is equals to the provided expected thread and logs violations.
	 *
	 * @param expected the expected main thread.
	 * @return true iff the current thread is equals to the provided expected thread.
	 */
	public static boolean isRunningInExpectedThread(@Nullable Thread expected) {
		Thread actual = Thread.currentThread();
		if (expected != actual) {

			String violationMsg = "Violation of main thread constraint detected: expected <"
				+ expected + "> but running in <" + actual + ">.";

			LOG.warn(violationMsg, new Exception(violationMsg));

			return false;
		}

		return true;
	}
}

Change the name of log into LOG