log4j-core/src/main/java/org/apache/logging/log4j/core/async/AbstractAsyncExceptionHandler.java

/*
 * 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.logging.log4j.core.async;

import com.lmax.disruptor.ExceptionHandler;

/**
 * Default disruptor exception handler for errors that occur in the AsyncLogger background thread.
 */
abstract class AbstractAsyncExceptionHandler<T> implements ExceptionHandler<T> {

    @Override
    public void handleEventException(final Throwable throwable, final long sequence, final T event) {
        try {
            // Careful to avoid allocation in case of memory pressure.
            // Sacrifice performance for safety by writing directly
            // rather than using a buffer.
            System.err.print("AsyncLogger error handling event seq=");
            System.err.print(sequence);
            System.err.print(", value='");
            try {
                System.err.print(event);
            } catch (final Throwable t) {
                System.err.print("ERROR calling toString() on ");
                System.err.print(event.getClass().getName());
                System.err.print(": ");
                System.err.print(t.getClass().getName());
                System.err.print(": ");
                System.err.print(t.getMessage());
            }
            System.err.print("': ");
            System.err.print(throwable.getClass().getName());
            System.err.print(": ");
            System.err.println(throwable.getMessage());
            // Attempt to print the full stack trace, which may fail if we're already
            // OOMing We've already provided sufficient information at this point.
            throwable.printStackTrace();
        } catch (final Throwable ignored) {
            // LOG4J2-2333: Not much we can do here without risking an OOM.
            // Throwing an error here may kill the background thread.
        }
    }

    @Override
    public void handleOnStartException(final Throwable throwable) {
        System.err.println("AsyncLogger error starting:");
        throwable.printStackTrace();
    }

    @Override
    public void handleOnShutdownException(final Throwable throwable) {
        System.err.println("AsyncLogger error shutting down:");
        throwable.printStackTrace();
    }
}