com.twitter.common.net.http.handlers.ContentionPrinter.java Source code

Introduction

Here is the source code for com.twitter.common.net.http.handlers.ContentionPrinter.java

Source

// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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.twitter.common.net.http.handlers;

import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.primitives.Longs;

import javax.servlet.http.HttpServletRequest;
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * HTTP request handler that prints information about blocked threads.
 *
 * @author William Farner
 */
public class ContentionPrinter extends TextResponseHandler {
    public ContentionPrinter() {
        ManagementFactory.getThreadMXBean().setThreadContentionMonitoringEnabled(true);
    }

    @Override
    public Iterable<String> getLines(HttpServletRequest request) {
        List<String> lines = Lists.newLinkedList();
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();

        Map<Long, StackTraceElement[]> threadStacks = Maps.newHashMap();
        for (Map.Entry<Thread, StackTraceElement[]> entry : Thread.getAllStackTraces().entrySet()) {
            threadStacks.put(entry.getKey().getId(), entry.getValue());
        }

        Set<Long> lockOwners = Sets.newHashSet();

        lines.add("Locked threads:");
        for (ThreadInfo t : bean.getThreadInfo(bean.getAllThreadIds())) {
            switch (t.getThreadState()) {
            case BLOCKED:
            case WAITING:
            case TIMED_WAITING:
                lines.addAll(getThreadInfo(t, threadStacks.get(t.getThreadId())));
                if (t.getLockOwnerId() != -1)
                    lockOwners.add(t.getLockOwnerId());
                break;
            }
        }

        if (lockOwners.size() > 0) {
            lines.add("\nLock Owners");
            for (ThreadInfo t : bean.getThreadInfo(Longs.toArray(lockOwners))) {
                lines.addAll(getThreadInfo(t, threadStacks.get(t.getThreadId())));
            }
        }

        return lines;
    }

    private static List<String> getThreadInfo(ThreadInfo t, StackTraceElement[] stack) {
        List<String> lines = Lists.newLinkedList();

        lines.add(String.format("'%s' Id=%d %s", t.getThreadName(), t.getThreadId(), t.getThreadState()));
        lines.add("Waiting for lock: " + t.getLockName());
        lines.add("Lock is currently held by thread: " + t.getLockOwnerName());
        lines.add("Wait time: " + t.getBlockedTime() + " ms.");
        for (StackTraceElement s : stack) {
            lines.add(String.format("    " + s.toString()));
        }
        lines.add("\n");

        return lines;
    }
}