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本文主要研究一下elasticsearch的DeadlockAnalyzer
DeadlockAnalyzer
elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/monitor/jvm/DeadlockAnalyzer.java
public class DeadlockAnalyzer { private static final Deadlock NULL_RESULT[] = new Deadlock[0]; private final ThreadMXBean threadBean = ManagementFactory.getThreadMXBean(); private static DeadlockAnalyzer INSTANCE = new DeadlockAnalyzer(); public static DeadlockAnalyzer deadlockAnalyzer() { return INSTANCE; } private DeadlockAnalyzer() { } public Deadlock[] findDeadlocks() { long deadlockedThreads[] = threadBean.findMonitorDeadlockedThreads(); if (deadlockedThreads == null || deadlockedThreads.length == 0) { return NULL_RESULT; } Map<Long, ThreadInfo> threadInfoMap = createThreadInfoMap(deadlockedThreads); Set<LinkedHashSet<ThreadInfo>> cycles = calculateCycles(threadInfoMap); Set<LinkedHashSet<ThreadInfo>> chains = calculateCycleDeadlockChains(threadInfoMap, cycles); cycles.addAll(chains); return createDeadlockDescriptions(cycles); } private Deadlock[] createDeadlockDescriptions(Set<LinkedHashSet<ThreadInfo>> cycles) { Deadlock result[] = new Deadlock[cycles.size()]; int count = 0; for (LinkedHashSet<ThreadInfo> cycle : cycles) { ThreadInfo asArray[] = cycle.toArray(new ThreadInfo[cycle.size()]); Deadlock d = new Deadlock(asArray); result[count++] = d; } return result; } private Set<LinkedHashSet<ThreadInfo>> calculateCycles(Map<Long, ThreadInfo> threadInfoMap) { Set<LinkedHashSet<ThreadInfo>> cycles = new HashSet<>(); for (Map.Entry<Long, ThreadInfo> entry : threadInfoMap.entrySet()) { LinkedHashSet<ThreadInfo> cycle = new LinkedHashSet<>(); for (ThreadInfo t = entry.getValue(); !cycle.contains(t); t = threadInfoMap.get(Long.valueOf(t.getLockOwnerId()))) { cycle.add(t); } if (!cycles.contains(cycle)) { cycles.add(cycle); } } return cycles; } private Set<LinkedHashSet<ThreadInfo>> calculateCycleDeadlockChains(Map<Long, ThreadInfo> threadInfoMap, Set<LinkedHashSet<ThreadInfo>> cycles) { ThreadInfo allThreads[] = threadBean.getThreadInfo(threadBean.getAllThreadIds()); Set<LinkedHashSet<ThreadInfo>> deadlockChain = new HashSet<>(); Set<Long> knownDeadlockedThreads = threadInfoMap.keySet(); for (ThreadInfo threadInfo : allThreads) { Thread.State state = threadInfo.getThreadState(); if (state == Thread.State.BLOCKED && !knownDeadlockedThreads.contains(threadInfo.getThreadId())) { for (LinkedHashSet<ThreadInfo> cycle : cycles) { if (cycle.contains(threadInfoMap.get(Long.valueOf(threadInfo.getLockOwnerId())))) { LinkedHashSet<ThreadInfo> chain = new LinkedHashSet<>(); ThreadInfo node = threadInfo; while (!chain.contains(node)) { chain.add(node); node = threadInfoMap.get(Long.valueOf(node.getLockOwnerId())); } deadlockChain.add(chain); } } } } return deadlockChain; } private Map<Long, ThreadInfo> createThreadInfoMap(long threadIds[]) { ThreadInfo threadInfos[] = threadBean.getThreadInfo(threadIds); Map<Long, ThreadInfo> threadInfoMap = new HashMap<>(); for (ThreadInfo threadInfo : threadInfos) { threadInfoMap.put(threadInfo.getThreadId(), threadInfo); } return unmodifiableMap(threadInfoMap); } //......}- DeadlockAnalyzer提供了findDeadlocks方法用于返回死锁线程的信息，该方法通过ThreadMXBean的findMonitorDeadlockedThreads方法获取deadlockedThreads数组，如果该数组为null或空，则返回NULL_RESULT，否则往下计算
- createThreadInfoMap方法根据threadIds从ThreadMXBean获取对应的threadInfo信息，然后组装成threadId与threadInfo的map；calculateCycles方法则是遍历该map，然后根据threadInfo的getLockOwnerId()构建cycles
- calculateCycleDeadlockChains方法则根据threadInfoMap及cycles构建cycleDeadlockChains，添加到cycles中，最后通过createDeadlockDescriptions方法构建Deadlock数组
Deadlock
elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/monitor/jvm/DeadlockAnalyzer.java
public static class Deadlock { private final ThreadInfo members[]; private final String description; private final Set<Long> memberIds; public Deadlock(ThreadInfo[] members) { this.members = members; Set<Long> builder = new HashSet<>(); StringBuilder sb = new StringBuilder(); for (int x = 0; x < members.length; x++) { ThreadInfo ti = members[x]; sb.append(ti.getThreadName()); sb.append(" > "); if (x == members.length - 1) { sb.append(ti.getLockOwnerName()); } builder.add(ti.getThreadId()); } this.description = sb.toString(); this.memberIds = unmodifiableSet(builder); } public ThreadInfo[] members() { return members; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Deadlock deadlock = (Deadlock) o; if (memberIds != null ? !memberIds.equals(deadlock.memberIds) : deadlock.memberIds != null) return false; return true; } @Override public int hashCode() { int result = members != null ? Arrays.hashCode(members) : 0; result = 31 * result + (description != null ? description.hashCode() : 0); result = 31 * result + (memberIds != null ? memberIds.hashCode() : 0); return result; } @Override public String toString() { return description; } }- Deadlock包含了members、description、memberIds三个属性，其构造器会根据members来构建description
小结
- DeadlockAnalyzer提供了findDeadlocks方法用于返回死锁线程的信息，该方法通过ThreadMXBean的findMonitorDeadlockedThreads方法获取deadlockedThreads数组，如果该数组为null或空，则返回NULL_RESULT，否则往下计算
- createThreadInfoMap方法根据threadIds从ThreadMXBean获取对应的threadInfo信息，然后组装成threadId与threadInfo的map；calculateCycles方法则是遍历该map，然后根据threadInfo的getLockOwnerId()构建cycles
- calculateCycleDeadlockChains方法则根据threadInfoMap及cycles构建cycleDeadlockChains，添加到cycles中，最后通过createDeadlockDescriptions方法构建Deadlock数组
doc
- DeadlockAnalyzer