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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
代码语言：javascript复制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
代码语言：javascript复制 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
