一、功能图

1.Put CompactionRequest to the compaction queue

?

2.Get CompactionRequest from the compaction queue

?

二、功能详解

1.Put CompactionRequest to the compaction queue

?1.1.HRegionServer

1.run()

1.1.preRegistrationInitialization()

Do pre-registration initializations; zookeeper, lease threads, etc.

1.1.1.initializeThreads()

    // Compaction thread
    this.compactSplitThread = new CompactSplitThread(this);

    // Background thread to check for compactions; needed if region
    // has not gotten updates in a while. Make it run at a lesser frequency.
    int multiplier = this.conf.getInt(HConstants.THREAD_WAKE_FREQUENCY +
      ".multiplier", 1000);
    this.compactionChecker = new CompactionChecker(this,
      this.threadWakeFrequency * multiplier, this);

hbase.server.thread.wakefrequency.multiplier = 1000

hbase.server.thread.wakefrequency = 10 * 1000

?

1.2.CompactionChecker

Inner class that runs on a long period checking?if regions need compaction.

1.CompactionChecker()

      sleepTime = 10000s
      LOG.info("Runs every " + StringUtils.formatTime(sleepTime));

hbase.regionserver.compactionChecker.majorCompactPriority = Integer.MAX_VALUE

2.chore()

CompactSplitThread.requestCompaction()

?

1.3.CompactSplitThread

1.requestCompaction()

1.1.

    CompactionRequest cr = s.requestCompaction(priority, request);

      ThreadPoolExecutor pool = s.throttleCompaction(cr.getSize())
          ? largeCompactions : smallCompactions;
      pool.execute(cr);
      if (LOG.isDebugEnabled()) {
        String type = (pool == smallCompactions) ? "Small " : "Large ";
        LOG.debug(type + "Compaction requested: " + cr
            + (why != null && !why.isEmpty() ? "; Because: " + why : "")
            + "; " + this);
      }

1.2.Store.requestCompaction()

1.3.Store.throttleCompaction()

?

1.4.Store

1.requestCompaction()

1.1.

        // candidates = all storefiles not already in compaction queue
        CompactSelection filesToCompact;
          filesToCompact = compactSelection(candidates, priority);

1.2.compactSelection()

Algorithm to choose which files to compact

参考资料：

? ? ? ?compaction配置参数

? ? ? ?Hbase选择Store file做compaction的算法

        // major compaction if all StoreFiles are included
        boolean isMajor = (filesToCompact.getFilesToCompact().size() == this.storefiles.size());
        if (isMajor) {
          // since we're enqueuing a major, update the compaction wait interval
          this.forceMajor = false;
        }

1.3.isMajor

2.throttleCompaction()

  boolean throttleCompaction(long compactionSize) {
    long throttlePoint = conf.getLong(
        "hbase.regionserver.thread.compaction.throttle",
        2 * this.minFilesToCompact * this.region.memstoreFlushSize);
    return compactionSize > throttlePoint;
  }

2.Get CompactionRequest from the compaction queue

2.1.CompactionRequest

1.run()

1.1.

        long start = EnvironmentEdgeManager.currentTimeMillis();
        boolean completed = r.compact(this);
        long now =