hbase 定时进行compact CompactionChecker类

 CompactionChecker类 定时判断是否进行compact，

  定时判断间隔hbase.server.compactchecker.interval.multiplier默认1000

@Override
    protected void chore() {
      for (HRegion r : this.instance.onlineRegions.values()) {
        if (r == null)
          continue;
        for (Store s : r.getStores().values()) {
          try {
            long multiplier = s.getCompactionCheckMultiplier();
            assert multiplier > 0;
            if (iteration % multiplier != 0) continue;
            if (s.needsCompaction()) {//compact判断
              // Queue a compaction. Will recognize if major is needed.
              this.instance.compactSplitThread.requestSystemCompaction(r, s, getName()
                  + " requests compaction");
            } else if (s.isMajorCompaction()) {//major判断
              if (majorCompactPriority == DEFAULT_PRIORITY
                  || majorCompactPriority > r.getCompactPriority()) {
                this.instance.compactSplitThread.requestCompaction(r, s, getName()
                    + " requests major compaction; use default priority", null);
              } else {
                this.instance.compactSplitThread.requestCompaction(r, s, getName()
                    + " requests major compaction; use configured priority",
                  this.majorCompactPriority, null);
              }
            }
          } catch (IOException e) {
            LOG.warn("Failed major compaction check on " + r, e);
          }
        }
      }
      iteration = (iteration == Long.MAX_VALUE) ? 0 : (iteration + 1);
    }
  }

  循环所有Store，

  定时判断循环次数 % 配置值 = 0 则不做操作

  否则进行判断needsCompaction，会调用策略类RatioBasedCompactionPolicy

       当store下的hfile个数>hbase.hstore.compaction.min，则进行compact

public boolean needsCompaction(final Collection<StoreFile> storeFiles,
      final List<StoreFile> filesCompacting) {
    int numCandidates = storeFiles.size() - filesCompacting.size();
    return numCandidates >= comConf.getMinFilesToCompact();
  }

   若不需要compact，还会查看是否需要major compact，

  HStore检查是否进行compact时候，现在now - 上次major时间(加一个波动，防止restart集中marjor compact)大于hbase.hregion.majorcompaction下次时间间隔  

  满足上边条件，并且hfile个数大于1

  满足上边条件，并且只有一个hfile（最早的ts>ttl）整个文件过期 => 进行marjor compact

public boolean isMajorCompaction(final Collection<StoreFile> filesToCompact)
      throws IOException {
    boolean result = false;
    long mcTime = getNextMajorCompactTime(filesToCompact);
    if (filesToCompact == null || filesToCompact.isEmpty() || mcTime == 0) {
      return result;
    }
    // TODO: Use better method for determining stamp of last major (HBASE-2990)
    long lowTimestamp = StoreUtils.getLowestTimestamp(filesToCompact);
    long now = System.currentTimeMillis();
    if (lowTimestamp > 0l && lowTimestamp < (now - mcTime)) {
      //现在now - 上次major时间(加一个波动，防止restart集中marjor compact)大于hbase.hregion.majorcompaction下次时间间隔 
      // Major compaction time has elapsed.
      long cfTtl = this.storeConfigInfo.getStoreFileTtl();//
      if (filesToCompact.size() == 1) {
        // Single file
        StoreFile sf = filesToCompact.iterator().next();
        Long minTimestamp = sf.getMinimumTimestamp();
        long oldest = (minTimestamp == null)
            ? Long.MIN_VALUE
            : now - minTimestamp.longValue();
        if (sf.isMajorCompaction() &&
            (cfTtl == HConstants.FOREVER || oldest < cfTtl)) {
          if (LOG.isDebugEnabled()) {
            LOG.debug("Skipping major compaction of " + this +
                " because one (major) compacted file only and oldestTime " +
                oldest + "ms is < ttl=" + cfTtl);
          }
        } else if (cfTtl != HConstants.FOREVER && oldest > cfTtl) {
        	//只有一个hfile（最早的ts>ttl）整个文件过期 => 进行marjor compact
          LOG.debug("Major compaction triggered on store " + this +
            ", because keyvalues outdated; time since last major compaction " +
            (now - lowTimestamp) + "ms");
          result = true;
        }
      } else {//hfile个数大于1个
        if (LOG.isDebugEnabled()) {
          LOG.debug("Major compaction triggered on store " + this +
              "; time since last major compaction " + (now - lowTimestamp) + "ms");
        }
        result = true;
      }
    }
    return result;
  }