[HBASE-18451] PeriodicMemstoreFlusher should inspect the queue before adding a delayed flush request

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0-alpha-1
• Fix Version/s: 3.0.0-alpha-1, 1.3.3, 2.2.0, 1.4.8, 2.1.1
• Component/s: regionserver
• Hadoop Flags: Reviewed
• Assignee: Xu Cang
• Reporter: Jean-Marc Spaggiari
• Created: 25/Jul/17 23:25
• Updated: 01/Feb/19 19:55
• Resolved: 28/Sep/18 20:29

Description

If you run a big job every 4 hours, impacting many tables (they have 150 regions per server), ad the end all the regions might have some data to be flushed, and we want, after one hour, trigger a periodic flush. That's totally fine.

Now, to avoid a flush storm, when we detect a region to be flushed, we add a "randomDelay" to the delayed flush, that way we spread them away.

RANGE_OF_DELAY is 5 minutes. So we spread the flush over the next 5 minutes, which is very good.

However, because we don't check if there is already a request in the queue, 10 seconds after, we create a new request, with a new randomDelay.

If you generate a randomDelay every 10 seconds, at some point, you will end up having a small one, and the flush will be triggered almost immediatly.

As a result, instead of spreading all the flush within the next 5 minutes, you end-up getting them all way more quickly. Like within the first minute. Which not only feed the queue to to many flush requests, but also defeats the purpose of the randomDelay.

    @Override
    protected void chore() {
      final StringBuffer whyFlush = new StringBuffer();
      for (Region r : this.server.onlineRegions.values()) {
        if (r == null) continue;
        if (((HRegion)r).shouldFlush(whyFlush)) {
          FlushRequester requester = server.getFlushRequester();
          if (requester != null) {
            long randomDelay = RandomUtils.nextInt(RANGE_OF_DELAY) + MIN_DELAY_TIME;
            LOG.info(getName() + " requesting flush of " +
              r.getRegionInfo().getRegionNameAsString() + " because " +
              whyFlush.toString() +
              " after random delay " + randomDelay + "ms");
            //Throttle the flushes by putting a delay. If we don't throttle, and there
            //is a balanced write-load on the regions in a table, we might end up
            //overwhelming the filesystem with too many flushes at once.
            requester.requestDelayedFlush(r, randomDelay, false);
          }
        }
      }
    }

2017-07-24 18:44:33,338 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 270785ms
2017-07-24 18:44:43,328 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 200143ms
2017-07-24 18:44:53,954 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 191082ms
2017-07-24 18:45:03,528 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 92532ms
2017-07-24 18:45:14,201 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 238780ms
2017-07-24 18:45:24,195 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 35390ms
2017-07-24 18:45:33,362 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 283034ms
2017-07-24 18:45:43,933 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 84328ms
2017-07-24 18:45:53,866 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 72291ms
2017-07-24 18:46:03,329 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 62658ms
2017-07-24 18:46:14,084 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 87491ms
2017-07-24 18:46:23,538 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 290170ms
2017-07-24 18:46:33,353 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 228541ms
2017-07-24 18:46:43,359 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 211814ms
2017-07-24 18:46:54,150 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 155167ms
2017-07-24 18:47:03,546 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 115318ms
2017-07-24 18:47:13,350 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 216662ms
2017-07-24 18:47:23,329 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 96018ms
2017-07-24 18:47:33,891 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 144751ms
2017-07-24 18:47:43,329 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 152461ms
2017-07-24 18:47:53,832 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 97352ms
2017-07-24 18:48:03,348 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 263910ms
2017-07-24 18:48:13,353 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 151793ms
2017-07-24 18:48:23,340 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 61926ms
2017-07-24 18:48:33,724 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 188901ms
2017-07-24 18:48:44,038 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 233148ms
2017-07-24 18:48:53,624 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 6206ms
2017-07-24 18:49:03,378 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: hbasetest2.domainname.com,60020,1500916375517-MemstoreFlusherChore requesting flush of testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. because f has an old edit so flush to free WALs after random delay 240946ms
2017-07-24 18:49:04,125 INFO org.apache.hadoop.hbase.regionserver.HRegion: Flushing 1/1 column families, memstore=160 B
2017-07-24 18:49:04,182 INFO org.apache.hadoop.hbase.regionserver.DefaultStoreFlusher: Flushed, sequenceid=6, memsize=160, hasBloomFilter=true, into tmp file hdfs://hbasetest1.domainname.com:8020/hbase/data/default/testflush/578c27d2eb7ef0ad437bf2ff38c053ae/.tmp/3609340d58ae4ca190e62c3b0fe415f4
2017-07-24 18:49:04,208 INFO org.apache.hadoop.hbase.regionserver.HStore: Added hdfs://hbasetest1.domainname.com:8020/hbase/data/default/testflush/578c27d2eb7ef0ad437bf2ff38c053ae/f/3609340d58ae4ca190e62c3b0fe415f4, entries=1, sequenceid=6, filesize=1015
2017-07-24 18:49:04,212 INFO org.apache.hadoop.hbase.regionserver.HRegion: Finished memstore flush of ~160 B/160, currentsize=0 B/0 for region testflush,,1500932649126.578c27d2eb7ef0ad437bf2ff38c053ae. in 87ms, sequenceid=6, compaction requested=false