[HBASE-19358] Improve the stability of splitting log when do fail over

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.98.24
• Fix Version/s: 1.4.1, 2.0.0-beta-1, 2.0.0
• Component/s: MTTR
• Hadoop Flags: Reviewed

Release Note

After HBASE-19358 we introduced a new property hbase.split.writer.creation.bounded to limit the opening writers for each WALSplitter. If set to true, we won't open any writer for recovered.edits until the entries accumulated in memory reaching hbase.regionserver.hlog.splitlog.buffersize (which defaults at 128M) and will write and close the file in one go instead of keeping the writer open. It's false by default and we recommend to set it to true if your cluster has a high region load (like more than 300 regions per RS), especially when you observed obvious NN/HDFS slow down during hbase (single RS or cluster) failover.

• Assignee: Jingyun Tian
• Reporter: Jingyun Tian
• Created: 28/Nov/17 06:08
• Updated: 01/Feb/19 20:19
• Resolved: 08/Jan/18 02:59

Description

The way we splitting log now is like the following figure:

The problem is the OutputSink will write the recovered edits during splitting log, which means it will create one WriterAndPath for each region and retain it until the end. If the cluster is small and the number of regions per rs is large, it will create too many HDFS streams at the same time. Then it is prone to failure since each datanode need to handle too many streams.

Thus I come up with a new way to split log.

We try to cache all the recovered edits, but if it exceeds the MaxHeapUsage, we will pick the largest EntryBuffer and write it to a file (close the writer after finish). Then after we read all entries into memory, we will start a writeAndCloseThreadPool, it starts a certain number of threads to write all buffers to files. Thus it will not create HDFS streams more than hbase.regionserver.hlog.splitlog.writer.threads we set.
The biggest benefit is we can control the number of streams we create during splitting log,
it will not exceeds hbase.regionserver.wal.max.splitters * hbase.regionserver.hlog.splitlog.writer.threads, but before it is hbase.regionserver.wal.max.splitters * the number of region the hlog contains.

Issue Links

• duplicates: HBASE-21651 when splitting hlog，occurred exception
• duplicates: HBASE-18971 Limit the concurrent opened wal writers when splitting

Sub-Tasks

• Enable hbase.split.writer.creation.bounded by default: Resolved