Make HBase client work better under concurrent clients
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Key: HBASE-3382
URL: https://issues.apache.org/jira/browse/HBASE-3382
Project: HBase
Issue Type: Bug
Reporter: ryan rawson
The HBase client uses 1 socket per regionserver for communication. This is
good for socket control but potentially bad for latency. How bad? I did a
simple YCSB test that had this config:
readproportion=0
updateproportion=0
scanproportion=1
insertproportion=0
fieldlength=10
fieldcount=100
requestdistribution=zipfian
scanlength=300
scanlengthdistribution=zipfian
I ran this with 1 and 10 threads. The summary is as so:
1 thread:
[SCAN] Operations 1000
[SCAN] AverageLatency(ms) 35.871
10 threads:
[SCAN] Operations 1000
[SCAN] AverageLatency(ms) 228.576
We are taking a 6.5x latency hit in our client. But why?
First step was to move the deserialization out of the Connection thread, this
seemed like it could have a big win, an analog change on the server side got a
20% performance improvement (already commited as HBASE-2941). I did this and
got about a 20% improvement again, with that 228ms number going to about 190
ms.
So I then wrote a high performance nanosecond resolution tracing utility.
Clients can flag an API call, and we get tracing and numbers through the client
pipeline. What I found is that a lot of time is being spent in receiving the
response from the network. The code block is like so:
NanoProfiler.split(id, "receiveResponse");
if (LOG.isDebugEnabled())
LOG.debug(getName() + " got value #" + id);
Call call = calls.get(id);
size -= 4; // 4 byte off for id because we already read it.
ByteBuffer buf = ByteBuffer.allocate(size);
IOUtils.readFully(in, buf.array(), buf.arrayOffset(), size);
buf.limit(size);
buf.rewind();
NanoProfiler.split(id, "setResponse", "Data size: " + size);
I came up with some numbers:
11726 (receiveResponse) split: 64991689 overall: 133562895 Data size: 4288937
12163 (receiveResponse) split: 32743954 overall: 103787420 Data size: 1606273
12561 (receiveResponse) split: 3517940 overall: 83346740 Data size: 4
12136 (receiveResponse) split: 64448701 overall: 203872573 Data size: 3570569
The first number is the internal counter for keeping requests unique from
HTable on down. The numbers are in ns, the data size is in bytes.
Doing some simple calculations, we see for the first line we were reading at
about 31 MB/sec. The second one is even worse. Other calls are like:
26 (receiveResponse) split: 7985400 overall: 21546226 Data size: 850429
which is 107 MB/sec which is pretty close to the maximum of gige. In my set
up, the ycsb client ran on the master node and HAD to use network to talk to
regionservers.
Even at full line rate, we could still see unacceptable hold ups of unrelated
calls that just happen to need to talk to the same regionserver.
This issue is about these findings, what to do, how to improve.
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