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From "Thangamani, Arun" <Arun.Thangam...@cdk.com>
Subject Re: Write path blocked by MetaDataEndpoint acquiring region lock
Date Wed, 17 Feb 2016 04:38:29 GMT
Hey Nick,

Looks like you are failing to find your table in meta data cache, if you don’t find it in
the meta data cache, we end up rebuilding the meta data from both the SYSTEM.CATALOG and SYSTEM.STATS
table
The rebuilding process from the meta data table is a scan on the both the tables. So we will
end up going to zookeeper and to find the region and execute the scan on the region, it is
a expensive operation, that explains the calls to a specific region and the zookeeper

Similar thing happens in PHOENIX-2607, but that is specifiically related to timestamps, if
the client timestamp is less than or equal to the stats timestamp of the table, I will end
up doing the above process rebuilding process repeatedly for every batch of insert from PhoenixMapReduceUtil.
I don’t believe you have an timestamp issue, but I have the repeated lookup and scans are
happening from what you have described

James has suggested a workaround for the meta data cache value refresh using UPDATE_CACHE_FREQUENCY,
and it will probably help  (we are trying it out for timestamp issue)

Hope this helps.

Thanks
Arun

Please look at the following lines in MetadataCacheImpl
private PTable doGetTable(byte[] key, long clientTimeStamp, RowLock rowLock) throws IOException,
SQLException {

    ImmutableBytesPtr cacheKey = new ImmutableBytesPtr(key);
    Cache<ImmutableBytesPtr, PMetaDataEntity> metaDataCache =
            GlobalCache.getInstance(this.env).getMetaDataCache();
    PTable table = (PTable)metaDataCache.getIfPresent(cacheKey);
    // We only cache the latest, so we'll end up building the table with every call if the
    // client connection has specified an SCN.
    // TODO: If we indicate to the client that we're returning an older version, but there's
a
    // newer version available, the client
    // can safely not call this, since we only allow modifications to the latest.
    if (table != null && table.getTimeStamp() < clientTimeStamp) {
        // Table on client is up-to-date with table on server, so just return
        if (isTableDeleted(table)) {
            return null;
        }
        return table;
    }
    // Ask Lars about the expense of this call - if we don't take the lock, we still won't
get
    // partial results
    // get the co-processor environment
    // TODO: check that key is within region.getStartKey() and region.getEndKey()
    // and return special code to force client to lookup region from meta.
    Region region = env.getRegion();
    /*
     * Lock directly on key, though it may be an index table. This will just prevent a table
     * from getting rebuilt too often.
     */
    final boolean wasLocked = (rowLock != null);
    if (!wasLocked) {
        rowLock = region.getRowLock(key, true);
        if (rowLock == null) {
            throw new IOException("Failed to acquire lock on " + Bytes.toStringBinary(key));
        }
    }
    try {
        // Try cache again in case we were waiting on a lock
        table = (PTable)metaDataCache.getIfPresent(cacheKey);
        // We only cache the latest, so we'll end up building the table with every call if
the
        // client connection has specified an SCN.
        // TODO: If we indicate to the client that we're returning an older version, but there's
        // a newer version available, the client
        // can safely not call this, since we only allow modifications to the latest.
        if (table != null && table.getTimeStamp() < clientTimeStamp) {
            // Table on client is up-to-date with table on server, so just return
            if (isTableDeleted(table)) {
                return null;
            }
            return table;
        }
        // Query for the latest table first, since it's not cached
        table = buildTable(key, cacheKey, region, HConstants.LATEST_TIMESTAMP);
        if (table != null && table.getTimeStamp() < clientTimeStamp) {
            return table;
        }
        // Otherwise, query for an older version of the table - it won't be cached
        return buildTable(key, cacheKey, region, clientTimeStamp);
    } finally {
        if (!wasLocked) rowLock.release();
    }
}





From: Nick Dimiduk <ndimiduk@gmail.com<mailto:ndimiduk@gmail.com>>
Reply-To: "user@phoenix.apache.org<mailto:user@phoenix.apache.org>" <user@phoenix.apache.org<mailto:user@phoenix.apache.org>>
Date: Tuesday, February 16, 2016 at 5:58 PM
To: "user@phoenix.apache.org<mailto:user@phoenix.apache.org>" <user@phoenix.apache.org<mailto:user@phoenix.apache.org>>
Cc: James Taylor <jamestaylor@apache.org<mailto:jamestaylor@apache.org>>, Lars
Hofhansl <larsh@apache.org<mailto:larsh@apache.org>>
Subject: Write path blocked by MetaDataEndpoint acquiring region lock

Hello,

I have a high throughput ingest pipeline that's seised up. My ingest application ultimately
crashes, contains the following stack trace [0].

Independently, I noticed that the RPC call time of one of the machines was significantly higher
than others (95pct at multiple seconds vs 10's of ms). I grabbed the RS log and a couple jstacks
from the process. In the logs I see handler threads creating ZK connections excessively (~50
INFO lines per second). The jstacks show handler threads parked while taking region row locks,
calling HRegion.getRowLockInternal() via MetaDataEndpointImpl.doGetTable() [1]. The one handler
thread I see that's in the same MetaDataEndpointImpl area but not under lock appears to be
making an RPC to read the statistics table [2].

I believe these two occurrences are related.

My working theory is that the metaDataCache object is performing poorly for some reason. This
results in excessive meta data lookups, some of which appear to require making an RPC call
while under lock.

What can I do to relive pressure on this rowlock? Looking at the code around the lock, this
looks like it's populating to a connection-level cache of schema metadata. The host with the
high RPC call time is hosting the SYSTEM.CATALOG table region. I see some configuration settings
that may be related (ie, phoenix.coprocessor.maxMetaDataCacheSize), but I see no way to get
debug information about cache size or evictions from this Guava cache instance.

I'll be digging into this further, but I appreciate any pointers you may have.

BTW, this is Phoenix 4.6.0 + HBase 1.1.2.

Thanks a lot,
-n

[0]: client-side stack
Caused by: org.apache.phoenix.exception.PhoenixIOException: Interrupted calling coprocessor
service org.apache.phoenix.coprocessor.generated.MetaDataProtos$MetaDataService for row \x00<schema>\x00<user_table>
        at org.apache.phoenix.util.ServerUtil.parseServerException(ServerUtil.java:108)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.metaDataCoprocessorExec(ConnectionQueryServicesImpl.java:1053)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.metaDataCoprocessorExec(ConnectionQueryServicesImpl.java:1016)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.getTable(ConnectionQueryServicesImpl.java:1289)
        at org.apache.phoenix.schema.MetaDataClient.updateCache(MetaDataClient.java:446)
        at org.apache.phoenix.schema.MetaDataClient.updateCache(MetaDataClient.java:389)
        at org.apache.phoenix.schema.MetaDataClient.updateCache(MetaDataClient.java:385)
        at org.apache.phoenix.execute.MutationState.validate(MutationState.java:369)
        at org.apache.phoenix.execute.MutationState.commit(MutationState.java:417)
        at org.apache.phoenix.jdbc.PhoenixConnection$3.call(PhoenixConnection.java:482)
        at org.apache.phoenix.jdbc.PhoenixConnection$3.call(PhoenixConnection.java:479)
        at org.apache.phoenix.call.CallRunner.run(CallRunner.java:53)
        at org.apache.phoenix.jdbc.PhoenixConnection.commit(PhoenixConnection.java:479)
        at org.apache.phoenix.mapreduce.PhoenixRecordWriter.write(PhoenixRecordWriter.java:84)

[1] rs handlers blocked stack
"B.defaultRpcServer.handler=48,queue=3,port=16020" #91 daemon prio=5 os_prio=0 tid=0x00007ff4ce458000
nid=0xca0a waiting on condition [0x00007ff47a607000]
   java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for  <0x0000000708ef59c0> (a java.util.concurrent.CountDownLatch$Sync)
at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedNanos(AbstractQueuedSynchronizer.java:1037)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(AbstractQueuedSynchronizer.java:1328)
at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:277)
at org.apache.hadoop.hbase.regionserver.HRegion.getRowLockInternal(HRegion.java:5047)
at org.apache.hadoop.hbase.regionserver.HRegion.getRowLock(HRegion.java:5013)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.doGetTable(MetaDataEndpointImpl.java:2397)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.doGetTable(MetaDataEndpointImpl.java:2365)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.getTable(MetaDataEndpointImpl.java:440)
at org.apache.phoenix.coprocessor.generated.MetaDataProtos$MetaDataService.callMethod(MetaDataProtos.java:11609)
at org.apache.hadoop.hbase.regionserver.HRegion.execService(HRegion.java:7435)
at org.apache.hadoop.hbase.regionserver.RSRpcServices.execServiceOnRegion(RSRpcServices.java:1875)
at org.apache.hadoop.hbase.regionserver.RSRpcServices.execService(RSRpcServices.java:1857)
at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:32209)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2114)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:101)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
at java.lang.Thread.run(Thread.java:745)

[2]: rs handler stats rpc stack
"B.defaultRpcServer.handler=19,queue=4,port=16020" #62 daemon prio=5 os_prio=0 tid=0x00007ff4ce420000
nid=0xc9ea in Object.wait() [0x00007ff47c323000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:460)
at java.util.concurrent.TimeUnit.timedWait(TimeUnit.java:348)
at org.apache.hadoop.hbase.client.ResultBoundedCompletionService.poll(ResultBoundedCompletionService.java:155)
- locked <0x00000007a3f5e030> (a [Lorg.apache.hadoop.hbase.client.ResultBoundedCompletionService$QueueingFuture;)
at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas.call(ScannerCallableWithReplicas.java:168)
at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas.call(ScannerCallableWithReplicas.java:59)
at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithoutRetries(RpcRetryingCaller.java:200)
at org.apache.hadoop.hbase.client.ClientScanner.call(ClientScanner.java:320)
at org.apache.hadoop.hbase.client.ClientScanner.loadCache(ClientScanner.java:403)
at org.apache.hadoop.hbase.client.ClientScanner.next(ClientScanner.java:364)
at org.apache.phoenix.schema.stats.StatisticsUtil.readStatistics(StatisticsUtil.java:99)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.getTable(MetaDataEndpointImpl.java:836)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.buildTable(MetaDataEndpointImpl.java:472)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.doGetTable(MetaDataEndpointImpl.java:2418)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.doGetTable(MetaDataEndpointImpl.java:2365)
at org.apache.phoenix.coprocessor.MetaDataEndpointImpl.getTable(MetaDataEndpointImpl.java:440)
at org.apache.phoenix.coprocessor.generated.MetaDataProtos$MetaDataService.callMethod(MetaDataProtos.java:11609)
at org.apache.hadoop.hbase.regionserver.HRegion.execService(HRegion.java:7435)
at org.apache.hadoop.hbase.regionserver.RSRpcServices.execServiceOnRegion(RSRpcServices.java:1875)
at org.apache.hadoop.hbase.regionserver.RSRpcServices.execService(RSRpcServices.java:1857)
at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:32209)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2114)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:101)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
at java.lang.Thread.run(Thread.java:745)

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