Can you tell us the version of HBase you are using ?
Gary did some cleanup in:
r1439723 | garyh | 2013-01-28 16:50:02 -0800 (Mon, 28 Jan 2013) | 1 line
HBASE-7626 Backport client connection cleanup from HBASE-7460
This is the current code in getConnection() in 0.94 branch:
ConnectionId remoteId = new ConnectionId(addr, protocol, ticket,
rpcTimeout);
synchronized (connections) {
connection = connections.get(remoteId);
if (connection == null) {
connection = createConnection(remoteId);
connections.put(remoteId, connection);
}
}
connection.addCall(call);
On Fri, Mar 29, 2013 at 11:41 AM, Jeff Whiting <[email protected]> wrote:
> After noticing a lot of threads, I turned on debugging logging for hbase
> client and saw this many times counting up constantly:
> HBaseClient:531 - IPC Client (687163870) connection to
> /10.1.37.21:60020from jeff: starting, having connections 1364
>
> At that point in my code it was up to 1364 different connections (and
> threads). Those connections will eventually drop off after the idle time
> is reached "conf.getInt("hbase.ipc.client.connection.maxidletime", 10000)".
> But during periods of activity the number of threads can get very high.
>
> Additionally I was able to confirm the large number of threads by doing:
>
> jstack <pid> | grep IPC
>
>
> So I started digging around in the code...
>
> In HBaseClient.getConnection it attempts to reuse previous connections:
>
> ConnectionId remoteId = new ConnectionId(addr, protocol, ticket,
> rpcTimeout);
> do {
> synchronized (connections) {
> connection = connections.get(remoteId);
> if (connection == null) {
> LOG.error("poolsize: "+getPoolSize(conf));
> connection = new Connection(remoteId);
> connections.put(remoteId, connection);
> }
> }
> } while (!connection.addCall(call));
>
>
> It does this by using the connection id as the key to the pool. All of this
> seems good except ConnectionId never hashes to the same value so it cannot
> reuse any connection.
>
> From my understanding of the code here is why.
>
> In HBaseClient.ConnectionId
>
> @Override
> public boolean equals(Object obj) {
> if (obj instanceof ConnectionId) {
> ConnectionId id = (ConnectionId) obj;
> return address.equals(id.address) && protocol == id.protocol &&
> ((ticket != null && ticket.equals(id.ticket)) ||
> (ticket == id.ticket)) && rpcTimeout == id.rpcTimeout;
> }
> return false;
> }
>
> @Override // simply use the default Object#hashcode() ?
> public int hashCode() {
> return (address.hashCode() + PRIME * (
> PRIME * System.identityHashCode(protocol) ^
> (ticket == null ? 0 : ticket.hashCode()) )) ^ rpcTimeout;
> }
>
> It uses the protocol and the ticket in the both functions. However going
> back through all of the layers I think I found the problem.
>
> Problem:
>
> HBaseRPC.java: public static VersionedProtocol getProxy(Class<? extends
> VersionedProtocol> protocol,
> long clientVersion, InetSocketAddress addr, Configuration conf,
> SocketFactory factory, int rpcTimeout) throws IOException {
> return getProxy(protocol, clientVersion, addr,
> User.getCurrent(), conf, factory, rpcTimeout);
> }
>
> User.getCurrent() always returns a new User object. That user instance is
> eventually passed down to ConnectionId. However the User object doesn't
> implement hash() or equals() so one ConnectionId won't ever match another
> ConnectionId.
>
>
> There are several possible solutions.
> 1. implement hashCode and equals for the User.
> 2. only create one User object and reuse it.
> 3. don't look at ticket in ConnectionId (probably a bad idea)
>
>
> Thoughts? Has anyone else noticed this behavior? Should I open up a jira
> issue?
>
> I originally ran into the problem due to OS X having a limited number of
> threads per user (and I was not able to increase the limit) and our unit
> tests making requests quick enough that I ran out of threads. I tried out
> all three solutions and it worked fine for my application. However I'm not
> sure what changing the behavior would do to other's applications especially
> those that use SecureHadoop.
>
>
>
> Thanks,
> ~Jeff
>
> --
> Jeff Whiting
> Qualtrics Senior Software Engineer
> [email protected]
>
