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From Frank Grimes <frankgrime...@yahoo.com>
Subject Re: Collector node failing with java.net.SocketException: Too many open files
Date Tue, 31 Jan 2012 15:33:06 GMT

On 2012-01-30, at 10:49 AM, Frank Grimes wrote:

> I think this bug might be addressed by making use of TCP keepalive on the Thrift server
socket. e.g.
> Index: flume-core/src/main/java/org/apache/thrift/transport/TSaneServerSocket.java
> ===================================================================
> --- flume-core/src/main/java/org/apache/thrift/transport/TSaneServerSocket.java	(revision
> +++ flume-core/src/main/java/org/apache/thrift/transport/TSaneServerSocket.java	(working
> @@ -132,6 +132,7 @@
>      }
>      try {
>        Socket result = serverSocket_.accept();
> +      result.setKeepAlive(true); 
>        TSocket result2 = new TBufferedSocket(result);
>        result2.setTimeout(clientTimeout_);
>        return result2;
> I believe that on Linux that would force the connections to be closed/cleaned up after
2 hours by default.
> This is likely good enough to prevent the "java.net.SocketException: Too many open files"
from occurring in our case.
> Note that it's also configurable as per http://tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/#usingkeepalive.
> Shall I open up a JIRA case for this and submit a patch?
> Should the keepalive be configurable or is it desirable to always have the Flume collector
protected from these kinds of killed connections?
> I can't think of any downsides to always having it on...
> Cheers,
> Frank Grimes
> On 2012-01-28, at 12:20 PM, Frank Grimes wrote:
>> We believe that we've made some progress in identifying the problem.
>> It appears that we have a slow socket connection leak on the Collector node due to
sparse data coming in on some Thrift RPC sources.
>> Turns out we're going through a firewall, and we believe that it is killing those
inactive connections.
>> The Agent node's Thrift RPC sink sockets are getting cleaned up after a socket timeout
on a subsequent append, but the Collector still has its socket connections open and they don't
appear to ever be timing out and closing.
>> I found the following which seems to describe the problem:
>>   http://mail-archives.apache.org/mod_mbox/incubator-flume-user/201107.mbox/%3C1311642202.14311.2155844361@webmail.messagingengine.com%3E
>> However, because presumably some other disconnect conditions could trigger the problem
as well, we are still looking for a solution that doesn't require fiddling with firewall settings.
>> Is there a way to configure the Collector node to drop/close these inactive connections?

>> i.e. either at the Linux network layer or through Java socket APIs within Flume?
>> Thanks,
>> Frank Grimes
>> On 2012-01-26, at 10:51 AM, Frank Grimes wrote:
>>> Hi All,
>>> We are using flume-0.9.5 (specifically, http://svn.apache.org/repos/asf/incubator/flume/trunk@1179275)
and occasionally our Collector node accumulates too many open TCP connections and starts madly
logging the following errors:
>>> WARN org.apache.thrift.server.TSaneThreadPoolServer: Transport error occurred
during acceptance of message.
>>> org.apache.thrift.transport.TTransportException: java.net.SocketException: Too
many open files
>>>        at org.apache.thrift.transport.TSaneServerSocket.acceptImpl(TSaneServerSocket.java:139)
>>>        at org.apache.thrift.transport.TServerTransport.accept(TServerTransport.java:31)
>>>        at org.apache.thrift.server.TSaneThreadPoolServer$1.run(TSaneThreadPoolServer.java:175)
>>> Caused by: java.net.SocketException: Too many open files
>>>        at java.net.PlainSocketImpl.socketAccept(Native Method)
>>>        at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:408)
>>>        at java.net.ServerSocket.implAccept(ServerSocket.java:462)
>>>        at java.net.ServerSocket.accept(ServerSocket.java:430)
>>>        at org.apache.thrift.transport.TSaneServerSocket.acceptImpl(TSaneServerSocket.java:134)
>>>        ... 2 more
>>> This quickly fills up the disk as the log file grows to multiple gigabytes in
>>> After some investigation, it appears that even though the Agent nodes show single
open connections to the Collector, the Collector node appears to have a bunch of zombie TCP
connections open back to the Agent nodes.
>>> i.e.
>>> "lsof -n | grep PORT" on the Agent node shows 1 established connection
>>> However, the Collector node shows hundreds of established connections for that
same port which don't seem to tie up to any connections I can find on the Agent node.
>>> So we're concluding that the Collector node is somehow leaking connections.
>>> Has anyone seen this kind of thing before?
>>> Could this be related to https://issues.apache.org/jira/browse/FLUME-857?
>>> Or could this be a Thrift bug that could be avoided by switching to Avro sources/sinks?
>>> Any hints/tips are most welcome.
>>> Thanks,
>>> Frank Grimes

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