Karl Wright created SOLR-4328:
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Summary: Simultaneous multiple connections to Solr example
sometimes fail with various IOExceptions
Key: SOLR-4328
URL: https://issues.apache.org/jira/browse/SOLR-4328
Project: Solr
Issue Type: Bug
Affects Versions: 3.6.2, 4.0
Environment: ManifoldCF, Solr connector, SolrJ, and Solr 4.0 or 3.6 on
Mac OSX or Ubuntu, all localhost connections
Reporter: Karl Wright
In ManifoldCF, we've been seeing problems with SolrJ connections throwing
java.net.SocketException's. See CONNECTORS-616 for details as to exactly what
varieties of this exception are thrown, but "broken pipe" is the most common.
This occurs on multiple Unix variants as stated. (We also occasionally see
exceptions on Windows, but they are much less frequent and are different
variants than on Unix.)
The exceptions seem to occur during the time an initial connection is getting
established, and seems to occur randomly when multiple connections are getting
established all at the same time. Wire logging shows that only the first few
headers are sent before the connection is broken. Solr itself does log any
error. A retry is usually sufficient to have the transaction succeed.
The Solr Connector in ManifoldCF has recently been upgraded to rely on SolrJ,
which could be a complicating factor. However, I have repeatedly audited both
the Solr Connection code and the SolrJ code for best practices, and while I
found a couple of problems, nothing seems to be of the sort that could cause a
broken pipe. For that to happen, the socket must be closed either on the
client end or on the server end, and there appears to be no mechanism for that
happening on the client end, since multiple threads would have to be working
with the same socket for that to be a possibility.
It is also true that in ManifoldCF we disable the automatic retries that are
normally enabled for HttpComponents HttpClient. These automatic retries likely
mask this problem should it be occurring in other situations.
Places where there could potentially be a bug, in order of likelihood:
(1) Jetty. Nobody I am aware of has seen this on Tomcat yet. But I also don't
know if anyone has tried it.
(2) Solr servlet. If it is possible for a servlet implementation to cause the
connection to drop without any exception being generated, this would be
something that should be researched.
(3) HttpComponents/HttpClient. If there is a client-side issue, it would have
to be because an httpclient instance was closing sockets from other instances.
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