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From Jason Gerlowski <>
Subject Re: Upgrade 6.2.1 to 7.5.0 - "Connection evictor" Threads not closed
Date Mon, 26 Nov 2018 16:54:38 GMT
Hey Sebastian,

As for how Solr/SolrJ compatibility is handled, the story for SolrJ
looks a lot like the story for Solr itself - major version changes can
introduce breaking changes, so it is best to avoid using SolrJ 6.x
with Solr 7.x.  In practice I think changes that break Solr/SolrJ
compatibility are relatively rare though, so it might be possible if
your hand is forced.

As for the behavior you described...I think I understand what you're
describing, but to make sure:  Are the "connection-evictor" threads
accumulating in your client application, on the Solr server itself, or

I suspect you're seeing this in your client code.  If so, it'd really
help us to help you if you could provide some more details on how
you're using SolrJ.  Can you share a small snippet (JUnit test?) that
reproduces the problem?  How are you creating the SolrClient you're
using to send requests?  Which SolrClient implementation(s) are you
using?  Are you providing your own HttpClient, or letting SolrClient
create its own?  It'll be much easier for others to help with a little
more detail there.



On Fri, Nov 23, 2018 at 10:38 AM Sebastian Riemer <> wrote:
> Hi,
> we've recently changed our Solr-Version from 6.2.1 to 7.5.0, and since then, whenever
we execute a query on solr, a new thread is being created and never closed.
> These threads are all labelled "Connection evictor" and the gather until a critical mass
is reached and either the OS cannot create anymore OS threads, or an out of memory error is
being produced.
> First I thought, that this might have as cause we were using a higher SolrJ-Version than
our Solr-Server (by mistakenly forgetting to uprade the server version too):
> So we had for SolrJ: 7.4.0
> <dependency>
>     <groupId>org.apache.solr</groupId>
>     <artifactId>solr-solrj</artifactId>
>     <version>7.4.0</version>
> </dependency>
> And for Solr-Server:  6.2.1
> But now I just installed the newest Solr-Server-Version 7.5.0 and still I see with each
Solr-Search performed an additional Thread being created and never released.
> When downgrading SolrJ to 6.2.1 I can verify, that no new threads are created when doing
a solr search.
> What do you think about this? Are there any known pitfalls? Maybe I missed some crucial
changes necessary when upgrading to 7.5.0?
> What about differing versions in SolrJ and Solr-Server? As far as I recall the docs,
one major-version-difference up/down in both ways should be o.k.
> Thanks for all your feedback,
> Yours sincerely
> Sebastian Riemer

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