On 7/11/2013 1:47 PM, Tom Burton-West wrote:
We are seeing the message "too many merges...stalling" in our indexwriter
log. Is this something to be concerned about? Does it mean we need to
tune something in our indexing configuration?
It sounds like you've run into the maximum number of simultaneous
merges, which I believe defaults to two, or maybe three. The following
config section in <indexConfig> will likely take care of the issue.
This assumes 3.6 or later, I believe that on older versions, this goes
in <indexDefaults>.
<mergeScheduler class="org.apache.lucene.index.ConcurrentMergeScheduler">
<int name="maxThreadCount">1</int>
<int name="maxMergeCount">6</int>
</mergeScheduler>
Looking through the source code to confirm, this definitely seems like
the case. Increasing maxMergeCount is likely going to speed up your
indexing, at least by a little bit. A value of 6 is probably high
enough for mere mortals, buy you guys don't do anything small, so I
won't begin to speculate what you'll need.
If you are using spinning disks, you'll want maxThreadCount at 1. If
you're using SSD, then you can likely increase that value.
Thanks,
Shawn
