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https://issues.apache.org/jira/browse/JENA-801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14176519#comment-14176519
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Bala Kolla commented on JENA-801:
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the QueryFilter is a way of limiting the query results to the specified query
scope. I can try to reproduce this without this Filter so that we can rule that
out..
I don't have the exact data on read/write ration but would guess it would be 70
to 30. In regard to CPU, the system is using around 40 to 50% cpu until it gets
into this state and then it goes to 100% CPU and stays there until the server
load is stopped or reduced significantly.
Can you give me some insight into how this cache handles the updates to
triplestore (write)? Also, how hard is it to experiment with using Guava
caching? I would like to experiment it and see if it helps..
> When the server is under load, many queries are piling up and seems to be in
> some kind of dead lock.
> ----------------------------------------------------------------------------------------------------
>
> Key: JENA-801
> URL: https://issues.apache.org/jira/browse/JENA-801
> Project: Apache Jena
> Issue Type: Bug
> Components: TDB
> Affects Versions: TDB 0.9.4, Jena 2.11.2
> Reporter: Bala Kolla
> Attachments: WAITDataReportShowingTheLockContention.zip
>
>
> We were testing our server with repositories of varied sizes and in almost
> all the cases when the server peaks its capacity (of maximum number of users
> it can support), It seems like the queries are piling up because of the lock
> contention in NodeTableCache.
> Here are some details about the repository..
> size of indices on disk - 150GB
> type of hard disk used - SSD and HDD with high RAM (seeing the same result in
> both the cases)
> OS - Linux
> Details on the user load;
> We are trying to simulate a very active user load where all the users are
> executing many usecases that would result in many queries and updates on TDB.
> I would like to know what are the possible solutions to work around and avoid
> this situation. I am thinking of the following, please let me know if there
> is any other way to work around this bottleneck.
> Control the updates to the triple store so that we only do it when there are
> not many queries pending. We would have to experiment how this impact the
> usecases..
> Is there any other way to make this lock contention go away? Can we have
> multiple instances of this cache? For example many (90%) of our queries are
> executed with a query scope (per project). So, can we have a separate
> NodeTable cache for each query scope (project in our case) and one for
> global?
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