[
https://issues.apache.org/jira/browse/JENA-801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14186902#comment-14186902
]
Andy Seaborne commented on JENA-801:
------------------------------------
Not quite. There should be one style of node cache. Any node cache can be come
multithreaded.
There is one node cache per transaction-generation. TDB provides serialized
transactions so you can have a long-running read transaction R1 on generation N
(maybe this is the main database), a write transaction W1 runs and commits
(generation N+1), then new read transactions R2, R3 using the view of the
database from the write transaction. They have different node caches - R2 and
all read transactions after W1 before another writer W2 commits, share the W1
node cache - while during W1, there is only one writer thread accessing the
node cache for W1, after W1 commits, many readers can use it. R1 can be
accessing it's cache (generation N) while R2,R3 access the cache from W1
(generation N+1).
> 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:
> ThreadLocksInBlockMgrJournalAfterGuavaCacheInNodeTable.htm,
> WAITDataReportShowingTheLockContention.zip,
> WAITDataReportShowingTheLockContentionWithoutQueryFilter.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?
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
