[jira] [Commented] (JENA-901) Make the cache of LPBRuleEngine bounded to avoid out-of-memory

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JENA-901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14523138#comment-14523138 ] 

ASF GitHub Bot commented on JENA-901:
-------------------------------------

Github user afs commented on a diff in the pull request:

    https://github.com/apache/jena/pull/47#discussion_r29499092
  
    --- Diff: jena-core/src/main/java/com/hp/hpl/jena/reasoner/rulesys/impl/LPBRuleEngine.java ---
    @@ -52,16 +66,22 @@
         protected boolean recordDerivations;
             
         /** List of engine instances which are still processing queries */
    -    protected List<LPInterpreter> activeInterpreters = new ArrayList<>();
    -    
    +    protected List<LPInterpreter> activeInterpreters = new LinkedList<>();
    +
    +    protected final int MAX_CACHED_TABLED_GOALS = 
    +			Integer.getInteger("jena.rulesys.lp.max_cached_tabled_goals", 512*1024);
    +
    --- End diff --
    
    getting System properties is problematic in some environments.  See JenaRuntime.getSystemProperty for some mitigation of this.


> Make the cache of LPBRuleEngine bounded to avoid out-of-memory
> --------------------------------------------------------------
>
>                 Key: JENA-901
>                 URL: https://issues.apache.org/jira/browse/JENA-901
>             Project: Apache Jena
>          Issue Type: Improvement
>          Components: Reasoners
>    Affects Versions: Jena 2.12.1
>            Reporter: Jan De Beer
>
> The class "com.hp.hpl.jena.reasoner.rulesys.impl.LPBRuleEngine" uses an in-memory cache named "tabledGoals", which has no limit as to the size/number of entries stored.
> {noformat}
>     /** Table mapping tabled goals to generators for those goals.
>      *  This is here so that partial goal state can be shared across multiple queries. */
>     protected HashMap<TriplePattern, Generator> tabledGoals = new HashMap<>();
> {noformat}
> We have experienced out-of-memory issues because of the cache being filled with millions of entries in just a few days under normal query usage conditions and a heap memory set to 3GB.
> In our setup, we have a dataset containing multiple graphs, some of them are actual data graphs (backed by TDB), and then there are two which are ontology models using a "TransitiveReasoner" and an "OWLMicroFBRuleReasoner", respectively. A typical query may run over all the graphs in the dataset, including the ontology ones (see below for a query template). Eventhough the ontology graphs would not yield any additional results for data queries (which is fine), the above mentioned cache would still fill up with new entries.
> {noformat}
> SELECT ?p ?o
> WHERE {
>   GRAPH ?g {
>     <some resource of interest> ?p ?o .
>   }
> }
> {noformat}
> As there is no upper bound to the cache, soon or later all available heap memory will be consumed by the cache, giving rise to an out-of-memory criticial error.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)