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From "Timothee Maret (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SLING-7969) Memory leak in DiscoveryLiteDescriptor
Date Tue, 02 Oct 2018 08:15:00 GMT

    [ https://issues.apache.org/jira/browse/SLING-7969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16635133#comment-16635133
] 

Timothee Maret commented on SLING-7969:
---------------------------------------

https://github.com/tmaret/sling-org-apache-sling-discovery-commons/commit/edba8e9d8a5ec21f6a95945440e9c9825f00e666

> Memory leak in DiscoveryLiteDescriptor
> --------------------------------------
>
>                 Key: SLING-7969
>                 URL: https://issues.apache.org/jira/browse/SLING-7969
>             Project: Sling
>          Issue Type: Bug
>          Components: Discovery
>    Affects Versions: Discovery Commons 1.0.20
>            Reporter: Timothee Maret
>            Assignee: Timothee Maret
>            Priority: Major
>              Labels: discovery
>
> As identified in [~volteanu]'s adaptTo [presentation|https://adapt.to/2018/en/schedule/sling-memory-deep-dive.html],
it seems that Sling Discovery on Oak is consuming 42MB of RAM on a standard instance.
> Sling discovery deals with transient states (the views, leases, etc.) and is not caching
significant amount of data. The 42MB figure for the discovery feature seems like a symptom
of a memory leak.
> [~volteanu] shared in his presentation that the 42MB worth of RAM was mainly consumed
by a Json Factory reference. There is one static JsonReaderFactory in the discovery commons
module, in the [DiscoveryLiteDescriptor|https://github.com/apache/sling-org-apache-sling-discovery-commons/blob/master/src/main/java/org/apache/sling/discovery/commons/providers/spi/base/DiscoveryLiteDescriptor.java].
> Looking at the code, it seems that each invocation of the [getDescriptorFrom|https://github.com/apache/sling-org-apache-sling-discovery-commons/blob/master/src/main/java/org/apache/sling/discovery/commons/providers/spi/base/DiscoveryLiteDescriptor.java#L51]
method creates a JSON reader but never close it. This may may leave resources behind as hinted
by the description of the [close|https://docs.oracle.com/javaee/7/api/javax/json/JsonReader.html#close--]
method in the API. AFAIK, the [getDescriptorFrom|https://github.com/apache/sling-org-apache-sling-discovery-commons/blob/master/src/main/java/org/apache/sling/discovery/commons/providers/spi/base/DiscoveryLiteDescriptor.java#L51] is
invoked periodically on a relatively high frequency (< seconds) which may be the trigger
for the leak on all instances.
> This is only a supposition for now, it should be investigated further, simply by running a
patched version of \{{org.apache.sling.discovery.commons}} that make sure each JSON reader
is properly closed.



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