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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-1947) OutOfMemoryError after repeated calls to boot and shutdown a database
Date Wed, 18 Apr 2007 16:20:16 GMT

    [ https://issues.apache.org/jira/browse/DERBY-1947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12489808
] 

Rick Hillegas commented on DERBY-1947:
--------------------------------------

Hi Dag,

>1) Maybe we could change the HashSet 'allContexts' of the
>   ContextService to use weak hash map perhaps, a WeakHashSet, if there
>   is such a thing. That way, the ContextManager objects would be
>   cleaned eventually.

Maybe you could press java.util.WeakHashMap into service. Its javadoc suggests the following
issues:

a) You would need to choose something innocuous for the values in this map. You're only interested
in the keys and garbage-collectible values would need to be wrapped in WeakReferences.

b) ContextService.notifyAllActiveThreads() would need to be insulated from disappearing keys.
Also, for the record, it looks to me as though the Thread.interrupt() call needs to be wrapped
in a privileged action block.


> OutOfMemoryError after repeated calls to boot and shutdown a database
> ---------------------------------------------------------------------
>
>                 Key: DERBY-1947
>                 URL: https://issues.apache.org/jira/browse/DERBY-1947
>             Project: Derby
>          Issue Type: Bug
>          Components: Services
>    Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1, 10.2.1.6
>         Environment: Any
>            Reporter: Rajesh Kartha
>         Assigned To: Dag H. Wanvik
>         Attachments: DERBY-1947-1.diff, DERBY-1947-1.stat, DERBY-1947-2.diff, DERBY-1947-2.stat,
HeapAnalysis_op.jpg, ProcedureInTriggerTest-threadstacks.txt, testEmbedAndClient.java
>
>
> I came across this OOM issue while running some system tests involving
> backup and restore against  Derby. The test is expected to run forever but
> using the default heap space it runs into OOM within 2 days. I earlier mentioned about
this
> in my reply to the 10.2.1.6 vote - http://www.nabble.com/Re%3A--VOTE--10.2.1.6-release-p6650528.html
> Also there has been some discussions on the list on the related topic:
> http://issues.apache.org/jira/browse/DERBY-23 and
> http://www.nabble.com/question-about-shutdown-tf2300504.html
> Basic Analysis:
> --------------------
> Wrote a simple Java app (attached to this issue) that booted and shutdown the same 
> database multiple times. Depending on the heapsize the program ran into the
> OOM at some point, as expected. Some heap dump analysis using the IBM HeapAnalyzer 
> and revealed that the HashSet (allContexts) within org.apache.derby.iapi.services.context.ContextService

> class seemed to be location of the leak (snapshot of the heapanalysis attached).
> A little bit of debugging shows that:
>  - for every:connection two ContextManager objects (say, cm1, cm2) are added to the HashSet
>  - for every shutdown a new ContextManager object (say, cm3) is added and two objects
are removed
>  - the object removed are cm2 and cm3 - in that sequence
>  - but the object cm1 gets left behind
> This happens for every connect/shutdown sequence and since one of the ContextManager
objects added to the 
> HashSet is not removed as a part of the cleanup, it contributes to growth in memory usage,
hence
> an OOM eventually.
> For example:
> ============
> A 64M heap could allow about 1107 iterations of connect/shutdown only before running
into OOM and 
> created 1108 un-used ContextManager objects in the memory.
> java -Xmx64M testEmbedAndClient
> ++++Debug: add() Size of allContexts HashSet obj= 1
> ----Debug: remove() Size of allContexts HashSet obj= 0
> ++++Debug: add() Size of allContexts HashSet obj= 1
> ----Debug: remove() Size of allContexts HashSet obj= 0
> ++++Debug: add() Size of allContexts HashSet obj= 1
> ++++Debug: add() Size of allContexts HashSet obj= 2
> ==== Database booted in embedded ====
> ++++Debug: add() Size of allContexts HashSet obj= 3
> ----Debug: remove() Size of allContexts HashSet obj= 2
> ----Debug: remove() Size of allContexts HashSet obj= 1
> ==== Shutdown complete in embedded ====
> ++++Debug: add() Size of allContexts HashSet obj= 2
> ++++Debug: add() Size of allContexts HashSet obj= 3
> ==== Database booted in embedded ====
> ++++Debug: add() Size of allContexts HashSet obj= 4
> ----Debug: remove() Size of allContexts HashSet obj= 3
> ----Debug: remove() Size of allContexts HashSet obj= 2
> ..
> ..
> ..
> ==== Database booted in embedded ====
> ++++Debug: add() Size of allContexts HashSet obj= 1109
> ----Debug: remove() Size of allContexts HashSet obj= 1108
> ----Debug: remove() Size of allContexts HashSet obj= 1107
> ==== Shutdown complete in embedded ====
> ++++Debug: add() Size of allContexts HashSet obj= 1108
> ++++Debug: add() Size of allContexts HashSet obj= 1109
> ----Debug: remove() Size of allContexts HashSet obj= 1108
> java.sql.SQLException: Failed to start database 'testdb', see the next exception
>  for details.
>         at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(SQLExceptionFactory.java:45)
>         at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:89)
>         at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:95)
>         at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Util.java:174)
>         at org.apache.derby.impl.jdbc.EmbedConnection.newSQLException(EmbedConnection.java:1985)
>         at org.apache.derby.impl.jdbc.EmbedConnection.bootDatabase(EmbedConnection.java:1649)
>         at org.apache.derby.impl.jdbc.EmbedConnection.<init>(EmbedConnection.java:223)
>         at org.apache.derby.impl.jdbc.EmbedConnection30.<init>(EmbedConnection30.java:73)
>         at org.apache.derby.jdbc.Driver30.getNewEmbedConnection(Driver30.java:74)
>         at org.apache.derby.jdbc.InternalDriver.connect(InternalDriver.java:210)
> ----Debug: remove() Size of allContexts HashSet obj= 1107
>         at org.apache.derby.jdbc.AutoloadedDriver.connect(AutoloadedDriver.java:117)
>         at java.sql.DriverManager.getConnection(DriverManager.java:525)
>         at java.sql.DriverManager.getConnection(DriverManager.java:193)
>         at testEmbedAndClient.testInEmbedded(testEmbedAndClient.java:40)
>         at testEmbedAndClient.main(testEmbedAndClient.java:19)
> java.lang.OutOfMemoryError: Java heap space
> OOM happened after 1107 iterations

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