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Marco edited comment on DERBY-7049 at 7/23/19 2:10 PM: ------------------------------------------------------- Thanks a lot for your quick reaction! [~bryanpendleton] I tried to create a test-case, but did not succeed, yet. In production, the problem occurs after _days_ (not hours) and much more complex queries than my test-case creates so far. I'll give the test-case another try, but I can only do this on the week-end (I have urgent work for a customer till then). [~rhillegas] => 1) I did not profile the memory usage, because I was not yet able to reproduce the problem myself. It occurs on a friend's machine 10000 km far away from me. And since he's a doctor, handles very sensitive patient data (which is *very* *large* – which is the very reason for this whole process to take so long and run into the OOM-error after more than a day) and the data is encrypted (that's the point of the project [subshare|http://subshare.org] ), I cannot easily reproduce it with his productive data. => 2) I use [DataNucleus|http://datanucleus.org], which is a persistence-layer, and do not write/manage the PreparedStatements myself. However, according to its documentation, PreparedStatement instances are created and forgotten by default, unless configured differently. => 3) As said, this is managed by DataNucleus. => 2), 3) I tried multiple things: a) I introduced the code to shut-down the derby-database once in (roughly) 20 minutes. This code also shuts down the DataNucleus-PersistenceManagerFactory and there should thus be nothing left holding any resources. b) My friend tried enabling PreparedStatement-caching in DataNucleus, but it had no effect. I did not (yet) dig into this further and I don't know how long the PreparedStatements are cached and in which scopes (e.g. whether it's only within a transaction). In general, most of the statements are static, i.e. annotated to the entity-classes. There are a few which are dynamic. But to say more about when statements are created or taken from a cache (by DataNucleus), I'd have to do more research. AFAIK DataNucleus translates all JDO-queries to SQL-PreparedStatement-instances using ?-parameters, i.e. it does _not_ use statements with inline-parameters. was (Author: nlmarco): Thanks a lot for your quick reaction! [~bryanpendleton] I tried to create a test-case, but did not succeed, yet. In production, the problem occurs after _days_ (not hours) and much more complex queries than my test-case creates so far. I'll give the test-case another try, but I can only do this on the week-end (I have urgent work for a customer till then). [~rhillegas] => 1) I did not profile the memory usage, because I was not yet able to reproduce the problem myself. It occurs on a friend's machine 10000 km far away from me. And since he's a doctor, handles very sensitive patient data (which is *very* *large* – which is the very reason for this whole process to take so long and run into the OOM-error after more than a day) and the data is encrypted (that's the point of the project [subshare|http://subshare.org] ), I cannot easily reproduce it with his productive data. => 2) I use DataNucleus, which is a persistence-layer, and do not write/manage the PreparedStatements myself. However, according to its documentation, PreparedStatement instances are created and forgotten by default, unless configured differently. => 3) As said, this is managed by DataNucleus. => 2), 3) I tried multiple things: a) I introduced the code to shut-down the derby-database once in (roughly) 20 minutes. This code also shuts down the DataNucleus-PersistenceManagerFactory and there should thus be nothing left holding any resources. b) My friend tried enabling PreparedStatement-caching in DataNucleus, but it had no effect. I did not (yet) dig into this further and I don't know how long the PreparedStatements are cached and in which scopes (e.g. whether it's only within a transaction). In general, most of the statements are static, i.e. annotated to the entity-classes. There are a few which are dynamic. But to say more about when statements are created or taken from a cache (by DataNucleus), I'd have to do more research. AFAIK DataNucleus translates all JDO-queries to SQL-PreparedStatement-instances using ?-parameters, i.e. it does _not_ use statements with inline-parameters. > OutOfMemoryError: Compressed class space > ---------------------------------------- > > Key: DERBY-7049 > URL: https://issues.apache.org/jira/browse/DERBY-7049 > Project: Derby > Issue Type: Bug > Components: SQL > Affects Versions: 10.13.1.1 > Reporter: Marco > Priority: Major > > After a few days of working with an embedded Derby database (currently > version 10.13.1.1 on Oracle Java 1.8.0_201-b09), the following error occurs: > *java.lang.OutOfMemoryError: Compressed class space* > {code:java} > java.lang.OutOfMemoryError: Compressed class space > at java.lang.ClassLoader.defineClass1(Native Method) ~[na:1.8.0_201] > at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[na:1.8.0_201] > at java.lang.ClassLoader.defineClass(ClassLoader.java:642) ~[na:1.8.0_201] > at > org.apache.derby.impl.services.reflect.ReflectLoaderJava2.loadGeneratedClass(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at > org.apache.derby.impl.services.reflect.ReflectClassesJava2.loadGeneratedClassFromData(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at > org.apache.derby.impl.services.reflect.DatabaseClasses.loadGeneratedClass(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at > org.apache.derby.impl.services.bytecode.GClass.getGeneratedClass(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at > org.apache.derby.impl.sql.compile.ExpressionClassBuilder.getGeneratedClass(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.sql.compile.StatementNode.generate(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source) > ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source) > ~[derby-10.13.1.1.jar:na] > at > org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.jdbc.EmbedPreparedStatement.<init>(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.jdbc.EmbedPreparedStatement42.<init>(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.jdbc.Driver42.newEmbedPreparedStatement(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown > Source) ~[derby-10.13.1.1.jar:na] > at > org.datanucleus.store.rdbms.datasource.dbcp.DelegatingConnection.prepareStatement(DelegatingConnection.java:259) > ~[datanucleus-rdbms-4.0.12.jar:na]{code} > I tried to solve the problem by periodically shutting down the database, > because I read that the generated classes as well as all other allocated > resources should be released when the DB is shut-down. > I thus perform the following code once per roughly 20 minutes: > {code:java} > String shutdownConnectionURL = connectionURL + ";shutdown=true"; > try { > DriverManager.getConnection(shutdownConnectionURL); > } catch (SQLException e) { > int errorCode = e.getErrorCode(); > if (DERBY_ERROR_CODE_SHUTDOWN_DATABASE_SUCCESSFULLY != errorCode && > DERBY_ERROR_CODE_SHUTDOWN_DATABASE_WAS_NOT_RUNNING != errorCode) { > throw new RuntimeException(e); > } > } > {code} > Unfortunately, this has no effect :( The OutOfMemoryError still occurs after > about 2 days. Do I assume correctly that the above code _should_ properly > shut-down the database? And do I assume correctly that this shut-down should > release the generated classes? > IMHO, it is already a bug in Derby that I need to shut-down the database at > all in order to prevent it from piling up generated classes. Shouldn't it > already release the generated classes at the end of each transaction? But > even if I really have to shut-down the DB, it is certainly a bug that the > classes are still kept in "compressed class space" even after the shut-down. > I searched the release notes and the existing bugs (here in JIRA) and did not > find anything related to this {{OutOfMemoryError}}. Hence, I open this > bug-report, now. > This issue was originally reported in > [subshare#74|https://github.com/subshare/subshare/issues/74], but it is IMHO > clearly a Derby bug. -- This message was sent by Atlassian JIRA (v7.6.14#76016)