understanding StatementSapDB.finalize to avoid BLOCKED threads.

[Former Member]

Hi,

again, my system get BLOCKED, and i'm try to figure why, i hope that someone can help me to understanding the use of StatementSapDB.finalize, first the facts:

1) Blocked thread

"Finalizer" daemon prio=10 tid=0x00000000481a7800 nid=0x1a12 waiting for monitor entry [0x0000000040dbb000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at com.sap.dbtech.jdbc.StatementSapDB.finalize(StatementSapDB.java:450)
        - waiting to lock <0x00002aaacb9253c8> (a com.sap.dbtech.jdbc.ConnectionSapDB)
        at java.lang.ref.Finalizer.invokeFinalizeMethod(Native Method)
        at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:83)
        at java.lang.ref.Finalizer.access$100(Finalizer.java:14)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:160)

2) Thread that blocks Finalizer

"Thread-9891" daemon prio=10 tid=0x00002aab24b4b800 nid=0x35e0 runnable [0x0000000044a23000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:129)
        at com.sap.dbtech.rte.comm.BasicSocketComm.receiveData(BasicSocketComm.java:745)
        at com.sap.dbtech.rte.comm.BasicSocketComm.receive(BasicSocketComm.java:837)
        at com.sap.dbtech.rte.comm.JdbcCommunication.execute(JdbcCommunication.java:41)
        at com.sap.dbtech.jdbc.ConnectionSapDB.execute(ConnectionSapDB.java:632)
        - locked <0x00002aaacb9253c8> (a com.sap.dbtech.jdbc.ConnectionSapDB)
        at com.sap.dbtech.jdbc.ConnectionSapDB.execute(ConnectionSapDB.java:563)
        at com.sap.dbtech.jdbc.CallableStatementSapDB.execute(CallableStatementSapDB.java:440)
        at com.sap.dbtech.jdbc.CallableStatementSapDB.execute(CallableStatementSapDB.java:312)
        at com.sap.dbtech.jdbc.CallableStatementSapDB.executeQuery(CallableStatementSapDB.java:730)
        at com.sap.dbtech.jdbc.trace.PreparedStatement.executeQuery(PreparedStatement.java:178)
        at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
        at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
        at com.supridatta.xml.ReportGenerator.executeParse(ReportGenerator.java:583)

3) at database side i have:

T101   7     -1 User      6668* TableRootShare        0 0         19617 14906136(s)
T108   7     -1 User      6668* TableRootShare        0 0         19617 14906136(s)
T109   7     -1 User      6668* TableRootExcl         0 0         19617 14906136(s)
T111   7     -1 User      6668* TableRootShare        0 0         19617 14906136(s)
...and much more like that...

Note that thread 1 get block because of waiting to lock <0x00002aaacb9253c8> (a com.sap.dbtech.jdbc.ConnectionSapDB) that is locked by Thread-9891, as this is a report in my system, the Finalizer cant finalize the statement until the report ends.

I think that because finalize dont occurs, i get the TableRootShare, and maybe the report need some data that must wait finalize occurs, then here we got a deadlock.

My doubt is, as i realease all resources, and connections get pooled by Tomcat DBM, maybe exists something specific in MaxDB JDBC driver that i must release, that i dont release today?

note, i think that statement at Finalizer was created by another Thread that was reach the end, then same connection get by a new thread from pool, and used, then Finalizer acts, and block all things.

i'm investigating the hprof file with MemoryAnalyzerTool MAT, i will try to find more info, but any insight about this problem, maybe help me to find the root of problem.

best regards.

Clóvis

[Former Member]

This problem occured again today, anyone have any idea?