The document discusses the issues of 'slowdown' and 'hang up' in WebLogic and other J2EE applications, detailing their definitions, common causes, and methods for diagnosis and resolution. Key points include thread management, understanding thread dumps, identifying lock contention and deadlocks, and optimizing resource usage such as memory and database response times. It emphasizes the importance of proactive measures like memory tuning and clustering to prevent performance issues.

1. BEA Systems Korea Byungwook Cho (bcho@bea.com) Analysis WebLogic Hang up & slow down

2. Agenda What is slowdown & hang up? 1 Slowdown in WAS 2 Slowdown in other resources 3 Common mistake in J2ee developer 4

3. What is the slowdown & hang up? Slowdown System runs very slowly like a stop Sometimes, system gets a lot of resources (CPU,Memory) Hang up System stops System has no response

4. What is the slowdown & hang up To solve this problem Find the reason Solve it!! With experience,tool and test Find the problem Development env : Stress Test (Load Runner,MS Stress -free) Production : Itself is a problem

5. What is the slowdown & hang up User AP WAS JVM DBMS Web Server Network Client < Basic J2ee architecture > Legacy

6. Slow down in WAS & User AP

7. Slow down in WAS & User AP User AP WAS JVM DBMS Web Server Network Client Legacy

8. Slow down in WAS & User AP Thread Pooling Thread Pool Idle Thread (Waiting) request Thread Pool Working Thread (Handling request) request response Thread Pool Working Thread

9. Slow down in WAS & User AP Basic structure of WAS WebServer OR Browser OR Client Dispatcher Request Queue Thread Pool Connection Pool Thread Queue JMS Thread Queue APP1 Thread Queue APP2 Thread Queue Other Resources Connector Working Thread Idle Thread

10. Slow down in WAS & User AP Java Thread State Runnable new start Blocked Sleep/done sleep Wait/notify Suspend/Resume Block on IO/IO complete dead stop << Thread State Diagram >> - Runnable : running - Suspended,Locked : waiting on monitor entry / waiting on condition /MW - Wait : Object.Wait()

11. Slow down in WAS & User AP Thread dump Snapshot of java ap (X-ray) We can recognize thread running tread state by “continuous thread dump”

12. Slow down in WAS & User AP Getting Thread Dump Unix : kill –3 pid , Windows : Ctrl + Break Get thread dump about 3~5 times between 3~5secs ※ Linux : pstree -pan Threads Time Working thread Thread dump

13. Slow down in WAS & User AP Thread dump It displays all of thread state by “THREAD STACK” &quot;ExecuteThread: '42' for queue: 'default'&quot; daemon prio=5 tid=0x3504b0 nid=0x34 runnable [0x9607e000..0x9607fc68] Thread name Thread id (signature) Thread State Program stack of this thread Sun JVM at java.net.SocketInputStream.read(SocketInputStream.java:85) at oracle.net.ns.Packet.receive(Unknown Source) at oracle.net.ns.NetInputStream.getNextPacket(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.jdbc.ttc7.MAREngine.unmarshalUB1(MAREngine.java:730) at oracle.jdbc.ttc7.MAREngine.unmarshalSB1(MAREngine.java:702) at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:373) at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1427) at oracle.jdbc.ttc7.TTC7Protocol.fetch(TTC7Protocol.java:911) at oracle.jdbc.driver.OracleStatement.doExecuteQuery(OracleStatement.java:1948) at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2137) at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:404) at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:344) at weblogic.jdbc.pool.PreparedStatement.executeQuery(PreparedStatement.java:51) at weblogic.jdbc.rmi.internal.PreparedStatementImpl.executeQuery(PreparedStatementImpl.java:56)

14. Slow down in WAS & User AP How to analysis thread dump MYTHREAD_RUN(){   call methodA(); } methodA(){ //doSomething();   call methodB(); } methodB(){ //call methodC();   } methodC(){ // doSomething   for(;;){// infinite loop }   } “ MYTHREAD” runnable   at …MYTHREAD_RUN() : “ MYTHREAD” runnable   at …methodA() at …MYTHREAD_RUN() : “ MYTHREAD” runnable   at …methodB() at …methodA() at …MYTHREAD_RUN() : “ MYTHREAD” runnable   at …methodC() at …methodB() at …methodA() at …MYTHREAD_RUN() : “ MYTHREAD” runnable at …methodC() at …methodB() at …methodA() at …MYTHREAD_RUN() : 계속 이모양이 반복됨 Source code Thread dumps

15. Slow down in WAS & User AP CASE 1. Lock contention In the java application java thread wait for lock in synchronized method Occurred in multi threaded program Reduce frequency of synchronized method Synchronized block must be implemented to be end as soon as possible ( ※ IO? ) public void synchronized methodA(Object param) { //do something while(1){} } < sample code >

16. Slow down in WAS & User AP CASE 1. Lock contention Thread1 Thread3 Thread2 Thread4 Sychronized MethodA Threads Time Thread1 – That has a lock Thread 2.3.4 – waiting for lock

17. Slow down in WAS & User AP CASE 1. Lock contention : Thread dump example &quot;ExecuteThread: '12' for queue: 'weblogic.kernel.Default'&quot; daemon prio=10 tid=0x0055ae20 nid=23 lwp_id=3722788 waiting for monitor entry [0x2fb6e000..0x2fb6d530] : at java.lang.ClassLoader.loadClass(ClassLoader.java:255) : at org.apache.xerces.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown Source) at org.apache.axis.utils.XMLUtils.getSAXParser(XMLUtils.java:252) - locked < 0x329fcf50 > (a java.lang.Class) &quot;ExecuteThread: '13' for queue: 'weblogic.kernel.Default'&quot; daemon prio=10 tid=0x0055bde0 nid=24 lwp_id=3722789 waiting for monitor entry [0x2faec000..0x2faec530] at org.apache.axis.utils.XMLUtils.getSAXParser(XMLUtils.java:247) - waiting to lock < 0x329fcf50 > (a java.lang.Class) : &quot;ExecuteThread: '15' for queue: 'weblogic.kernel.Default'&quot; daemon prio=10 tid=0x0061dc20 nid=26 lwp_id=3722791 waiting for monitor entry [0x2f9ea000..0x2f9ea530] at org.apache.axis.utils.XMLUtils.releaseSAXParser(XMLUtils.java:283) - waiting to lock < 0x329fcf50 > (a java.lang.Class) at

18. Slow down in WAS & User AP CASE 2. Dead lock CWC “Circular waiting condition” Commonly it makes WAS hang up Remove CWC by changing lock direction Some kind of JVM detects dead lock automatically sychronized methodA(){ call methodB(); } sychronized methodB(){ call methodC(); } sychronized methodC(){ call methodA(); } < sample code >

19. Slow down in WAS & User AP CASE 2. Dead lock Thread1 Sychronized MethodA Thread2 Sychronized MethodB Thread3 Sychronized MethodC Threads Time Thread 1 Thread 2 Thread 3 Circular waiting condition

20. Slow down in WAS & User AP CASE 2. Dead lock FOUND A JAVA LEVEL DEADLOCK: ---------------------------- &quot;ExecuteThread: '12' for queue: 'default'&quot;: waiting to lock monitor 0xf96e0 (object 0xbd2e1a20, a weblogic.servlet.jsp.JspStub ), which is locked by &quot;ExecuteThread: '5' for queue: 'default'&quot; &quot;ExecuteThread: '5' for queue: 'default'&quot;: waiting to lock monitor 0xf8c60 (object 0xbd9dc460, a weblogic.servlet.internal.WebAppServletContext ), which is locked by &quot;ExecuteThread: '12' for queue: 'default'&quot; JAVA STACK INFORMATION FOR THREADS LISTED ABOVE: ------------------------------------------------ Java Stack for &quot;ExecuteThread: '12' for queue: 'default'&quot;: ========== at weblogic.servlet.internal.ServletStubImpl.destroyServlet(ServletStubImpl.java:434) - waiting to lock <bd2e1a20> (a weblogic.servlet.jsp.JspStub) at weblogic.servlet.internal.WebAppServletContext.removeServletStub(WebAppServletContext.java:2377) at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:207) : Java Stack for &quot;ExecuteThread: '5' for queue: 'default'&quot;: ========== at weblogic.servlet.internal.WebAppServletContext.removeServletStub(WebAppServletContext.java:2370) at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:207) at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:154) - locked <bd2e1a20> (a weblogic.servlet.jsp.JspStub) at weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:368) : Found 1 deadlock.======================================================== Deadlock auto detect in Sun JVM

21. Slow down in WAS & User AP CASE 2. Dead lock &quot;ExecuteThread-6&quot; (TID:0x30098180, sys_thread_t:0x39658e50, state:MW , native ID:0xf10) prio=5 at oracle.jdbc.driver.OracleStatement.close (OracleStatement.java(Compiled Code)) at weblogic.jdbc.common.internal.ConnectionEnv.cleanup(ConnectionEnv.java(Compiled : &quot;ExecuteThread-8&quot; (TID:0x30098090, sys_thread_t:0x396eb890, state:MW , native ID:0x1112) prio=5 at oracle.jdbc.driver.OracleConnection .commit(OracleConnection.java(Compiled Code)) at weblogic.jdbcbase.pool.Connection.commit(Connection.java(Compiled Code)) : sys_mon_t:0x39d75b38 infl_mon_t: 0x39d6e288: oracle.jdbc.driver.OracleConnection @310BC380/310BC388: owner &quot; ExecuteThread-8 &quot; (0x396eb890) 1 entry  1) Waiting to enter: &quot;ExecuteThread-10&quot; (0x3977e2d0) &quot; ExecuteThread-6 &quot; (0x39658e50) sys_mon_t:0x39d75bb8 infl_mon_t: 0x39d6e2a8: \ oracle.jdbc.driver.OracleStatement@33AA1BD0/33AA1BD8 : owner &quot; ExecuteThread-6 &quot; (0x39658e50) 1 entry  2) Waiting to enter: &quot; ExecuteThread-8 &quot; (0x396eb890 Deadlock trace in AIX JVM

22. Slow down in WAS & User AP CASE 3. Wait for IO Response Situation in waiting for IO response (DB,Network) Commonly occurred caused by DB locking or slow response Threads Time Wait for IO response

23. Slow down in WAS & User AP CASE 3. Wait for IO Response &quot;ExecuteThread: '42' for queue: 'default'&quot; daemon prio=5 tid=0x3504b0 nid=0x34 runnable [0x9607e000..0x9607fc68] at java.net.SocketInputStream.socketRead(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:85) at oracle.net.ns.Packet.receive(Unknown Source) at oracle.net.ns.NetInputStream.getNextPacket(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.jdbc.ttc7.MAREngine.unmarshalUB1(MAREngine.java:730) at oracle.jdbc.ttc7.MAREngine.unmarshalSB1(MAREngine.java:702) at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:373) at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1427) at oracle.jdbc.ttc7.TTC7Protocol.fetch(TTC7Protocol.java:911) at oracle.jdbc.driver.OracleStatement.doExecuteQuery(OracleStatement.java:1948) at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2137) at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:404) at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:344) at weblogic.jdbc.pool.PreparedStatement.executeQuery(PreparedStatement.java:51) at weblogic.jdbc.rmi.internal.PreparedStatementImpl.executeQuery(PreparedStatementImpl.java:56) at weblogic.jdbc.rmi.SerialPreparedStatement.executeQuery(SerialPreparedStatement.java:42) at com.XXXX 생략 at ……..

24. Slow down in WAS & User AP CASE 4. High CPU usage When monitoring CPU usage by top,glance. WAS process consumes a lot of CPU - almost 90~100% Find it using tools below Sun : prstat,pstack,thread dump AIX : ps –mp,dbx,thread dump HP : glance,thread dump See a document “How to find bottleneck in J2EE application “ in http://www.j2eestudy.co.kr

25. Slow down in WAS & User AP CASE 4. High CPU usage Example in HP UX HP glance Start “glance” Press “G” and enter the WAS PID Find the TID that consumes a lot of CPU resource Get a thread dump Find the thread in Thread dump that has a matched LWID with this TID And find the reason and fix it

26. Slow down in WAS & User AP How to prevent slow down & hang up Use clustering (use more than 2 WAS instance) Make “Dedicate thread group” for each work Plz make “Good Application that has no risk!!”

27. Slow down in WAS & User AP Summarize Thread dump is snapshot of Java Application. If u meet a slowdown situation, Get a thread dump. Analysis thread dump. And fix it..

28. Slow down in other resources

29. Slow down in other resources User AP WAS JVM DBMS Web Server Network Client Legacy

30. Slow down in other resources Slow down in JVM JVM memory layout Minor GC,Full GC

31. Slow down in other resources Slow down in JVM Full GC takes a lot of time and it freeze the WAS. In the high load, after full GC finished, request can be gathered suddenly. Reduce un-needed memory usage JVM Memory tuning is needed

32. Slow down in other resources Slow down in WebServer Webserver doesn’t make a slow down almost time Use Keep-Alive between WebServer and Client ※ Apache Keep Alive http:// httpd .apache.org/docs-2.0/mod/core.html# keepalive

33. Slow down in other resources Slow down in network Get a enough bandwidth Tuning TCP/IP Kernel parameter in OS  some times it brings slowdown Tuning buffer size Connection abort secs etc. This parameter is provided from WAS vendor ※ WebLogic TCP/IP Kernel Parameter http://e-docs. bea .com/ wls /docs81/ plugins / plugin _ params .html#1143055

34. Slow down in other resources Slow down in DBMS Tune DBMS (It’s not a issue of this session) We can profiling execute time of SQL ※ h ttp://eclipse.new21.org/phpBB2/viewtopic.php?printertopic=1&t=380&start=0&postdays=0&postorder=asc&vote=viewresult ※ http://www.j2eestudy.co.kr/qna/bbs_read.jsp?table=j2ee&db=qna0104&id=5&searchBy=subject&searchKey=sql&block=0&page=0

35. Common mistake in J2ee developer

36. Common mistake in J2ee developer Java Programming Servlet/JSP Programming JDBC Programming EJB Programming

37. Common mistake in J2ee developer Common mistake in Java Programming Do not use String class in complex string operation Close socket and file after use it Use synchronized block appropriately

38. Common mistake in J2ee developer Common mistake in Servlet/JSP programming JSP buffer size <% page buffer=“128kb” %> Member variable <%! Parameter param; %> Use synchronized mehtod Out of memory in file uploading

39. Common mistake in J2ee developer Common mistake in JDBC programming Close stmt, pstmt when using Connection Pooling Out of memory in Bigsize query result Do not save the result in memory (Vector etc..) Connection Leak conn = getConnection(); try{ do something }catch(Exception e){ dosomething(); } }finally{ if(stmt!=null) stmt.close(); if(conn!=null) conn.close(); }

40. Common mistake in J2ee developer Common mistake in EJB programming Study and use EJB in appropriate place Remove EJB after use it (SFSB) Reduce JNDI look up Caching Home Interface Do not use!! Rollback & Commit in CMT. Do not!! use hot deploy in production mode

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