C3P0 apparent deadlock when the threads are all empty?
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C3P0 apparent deadlock when the threads are all empty?
I'm using C3P0 as a connection pool in Tomcat, and I'm seeing very worrying errors:
2010-09-16 13:25:00,160 [Timer-0] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks! 2010-09-16 13:25:01,407 [Timer-0] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Complete Status: Managed Threads: 10 Active Threads: 0 Active Tasks: Pending Tasks: com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@6e4151a7 Pool thread stack traces: Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#6,5,main] java.lang.Object.wait(Native Method) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main] java.lang.Object.wait(Native Method) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main] java.lang.Object.wait(Native Method) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main] java.lang.Object.wait(Native Method) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#5,5,main] java.lang.Object.wait(Native Method) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4,5,main] java.lang.Object.wait(Native Method) ... many more, exact same stack trace Line 534 is:
while (true) { Runnable myTask; synchronized ( ThreadPoolAsynchronousRunner.this ) { while ( !should_stop && pendingTasks.size() == 0 ) ThreadPoolAsynchronousRunner.this.wait( POLL_FOR_STOP_INTERVAL ); // <- here if (should_stop) ... It looks very much like all the threads are idle. They're waiting for work. 0 active threads, and only 1 task to complete. Any clues on what's going wrong?
Here's the configuration:
ds.setUser(userName); ds.setPassword(password); ds.setMaxPoolSize(16); ds.setMaxConnectionAge(1800); ds.setAcquireRetryAttempts(4); ds.setMaxIdleTime(900); ds.setNumHelperThreads(10); ds.setCheckoutTimeout(1000); Answer by Thomas Weber for C3P0 apparent deadlock when the threads are all empty?
This sounds like you have already acquired a connection from the pool and do not return it in time.
C3P0 determines "apparent deadlocks" when a connection is acquired but not returned to the pool within the deadlock detection timeout.
If you move the connection acquisition closer to the "action" and immediately return it to the pool after the database work is done, this message will disappear.
Answer by ChristiaanP for C3P0 apparent deadlock when the threads are all empty?
This will sort out your problem
ds.setMaxStatements(1000); ds.setMaxStatementsPerConnection(100); (the maximum number of prepared statments your system can execute on a single connection) check out : https://forum.hibernate.org/viewtopic.php?t=947246&highlight=apparent+deadlock+c3p0
Remember to close your statements after you are done with them !!
Answer by Zon for C3P0 apparent deadlock when the threads are all empty?
I had the same (ustable to detect) problem solved by correctly closing Statement and Resultset instances (somehow left unclosed):
String SQL = "SELECT 1"; try { con = DriverManager.getConnection(host, userName, userPassword); stmt = con.prepareStatement(SQL, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); try { rs = stmt.executeQuery(SQL); try { rs.next(); // ... } finally { rs.close(); } } finally { stmt.close(); } } catch (SQLException ex) { Logger.getLogger(MyClass.class.getName()).log(Level.SEVERE, null, ex); } Answer by eebbesen for C3P0 apparent deadlock when the threads are all empty?
I just experienced a similar issue against an Oracle database, but in my case Managed Thread and Active Thread counts were the same.
Managed Threads: 3 Active Threads: 3 For me it was actually an authentication error but appeared as the APPARENT DEADLOCK error because of the way I was doing login auditing.
2013-08-12 11:29:04,910 [Timer-4] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@34996454 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks! 2013-08-12 11:29:04,914 [Timer-4] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@34996454 -- APPARENT DEADLOCK!!! Complete Status: Managed Threads: 3 Active Threads: 3 Active Tasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@6730b844 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2f91ad49 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@507ac05 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1) Pending Tasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3aae7ed7 Pool thread stack traces: Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main] java.net.SocketInputStream.socketRead0(Native Method) java.net.SocketInputStream.read(SocketInputStream.java:150) java.net.SocketInputStream.read(SocketInputStream.java:121) oracle.net.ns.Packet.receive(Packet.java:300) oracle.net.ns.DataPacket.receive(DataPacket.java:106) oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315) oracle.net.ns.NetInputStream.read(NetInputStream.java:260) oracle.net.ns.NetInputStream.read(NetInputStream.java:185) oracle.net.ns.NetInputStream.read(NetInputStream.java:102) oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124) oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80) oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137) oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290) oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760) oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401) oracle.jdbc.driver.PhysicalConnection.(PhysicalConnection.java:546) oracle.jdbc.driver.T4CConnection.(T4CConnection.java:236) oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32) oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main] java.net.SocketInputStream.socketRead0(Native Method) java.net.SocketInputStream.read(SocketInputStream.java:150) java.net.SocketInputStream.read(SocketInputStream.java:121) oracle.net.ns.Packet.receive(Packet.java:300) oracle.net.ns.DataPacket.receive(DataPacket.java:106) oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315) oracle.net.ns.NetInputStream.read(NetInputStream.java:260) oracle.net.ns.NetInputStream.read(NetInputStream.java:185) oracle.net.ns.NetInputStream.read(NetInputStream.java:102) oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124) oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80) oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137) oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290) oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760) oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401) oracle.jdbc.driver.PhysicalConnection.(PhysicalConnection.java:546) oracle.jdbc.driver.T4CConnection.(T4CConnection.java:236) oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32) oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main] java.net.SocketInputStream.socketRead0(Native Method) java.net.SocketInputStream.read(SocketInputStream.java:150) java.net.SocketInputStream.read(SocketInputStream.java:121) oracle.net.ns.Packet.receive(Packet.java:300) oracle.net.ns.DataPacket.receive(DataPacket.java:106) oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315) oracle.net.ns.NetInputStream.read(NetInputStream.java:260) oracle.net.ns.NetInputStream.read(NetInputStream.java:185) oracle.net.ns.NetInputStream.read(NetInputStream.java:102) oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124) oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80) oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137) oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290) oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380) oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760) oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401) oracle.jdbc.driver.PhysicalConnection.(PhysicalConnection.java:546) oracle.jdbc.driver.T4CConnection.(T4CConnection.java:236) oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32) oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547) Answer by atzu for C3P0 apparent deadlock when the threads are all empty?
I've had the same problem but the cause was a bit hard to spot as it was caused by some simultaneous resources trying to acquire a connection at the same time.
As you can read if the pool had not been initialized the code provided to init it by calling a setup function.
public Connection getConnection() throws SQLException { if (mCPDS == null) { setupPool(); } return mCPDS.getConnection(); } The problem was that many resources were trying to acquire the connection at the beginning of the program so more than one were instantiating the pool causing your problem after a while.
The solution was just to declare the method synchronized to keep out other resources while one has called the method and it's still inside instantiating the pool for instance.
public synchronized Connection getConnection() throws SQLException { if (mCPDS == null) { setupPool(); } return mCPDS.getConnection(); } This may be a design error for not using a singleton but fixes the problem lacking some performance.
Answer by colin for C3P0 apparent deadlock when the threads are all empty?
We ran into this problem and solved it by adding this to the C3P0 config:
as per: this from the C3P0 doc
Fatal error: Call to a member function getElementsByTagName() on a non-object in D:\XAMPP INSTALLASTION\xampp\htdocs\endunpratama9i\www-stackoverflow-info-proses.php on line 72
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