问题
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);
回答1:
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.<init>(PhysicalConnection.java:546)
oracle.jdbc.driver.T4CConnection.<init>(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.<init>(PhysicalConnection.java:546)
oracle.jdbc.driver.T4CConnection.<init>(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.<init>(PhysicalConnection.java:546)
oracle.jdbc.driver.T4CConnection.<init>(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)
回答2:
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.
回答3:
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 !!
回答4:
My comment on answer https://stackoverflow.com/a/18192588/1019307 received enough up-votes to suggest it should be an answer.
I received this error because I couldn't get through the firewall to the database server. Check to see if that is your problem.
回答5:
@eebbesen, I got the same error as you did. I am running Tomcat version 9.0.6. I have hibernate core ver 5.2.10, hibernate c3p0 ver 3.6.3 in my maven project. Mine was not an authentication error, but rather due to me having previously changed the name of my computer. This did not have an immediate effect on tomcat, but upon a restart of my machine, when I tried to bring up tomcat again via eclipse (Oxygen 2), I could no longer start eclipse due exactly to the issue you raised.
I googled this and I found this link, which tipped me off to the issue:
https://community.oracle.com/thread/339825
where it says:
First see if OracleServiceXE and OracleXETNSListener services are running. Replace 127.0.0.1 in the url, with the IP or the name of your machine. It must match the host declared in the tnsnames.ora file.
Later it mentions where to find this tnsnames.ora file, and for me it was here:
C:\oraclexe\app\oracle\product\11.2.0\server\network\ADMIN
Looking at this tnsnames.ora file, I saw this:
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = MyMachineName-7)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
)
)
But I had recently renamed my machine to MyMachineName-5. I changed the 7 to a 5 and saved the file. I checked the "listener.ora" file in this directory, and it had the same issue:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = MyMachineName-7)(PORT = 1521))
)
)
I changed the 7 to a 5 and saved the file.
Then I opened Task Manager, clicked the "Services" tab, and looked at the "Oracle" services. I did a restart on: OracleXETNSListener, OracleXEClrAgent, OracleServiceXE. I went to restart tomcat in eclipse again, and this time there was now problem.
Appendix:
I also googled this:
https://community.oracle.com/thread/2267906
This lead me to try:
1) Turned off the firewall in Windows Defender (already turned off mcaffee firewall)
2) Started sqlplus to make sure that I could log in with the credentials I was using in my hibernate file: hibernate.cfg.xml
C:\oraclexe\app\oracle\product\11.2.0\server\bin\sqlplus.exe
3) Started the desktop shortcut to Oracle Database 11g
This failed for me even after I fixed the machine name issue though, something I still have to look into.
4) Using dbVisualizer, I tried making a connection to Oracle. This only worked after I resolved the .ora file machine name issue: double click the connection and click the "ping server" button.
回答6:
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.
回答7:
I had the same (was unable 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);
}
回答8:
Hi my friend just to comment, I had the same case. I just configured my spring-hibernate eclipse project and showed up the same exception, it should be noted that my project still does not have any query.
I resolved that issue with below steps:
1) Clean project : Project--> Clean... 2) Build project : Project--> Build Project
I hope it works for you.
回答9:
I've just had the same problem suddenly: after noticing that the deadlock was present only when launching my application in debug mode (I'm using IntelliJ) and it was fine when running with normal run, I started to dig it.
I finally figured out that a breakpoint was blocking the connection: I don't know why Intellij didn't "listen" that the application was passing through that breakpoint, but was hanged somewhere cause of a breakpoint, and this was causing appartent deadlock
After removing all breakpoints in my project, everything started smooth again.
Hope this helps someone
回答10:
We ran into this problem and solved it by adding this to the C3P0 config:
<property name="statementCacheNumDeferredCloseThreads" value="1"/>
as per: this from the C3P0 doc
回答11:
Similar problem was encountered on glassfish4 server while deploying the application. Turned out it was a database configuration issue. Just make sure your database connectivity configurations are proper, verify that the hostname provided in the configuration allows the connection to database. Try connecting to the database manually with the configured username and the hostname/domain. If required, allow the db user to connect from the required domain. Rebuild the application with correct db configurations and then deploy it.
来源：https://stackoverflow.com/questions/3730844/c3p0-apparent-deadlock-when-the-threads-are-all-empty