Failure executing GET /engine and Possible Related DB Pool Exhaustion


#1

We run a periodic health check against our Camunda engine to ensure that it is healthy. This health check simply issues the REST API request: GET /engine.

We noticed this morning that this request was failing. The Catalina log for this time period has numerous log entries consisting of two types of errors:

  1. a failure executing GET /engine due to java.io.IOException: Broken pipe
  2. a database error due to an empty connection pool.

It seems that these errors are related, as they are interspersed in the log. But I am not sure if they are related or not.

The log entries are shown below at the end of this post.

We are running Camunda 7.5, stand-alone, using an AWS Aurora DB.

Here is our DB configuration:

<Resource name="jdbc/ProcessEngine" auth="Container" type="javax.sql.DataSource" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" uniqueResourceName="process-engine" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://<redacted>?autoReconnect=true" username="<redacted" password="<redacted>" maxActive="20" minIdle="5"/>

Do you have any ideas of the cause of either of these errors?
Do you believe that the 2 errors are related?
Perhaps we need some additional DB configuration options?

Here are some of the log entries:

03-Feb-2017 10:08:45.628 SEVERE [http-nio-8080-exec-6076] org.jboss.resteasy.logging.impl.Slf4jLogger.error Failed executing GET /engine
 org.jboss.resteasy.spi.WriterException: org.apache.catalina.connector.ClientAbortException: java.io.IOException: Broken pipe
	at org.jboss.resteasy.core.ServerResponse.writeTo(ServerResponse.java:262)
	at org.jboss.resteasy.core.SynchronousDispatcher.writeJaxrsResponse(SynchronousDispatcher.java:602)
	at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:528)
	at org.jboss.resteasy.core.SynchronousDispatcher.invokePropagateNotFound(SynchronousDispatcher.java:169)
	at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:212)
	at org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.doFilter(FilterDispatcher.java:59)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.camunda.bpm.engine.rest.filter.CacheControlFilter.doFilter(CacheControlFilter.java:41)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1527)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1484)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.connector.ClientAbortException: java.io.IOException: Broken pipe
	at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:393)
	at org.apache.tomcat.util.buf.ByteChunk.flushBuffer(ByteChunk.java:426)
	at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:342)
	at org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:317)
	at org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:110)
	at org.jboss.resteasy.plugins.server.servlet.HttpServletResponseWrapper$DeferredOutputStream.flush(HttpServletResponseWrapper.java:52)
	at org.jboss.resteasy.util.CommitHeaderOutputStream.flush(CommitHeaderOutputStream.java:59)
	at com.fasterxml.jackson.core.json.UTF8JsonGenerator.flush(UTF8JsonGenerator.java:1022)
	at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:891)
	at com.fasterxml.jackson.jaxrs.base.ProviderBase.writeTo(ProviderBase.java:635)
	at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:117)
	at org.jboss.resteasy.plugins.interceptors.encoding.GZIPEncodingInterceptor.write(GZIPEncodingInterceptor.java:104)
	at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:123)
	at org.jboss.resteasy.core.ServerResponse.writeTo(ServerResponse.java:250)
	... 26 more
Caused by: java.io.IOException: Broken pipe
	at sun.nio.ch.FileDispatcherImpl.write0(Native Method)
	at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:47)
	at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93)
	at sun.nio.ch.IOUtil.write(IOUtil.java:65)
	at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:471)
	at org.apache.tomcat.util.net.NioChannel.write(NioChannel.java:127)
	at org.apache.tomcat.util.net.NioBlockingSelector.write(NioBlockingSelector.java:101)
	at org.apache.tomcat.util.net.NioSelectorPool.write(NioSelectorPool.java:173)
	at org.apache.coyote.http11.InternalNioOutputBuffer.writeToSocket(InternalNioOutputBuffer.java:139)
	at org.apache.coyote.http11.InternalNioOutputBuffer.addToBB(InternalNioOutputBuffer.java:197)
	at org.apache.coyote.http11.InternalNioOutputBuffer.access$000(InternalNioOutputBuffer.java:41)
	at org.apache.coyote.http11.InternalNioOutputBuffer$SocketOutputBuffer.doWrite(InternalNioOutputBuffer.java:320)
	at org.apache.coyote.http11.filters.IdentityOutputFilter.doWrite(IdentityOutputFilter.java:93)
	at org.apache.coyote.http11.AbstractOutputBuffer.doWrite(AbstractOutputBuffer.java:256)
	at org.apache.coyote.Response.doWrite(Response.java:503)
	at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:388)
	... 39 more

03-Feb-2017 10:08:45.629 WARNING [http-nio-8080-exec-6047] org.camunda.bpm.engine.rest.exception.ProcessEngineExceptionHandler.toResponse org.camunda.bpm.engine.ProcessEngineException: Process engine persistence exception
	at org.camunda.bpm.engine.impl.interceptor.CommandInvocationContext.rethrow(CommandInvocationContext.java:60)
	at org.camunda.bpm.engine.impl.interceptor.CommandContext.close(CommandContext.java:291)
	at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:113)
	at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(ProcessApplicationContextInterceptor.java:66)
	at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
	at org.camunda.bpm.engine.impl.TaskServiceImpl.getVariablesTyped(TaskServiceImpl.java:205)
	at org.camunda.bpm.engine.rest.sub.task.impl.TaskVariablesResource.getVariableEntities(TaskVariablesResource.java:45)
	at org.camunda.bpm.engine.rest.sub.impl.AbstractVariablesResource.getVariables(AbstractVariablesResource.java:64)
	at sun.reflect.GeneratedMethodAccessor245.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:167)
	at org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:257)
	at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:222)
	at org.jboss.resteasy.core.ResourceLocator.invokeOnTargetObject(ResourceLocator.java:159)
	at org.jboss.resteasy.core.ResourceLocator.invoke(ResourceLocator.java:107)
	at org.jboss.resteasy.core.ResourceLocator.invokeOnTargetObject(ResourceLocator.java:154)
	at org.jboss.resteasy.core.ResourceLocator.invoke(ResourceLocator.java:107)
	at org.jboss.resteasy.core.ResourceLocator.invokeOnTargetObject(ResourceLocator.java:154)
	at org.jboss.resteasy.core.ResourceLocator.invoke(ResourceLocator.java:92)
	at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:542)
	at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:524)
	at org.jboss.resteasy.core.SynchronousDispatcher.invokePropagateNotFound(SynchronousDispatcher.java:169)
	at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:212)
	at org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.doFilter(FilterDispatcher.java:59)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.camunda.bpm.engine.rest.filter.CacheControlFilter.doFilter(CacheControlFilter.java:41)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1527)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1484)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.tomcat.jdbc.pool.PoolExhaustedException: [http-nio-8080-exec-6047] Timeout: Pool empty. Unable to fetch a connection in 30 seconds, none available[size:20; busy:17; idle:3; lastwait:30000].
### The error may exist in org/camunda/bpm/engine/impl/mapping/entity/Task.xml
### The error may involve org.camunda.bpm.engine.impl.persistence.entity.TaskEntity.selectTask
### The error occurred while executing a query
### Cause: org.apache.tomcat.jdbc.pool.PoolExhaustedException: [http-nio-8080-exec-6047] Timeout: Pool empty. Unable to fetch a connection in 30 seconds, none available[size:20; busy:17; idle:3; lastwait:30000].
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:111)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:66)
	at org.camunda.bpm.engine.impl.db.sql.DbSqlSession.selectById(DbSqlSession.java:100)
	at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.selectById(DbEntityManager.java:199)
	at org.camunda.bpm.engine.impl.persistence.entity.TaskManager.findTaskById(TaskManager.java:115)
	at org.camunda.bpm.engine.impl.cmd.GetTaskVariablesCmd.execute(GetTaskVariablesCmd.java:51)
	at org.camunda.bpm.engine.impl.cmd.GetTaskVariablesCmd.execute(GetTaskVariablesCmd.java:33)
	at org.camunda.bpm.engine.impl.interceptor.CommandExecutorImpl.execute(CommandExecutorImpl.java:24)
	at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:104)
	... 43 more
Caused by: org.apache.tomcat.jdbc.pool.PoolExhaustedException: [http-nio-8080-exec-6047] Timeout: Pool empty. Unable to fetch a connection in 30 seconds, none available[size:20; busy:17; idle:3; lastwait:30000].
	at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:672)
	at org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:186)
	at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:127)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:134)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:279)
	at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:72)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:59)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:267)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:137)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:96)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:77)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108)
	... 52 more

#2

I am no Camunda expert, but I have seen errors like that in our WildFly environment (you appear to be using Tomcat). Almost without exception they are the result of Camunda not being able to talk to its back end database.

When using connection pools in WildFly, there is a hard limit on the number of simultaneous connections that are supported. If Camunda exceeds that hard limit, there is generally no fallback other than to throw errors. Unlike configuration that do not use connection pools but instead instantiate a new connection for each transaction, database pools in WildFly have a fixed number of connections. Single transaction sessions are limited only be the number of connections the database itself will support.

Therefore, I would check the statistics, if available, on your database pool connections to see if you have exceeded the predefined limit. In WildFly you can set both an initial and upper limit for the number of pool connections to be used. Depending upon your environment and the database you are using, these settings could be in the thousands if you have an extremely busy server.

Finally, transient errors could manifest themselves in this manner. Camunda is essentially a database driven application so anything that disrupts transactions between Camunda and the database will throw errors. Most every REST call made, particularly those getting history or current data, involve a database transaction. Therefore, check the database server logs for any errors there that might indicate issues. Also, when performing your periodic checks, be sure to retry over a reasonable period before deciding there’s an issue. Camunda is pretty resilient and it can generally ride through any transient problems.


#3

Thank you for your response.

Does anyone from Camunda have anything to add here? Any suggestions for database configuration options with regards to db connections?


#4

Personally, I would just provide as many connections as you think your application server and database can handle, setting a reasonable initial pool. If they don’t “cost” anything, why not?


#5

I am having a very similar problem/stacktrace (see below). It’d be useful to know how this can be resolved/which settings should be changed.

05-Apr-2017 00:11:16.409 SEVERE [http-nio-8080-exec-11] org.jboss.resteasy.logging.impl.Slf4jLogger.error Failed executing POST /process-definition/key/example-waterfall/submit-form
 org.jboss.resteasy.spi.WriterException: org.apache.catalina.connector.ClientAbortException: java.io.IOException: Broken pipe
        at org.jboss.resteasy.core.ServerResponse.writeTo(ServerResponse.java:262)
        at org.jboss.resteasy.core.SynchronousDispatcher.writeJaxrsResponse(SynchronousDispatcher.java:602)
        at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:528)
        at org.jboss.resteasy.core.SynchronousDispatcher.invokePropagateNotFound(SynchronousDispatcher.java:169)
        at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:212)
        at org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.doFilter(FilterDispatcher.java:59)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.camunda.bpm.engine.rest.filter.CacheControlFilter.doFilter(CacheControlFilter.java:41)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
        at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1527)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1484)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.connector.ClientAbortException: java.io.IOException: Broken pipe
        at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:393)
        at org.apache.tomcat.util.buf.ByteChunk.flushBuffer(ByteChunk.java:426)
        at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:342)
        at org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:317)
        at org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:110)
        at org.jboss.resteasy.plugins.server.servlet.HttpServletResponseWrapper$DeferredOutputStream.flush(HttpServletResponseWrapper.java:52)
        at org.jboss.resteasy.util.CommitHeaderOutputStream.flush(CommitHeaderOutputStream.java:59)
        at com.fasterxml.jackson.core.json.UTF8JsonGenerator.flush(UTF8JsonGenerator.java:1022)
        at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:891)
        at com.fasterxml.jackson.jaxrs.base.ProviderBase.writeTo(ProviderBase.java:635)
        at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:117)
        at org.jboss.resteasy.plugins.interceptors.encoding.GZIPEncodingInterceptor.write(GZIPEncodingInterceptor.java:104)
        at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:123)
        at org.jboss.resteasy.core.ServerResponse.writeTo(ServerResponse.java:250)
        ... 26 more
Caused by: java.io.IOException: Broken pipe
        at sun.nio.ch.FileDispatcherImpl.write0(Native Method)
        at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:47)
        at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93)
        at sun.nio.ch.IOUtil.write(IOUtil.java:65)
        at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:471)
        at org.apache.tomcat.util.net.NioChannel.write(NioChannel.java:127)
        at org.apache.tomcat.util.net.NioBlockingSelector.write(NioBlockingSelector.java:101)
        at org.apache.tomcat.util.net.NioSelectorPool.write(NioSelectorPool.java:173)
        at org.apache.coyote.http11.InternalNioOutputBuffer.writeToSocket(InternalNioOutputBuffer.java:139)
        at org.apache.coyote.http11.InternalNioOutputBuffer.addToBB(InternalNioOutputBuffer.java:197)
        at org.apache.coyote.http11.InternalNioOutputBuffer.access$000(InternalNioOutputBuffer.java:41)
        at org.apache.coyote.http11.InternalNioOutputBuffer$SocketOutputBuffer.doWrite(InternalNioOutputBuffer.java:320)
        at org.apache.coyote.http11.filters.IdentityOutputFilter.doWrite(IdentityOutputFilter.java:93)
        at org.apache.coyote.http11.AbstractOutputBuffer.doWrite(AbstractOutputBuffer.java:256)
        at org.apache.coyote.Response.doWrite(Response.java:503)
        at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:388)
        ... 39 more

#6

Are you saying that you’re exhausting your data source pool connections or that you want to set a data source pool?

I don’t see anything in your post that would indicate this is related to the database. Please provide more details.


#7

Am I saying anything at all? I am just asking what this is about, and how to fix it. And the stacktrace in the initial post seems to be related. Do you suggest posting somewhere else, opening a new post? It’d title it “no idea what’s going on - weird stacktrace, please help”


#8

ok, I’ll raise this as an issue in jira to get some help. Thanks.


#9

Hi - just came across this…

OK you have a maximum of 20 connections in the connection pool. If the pool is exhausted, a thread will wait 30s (default) for one to become available. Hence for this exception to be thrown is very unusual.

Heres a few things to consider;
Number of concurrent threads is max size of job executor thread pool plus max concurrent foreground (http connector) threads. Hence you may want to consider setting DB connections to the same number…

That the pool is exhausted with a 30s wait time is possibly a smoking gun - its possible network comms dropped and thus all requests queue up behind the db connection pool. This could be a failover event, a large file transfer across a network etc. You could consider setting test on borrow to true…

regards

Rob


#10

Hey Rob,
thanks for that. We’ll look into this.

Not sure what this here means though (please explain?):

Cheers!
Ben.


#11

Hi Ben,

Test on borrow is a setting in the connection pool settings where a small sql query (eg select 1) is performed to test the connection before use. On reflection Im not sure that this will help that much as you may not be experiencing fine grained transient network failures…

regards

Rob


#12

Thanks again! I think this might be useful as well. We’ll try it out.