https://issues.apache.org/bugzilla/show_bug.cgi?id=56717
Bug ID: 56717
Summary: MapperListener does not remove its listeners. It
matters for repeated starts of embedded Tomcat,
Product: Tomcat 8
Version: 8.0.9
Hardware: PC
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
Assignee: dev@tomcat.apache.org
Reporter: knst.koli...@gmail.com
Debugged om the current trunk at 1610244, between 8.0.10 and 8.0.11.
Steps to reproduce:
1. Add the following lines to build.properties
test.entry=org.apache.catalina.core.TestStandardContext
test.entry.methods=testFlagFailCtxIfServletStartFails
2. I added log.info("...", new RuntimeException()) to Mapper.addHost(),
Mapper.removeHost()
3. Run the test case.
The test case performs "tomcat.stop(); tomcat.start();" twice.
Actual behaviour:
During the second tomcat.start() the Mapper.addHost() is called twice with the
same host. It results in an error message,
> SEVERE [main] org.apache.catalina.mapper.Mapper.addHost Duplicate Host
> [localhost]. The name is already used by Host [localhost]. This Host will be
> ignored.
Expected behaviour:
No such message.
>From debug stacktraces that I printed in addHost(), I see that during the
second start the two addHost() calls have the following stack traces:
[[[
java.lang.RuntimeException
at org.apache.catalina.mapper.Mapper.addHost(Mapper.java:95)
at
org.apache.catalina.mapper.MapperListener.registerHost(MapperListener.java:295)
at
org.apache.catalina.mapper.MapperListener.lifecycleEvent(MapperListener.java:482)
at
org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at
org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at
org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:402)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:168)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1396)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1386)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
]]]
and
[[[
java.lang.RuntimeException
at org.apache.catalina.mapper.Mapper.addHost(Mapper.java:95)
at
org.apache.catalina.mapper.MapperListener.registerHost(MapperListener.java:295)
at
org.apache.catalina.mapper.MapperListener.startInternal(MapperListener.java:110)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at
org.apache.catalina.core.StandardService.startInternal(StandardService.java:450)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at
org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:760)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.startup.Tomcat.start(Tomcat.java:340)
at
org.apache.catalina.startup.TomcatBaseTest$TomcatWithFastSessionIDs.start(TomcatBaseTest.java:410)
at
org.apache.catalina.core.TestStandardContext.testFlagFailCtxIfServletStartFails(TestStandardContext.java:917)
(... JUnit code...)
]]]
The second stack trace with "MapperListener.startInternal()" is the expected
one. The same stack trace is observed during the first tomcat.start().
The first stack trace with "MapperListener.lifecycleEvent()" is an unexpected
one. It is caused by the lifecycle listener still being registered on Host.
The MapperListener.startInternal() method contains line
> addListeners(engine);
As listeners are stored in a list, it means that the same listener will be
added the second time. I expect that if one adds the thirds tomcat.start() call
to the test case, it will cause Mapper.addHost() to be called three times.
That said, I think there is not much of a problem from calling addHost() more
than once for the same host (e.g. Mapper.addContextVersion() may call it
silently). Thus I'll change Mapper.addHost() to do not treat such repeated
calls as an error.
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