Bug 56717

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.