https://bz.apache.org/bugzilla/show_bug.cgi?id=57743
Bug ID: 57743
Summary: Jar files in <webapp>/WEB-INF/lib are kept open,
preventing redeploy
Product: Tomcat 8
Version: 8.0.20
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
Assignee: dev@tomcat.apache.org
Reporter: pa...@semmle.com
Created attachment 32592
--> https://bz.apache.org/bugzilla/attachment.cgi?id=32592&action=edit
A patch against AbstractResourceSet.java, adding a call to gc() when it is
destroyed.
As described in 56390, keeping jar files in a webapp folder open will prevent
the application from being undeployed/redeployed on file systems which don't
like open files to be deleted (in practice, that seems to mean Windows-based
systems or NFS mounts).
Having observed the problem with tomcat 8.0.20, which is meant to contain the
fix for 56390, I believe I have uncovered the root cause. Here's what happens,
in my scenario:
- A new .war is copied into $CATALINA_HOME/webapps; this is picked up by
`HostConfig.checkResources()`, which decides to redeploy the app.
- To do this, it first undeploys it (HostConfig.java:1250 in the TOMCAT_8_0_20
tag), and then attempts to delete the exploded war (line 1251).
- In my case, the undeploy triggered a servlet's `destroy()` method, which
triggered some class loading from WEB-INF/lib. Thus, the context's
`WebResourceRoot` was used immediately before the attempt to delete the webapp
folder, and opened a jar file.
- Even though the `JarInputStreamWrapper` was properly closed, the handle to
the jar remains open -- by design of `AbstractArchiveResource`, it is not
closed immediately but with the next periodically scheduled call to `gc()`, as
part of `StandardRoot.backgroundProcess()`.
As a result, when $CATALINA_HOME is on an NFS mount tomcat fails to delete the
exploded webapp directory, and things go bad.
The attached patch fixes the problem in my testing; it simply changes
`AbstractResourceSet.destroyInternal()` so that instead of doing nothing it
calls `gc()`, which will close any jar files which no longer have open input
streams. This seems like it's necessary to avoid a resource leak even on
systems that allow the deletion of open files, since if I'm not mistaken after
the context has been detached it will no longer receive `gc()` calls from the
background process thread.
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