[Bug 56139] New: "SeedGenerator Thread" warnings when running tests on Windows

[bu...@apache.org]

https://issues.apache.org/bugzilla/show_bug.cgi?id=56139

            Bug ID: 56139
           Summary: "SeedGenerator Thread" warnings when running tests on
                    Windows
           Product: Tomcat 8
           Version: 8.0.3
          Hardware: PC
            Status: NEW
          Severity: minor
          Priority: P2
         Component: Catalina
          Assignee: dev@tomcat.apache.org
          Reporter: knst.kolinko@gmail.com

Reviewing testsuite logs when running on Windows, I noted the following error
messages:

<date, time> org.apache.catalina.loader.WebappClassLoader
clearReferencesThreads
SEVERE: The web application [/foo] appears to have started a thread named
[SeedGenerator Thread] but has failed to stop it. This is very likely to create
a memory leak.

The above warning is from
org.apache.catalina.authenticator.TestDigestAuthenticator, but there are other
test cases that display it.

This is observed when testing on Windows 7 using
Tomcat 8.0.3 +Oracle Java 7u51 (32-bit)
Tomcat 7.0.52 +Oracle Java 6u45 (32-bit)
Tomcat 7.0.52 +Oracle Java 7u51 (32-bit)


Googling by the thread name, I found openjdk7 source code for
sun.security.provider.SeedGenerator class at [1]

[1]
http://www.docjar.com/html/api/sun/security/provider/SeedGenerator.java.html


To reproduce on an usual Tomcat instance, on Windows:
1). Create bin/setenv.bat:

set CATALINA_OPTS=-Djava.security.egd=file:/dev/./urandom

2). Start Tomcat. Note what web application was deployed and started first. In
my case it is "docs".

3). Trigger reload or redeploy of the web application (touch its
WEB-INF/web.xml, or rename docs -> docs1).

After this, an "appears to have started a thread named [SeedGenerator Thread]"
message is logged in catalina.<date>.log file.

(It does not matter whether the application actually generates session ids. It
matters that it was the first to start session id generator).



My conclusion:
===============
1. This is triggered by the following setting in build.properties.default file:
test.jvmarg.egd=-Djava.security.egd=file:/dev/./urandom

If the file "/dev/urandom" is not readable (e.g. on Windows, may be on some
unix systems as well), SeedGenerator fallbacks to an algorithm that creates
that "SeedGenerator Thread" thread.

2. Workaround:
Redefine this property in custom build.properties file.
Using any 1 of the following 2 lines works. The message disappears from test
logs.

test.jvmarg.egd=-Djava.security.egd=file:/dev/urandom

test.jvmarg.egd=

(The "file:/dev/urandom" value is considered by SeedGenerator class as a
special value, a marker to use native implementation of random seed generator).


Possible fixes:
================
1. Document this effect in places where "java.security.egd" property is
mentioned.

A web application should not use such value of "java.security.egd" property
when /dev/urandom is not readable.

(I know two places: Migration guide, "FasterStartUp" wiki page)

2. Fix configuration of the tests.

Maybe either document this in testing section of BUILDING.txt,
or move this property definition into build.xml, making it conditional on
<available file="/dev/urandom">.

3. Can JreMemoryLeakPreventionListener guard against this?
Maybe it can, by creating a SecureRandom instance.

Generally, I see no need for such guard there, because trying to use
/dev/urandom on a system where such file is not readable  is a blatant
configuration error.


4. Can clearReferencesThreads turn a deaf ear to SeedGenerator thread?

I think it should not. I think it is a read issue that pins TCCL in memory.

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[Bug 56139] "SeedGenerator Thread" warnings when running tests on Windows

[bu...@apache.org]

https://issues.apache.org/bugzilla/show_bug.cgi?id=56139

Mark Thomas <ma...@apache.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
                 OS|                            |All

--- Comment #1 from Mark Thomas <ma...@apache.org> ---
Possible fix 2 looked like the best option to me so I implemented in trunk for
8.0.4 and 7.0.x for 7.0.53.

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