This configuration & test worked just fine with 1.2.3.Final and it is broken in 1.2.4.Final, so we have a regression here, I guess.

ProxyPassMatch ^/app/static/ !
ProxyPass /app balancer://qacluster stickysession=JSESSIONID|jsessionid nofailover=on
ProxyPass / !
ProxyPassReverse /app balancer://qacluster
ProxyPassReverseCookieDomain / /app/
ProxyPassReverseCookiePath / /app/
ProxyPreserveHost on

Accessing e.g. /app/clusterbench/requestinfo/ returns HTTP 503. requestinfo comes from the famous CommonRequestInfoServlet.java.

mod_cluster 1.2.3 ProxyPass test:

Failed tests

• modProxyOnlyPartOfUrlSpaceTest: Known fail: JBQA-7899 Assert #10 Session ID must always be the same.
• modProxyWithoutSessionId: Assert #1, fail, known as MODCLUSTER-334, http://10.16.45.160:2080/clusterbench/requestinfo/ should have been available...

mod_cluster 1.2.4 ProxyPass test:

Failed tests

• modProxyOnlyPartOfUrlSpaceTest: Assert #1, fail, http://10.16.45.160:2080/app/clusterbench/requestinfo/ should have been available...
• modProxyWithoutSessionId: Assert #1, fail, known as MODCLUSTER-334, http://10.16.45.160:2080/clusterbench/requestinfo/ should have been available...

What the test does is it accesses various URLs, getting either static content from httpd or a dynamic one from application server.

Browse the attached files for complete configs, debug logs and test results. Ping me, if the zipped file structure does not make sense to you...