Tomcat sometimes loses HttpSession when 2 mod_jk workers have different hosts

[David Crane <da...@donorschoose.org>]

Has anyone had problems with Tomcat losing the HttpSession when Apache
uses mod_jk configured with 2 normal workers connected to *different*
hosts?  I have boiled down to the following test case:

 

    worker.list=customers,staff

 

    worker.customers.type=ajp13

    worker.customers.host=host01

    worker.customers.port=8009

    worker.customers.retries=4

    worker.customers.connect_timeout=10000

    worker.customers.prepost_timeout=10000

    worker.customers.connection_pool_timeout=600

 

    worker.staff.reference=worker.customers

    worker.staff.host=host02

 

This is a simplified version of my Apache directives that route to those
workers:

 

   JkMount /* customers

   JkMount /admin/* staff

   JkUnMount /images/* customers

 

The failure surfaces in our code when the Tomcat HttpServletRequest
request.getSession(false) returns null while processing the POST of the
form request.  The JSESSION cookie in the browser when the form loaded
was correct, i.e., the same as the value right after I submitted my
successful request to the login form.

 

Strangely the failure only affects a couple of our /admin/* pages and --
stranger still -- only when worker.list includes both workers and the
host set for those workers is different.  If I only activate "staff", it
works.  If I change worker.customers.host=host02 to match with "staff",
it works.  It doesn't matter if either or both hosts are actually the
localhost or a remote host -- if they differ, there is a failure, but
only for a couple page requests.  

 

Finally, all of these pages worked with the identical JkMount directives
with an older, more complicated version of workers.properties that used
a load-balanced worker pool in place of "customers" (yes, the pool
included a connection to host02).

 

We have the following platform:

 

  Linux:    Red Hat Enterprise Linux ES release 4 (Nahant Update 4)

            Kernel 2.6.9-42.0.3.ELsmp

  Apache:   2.2.3

            Using prefork MPM

            Apache Tomcat Connector mod_jk/1.2.21

  Tomcat:   5.5.17.0

  JVM:      1.5.0_08-b03

  Spring:   Framework: 1.2.9

            Web Flow: 1.0.3

 

Thanks,

David Crane

DonorsChoose.org