mod_jserv/7275: JServServletManager starts a new "session check thread" on each zone reload!

[Babak Kunze <bk...@cm-ag.de>]

>Number:         7275
>Category:       mod_jserv
>Synopsis:       JServServletManager starts a new "session check thread" on each zone reload!
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    jserv
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Mon Feb 19 09:40:02 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     bk@cm-ag.de
>Release:        1.3.17
>Organization:
apache
>Environment:
All machines (plattform independent)
>Description:
When JServServletManager.checkReload(JServSendError errorHanlder) decides to perform a reload it calls init(JServSendError errorHanlder) after reinstantiating the classloader! After all the work is done, a new Housekeeping thread is started.

Each time init has been called, a new housekeeping-thread is started, whether or not we allready have a housekeeper. This leads to an increasing number of threads after servlets have been refreshed several times. Since these threads continue to work as daemons without termination-condition, the environment will be populated with useless threads all doing the same thing an synchronizing on all sessions every 5 seconds!
>How-To-Repeat:
Touch the zone file of a running jserv several times and take a look at the number of threads in the VM. 
>Fix:
Include a instance variable:

	boolean haveHousekeeper = false;

Check for this flag to see, if we need a new thread or we allready have one! 

Another way is to ask the housekeeper to terminate gracefully before init() is called. The second way is more preferable, since it prevents the housekeeper to disturb the serialization of the sessions, during reinit.

>Release-Note:
>Audit-Trail:
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