Newbie Qu - details of graceful restart on Windows

[dh...@lexmark.com]

[I asked this on the user list, and think it should have been asked
here...]

Hi,

I'm quite new to Apache, and trying to understand what a graceful restart
on Windows actually does.  I'm running Apache with mod_jk with multiple
Tomcats.  When we add a new Tomcat, I would like to update the
workers.properties file and then restart Apache so the changes take effect.

Would anybody be able to explain exactly what happens, or point me to
documentation that already exists?  I've searched the mailing lists and
googled a lot, with not much detail.

My main concern is whether its possible for requests to be dropped during
this process, and whether session affinity is maintained - eg if a browser
is already talking to a certain Tomcat, will it continue to talk to exactly
that one after the restart?

Many thanks,

David

Re: Newbie Qu - details of graceful restart on Windows

["William A. Rowe, Jr." <wr...@rowe-clan.net>]

At 11:38 AM 6/6/2005, dhay@lexmark.com wrote:
>[I asked this on the user list, and think it should have been asked
>here...]

Off topic.  See my response to users@.

[users@httpd] Re: Newbie Qu - details of graceful restart on Windows

["William A. Rowe, Jr." <wr...@rowe-clan.net>]

At 11:38 AM 6/6/2005, dhay@lexmark.com wrote:
>[I asked this on the user list, and think it should have been asked
>here...]

No, it did belong on the users list :)

>I'm quite new to Apache, and trying to understand what a graceful restart
>on Windows actually does.  I'm running Apache with mod_jk with multiple
>Tomcats.  When we add a new Tomcat, I would like to update the
>workers.properties file and then restart Apache so the changes take effect.
>
>Would anybody be able to explain exactly what happens, or point me to
>documentation that already exists?  I've searched the mailing lists and
>googled a lot, with not much detail.

The defintion of graceful means that existing requests are served
out, and when all are finished, that worker process ends.  In the
interim, new worker process(es - 1 on win32) are started to serve
every new incoming request.

>My main concern is whether its possible for requests to be dropped during
>this process, and whether session affinity is maintained - eg if a browser
>is already talking to a certain Tomcat, will it continue to talk to exactly
>that one after the restart?

Of course not, when you talk about a 'browser talking to Apache'
this usually consists of many separate requests, one after another
(and sometimes in parallel.)  The next request initiated after the
graceful restart will speak to a new Apache instance.

The exception is a keep-alive request.  When Apache is gracefully
restarting, the old process is told to honor no more keep-alive
requests, and terminates the connections after satisfying the next
request.  (It tells the client that the connection will not be 
kept-alive, of course.)

How you configure or restart tomcat on the backend is a different 
issue altogether.

Bill






---------------------------------------------------------------------
The official User-To-User support forum of the Apache HTTP Server Project.
See <URL:http://httpd.apache.org/userslist.html> for more info.
To unsubscribe, e-mail: users-unsubscribe@httpd.apache.org
   "   from the digest: users-digest-unsubscribe@httpd.apache.org
For additional commands, e-mail: users-help@httpd.apache.org