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Posted to users@tomcat.apache.org by lightbulb432 <ve...@hotmail.com> on 2007/09/12 16:59:58 UTC
Servlet Redeployment in Production
What does Tomcat do when, in production, a new version of a WAR file that's
currently being accessed is deployed? I've heard generally that you don't
enable the auto-deployment feature in production, but assume you're aiming
for a five-nines environment and the requirement is hot redeployment of the
application.
So here's the scenario: users are accessing a given context continually. An
administrator literally drops into the webapps folder a new WAR file with
the same name as the context above. What happens from a technical
perspective, in terms of synchronization, consistency of existing sessions
that were on the old webapp, and much more?
Before spoiling the surprise for me, can anyone point me to the relevant
classes/methods in the Tomcat source code to take a look at? (Then when I
can't figure it out, I'll come back and ask you to spoil the surprise :) I'd
like to get better at looking through a code base and figuring these things
out, so hopefully someone can guide me in this.
Thanks.
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Re: Servlet Redeployment in Production
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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lb,
lightbulb432 wrote:
>
>
> Christopher Schultz-2 wrote:
>> I would argue that autodeploy doesn't help much in this case, but we'll
>> stick with that assumption for this discussion.
>
> I realize it wouldn't help for things like database changes, but what about
> changes to the structure of the HttpSession map, or the cookie structure, or
> something that has to do at the web application?
I just meant that auto-deployment doesn't really help with uptime.
I'm not sure I understand your follow-up question.
>> I'd start with org.apache.catalina.StandardContext (and, specifically,
>> the "reload" method), since that's the thing being reloaded.
>
> Where could I find the code where Tomcat stores its definitive list of all
> the current, active HttpSessions? (Where's the structure that Tomcat adds a
> newly created HttpSession to, and from which it removes timed-out or
> invalidated HttpSessions, and the code that manipulates it?)
You should just download the code and start looking around. It's not
hard to follow the action starting from what happens when the request
has getSession() called.
- -chris
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Re: Servlet Redeployment in Production
Posted by lightbulb432 <ve...@hotmail.com>.
Christopher Schultz-2 wrote:
>
>> What does Tomcat do when, in production, a new version of a WAR file
>> that's
>> currently being accessed is deployed? I've heard generally that you don't
>> enable the auto-deployment feature in production, but assume you're
>> aiming
>> for a five-nines environment and the requirement is hot redeployment of
>> the
>> application.
>
> I would argue that autodeploy doesn't help much in this case, but we'll
> stick with that assumption for this discussion.
I realize it wouldn't help for things like database changes, but what about
changes to the structure of the HttpSession map, or the cookie structure, or
something that has to do at the web application?
I'd start with org.apache.catalina.StandardContext (and, specifically,
> the "reload" method), since that's the thing being reloaded.
Where could I find the code where Tomcat stores its definitive list of all
the current, active HttpSessions? (Where's the structure that Tomcat adds a
newly created HttpSession to, and from which it removes timed-out or
invalidated HttpSessions, and the code that manipulates it?)
--
View this message in context: http://www.nabble.com/Servlet-Redeployment-in-Production-tf4429878.html#a12758041
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Re: Servlet Redeployment in Production
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA1
Lb,
lightbulb432 wrote:
> What does Tomcat do when, in production, a new version of a WAR file that's
> currently being accessed is deployed? I've heard generally that you don't
> enable the auto-deployment feature in production, but assume you're aiming
> for a five-nines environment and the requirement is hot redeployment of the
> application.
I would argue that autodeploy doesn't help much in this case, but we'll
stick with that assumption for this discussion.
> So here's the scenario: users are accessing a given context continually. An
> administrator literally drops into the webapps folder a new WAR file with
> the same name as the context above. What happens from a technical
> perspective, in terms of synchronization, consistency of existing sessions
> that were on the old webapp, and much more?
Reading the code would provide a much better explanation that one of us
essentially regurgitating the code as pseudocode.
> Before spoiling the surprise for me, can anyone point me to the relevant
> classes/methods in the Tomcat source code to take a look at? (Then when I
> can't figure it out, I'll come back and ask you to spoil the surprise :) I'd
> like to get better at looking through a code base and figuring these things
> out, so hopefully someone can guide me in this.
I'd start with org.apache.catalina.StandardContext (and, specifically,
the "reload" method), since that's the thing being reloaded.
- -chris
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