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Posted to dev@tomcat.apache.org by Mladen Turk <mt...@apache.org> on 2010/03/10 14:55:41 UTC
Reusing instances
Hi,
Anyone knows what would be the major points that would
be problematic when launching multiple instances in the same
directory.
Lets presume that connectors share the same sockets among
multiple virtual machines using the JVM loaded inside each
Httpd or IIS worker process for example.
As I see it there are few things that would have to be addressed.
1. Session sharing
2. Logging issues (multiple processes write to the same file)
3. What about war deployments
4. Do we have any other resources which access should be
synchronized?
Regards
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Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/11/2010 05:49 PM, jean-frederic clere wrote:
> On 03/11/2010 05:27 PM, Mladen Turk wrote:
>> More important one is to use the web server connectors directly.
>> It's not about speed, but about eliminating connector as a
>> point of failure.
>>
>
> hm You still have to move the data for httpd (in C) to Tomcat (in JAVA)
> so you still have a connector, no?
>
Sort of. However there is no network involved and there are
no protocol issues that arise from marshalling via proxy.
Regards
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Re: Reusing instances
Posted by jean-frederic clere <jf...@gmail.com>.
On 03/11/2010 05:27 PM, Mladen Turk wrote:
> More important one is to use the web server connectors directly.
> It's not about speed, but about eliminating connector as a
> point of failure.
>
hm You still have to move the data for httpd (in C) to Tomcat (in JAVA)
so you still have a connector, no?
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Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/11/2010 05:17 PM, Costin Manolache wrote:
> And what is the problem you are trying to solve ?
>
Those are the same one for which modern web servers
have multiple worker processes.
One JVM crash doesn't kill the server, recycle the
worker process on some condition (memory leak, number of
requests, cpu outage, etc. )
> The old in-process' goal was speed - replacing marshalling with JNI. I don't
> think it gained much.
>
More important one is to use the web server connectors directly.
It's not about speed, but about eliminating connector as a
point of failure.
Regards
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Re: Reusing instances
Posted by Costin Manolache <co...@gmail.com>.
And what is the problem you are trying to solve ?
The old in-process' goal was speed - replacing marshalling with JNI. I don't
think it gained much.
I think app isolation/chrooting and clean versioning/reload are great goals
- but the model is
one app per process.
I fail to see use cases for having multiple webapps in different processes
on same machine, still sharing
directories. Is it to allow >4G heap ? 64bit VMs solve this. Scale ? Better
done with more machines.
Maybe too many cores ?
Costin
On Thu, Mar 11, 2010 at 12:09 AM, Mladen Turk <mt...@apache.org> wrote:
> On 03/11/2010 08:50 AM, jean-frederic clere wrote:
>
>> On 03/11/2010 08:30 AM, Mladen Turk wrote:
>>
>>> On 03/11/2010 07:52 AM, Costin Manolache wrote:
>>>
>>>> On Wed, Mar 10, 2010 at 10:28 PM, Mladen Turk<mt...@apache.org>
>>>> wrote:
>>>>
>>>> On 03/10/2010 11:10 PM, Costin Manolache wrote:
>>>>>
>>>>> You want to have each webapp served by a different process ?
>>>>>> Or even different versions of a webapp in a different process ?
>>>>>>
>>>>>>
>>>>>> First goal is to get rid of connectors and use Tomcat
>>>>> directly inside httpd or IIS or new Commons Runtime
>>>>> (replacing Tomcat Native and Daemon) I'm working on.
>>>>>
>>>>>
>>>> It used to work - about 10 years ago :-)
>>>>
>>>>
>>> Actually didn't. It worked for IIS and Httpd on windows
>>> only since at that time they had a single child process.
>>> Now IIS is the same as httpd with worker mpm.
>>>
>>> That was on of the reasons we kill JK2.
>>> JNI inproc connector simply didn't work.
>>>
>>
>> One of the big problem is that the prefork and worker models may use
>> several process for the same session and you can't fix a session to a
>> JVM process...
>>
>
> Sure. See the initial post. Session sharing is one
> of the things that has to be done.
> However this can be easily managed using shared memory
> or even using memcached
>
>
>
> At the end you needed a flat cluster with one node for
>> each process and that doesn't scale.
>>
>>
> In essence it is a cluster, and that's why the subject title
> is 'reusing instances' since it lives in the same directory.
>
>
> Regards
> --
> ^TM
>
>
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Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/11/2010 08:50 AM, jean-frederic clere wrote:
> On 03/11/2010 08:30 AM, Mladen Turk wrote:
>> On 03/11/2010 07:52 AM, Costin Manolache wrote:
>>> On Wed, Mar 10, 2010 at 10:28 PM, Mladen Turk<mt...@apache.org> wrote:
>>>
>>>> On 03/10/2010 11:10 PM, Costin Manolache wrote:
>>>>
>>>>> You want to have each webapp served by a different process ?
>>>>> Or even different versions of a webapp in a different process ?
>>>>>
>>>>>
>>>> First goal is to get rid of connectors and use Tomcat
>>>> directly inside httpd or IIS or new Commons Runtime
>>>> (replacing Tomcat Native and Daemon) I'm working on.
>>>>
>>>
>>> It used to work - about 10 years ago :-)
>>>
>>
>> Actually didn't. It worked for IIS and Httpd on windows
>> only since at that time they had a single child process.
>> Now IIS is the same as httpd with worker mpm.
>>
>> That was on of the reasons we kill JK2.
>> JNI inproc connector simply didn't work.
>
> One of the big problem is that the prefork and worker models may use
> several process for the same session and you can't fix a session to a
> JVM process...
Sure. See the initial post. Session sharing is one
of the things that has to be done.
However this can be easily managed using shared memory
or even using memcached
> At the end you needed a flat cluster with one node for
> each process and that doesn't scale.
>
In essence it is a cluster, and that's why the subject title
is 'reusing instances' since it lives in the same directory.
Regards
--
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Re: Reusing instances
Posted by jean-frederic clere <jf...@gmail.com>.
On 03/11/2010 08:30 AM, Mladen Turk wrote:
> On 03/11/2010 07:52 AM, Costin Manolache wrote:
>> On Wed, Mar 10, 2010 at 10:28 PM, Mladen Turk<mt...@apache.org> wrote:
>>
>>> On 03/10/2010 11:10 PM, Costin Manolache wrote:
>>>
>>>> You want to have each webapp served by a different process ?
>>>> Or even different versions of a webapp in a different process ?
>>>>
>>>>
>>> First goal is to get rid of connectors and use Tomcat
>>> directly inside httpd or IIS or new Commons Runtime
>>> (replacing Tomcat Native and Daemon) I'm working on.
>>>
>>
>> It used to work - about 10 years ago :-)
>>
>
> Actually didn't. It worked for IIS and Httpd on windows
> only since at that time they had a single child process.
> Now IIS is the same as httpd with worker mpm.
>
> That was on of the reasons we kill JK2.
> JNI inproc connector simply didn't work.
One of the big problem is that the prefork and worker models may use
several process for the same session and you can't fix a session to a
JVM process... At the end you needed a flat cluster with one node for
each process and that doesn't scale.
Cheers
Jean-Frederic
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Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/11/2010 07:52 AM, Costin Manolache wrote:
> On Wed, Mar 10, 2010 at 10:28 PM, Mladen Turk<mt...@apache.org> wrote:
>
>> On 03/10/2010 11:10 PM, Costin Manolache wrote:
>>
>>> You want to have each webapp served by a different process ?
>>> Or even different versions of a webapp in a different process ?
>>>
>>>
>> First goal is to get rid of connectors and use Tomcat
>> directly inside httpd or IIS or new Commons Runtime
>> (replacing Tomcat Native and Daemon) I'm working on.
>>
>
> It used to work - about 10 years ago :-)
>
Actually didn't. It worked for IIS and Httpd on windows
only since at that time they had a single child process.
Now IIS is the same as httpd with worker mpm.
That was on of the reasons we kill JK2.
JNI inproc connector simply didn't work.
Regards
--
^TM
---------------------------------------------------------------------
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Re: Reusing instances
Posted by Costin Manolache <co...@gmail.com>.
On Wed, Mar 10, 2010 at 10:28 PM, Mladen Turk <mt...@apache.org> wrote:
> On 03/10/2010 11:10 PM, Costin Manolache wrote:
>
>> You want to have each webapp served by a different process ?
>> Or even different versions of a webapp in a different process ?
>>
>>
> First goal is to get rid of connectors and use Tomcat
> directly inside httpd or IIS or new Commons Runtime
> (replacing Tomcat Native and Daemon) I'm working on.
>
It used to work - about 10 years ago :-)
> Second is to have application pools where one could
> say: Serve WebAppX inside Default Application Pool
> consisting of 1 ... N processes or use Custom Application
> pool with some process limitation factors (memory, cpu usage, etc)
>
This sounds a bit complex - but the big question is "why" ?
If you do multi-process, you can just go simple and say that one process
runs a single app - thus resolving most security issues ( no longer need
a sandbox ), you can set use limits, etc. Upgrading the app will no longer
leak resources, you can have the old version running for a while, in
parallel
with the new one ( with some tricks in the lb - for example use session to
direct
to the right version ).
Having multi-process and combining multiple apps in a single process
seems pointless.
The other nice thing would be to fire up the process on demand, and kill
them
if not used - and maybe start new processes if needed.
>
> Third goal is to allow graceful restarts which would
> allow to reconfigure the entire VM or redeploy the
> application without down time.
>
Yes, but 1 app ( and one version ) per process would make it easier.
> Those kind of things is done nowadays by using some sort
> of clustering where each node actually behaves like one
> of Httpd's child processes.
>
> First thing I'm going to do is the thorough analysis
> of what actually happens under the hood during different
> engine life stages and see what resources might require
> the synchronization or cross-process sharing and
> how to do that.
>
IMHO if you use such a model, it may be better to change the
directory structure - and have all the files ever created by
an webapp ( including logs, work dir, etc ) under a single tree.
Than you can chroot to it, versioning may also be easier.
>
> I know it might sound very complex, but it's actually
> doing what Tomcat is suppose to do (be a servlet engine),
> so perhaps Tomcat Light would fit in that story.
I don't think it's that hard - starting tomcat7 'standalone', with minimal
config and a different dir structure is easy.
The trick will be the frontend - load balancer plus logic to start the
right
processes.
Costin
>
>
>
> Regards
> --
> ^TM
>
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>
>
Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/12/2010 05:54 PM, Konstantin Kolinko wrote:
> I think that /work folder sharing is out of question. Most of concern
> here is with Jasper, but there can be also other files, and files
> written by applications.
>
That shouldn't be a problem if guarded with some global mutex.
Other option is to have separate work dirs with child id suffix.
> The /webapps folder sharing depends on whether autodeploy feature is
> enabled. Expanding deployed wars and deleting folders when undeploying
> must be done in a single thread. Otherwise there can be security
> issues.
>
Again with global mutex it should work on first served basis.
Regards
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Re: Reusing instances
Posted by Konstantin Kolinko <kn...@gmail.com>.
2010/3/11 Mladen Turk <mt...@apache.org>:
> Second is to have application pools where one could
> say: Serve WebAppX inside Default Application Pool
> consisting of 1 ... N processes or use Custom Application
> pool with some process limitation factors (memory, cpu usage, etc)
>
Note, that ServletContext.getContext(String) allows interaction
between different web applications on the same server. That is when
crossContext=true for the application.
I wonder, how much will be the overhead from having several JVMs, each
with its heap.
I think that /work folder sharing is out of question. Most of concern
here is with Jasper, but there can be also other files, and files
written by applications.
The /webapps folder sharing depends on whether autodeploy feature is
enabled. Expanding deployed wars and deleting folders when undeploying
must be done in a single thread. Otherwise there can be security
issues.
Best regards,
Konstantin Kolinko
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Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/10/2010 11:10 PM, Costin Manolache wrote:
> You want to have each webapp served by a different process ?
> Or even different versions of a webapp in a different process ?
>
First goal is to get rid of connectors and use Tomcat
directly inside httpd or IIS or new Commons Runtime
(replacing Tomcat Native and Daemon) I'm working on.
Second is to have application pools where one could
say: Serve WebAppX inside Default Application Pool
consisting of 1 ... N processes or use Custom Application
pool with some process limitation factors (memory, cpu usage, etc)
Third goal is to allow graceful restarts which would
allow to reconfigure the entire VM or redeploy the
application without down time.
Those kind of things is done nowadays by using some sort
of clustering where each node actually behaves like one
of Httpd's child processes.
First thing I'm going to do is the thorough analysis
of what actually happens under the hood during different
engine life stages and see what resources might require
the synchronization or cross-process sharing and
how to do that.
I know it might sound very complex, but it's actually
doing what Tomcat is suppose to do (be a servlet engine),
so perhaps Tomcat Light would fit in that story.
Regards
--
^TM
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Re: Reusing instances
Posted by Costin Manolache <co...@gmail.com>.
You want to have each webapp served by a different process ?
Or even different versions of a webapp in a different process ?
Sounds very good !
Costin
On Wed, Mar 10, 2010 at 6:17 AM, Mladen Turk <mt...@apache.org> wrote:
> On 03/10/2010 02:58 PM, Mark Thomas wrote:
>
>>
>> Work directory, temp directory come to mind.
>>
>> Easier to use a CATALINA_HOME/CATALINA_BASE style approach.
>>
>>
> The idea IS to use the same directory and same files.
> I'm trying to locate things that presume Tomcat is running
> as self contained singleton application and see whether
> it can be made to be aware of multiple processes that
> constitute a single servlet engine instance.
>
> Work and temp could probably have their own process-id
> like prefix if not possible to reuse the files or if
> sync would be too complex.
>
>
> Regards
> --
> ^TM
>
>
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>
Re: Reusing instances
Posted by Mladen Turk <mt...@apache.org>.
On 03/10/2010 02:58 PM, Mark Thomas wrote:
>
> Work directory, temp directory come to mind.
>
> Easier to use a CATALINA_HOME/CATALINA_BASE style approach.
>
The idea IS to use the same directory and same files.
I'm trying to locate things that presume Tomcat is running
as self contained singleton application and see whether
it can be made to be aware of multiple processes that
constitute a single servlet engine instance.
Work and temp could probably have their own process-id
like prefix if not possible to reuse the files or if
sync would be too complex.
Regards
--
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Re: Reusing instances
Posted by Mark Thomas <ma...@apache.org>.
On 10/03/2010 13:55, Mladen Turk wrote:
> Hi,
>
> Anyone knows what would be the major points that would
> be problematic when launching multiple instances in the same
> directory.
> Lets presume that connectors share the same sockets among
> multiple virtual machines using the JVM loaded inside each
> Httpd or IIS worker process for example.
>
> As I see it there are few things that would have to be addressed.
> 1. Session sharing
> 2. Logging issues (multiple processes write to the same file)
> 3. What about war deployments
> 4. Do we have any other resources which access should be
> synchronized?
Work directory, temp directory come to mind.
Easier to use a CATALINA_HOME/CATALINA_BASE style approach.
Mark
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