Hi Christopher,
On 04/02/2014 12:21 AM, Christopher Schultz wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Frederik,
On 3/26/14, 9:32 PM, Frederik Nosi wrote:
My scenario is Apache httpd + mod_jk + N Tomcat's in. The default
behaviour of load balanced workers in mod_jk in my testing is that
when a client requests a page (GET / POST / Whatever), the LB
worker tries the request to every ajp worker. This in contrast with
what i read here:
http://people.apache.org/~mturk/docs/article/ftwai.html
<http://people.apache.org/%7Emturk/docs/article/ftwai.html>
Expecially this part:
When having multiple nodes in a cluster you can improve your
application availability by implementing failover. The failover
means that if the particular elected node can not fulfill the
request the another node will be selected automatically. In case of
three nodes you are actually doubling your application
availability. The application response time will be slower during
failover, but none of your users will be rejected. Inside the
mod_jk configuration there is a special configuration parameter
called worker.retries that has default value of 3, but that needs
to be adjusted to the actual number of nodes in the cluster.
... worker.list=lbworker worker.lbworker.type=lb # Adjust to the
number of workers worker.retries=4
worker.lbworker.balance_workers=node1,node2,node3,node4 If you add
more then three workers to the load balancer adjust the retries
parameter to reflect that number. It will ensure that even in the
worse case scenario the request gets served if there is a single
operable node.
From that it seems that the "retries" parameter in a load balancer
worker context should mean the number of real (AJP) workers to
try. (what i need indeed) but in my testing, that LB worker
parameter is the number of times that all the AJP workers that are
part of the LB worker get a round retry. In eg, having a LB worker
with 4 AJP workers, setting LB Worker's retries = 2, the behaviour
i see is that the AJP workers get called this way:
AJP1 -> timeout [...] AJP4 -> timeout
===> repeat again (retries == 2)
AJP1 -> timeout [...] AJP4 -> timeout
--> LB sends an error to the client.
Now from the online documentation the meaning of that parameter in
a load balancer worker context is'nt that clear, but from the link
i provided seems it was exactly what i needed, not the number of
retries to all AJP workers, but the number of single AJP workers to
try..
If that is not correct i can fill a bug report. If instead it's by
design, the attached patch adds a new parameter, "lb_retries", that
does what i need. Of course it's a bit rough, but works.
Any comments? Am I getting stuff wrong?
I'm bumping this because I can see Rainer has fixed a bunch of things
in mod_jk over the last few days. Perhaps he's getting ready to do a
release or something.
Thanks Christopher, BTW on this issue I'm not even sure it's a
documentation bug, a bug in mod_jk or an unfullfilled expectation of
mine :-)
Thing is, i had to use this cure.
I'm sure my patch is a bit faulty, the HTTP status codes returned are >
500, but i'm not sure they are in line with the protocol (503 / 504).
but for now it works for me though.
Noticed there were changes in mod_jk's git repo, i'm following it.
Thanks for your attention and have fun at ApacheCon!
- Fredi
- -chris
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: GPGTools - http://gpgtools.org
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/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=GEhg
-----END PGP SIGNATURE-----
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org
