# Dynamically add/remove mongrel on EC2 from Apache balancer **URL:** \ **Category:** Deployment\ **Created:** [February 19, 2008, 1:41am UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491 "2008-02-19T01:41:04Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![yaxm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/54ee81/32.png) [@yaxm](https://www.ruby-forum.com/u/yaxm)\ **Post date:** [February 19, 2008, 1:41am UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491/1 "2008-02-19T01:41:04Z")
Hi, I’d like to scale out by adding more EC2 mongrel instances, and scale down by removing EC2 mongrel instances. Is there a way to dynamically add/remove mongrel instances from Apache mod\_proxy\_balancer. It seems that I’d have to manually change the configuration file and restart apache whenever I add/remove a new mongrel. Yaxm ---
**Author:** ![yaxm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/54ee81/32.png) [@yaxm](https://www.ruby-forum.com/u/yaxm)\ **Post date:** [February 19, 2008, 11:06am UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491/2 "2008-02-19T11:06:21Z")
> Is there a way to dynamically add/remove mongrel instances from Apache > mod\_proxy\_balancer. It seems that I’d have to manually change the > configuration file and restart apache whenever I add/remove a new > mongrel. Well, you could write a script to edit the config for you and send apache a usr1 signal ( “kill -usr1 [pid]” ) to cause it to reload the updated config, then trigger the script whenever a new EC2 instance is started or stopped. Another approach could be to proxy everything to swiftiply ( [http://swiftiply.swiftcore.org/](http://swiftiply.swiftcore.org/) ), and have each new EC2 instances mongrels register/deregister with the swiftiply proxy. Yet another option would be to use switchpipe ( [http://switchpipe.org/](http://switchpipe.org/) ) to manage things. I haven’t done any of these, of course, so I’m basically talking through my hat, but they all sound plausible! Good luck David ---
**Author:** ![yaxm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/54ee81/32.png) [@yaxm](https://www.ruby-forum.com/u/yaxm)\ **Post date:** [February 19, 2008, 4:01pm UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491/3 "2008-02-19T16:01:37Z")
On Tue, 2008-02-19 at 01:41 +0100, Yaxm Y. wrote: > Is there a way to dynamically add/remove mongrel instances from Apache > mod\_proxy\_balancer. It seems that I’d have to manually change the > configuration file and restart apache whenever I add/remove a new > mongrel. mod\_proxy\_balancer comes with the “balancer manager” with which can toggle a member of the cluster offline and back online: [http://httpd.apache.org/docs/2.2/mod/mod\_proxy\_balancer.html](http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html) You could script that interface and then call it from Capistrano. I Googled around but couldn’t find an existing library for this… kind of surprising. Maybe most folks are just going the “rewriting the config file and send USR1” route. Yours, Tom ---
**Author:** ![yaxm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/54ee81/32.png) [@yaxm](https://www.ruby-forum.com/u/yaxm)\ **Post date:** [February 22, 2008, 7:52pm UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491/4 "2008-02-22T19:52:00Z")
On Feb 19, 10:05 am, digitalronin [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Is there a way to dynamically add/remove mongrel instances from Apache > > mod\_proxy\_balancer. It seems that I’d have to manually change the > > configuration file and restart apache whenever I add/remove a new > > mongrel. > > [snip] > > Yet another option would be to use switchpipe ([http://switchpipe.org/](http://switchpipe.org/) > ) to manage things. Yep, that’s exactly what SwitchPipe does. Dynamically launches, manages, and kills backend processes that speak HTTP. Even better than that, it’ll kill Mongrels that aren’t in use for a certain period of time… so rather than having, say, 3 Mongrels running ALL the time on a quiet app, it’ll scale it back to zero Mongrels after X seconds of inactivity if you like. Alternatively you can make it keep 1 Mongrel up to pick up requests before scaling up to meet demand. Whatever you want to do, it does it. Cheers, Peter C. [http://www.petercooper.co.uk/](http://www.petercooper.co.uk/) ---
**Author:** ![yaxm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/54ee81/32.png) [@yaxm](https://www.ruby-forum.com/u/yaxm)\ **Post date:** [March 4, 2008, 5:57pm UTC](https://www.ruby-forum.com/t/dynamically-add-remove-mongrel-on-ec2-from-apache-balancer/129491/5 "2008-03-04T17:57:03Z")
While dorking around, I found you can disable/enable mongrel instances in apache via curl. I added these two functions to my mongrel init file: enable\_mongrel () { curl -s -o /dev/null [http://127.0.0.1:8888/balancer-manager\?b=mongrel\_cluster\&w=http://127.0.0.1:$1\&dw\=ENABLE](http://127.0.0.1:8888/balancer-manager%5C?b=mongrel_cluster%5C&w=http://127.0.0.1:$1%5C&dw%5C=ENABLE) } disable\_mongrel () { curl -s -o /dev/null [http://127.0.0.1:8888/balancer-manager\?b=mongrel\_cluster\&w=http://127.0.0.1:$1\&dw\=DISABLE](http://127.0.0.1:8888/balancer-manager%5C?b=mongrel_cluster%5C&w=http://127.0.0.1:$1%5C&dw%5C=DISABLE) } in the case statement: ``` enable) enable_mongrel $2 RETVAL=$? ``` ;; disable) disable\_mongrel $2 RETVAL=$? ;; They accept the port number as an option. I use this as part of my monit system to keep things in check. I have a very high traffic site and I found proxy\_balancer didn’t react quick enough. usage: service monit disable 8081 service monit enable 8081