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Migrating an existing deployment to Heroku

It was fun — pure unadulterated fun!!

Now, I started looking at heroku since our current deployment on a linode was getting a little bulky. Our client has been complaining of ‘suddenly things slowing down’ and ‘site not working’. The site is used at a hit rate of 36 Requests per minute and we need to keep our hosting costs down — so what is the solution???

Currently, its hosted on a linode (740MB) memory and and nginx + 3 thin cluster. There is monit which ensures that ANY thin server going above 140MB is restarted. BackgrounDrb is taking a lot of memory too ( an unavoidable 160MB) and we have ferret to make things more complicated !! :)

Enter Heroku – first thing that got me hooked was a ‘git push heroku’ DEPLOYS your application! Fantastic. I have been a capistrano freak till now and loved it – but its all gone now! (wonder if thats good or bad though).  LoL :)

So, to get started, you sign-up on heroku and follow instructions on your My Apps page:

$ heroku create
$ git init && git add . && git commit -m"initial checkins"
$ git push heroku

I used the Blossom account (5 MB space) and was pleasantly surprised to see it work ‘out of the box’. It created some wierd named sub-domain for me which I changed using

$ heroku rename <new-name>

Digging deeper, I wanted to deploy the application ‘as is’ but that was not to be:

Setup Woes

Heroku uses PostGres and we had used MySQL – you need to ensure that there are no special data types being used. As goes Murphy’s law – we had used blob and had to change that the bytea (bytearray in PG). The interesting thing I found was that there is NO way to drop the database and re-create it. The answer lies in:

$ heroku rake db:schema:load

Production environment is assumed. I was not sure which environment I am in till I issued the command (after reading up) that I was in production mode:

$ heroku config
RACK_ENV => production

I was also curious to see how I get the logs and check the console and it really ROCKS:

$ heroku logs
$ heroku console

Alas I could not find a way to access the dbconsole (like what I do sometimes with script/dbconsole -p). Well, that is the way it is!

Ferret Woes

Heroku does not use ferret – it uses solr and sunspot. I had to install these additional gems using the gem manifest i.e. the .gems file located at RAILS_ROOT.

rupport
acts_as_ferret
prawn
$ git commit
$ git push heroku

Since acts_as_ferret is installed, it loads the Rails models and ‘expects’ the database to be in place. So, I had to comment out ALL the references to acts_as_ferret to be able to run a

$ heroku rake db:migrate

So far so good. Now, since ferret requires to index files and heroku mounts the deployment on a read-only filesystem, we need to tweak the configurations to ensure that the index is created in tmp/ (the are where we can write stuff). Add the following lines to the config/environments/production.rb

require 'acts_as_ferret'
ActsAsFerret.index_dir = "#{RAILS_ROOT}/tmp/index"

Now, default ferret production environment is to start a Drb server on 9010 port — and Heroku will not allow this! So, we have to comment out all the configuration in config/ferret_server.yml to ensure that this loads like it does in development. I hate this but no alternative for now. I do plan to migrate to the WebSolr that Heroku is offering but its at 20$ per month! Lets see how that works out.

This should at least get you started on ferret – phew!

BackgrounDrb woes

BackgrounDrb comes with its own baggage I must say. Heroku proposes the use of DelayedJob (yippee) and I have just this plan, so rather than even try to figure out a way to get backgrounDrb to work on Heroku, I simply commented out the config/backgroundrb.yml settings (to ensure it does not get initialized).

I also had to comment out all the MiddleMan references in the controller. The backgrounDrb workers are easily  modified so that they can work as DelayedJob objects ;). I have mentioned this in my earlier posts Moving from BackgrounDrb to DelayedJob

Once this was done, I did not face any problems and after some quick code fixes, git commits and git push’es, I was able to get my heroku application up and running.

All in a days work! Thats really amazing. Now, the next step is to get WebSolr  and DelayedJob integrated and see if I can move onto a bigger storage setup — a couple of months will let me know if this move was right.

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  1. shailesh
    December 2, 2009 at 11:08 am

    testing rss -amit

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