I am actually doing a side project which you will heard of very soon. For this project I am using Play! Framework v2 with the server side being developed in Scala. To efficiently push this new application to production, I am using the Heroku platform

While my initial thoughts were using MySQL as my relational backend, the default stack provided by Heroku made me switch to postgresql that I have barely used in the past. I attempted to set it up on my machine, but with no luck, Mountain Lion is bundling an old version (8.4) whereas I wanted the same as on the Heroku platform. My first attempt with Homebrew was quite a disaster, I never managed to correctly connect my newly created user.

After a few hours mumbling, I looked for an alternative to the Homebrew version. Luckily, the guys at Heroku provide a neat application to drop that allows to quickly start/stop a postgresql server. My problem was I didn't had enough connections to allow my application to start, I was always getting this message : remaining connection slots are reserved for non-replication superuser connections.

I edited the configuration file

vim "~/Library/Application Support/Postgres/var/postgresql.conf"
to bump the number of connections to a lot more (20 instead of 10) but it prevented my server to start. With a lot of file editing and restarts, I found that the limit for my machine was 11 connections.

The solution to this problem resides in a special setup of the mac os kernel which defines the amount of shared memory a process can allocate. To get rid of this, you can edit your /etc/sysctl.conf file (root required) and put the following lines (it will persist across reboots)


Credits for this tip comes from