I'm running PostgreSQL 8.4.5 on Ubuntu 10.04. I run an EC2 instance with a few sites running on nginx. Most of these sites run on Django and connect to this Postgres instance.
For some reason, at 8:45pm tonight, Postgres went down. I logged into the machine, and I see this error message:
* Starting PostgreSQL 8.4 database server * The PostgreSQL server failed to start. Please check the log output: 2011-04-17 04:46:49 UTC FATAL: could not create shared memory segment: Cannot allocate memory 2011-04-17 04:46:49 UTC DETAIL: Failed system call was shmget(key=5432001, size=16211968, 03600). 2011-04-17 04:46:49 UTC HINT: This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory or swap space. To reduce the request size (currently 16211968 bytes), reduce PostgreSQL's shared_buffers parameter (currently 1792) and/or its max_connections parameter (currently 53). The PostgreSQL documentation contains more information about shared memory configuration. ...fail!
The first thing I did was change the Linux shared memory allocation.
sysctl -w kernel.shmmax=367108864> sysctl -p /etc/sysctl.conf
That didn't do it. So then I edited
/etc/postgresql/8.4/main/postgresql.conf and lowered the
max_connections value. That worked...for about 10 minutes.
Now I'm getting the same error, no matter how low
max_connections is. I need to set it to at least 9 (since that's the number of Django projects that need access to this Postgres server).
Any thoughts on how I might go about fixing this?