We are having a problem where our Postgres 9.0 server occasionally locks up and kills our webapp. Restarting Postgres fixes the problem.

Here's what I've been able to observe:

• First, usage of one CPU jumps to 100% for a few minutes
  • Disk operations drop to ~0 during this time
  • Database operations drop to 0 (blocks and tuples per sec)
  • Logs show during this time:
    • WARNING: worker took too long to start; cancelled
    • WARNING: worker took too long to start; cancelled
    • No Queries in logs (only those over 200ms are logged)
  • No unusually long-running queries logged before or during
• Then the second CPU jumps to 100%
  • The number of postgres processes jumps from the usual 8-10 to ~20
  • Matched by a spike in Postgres Blocks per second (about twice normal)
  • Logs show
    • LOG: could not accept SSL connection: EOF detected
    • Queries are running but slow
• Restarting postgres returns everything to normal

Setup:

Server: Amazon EC2 Large
Ubuntu 10.04.2 LTS
Postgres 9.0.3
Dedicated DB server

Does anyone have any idea what's causing this? Or any suggestions about what else I should be checking out?