Hi there!
I am using Ruby 1.9.3 in my app server that is running on an AWS EC2
instance. I have my Postgres DB running on a separate EC2 instance but both
instances are in the same security group. When m Ruby code connects to the
DB, it uses the Sequel ORM gem ( http://sequel.rubyforge.org/ )
Now, I have configured that Postgres 9.1.4 DB to be able to accept
connections properly from the app server instance.
However, every now and then, I noticed on the app server's logs that it
will have trouble connecting to the Postgres DB instance and I would see
error messages like these :
* PG::Error: could not receive data from server: Connection timed out*
or
* PG::Error: connection not open*
So I went to the Postgres DB instance and looked in
/var/log/postgresql/postgresql-9.1-main.log and I see a bunch of messages
like these:
* 2012-11-07 08:15:17 UTC LOG: could not receive data from client:
Connection timed out*
* 2012-11-07 08:15:17 UTC LOG: unexpected EOF on client connection*
I did searching around the web including stack overflow, and have made sure
that my PostgreSQL does not have SSL enabled ( I have "ssl=off" inside my
postgresql.conf file )
At this point, I am not exactly sure what exactly is the issue in the
Postgres configuration. I do not what to mess with the maximum # of
connections or maximum timeout values on my production server without a
good proven reason.
The app server can connect to the DB most of the time, and this problem
only shows up intermittently.
On the Ruby-side, this is the error trace for "connection not open" when
making the Postgres call :
PG::Error: connection not open
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:145:in
`async_exec'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:145:in
`block in execute_query'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/database/logging.rb:33:in
`log_yield'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:145:in
`execute_query'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:132:in
`block in execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:111:in
`check_disconnect_errors'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:132:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:372:in
`_execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`block (2 levels) in execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:379:in
`check_database_errors'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`block in execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/database/connecting.rb:229:in
`block in synchronize'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/connection_pool/threaded.rb:105:in
`hold'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/database/connecting.rb:229:in
`synchronize'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/dataset/actions.rb:744:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:483:in
`fetch_rows'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/model/base.rb:785:in
`primary_key_lookup'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/model/base.rb:124:in
`[]'
Similarly, this is the trace for "could not receive data from server" :
PG::Error: could not receive data from server: Connection timed out
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:124:in
`block'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:124:in
`ensure in check_disconnect_errors'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:124:in
`check_disconnect_errors'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:132:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:372:in
`_execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`block (2 levels) in execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:379:in
`check_database_errors'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`block in execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/database/connecting.rb:229:in
`block in synchronize'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/connection_pool/threaded.rb:105:in
`hold'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/database/connecting.rb:229:in
`synchronize'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:234:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/dataset/actions.rb:744:in
`execute'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/adapters/postgres.rb:483:in
`fetch_rows'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/model/base.rb:785:in
`primary_key_lookup'
/var/lib/gems/1.9.1/gems/sequel-3.38.0/lib/sequel/model/base.rb:124:in
`[]'
Please let me know what I might have missed, I appreciate it!
IS
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