Re: Postgres errors in Drupal install.

Thank you very much for your responses.

On 26 June 2011 21:54, Peter Bex <Peter(dot)Bex(at)xs4all(dot)nl> wrote:
> Do you get the error in the logs or do you see it while going to the
> site manually and does it show this instead of rendering a page?

The log don't really give much indication of anything untoward
happening. It's really that the page stops rendering and displays the
message.

> If it's in the logs, and you're running cron or poorman's cron once
> an hour, it could be that's where these messages are coming from.
>
> You can run cron manually from the interface somewhere, so you
> can try if you can reproduce the error more reliably and work from
> there.

It doesn't seem quite regular enough to be part of the cron job.
Having said that the errors below do make reference to cron.

----------------------------------- snip
--------------------------------------------------
2011-06-26 15:57:15 EDT STATEMENT: SELECT base.fid AS fid, base.uid
AS uid, base.filename AS filename, base.uri AS uri, base.filemime AS
filemime, base.filesize AS filesize, base.status AS status,
base.timestamp AS timestamp
FROM
file_managed base
WHERE (base.fid IN ('0', 'Upload', 'Remove', ''))
2011-06-26 15:57:15 EDT WARNING: nonstandard use of \\ in a string
literal at character 185
2011-06-26 15:57:15 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:30 EDT WARNING: nonstandard use of \\ in a string
literal at character 115
2011-06-26 15:57:30 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:31 EDT WARNING: nonstandard use of \\ in a string
literal at character 256
2011-06-26 15:57:31 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:31 EDT WARNING: nonstandard use of \\ in a string
literal at character 248
2011-06-26 15:57:31 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:31 EDT WARNING: nonstandard use of \\ in a string
literal at character 256
2011-06-26 15:57:31 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:31 EDT WARNING: nonstandard use of \\ in a string
literal at character 248
2011-06-26 15:57:31 EDT HINT: Use the escape string syntax for
backslashes, e.g., E'\\'.
2011-06-26 15:57:31 EDT ERROR: duplicate key value violates unique
constraint "semaphore_pkey"
2011-06-26 15:57:31 EDT STATEMENT: INSERT INTO semaphore (name,
value, expire) VALUES ('cron', '2399653214e078f2b5a48e5.75113719',
'1309118491.3697')
----------------------------------- snip
--------------------------------------------------

Here are the messages in the logs of the last crash which might throw
a bit of light onto the subject for anyone rather more knowledgeable
than I:
----------------------------------- snip
--------------------------------------------------
2011-06-26 17:13:24 EDT LOG: background writer process (PID 505) was
terminated by signal 9: Killed
2011-06-26 17:13:24 EDT LOG: terminating any other active server processes
2011-06-26 17:13:24 EDT WARNING: terminating connection because of
crash of another server process
2011-06-26 17:13:24 EDT DETAIL: The postmaster has commanded this
server process to roll back the current transaction and exit, because
another server process exited abnormally and possibly corrupted shared
memory.
2011-06-26 17:13:24 EDT HINT: In a moment you should be able to
reconnect to the database and repeat your command.
2011-06-26 17:13:24 EDT LOG: all server processes terminated; reinitializing
2011-06-26 17:13:24 EDT FATAL: could not create shared memory
segment: Cannot allocate memory
2011-06-26 17:13:24 EDT DETAIL: Failed system call was
shmget(key=5432001, size=29278208, 03600).
2011-06-26 17:13:24 EDT 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 29278208
bytes), reduce PostgreSQL's shared_buffers parameter (currently 3072)
and/or its max_connections parameter (currently 103).
The PostgreSQL documentation contains more information about shared
memory configuration.
----------------------------------- snip
--------------------------------------------------

While the server is a little challenged in the way of RAM, it is by no
means under any sort of load.