perl-modperl mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Perrin Harkins <phark...@gmail.com>
Subject Re: Apache::DBI "connection lost contact" error
Date Wed, 05 Jun 2013 16:08:47 GMT
On Tue, Jun 4, 2013 at 2:32 PM, Xinhuan Zheng <xzheng@christianbook.com>
wrote:
> I have seen in other web servers when apachectl starts, there is no
"connect lost contact" error but it did happen when apachectl stops.

If your server does not receive constant requests, you may see this error
on shutdown because cached database handles are being destroyed but the
connection to the database has already timed out.

> If child process uses ping the inherited database handle and it is
ping-able, then the child process may use it. That'll be a problem.

The debugging log you showed us makes me think that won't happen.  It looks
like the handle fails immediately when used after a fork.

> When child process exits, it calls rollback if AutoCommit is off, but
when another new child process is just born and uses its connection to send
> database updates, will that rollback interfere with new child process
attempt to update database?

If the same connection was being used in multiple processes, many things
could go wrong, including that.  However, Since the connections die
immediately when you use them after a fork, this won't happen.

> Is the rollback necessary?

It's very necessary.  Otherwise, if your code throws an uncaught exception
in the middle of some database work, the next request would reuse the same
handle with uncommitted changes left on it.  In my opinion, this is the
most important thing about Apache::DBI.

I understand you're worried about it.  I should be able to send you a patch
to try within a few days, so you can wait for that if you want.  Or you can
try to fix it yourself.  My plan is to replace that line of code I showed
with some code that checks current_callback() to make sure we're not in a
startup phase.

- Perrin

Mime
View raw message