[dancer-users] Dancer::Plugin::Database Hangs Randomly on check_connection

[David Precious]

Whilst the actual problem may well be network-level, it would be far
better if D::P::D didn't hang for unacceptable periods waiting to
determine if the connection is still usable, and instead decided that
if $dbh->ping didn't return in a reasonable time, that it would give up
on that connection and throw it away and get a new one.

My kneejerk reaction is that I could change that bit of code to call
the $dbh->ping in an eval block with a timeout - that ought to do the
job, I'd think.


On Mon, 21 Apr 2014 22:34:43 +0200 Hugues <hugues at max4mail.com> wrote:

> Hello James
> if you app works well on localnetwork, the problem come from your
> vpn connection.
> Please check MTU and fragmantion packet of your vpn ( depend of vpn 
> type, ipsec, ssl , other )
> see 
> http://codeidol.com/telecommunications/vpn/Scaling-and-Optimizing-IPsec-VPNs/MTU-and-Fragmentation-Considerations-in-an-IPsec-VPN/
> bye
> Hugues.
> 
> 
> Le 21/04/2014 18:55, James Baer a écrit :
> > Hello - I'm having an issue with Dancer::Plugin::Database that has 
> > been hard to reproduce and track down.
> >
> > I have a new app that I just moved to its production environment.
> > It connects to a database that is in a remote data center over a
> > vpn tunnel. Everything functions normally as expected 98% of the
> > time, however occasionally I will hit a worker thread (deployed via
> > Starman) that just hangs trying to get a database handle. It hangs
> > in the _check_connection subroutine until it reaches some timeout.
> > Then will reconnect just fine with a new connection.
> >
> > I'm using plugin version 1.82 and I have traced it down to this
> > line in the plugin:
> > if ($dbh->{Active} && (my $result = $dbh->ping)) {
> >
> > Right at this if statement is where it hangs, i assume while
> > calling the ping function. It seems there is some confusion as to
> > whether the dbh is still active, it then calls ping which hangs for
> > a number of minutes (not sure how many exactly yet, b/t 3-5). This
> > renders this worker thread unresponsive until it times out. It will
> > eventuall fall into the else block and just return false, which
> > then a new connection is established just fine.
> >
> > I have successfully deployed a number of apps using this same
> > plugin with no problems this only difference here is the physical
> > location so there maybe something network related, just not sure
> > where.
> >
> > I have dug into DBI, etc and the ping functions works fine on all
> > my test scripts. Again, this only happens once in a while so I
> > cannot reproduce on command, which makes it difficult to debug.
> >
> >
> > Here is the output of my debug statements, showing the one thread
> > that hangs:
> >
> > [27037] debug @0.005053> [hit #4]Database
> > connection_check_threshold [30]
> > in /usr/local/share/perl5/Dancer/Plugin/Database.pm l. 69 [27037]
> > debug @0.005189> [hit #4]Database handle last check [1398093938]
> > in /usr/local/share/perl5/Dancer/Plugin/Database.pm l. 70 [27037]
> > debug @0.005345> [hit #4]Database calling check_connection
> > in /usr/local/share/perl5/Dancer/Plugin/Database.pm l. 83 [27037]
> > debug @0.005481> [hit #4]Database.pm in check_connection before if
> > active and ping in /usr/local/share/perl5/Dancer/Plugin/Database.pm
> > l. 265 ... other threads working ...
> > [27037] debug @962.134467> [hit #4]Database in check_connectiion
> > false return  in /usr/local/share/perl5/Dancer/Plugin/Database.pm
> > l. 285 [27037] debug @962.134667> [hit #4]Database connection went
> > away, reconnecting
> > in /usr/local/share/perl5/Dancer/Plugin/Database.pm l. 90 [27037]
> > debug @962.134894> [hit #4]Database calling get_connection
> > in /usr/local/share/perl5/Dancer/Plugin/Database.pm l. 97 [27037]
> > debug @962.135059> [hit #4]Adding mysql_enable_utf8 to DBI
> > connection params to enable UTF-8 support
> > in /usr/local/share/perl5/Dance
> >
> >
> >
> > Any help or suggestions on where to look next is appreciated.
> >
> > Thank you.
> >
> >
> >
> >
> > _______________________________________________
> > dancer-users mailing list
> > dancer-users at dancer.pm
> > http://lists.preshweb.co.uk/mailman/listinfo/dancer-users
> 



-- 
David Precious ("bigpresh") <davidp at preshweb.co.uk>
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