[Catalyst] MySQL server has gone away

[Oleg Pronin]

I give more details:

1) simple
$dbh->ping; #ok
#database connection lost here
$resultset->search(..); # ooops.

2) for example, inside DBIC
$dbh->ping; #ok
$sth =3D $dbh->prepare(..); #ok
$dbh->ping; #ok
#database connection lost;
$sth->execute(...); #oops

with this module you can just do
$dbh->prepare(...); # anyway ok
$sth->execute(...); #anyway ok

It will block you program until it reconnects and re-execute your query. (or
number of retries reached).
Of course in case of any non-connection error you will give an error :)


2007/4/27, Oleg Pronin <syber.rus at gmail.com>:
>
> No. SQL query may produce various errors. Imagine that you got an ordinary
> SQL syntax error (you dont know that) and then you want to check $dbh->pi=
ng
> in order to know was there disconnect or not. But between this short mome=
nts
> database connection was lost. And you will think that it was disconnect
> while it was sql error. I can give you more similar "race condition"
> examples. The problem is that between any ping checks and sql queries
> anything can happen.
> Only evaling prepare, execute, etc. and parsing results can give you true
> answer.
>
>
> 2007/4/26, Wade.Stuart at fallon.com <Wade.Stuart at fallon.com>:
> >
> >
> >
> >
> >
> >
> >
> > "Oleg Pronin" <syber.rus at gmail.com > wrote on 04/26/2007 01:29:23 PM:
> >
> > > Hi all!
> > >
> > > Unfortunately, Catalyst::Model::DBI and similar modules are too
> > > simple to avoid some more rare situations.
> > > For example, what if $dbh->prepare result is fine but before you
> > > call $dbh->execute the database will be "gone away"?
> > >
> > > I'm creating a DBI wrapper (it will be called DBIx::Safe) that
> > > handles all disconnections transparently.
> > > If there is no transaction this module gives you 100% guarantee that
> > > your query will be executed without disconnection errors.
> > > In case of transaction it will notify you when you can safely
> > > restart the transaction (when it fails because of disconnection).
> > > This is very good feature for DBIx:Class's txn_do method. DBIC could
> > > restart the transaction (which is coderef) until it is completed
> > succesfully.
> > > Together it could be 100% disconnections-safe system.
> > >
> > > And I need your help.
> > > I use $dbh->err to determine that query fails because of
> > disconnection.
> > > I noticed that posgresql 8.0-8.2 returns errcode "7" when connection
> > > with database lost.
> > > Mysql 4.1 returns "2006".
> > >
> > > Can you please send me database versions and errcodes for
> > > disconnects that you know?
> > > I didn't find it neither in DBD::* nor at database docs website.
> > >
> > >
> >
> > Isn't this what dbi's ping is to be used for?
> >
> >
> > >
> > > 2007/4/19, Jon < jon+catalyst at youramigo.com>:
> > >
> > > On Thu, 2007-04-19 at 13:54 +0100, Adeola Awoyemi wrote:
> > > > Hi all,
> > > >
> > > > I have problem that when I run my app via fastcgi I get an error
> > > > where one of my models can't connect to the database with the
> > message
> > > > "MySQL server has gone away". When I start it using 'script/
> > > > myapp_server.pl' it works fine.
> > > >
> > >
> > > Would I be correct in guessing that you're using DBI directly, not
> > > Catalyst::Model::DBI or Catalyst::Model::DBIC::Schema ?
> > >
> > > This problem will occur when a process forks after creating a DBI
> > > connection, since the connection becomes invalid in the child process.
> > > See the code in Catalyst::Model::DBI for ways to handle this.
> > >
> > > Having said that, I can't think how fastcgi would be forking after
> > > initialising DBI - fastcgi forks first and runs perl later.
> > >
> > > Nevertheless I'd still refer you to the automatic connection checking
> > > and reconnection code in Catalyst::Model::DBI (credit Alex Pavlovic).
> > >
> > >
> > > --
> > >
> > > Jon
> > >
> > >
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>
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