LunarCowgirl has asked for the wisdom of the Perl Monks concerning the following question:

I'm having trouble with session variables in Catalyst. I'm new to Catalyst, so it's likely I don't fully understand how to use Session::Store. I've found, on all the web, only two examples of how to add items to $c->session:

push @{ $c->session->{items} }, $item_id;

$c->session->{cart}{$item_id} += $quantity;

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I know $c->session is a hash ref, and I've tried variations on both above. What I'm trying to do is create a hidden token in a form for validation upon POST. This is my GET routine:

sub contact_GET {
    my ( $self, $c ) = @_;

    # Using Crypt::Random
    my $token = makerandom( Size => 128, Strength => 0 );

    $c->session->{token} = $token;

    $c->load_status_msgs;

    $c->stash(
        template    => 'contact.tt',
        title       => 'Contact Us',
        token       => $token,
    );
}

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I've also tried:

push @{ $c->session->{token} }, $token;

The contact page won't load when I use either, and it crashes the server, so I get no error or debugging messages to indicate what's happening. I have to kill the server and restart it. If I comment out the line for $c->session, everything works fine. If I uncomment it though, things crash again.

The odd thing is that it suddenly starting working with the line uncommented. I had the token set at 512 bits from a copy and paste example. Changing the size to 128 made everything start working. Then, all of a sudden, without any changes to the method, it stopped and I have to comment out the line to get the page to load. Setting the token at 12 bits made no change, so I doubt it had anything to do with the variable size. I'm really confused here. What is the proper way to push a variable into a Catalyst session? Or if I'm doing it right, why is the page crashing the server?

Replies are listed 'Best First'.
Re: Problems with setting session variables in Catalyst
by thomas895 (Deacon) on Aug 11, 2014 at 22:52 UTC

    Perhaps Catalyst::Plugin::Session does not play well with binary data? Try storing the data as text using (un)pack or MIME::Base64?

    Also try a different storage backend. Maybe that doesn't like binary data either(if you find that to be the case, you might want to file a bug report). 

    ~Thomas~ 
    
"Excuse me for butting in, but I'm interrupt-driven..."
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Re: Problems with setting session variables in Catalyst
by LunarCowgirl (Sexton) on Aug 12, 2014 at 02:41 UTC

    Actually, you both were on the right track. Using the example from Catalyst::Plugin::Session::Store worked. I did look at the docs while I was doing this -- several times -- but not this one. This is completely different than the example given in the Catalyst tutorial and in Catalyst::Plugin::Session, which were the two examples I cited.

    Also, the generated token wasn't playing well with Memcached. I discovered Session::Token though and that works perfectly in place of Crypt::Random. It's been a while since I've done any serious Perl coding, so I'm still getting back on my feet again and relearning the ecosystem.

    Thanks for both your help.

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      Actually, you both were on the right track. ...Using the example from Catalyst::Plugin::Session::Store worked. I did look at the docs while I was doing this -- several times -- but not this one....

      Yup, you normally wouldn't use this API (its the low level), but if it doesn't work using this api, then something is really wrong :)

      OTOH, have you seen ?? Catalyst::Controller::RequestToken - Handling transaction tokens across forms update: nevermind, doesn't seem to use Session::Token probably not worth investigating further :)

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        I did look at that, yes, but it seemed to conflict with using Catalyst::Controller::REST, so I went with my own solution. I'm much happier with Session::Token.
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Re: Problems with setting session variables in Catalyst
by Anonymous Monk on Aug 11, 2014 at 23:36 UTC

    I'm new to Catalyst, so it's likely I don't fully understand how to use Session::Store. I've found, on all the web, only two examples of how to add items to $c->session:

    Try looking at the docs?

    Yeah Catalyst::Plugin::Session::Store - Base class for session storage drivers. 

    my $data = $c->get_session_data( $key );
$c->store_session_data( $key, $data );

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    Where $data is a hashref , arrayref or scalar
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