November 2015 - dancer-users - lists.preshweb.co.uk

Non-blocking stuff
by David H 12 Jan '16

12 Jan '16

Hi All, I'm looking for some advice/pointers on having stuff non-block in my code. I have an application which runs on Dancer2 and is ~12,000 lines of code. It is actually (currently) four separate applications. It works really really well at the moment but for one thing, and that is that it continually blocks on pretty much everything. I've tried various solutions including starman which doesn't seem to run its allocated 10 workers for some reason. I've seen the model of nodejs and I'm looking for something similar to the call-back event non-blocking model of nodejs. I've tried using the apache road but that seems to recompile on every request, which adds ~ 1.5 seconds to each request, since that is the application startup time. Keen to see how other people solve this. Thanks, David

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Dancer2 deployment
by Richard Reina 09 Dec '15

09 Dec '15

Happy Saturday All, For the past few months I've been playing around with dancer on a machine at home. I am wanting to now experiment with creating and perhaps deploying a simple web app on digitalocean. However, I am not clear why I need a web server such as Starman. Can I not just install Dancer2 and plackup like I do on my local machine? Thanks

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Re: [dancer-users] single-threaded
by Rick Leir 24 Nov '15

24 Nov '15

On Tue, Nov 24, 2015 at 7:00 AM, <dancer-users-request(a)dancer.pm> wrote: > > This means that if you write your Dancer route handlers to be efficient, > so that they return within a few milliseconds at most, you can in effect > serve a great many clients, since most of them will be idle most of the > time. > > The single-threaded web server only breaks down when you start getting to > load levels where the server is handling at least one connection all the > time, so that allowing to to handle a second or third in parallel can > provide some benefit. > What if your route handler goes to disk for something (perhaps a DB access)? Your other Starman process(es) could start handling another connection in the meantime. What if your CPU has 2 or more cores (likely)? Again, the other process could get going. Maybe you have low traffic on an Intranet. But out on the Internet, you could have bots and spiders bothering your route handlers just when you have a real client to serve. Cheers -- Rick

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Re: [dancer-users] session cookies
by Rick Leir 19 Nov '15

19 Nov '15

On Thu, Nov 19, 2015 at 7:00 AM, <dancer-users-request(a)dancer.pm> wrote: > > This blog of mine might be helpful in understanding how it all works: > > http://blog.geekuni.com/2015/06/three-ways-to-implement-sessions.html > We should also be talking about JWT JSON Web Tokens because the Cookie scheme is broken. I use Crypt::JWT . These links explain it nicely: https://auth0.com/blog/2014/01/27/ten-things-you-should-know-about-tokens-a… http://jwt.io/ JWS https://tools.ietf.org/html/rfc7515 JWT https://tools.ietf.org/html/rfc7519 http://stackoverflow.com/questions/20504846/why-is-it-common-to-put-csrf-pr… Cheers -- Rick

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Question About Session Variables
by Richard Reina 19 Nov '15

19 Nov '15

Hello All, Hypothtetical question: When user 'A' logs in to my Dancer2 App, the app creates the session variable 'user_id' after authenticaltion and passes it to to other routes throughout the app. If at that point another user logs in, user B or even multiple users, is there any risk of the session 'user_id' getting overwritten by another user?

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No Advent Calendar this year
by Sawyer X 18 Nov '15

18 Nov '15

Hi everyone, I'm sorry to say, but we do not have enough time and volunteers to put out an Advent Calendar this year. I appreciate the comments made on the thread I started on it - and the ideas raised remain in the Calendar repo and I hope we will reach them eventually. Unfortunately, it will not be this year. My apologies and thanks again for the support and understanding. Sawyer.

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Re: [dancer-users] blocking
by Rick Leir 18 Nov '15

18 Nov '15

On Tue, Nov 17, 2015 at 7:00 AM, <dancer-users-request(a)dancer.pm> wrote: > > delayed { > my $TextToWrite = ReturnText(); > sleep(10); # Do something that takes a few seconds > content "$TextToWrite"; > done; > }; The sleep call will always cause blocking, even a sleep(0). Likewise a flush. In the sense that there is a context switch to some other thread or process. How are you testing whether it is blocking? Sorry, I do not know what you are trying to do. Linux will not schedule a cpu intensive task to the exclusion of I/O. You can affect its scheduling using nice: http://stackoverflow.com/questions/2012852/control-a-perl-scripts-cpu-utili… If you really want nonblocking then you can look at nice for io http://linux.die.net/man/1/ionice or spawn a C program with pthreads and freeze your screen! cheers -- Rick

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Dancer2 Deployment
by David H 16 Nov '15

16 Nov '15

Hi All, I just need some basic advice on deploying Dancer2 onto RedHat. I am wanting to deploy it to be multithreaded, or at least not to block when it is running requests. Starman and Twiggy both seem to not want to run multithreads for some reason and I tried the Apache way and it just seems to compile the code everytime which ended up being not any faster than a single thread. What ways do people here deploy the app to be fast/multi-threaded? I tried this: http://search.cpan.org/dist/Dancer/lib/Dancer/Deployment.pod#Running_as_a_c… However it seemed to recompile everything for every request. I understand about static files being hosted in front etc...as well, which I may do in the future. Thanks, David

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Single Page Application with Perl Dancer and AngularJS
by Gabor Szabo 15 Nov '15

15 Nov '15

I love the new -s flag that allows us to create our own Dancer skeletons. I've started to create one that include AngularJS and a simple example of a Single-Page Application http://perlmaven.com/dancer2-angularjs-single-page-application Gabor

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Triggering 404 error from a hook
by Hermann Calabria 13 Nov '15

13 Nov '15

Hi all, My application uses different databases depending on the client, which is always the first parameter in each route. Example: /:client/home /:client/list ... I’m using the following ‘before’ hook to set the database handle dbh: # Figure out client, if any my $client = param('client') || ''; unless ($client =~ /^[a-z0-9]{2,20}$/) { $client = ''; } # If $client, get client dbh if ($client) { if (!vars->{'dbh'}) { eval { var dbh => database({ driver => "mysql", host => "localhost", dbi_params => ... database => "s_".$client, ... }); } } if (!vars->{'dbh'}) { warning “Could not open client database”; # Warning is present pass; # Internal Server Error thrown } } I’d like Dancer to gracefully fall through to a 404 error in case s1_$client is not found or cannot be opened. I’ve tried “pass” and “forward”, but I receive a cryptic “Internal Server Error” which I assume is because these keywords are not valid within hooks, but I’m not sure. Any ideas on how to implement this without having to repeat this code over and over and over within each route? I’m also open to other ideas/approaches to implement this general scheme as long as I get a separate database for each :client (i.e., “create one huge database” is not a valid solution given the application requirements). Thanks in advance for any thoughts! Hermann

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