July 2016 - dancer-users - lists.preshweb.co.uk

Specific subroutines cannot be exported from plugin
by Gabor Szabo 30 Jul '16

30 Jul '16

Hi there, I just got back looking at a Dancer application and noticed use Dancer2::Plugin::Passphrase qw(passphrase); now throws an exception "Specific subroutines cannot be exported from plugin" I see it mentioned a year and a half ago: https://github.com/PerlDancer/Dancer2/issues/1078#issuecomment-167605120 Then I saw this comment: "The new (soon to be released) Dancer2::Plugin code no longer allows subroutine import list to be supplied when plugin is used." https://github.com/ironcamel/Dancer2-Plugin-DBIC/pull/13#issue-124093181 I think explicitly stating what functions I would like to import from a module is a very useful tool for documenting code even if that module only exports a single function. So I wonder what is the logic behind this decision? Has that been explained somewhere where I could educate myself? regards Gabor

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Dancer 0.201000 Released
by Jason A. Crome 22 Jul '16

22 Jul '16

Dancer 0.201000 is on its way to a CPAN mirror near you. The Dancer Core Developers are sad to announce the retirement of David Golden (xdg) from the core team. Dancer2 was made much better by his many contributions, and we are extremely grateful for all he has done. We'd also like to announce the addition of Peter Mottram (SysPete) to the core team. SysPete has been working quietly behind the scenes on a number of projects, but has been a valuable member of the core team for some time now, and we are happy to have him aboard. The core developers would most importantly like to give thanks to our awesome community for the numerous contributions towards this release. You rock! We realize the long delay between releases in leading up to 0.200000, and it is our sincere hope to not go so long between releases in the future. The upgrade to Plugin2 was extremely long and complicated, but the core team is hopeful to get to a more regular release cycle going forward. If you have any questions, please find us on #dancer on irc.perl.org. The full changelog is as follows: 0.201000 2016-07-22 08:26:18-05:00 America/Chicago [ BUG FIXES ] * GH #1216: Make DSL work in edge-case of plugins calling DSL before the app class loaded Dancer2. (Sawyer X) * GH #1210: Show proper module/line number in log output (Masaaki Saito) [ ENHANCEMENTS ] * GH #900: Switch from to_json to encode/encode_json (Nuno Ramos Carvalho) * GH #1196: Move serializer from JSON to JSON::MaybeXS (Nuno Ramos Carvalho) * GH #1215: Remove unused DANCER2_SHARE_DIR env variable (Jason A. Crome) [ DOCUMENTATION ] * PR #1213: Clarify params merging docs and related examples (Daniel Perrett) * Add Peter Mottram (@SysPete) to list of core developers. (Russell Jenkins) * PR #1208: Introduce appdir before it's used; simplify description of what a view is (James E Keenan) * GH #1218: By request, remove David Golden from list of core developers. Created "emeritus" section to honor the contributions of former core developers. Thanks, xdg! Happy Dancing! Jason A. Crome / CromeDome

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"Route exception: Bad Content-Length: maybe client disconnect?" with JSON POST and request->content
by Lennart Hengstmengel 22 Jul '16

22 Jul '16

Hi all, I'm running into an issue that looks like a bug, but I'm unsure where it comes from. Could be in Dancer2, but maybe in Plack::Request, or even in Plack::Test, HTTP::Request, or somewhere else. I'm kinda lost in the woods. I was hoping that a mind greater than mine can shed some light on this. I get an error "Route exception: Bad Content-Length: maybe client disconnect? (xx bytes remaining)" where xx is the total content length of the request body. But only under the following conditions: - (valid) JSON POST to a Dancer2 app - the app is configured with serializer = JSON - in the route there's a call to: request->content - using Plack::Test and HTTP::Request Attached is a minimal test to demonstrate the issue. Test no 5 fails. I cannot reproduce this issue when using f.e. curl, this call works without errors: curl --data-binary '{ "foo": "123" }' --header 'Content-type: application/json' http://localhost:3000/nok I am using the latest version of Dancer (0.200003) and also latest CPAN versions of Plack and HTTP::Request. Any insights? Thanks, Lennart

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Dancer2::Manual: confused as to use of 'appname' keyword to distribute code across packages
by James E Keenan 15 Jul '16

15 Jul '16

As I work my way through Dancer2::Manual, I am having difficulty understanding how to use the 'appname' keyword to distribute code among different packages in order to improve maintainability. I. Starting point: two packages, each in separate file, using 'builder'. cat lib/mywebapp.pm ##### package mywebapp; use v5.10.1; use Dancer2; use Dancer2::Plugin::Database; use Crypt::SaltedHash; use Data::Dump; use Dancer2::Core::Request::Upload; use URL::Encode qw (url_decode); our $VERSION = '0.1'; set session => 'Simple'; hook before => sub { if (!session('user') && request->dispatch_path !~ m{^/login}) { forward '/login', { requested_path => request->dispatch_path }; } }; get '/' => sub { template 'index'; }; get '/index' => sub { redirect '/' }; get '/login' => sub { # Display a login page; the original URL they requested is available as # param('requested_path'), so could be put in a hidden field in the form template 'login', { path => param('requested_path') }; }; post '/login' => sub { my $user_value = body_parameters->get('user'); my $pass_value = url_decode(body_parameters->get('pass')); my $user = database->quick_select('users', { username => $user_value }); if (! $user) { warning "Failed login for unrecognised user $user_value"; redirect '/login?failed=1'; } else { my $csh = Crypt::SaltedHash->new(algorithm => 'SHA-1'); $csh->add($user->{password}); my $salted = $csh->generate; if (Crypt::SaltedHash->validate($salted, $pass_value)) { debug "Password correct"; session user => $user; redirect body_parameters->get('path') || '/'; # Note: When using curl and supplying a value for 'path' among the # KVPs for POST /login, any such endpoint must be defined herein # as: any ['get', 'post'] => '/my_endpoint' to work around curl's # apparent refusal to switch from POST to GET } else { debug "Login failed; password incorrect for: " . $user_value; redirect '/login?failed=1'; } } }; get '/logout' => sub { app->destroy_session; }; any ['get', 'post'] => '/hello' => sub { return "Hello World\n"; }; { hook before => sub { var time => scalar(localtime) }; any ['get', 'post'] => '/welcome/:name' => sub { my $name = route_parameters->get('name'); template 'welcome.tt', { name => $name }; }; } any ['get', 'post'] => '/appname' => sub { return "This is " . config->{appname} . "\n"; }; start; ##### Serialized responses must go into a separate package. Hence, I have written, and successfully used, this package: cat lib/mywebapp/api.pm ##### package mywebapp::api; use v5.10.1; use Dancer2; use Dancer2::Plugin::Database; use Crypt::SaltedHash; use Data::Dump; use Dancer2::Core::Request::Upload; use URL::Encode qw (url_decode); use HTTP::Status qw(:constants status_message); our $VERSION = '0.1'; set session => 'Simple'; set views => path( app->location, "templates" ); set serializer => 'JSON'; any ['get', 'post'] => '/userdata/:user' => sub { my $user_value = route_parameters->get('user'); my $user = database->quick_select('users', { username => $user_value }); if (! $user) { warning "Failed to recognize user '$user_value'"; my $code = HTTP_BAD_REQUEST; { status_code => $code, message => status_message($code), } } else { { username => $user->{username}, first_name => $user->{first_name}, last_name => $user->{last_name}, } } }; start; ##### And, following earlier documentation in Dancer2::Manual, I have gotten these two packages to work together via: ##### $ cat bin/app.psgi #!/usr/bin/env perl use strict; use warnings; use FindBin; use lib "$FindBin::Bin/../lib"; use mywebapp; use mywebapp::api; use Plack::Builder; builder { mount '/' => mywebapp->to_app; mount '/api' => mywebapp::api->to_app; }; ##### With a valid user 'dancer_operator', I am able to say: ##### http://localhost:5000/api/userdata/dancer_operator ##### ... and get back in browser: ##### {"username":"dancer_operator","last_name":"Operator","first_name":"Dancer"} ##### II. Attempt to refactor this with 'appname' If I am reading documentation in Dancer2::Manual and Dancer2::Cookbook correctly, I believe I should be able to make the following revisions and have all my endpoints just work. $ git diff | cat ##### diff --git a/bin/app.psgi b/bin/app.psgi index 46d8845..b236a2d 100755 --- a/bin/app.psgi +++ b/bin/app.psgi @@ -6,11 +6,5 @@ use FindBin; use lib "$FindBin::Bin/../lib"; use mywebapp; -use mywebapp::api; -use Plack::Builder; - -builder { - mount '/' => mywebapp->to_app; - mount '/api' => mywebapp::api->to_app; -}; +mywebapp->to_app; diff --git a/lib/mywebapp/api.pm b/lib/mywebapp/api.pm index 3af1adf..97a9d0e 100644 --- a/lib/mywebapp/api.pm +++ b/lib/mywebapp/api.pm @@ -1,6 +1,6 @@ package mywebapp::api; use v5.10.1; -use Dancer2; +use Dancer2 appname => mywebapp; use Dancer2::Plugin::Database; use Crypt::SaltedHash; use Data::Dump; ##### All the endpoints defined in lib/mywebapp.pm continue to function as expected. But the endpoint, /api/userdata/:user, defined in lib/mywebapp/api.pm, no longer works. When I call, ##### http://localhost:5000/api/userdata/dancer_operator ##### ... I get a 404 NOT_FOUND response. If I omit the '/api' from the URL above, I also get a 404 -- though that's more expected. And when I try using "prefix = '/api'" as suggested by Dancer2::Cookbook, I still get 404s. What am I missing and/or what are the docs failing to explain clearly? Thank you very much. Jim Keenan

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Methods Of retrieving request parameters
by Kadir Beyazlı 14 Jul '16

14 Jul '16

Hi, At my projects I always used params hash reference to retrieve request parameters as follow: get '/hello/:name' => sub { return "Hi there " . params->{name}; }; I started reading Dancer ManuaI again to discover new features whether I missed and realized that using following ones are safer: route_parameters->get('name'); query_parameters->get('name'); There is also param('name') method. As a result I see that there are 4 ways: get '/hello/:name' => sub { return "Hi there " . params->{name}; # or return "Hi there " . route_parameters->get('name'); # or return "Hi there " . query_parameters->get('name'); # or return "Hi there " . param('name'); }; Is there any technical difference between these ways that one of them can work at a special case but others don't? If there is no difference except being safer (I got this info from manual), is the reason of this diversity to support Perl motto TMTOWTDI? Which ones are you using at your projects? Thanks Kadir Beyazlı GSM : +90 535 821 50 00

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Dancer2 appname
by Daniel Perrett 14 Jul '16

14 Jul '16

It seems from examples that appname must be a package (specifically, a package which uses Dancer2) but I don't think it's spelled out anywhere that this is a requirement (I've looked in Manual and Manual::Migration). I notice that Dancer2::Plugin seems to depend on this - https://github.com/PerlDancer/Dancer2/blob/c598c4c45db729ba9e8a9af79a0afcb3… . Could you confirm this is the intention and that arbitrary app names are not permitted? Happy to write a docs patch to make it clearer if so. Daniel -- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE.

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Perl Dancer Conference 2016 - Call for speakers
by Stefan Hornburg (Racke) 14 Jul '16

14 Jul '16

Hello, please note our Call for Speakers for the upcoming 3rd Perl Dancer Conference in Vienna, 21st and 22nd September. Join us in Vienna and have fun with an amazing presentation. There is absolutely no need to stick to a Dancer or even a webapp theme, just pick something that will entice the attendees. The deadline for submissions is the 30th August. However, as we accept talks as we go, this might be too late. You find details on our website: https://www.perl.dance/talks/submit So share your experience, tell us about your awesome ideas and best practices. Last but not least we offer free admission to the conference including free T-Shirt and social event for all speakers (except lightning talks). Please contact 2016(a)perl.dance if you have any questions. Regards Racke -- Ecommerce and Linux consulting + Perl and web application programming. Please visit our Perl Dancer Conference in Vienna: https://www.perl.dance. Next presentation at YAPC Europe in Cluj: http://act.yapc.eu/ye2016/talk/6780.

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Multiple apps with Plack and Apache
by janet davis 14 Jul '16

14 Jul '16

Hi there, I have a web server running Apache with a single vhost that serves a lot of Perl cgi scripts from cgi-bin. I've been trying out Dancer, which I really like, but I can't figure out the best way to deploy apps in my Apache environment. I want to keep my Apache cgi configuration to serve legacy scripts but I want to start building new projects based on psgi in something like Dancer. I want Apache to use www.myserver/cgi-bin/appname/script.pl for old code (which currently works) and www.myserver/app1 for newer Dancer based apps. Please don't think I'm being lazy by asking, I have read the documentation and looked at the example for deploying multiple apps via fcgi but I am still confused as I have limited experience with Apache - I am working on that. What's the best way to set this up, bearing in mind that I may want to run say 10-15 Dancer apps from my server alongside my cgi-scripts? Do I have to set up a vhost for each app? I have Apache::Plack::Handler but I'm not sure whether I should be using Plack::Builder to mount my apps (which is mentioned in an older Dancer Cookbook, but not the current deployment guide. Can someone help me get on the right track please? Thanks.

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little comparison of frameworks
by WK 12 Jul '16

12 Jul '16

Hi! I watched Kirsten Hunter's "Becoming a polyglot‎" talk at YAPC:NA (https://www.youtube.com/watch?v=pJgpaJpz6sI) and as she made it so easy with her docker container to use, i made simple benchmarking for all those 5 (6) examples of implementations (same API in 5 languages). For every implementation I run at least 5 times following test: $ ab -n 1000 -c 5 localhost:8080/api/quotes/random And here come best results for every participant: Node (express) ============== Requests per second: 882.22 [#/sec] (mean) Node (hapi) =========== Requests per second: 652.65 [#/sec] (mean) Perl (Dancer) ============= Requests per second: 184.71 [#/sec] (mean) PHP === Requests per second: 132.61 [#/sec] (mean) Python (Flask) ============== Requests per second: 69.33 [#/sec] (mean) Ruby (Sinatra) ============== Requests per second: 39.78 [#/sec] (mean) Note: every participant's worst result was better than next result. All servers were run as they are, without tweaking or using alternative deployments. As you may see, if you want to write really fast web framework, you must give right name to it ;) (hint: results are in alphabetical order) Wbr, -- Kõike hääd, Gunnar

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Support for XML serialization in Dancer2
by James E Keenan 10 Jul '16

10 Jul '16

The Dancer2::Cookbook suggests that, when writing REST applications with Dancer2, it should be easy to serialize data to XML as well as to JSON, YAML and Data::Dumper. (See: https://metacpan.org/source/XSAWYERX/Dancer2-0.200002/lib/Dancer2/Cookbook.….) However, there exists no Dancer2::Serializer::XML package, so this part of the Cookbook is misleading. The absence of XML support came up in this StackOverflow thread: http://stackoverflow.com/questions/28236767/how-can-i-use-xml-serializer-in…. A first draft of a Dancer2::Serializer::XML package was provided there by Daniel Böhmer. Granted, it uses XML::Simple, whose maintainer discourages new usage of that library. But apart from this, is there any reason why to date there is no support for XML serialization in Dancer2? Thank you very much. Jim Keenan

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