Dancing with websocket

1. Dancing with websockets

2. Dancer • You’ve heard about it • It’s simple, powerful, ﬂexible

3. This talk • Not an hello world • real life example • unusual web app • unusual technologies • goal: show easiness

4. The background

5. At $company, • Many Perl products • Lot of modules + deps • Come from CPAN

6. But, • CPAN = moving target • need to stay stable • local CPAN mirror • but we need to catch up, sometimes

7. • We have a CLI injecter • We want a web injecter • Let’s see the process

8. The process • mirror created with minicpan • it’s «single threaded» • managed with CPAN::Mini • one mirror at a time • injecting = calling • one injection at a time CPAN::Mini::Inject::inject • one command to perform • with the mirror’s conﬁg ﬁle

9. no user no database but, no session a forking process

10. The web interface • everything on a single page • input a string, verify • get corresponding CPAN module • check there is a newer version • conﬁrm/cancel • inject the module in the mirror • display the process log • keep track of the log and the status

11. W Status ire fra input me schedule conﬁrm cancel logs

12. Technologies We need We choose • « instantaneous » update of the logs • WebSockets • every user see the same • Event programming thing • MetaCPAN::API • info about the module

13. Dancer in one sentence • « Dancer allows you to easily create web applications where you can associate http routes to code, which usually end up sending back data via a template engine » • dancer -a plop creates a new application • templating system: • a layout, with a [% content %] placeholder • views, template page, that are injected as content

14. WebSocket • What are WebSockets ? bidirectional web communication • The server can push to the client (e.g. add more log lines) • Dancer::Plugin::WebSocket • uses Web::Hippie, websocket/comet Plack implementation • which uses AnyEvent • so we need an AnyEvent Plack web server : Twiggy

15. forked injection AnyEvent run_cmd process WebSocket logs + status javascript status server process logs server side client side

16. Show me the GUI

17. Show me the code

18. bin/app.pl conﬁg.yml use Dancer; layout: "main" use My::Mirror::Injector; template: "template_toolkit" dance; engines: template_toolkit: encoding: 'utf8' views/layouts/main.tt start_tag: '[%' <html> end_tag: '%]' <head> <title>My cool Injector</title> <script src="...">jquery</script> </head> <body> [% content %] </body> </html> launch.sh plackup -s Twiggy ./bin/app.pl -p 5005

19. views/index.tt <b>Status</b> : <span id="status"> <span id="status_text">[% status %]</span> </span> <form action="/" method="post"> Module names (space seperated): <input type="text" name="module_name" value="[% module_name %]"> <br/> <input type="submit" name="schedule" value="Schedule"> <input type="submit" name="confirm" value="Confirm"> <input type="submit" name="cancel" value="Cancel"> </form> <pre> <div id="injection_log">[% log %]</div> </pre> then some javascript...

20. setup the websocket, handle logs var socket = new WebSocket( "ws://[% server_host %]:[% server_port %]/_hippie/ws" ); socket.onmessage = function(e) { var data = JSON.parse(e.data); if (data.msg) { $('#injection_log').append(data.msg); } }; function send_msg(message) { socket.send(JSON.stringify({ msg: message })); }

21. handle status change var status_regex = /__STATUS_CHANGED:/; if (status_regex.test(data.msg)) { var new_status = data.msg; new_status = new_status.replace(/__STATUS_CHANGED:(.*)__/, "$1"); $('#status_text').remove(); $('#status').append( '<span id="status_text">' + new_status + '</span>' ); }

22. package My::Mirror::Injector; use Dancer; use Dancer::Plugin::FlashMessage; # for status message use Dancer::Plugin::WebSocket; # for WebSocket write use AnyEvent::Util; # for run_cmd my $status = 0; my $log = ''; # OMG GLOBAL VARIABLES !!!111 my $module_name; get '/' => &display_page; sub display_page { my $uri = request->uri_base; my $scheme = request->scheme; my $host = $uri =~ m|$scheme://(.*?):|; template index => { status => $status, module_name => $module_name, server_host => $host, server_port => request->port, log => $log }; }

23. post '/' => sub { param 'confirm' or $module_name = param 'module_name'; if (defined param 'schedule') { $status = 1; flash info => "Scheduled injection"; $log = ''; launch_command( "mirror-inject --autoflush --dryrun --module $module_name" ); } elsif (defined param 'confirm') { # Same, but status = 2 # and run command with no --dryrun } elsif (defined param 'cancel') { # User clicked on Cancel $status = 0; flash info => "Cancelled injection"; } display_page(); }

24. my $next_status; sub launch_command { my ($cmd) = @_; run_cmd( $cmd , '>' => sub { my ($data) = @_; if ( defined $data ) { $data =~ s/__CONFIRM__// and $next_status = 2; $data =~ s/__FINISHED__// and $next_status = 0; $log .= $data; ws_send $data; } else { # End of execution if (defined $next_status) { $status = $next_status; $next_status = undef; ws_send '__STATUS_CHANGED:' . $status . "__n"; } }}); }

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Dancing with websocket

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Dancing with websocket

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