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Streaming binary data without known size? Content-length problem.
by Andy Walker 12 May '13

12 May '13

While $working on a RESTFul application, I came across a situation where I needed to pack up a directory of files (already gzipped) and send them to the user. Rather than pulling everything into memory with Archive::Tar or creating a temporary file with File::Temp that would meet an uncertain fate after file_send depending on the deployment, I decided I would try and forkexec using a pipe and just stream the tar to the user. This was easy enough to accomplish with open and '-|' and then exec ('/path/to/tar', '-c', '-f', '-' ...); in the child. After that, it was a matter of duplicating parts of send_file, and I think this is where I got it wrong. Testing with raw Telnet saw the binary data come through, so I know that at least the piping worked, but when I tested the route as users would use it, the browser downloaded an empty file and curl -v, mentioned something about "* Excess found in a non pipelined read: excess = 7989". I looked in the printed headers, and saw that it defined Content-Length: 0, which I assume is part of the problem. I tried NOT sending it using the code below using: $response->{headers}->remove_header('Content-Length'); but was unable to remove it, and I'm not sure that's what I want to do anyway. Hijacking the stream and just catting binary data doesn't seem to be part of the spec, though I'd swear I've seen it done elswhere before, but I thought I would pick the collective brains of the mailing list and see. I eventually ended up just using File::Temp::tmpnam and having tar output to that file, which I then added to a var called 'cleanup' that an after hook deletes. Then I sent with file_send as normal. So, I suppose my main question is: would this work if I were somehow able to remove the Content-Length header? I'm thinking not and, if not, should I be using chunked transfer instead? Does Dancer support this? CODE: sub send_data { Dancer::Continuation::Route::FileSent->new( return_value => _send_data(@_) )->throw } sub _send_data { my ($fh, %options) = @_; my $env = Dancer::SharedData->request->env; die "Must have streaming" if ! $env->{'psgi.streaming'}; die "Must provide content_type\n" unless $options{content_type}; die "Must provide filename\n" unless $options{filename}; binmode $fh; my $response = Dancer::SharedData->response() || Dancer::Response->new(); $response->header('Content-Type' => $options{content_type}); $response->push_header('Content-Disposition' => "attachment; filename=\"$options{filename}\"" ); $response->streamed( sub { my ( $status, $headers ) = @_; return sub { my $respond = shift; my $writer = $respond->( [ $status, $headers, ] ); my $content = $response->content; my $bytes = $options{'bytes'} || '43008'; my $buf; while ( ( my $read = sysread $fh, $buf, $bytes ) != 0 ) { $writer->write($buf); } }; } ); return $response if $response; }

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Dancer v1.3113 on its way to CPAN
by Yanick Champoux 09 May '13

09 May '13

As the subject line says, a maintenance version of Dancer is on its way to CPAN (changelog excerpt below). Nothing major there, just a few fixes and improvements. As usual, thanks a bunch to all patch submitters and bug reporters! Enjoy! `/anick 1.3113 08.05.2013 [ ENHANCEMENTS ] * GH #869: leave body parameters alone if deserialization failed (brianphillips). * GH #914: add link to melezhik's psgi chef cookbook. * GH #923: implement lazy session flushing. (David Golden) [ BUG FIXES ] * GH #920: fix pod for Dancer::Development. (ppisar) [ DOCUMENTATION ] * GH #915: add warning about behaviour of hooks with multiple packages loaded by load_app (racke). * GH #918: Fix headers syntax in Dancer::Response perldoc (Vyacheslav Matyukhin).

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What versions Moo has Dancer2 been tested with?
by Mark Wood-Patrick 01 May '13

01 May '13

What versions Moo has Dancer2 been tested with running the following program use Dancer2; get '/' => sub { "Hello World" }; dance; I get Can't locate object method "apply_roles_to_package" via package "Moo::Role" at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Moo-1.001000/lib/Moo/Role.pm line 208. Compilation failed in require at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer2/lib/Dancer2.pm line 8. BEGIN failed--compilation aborted at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer2/lib/Dancer2.pm line 8. Compilation failed in require at simple.pl line 16. BEGIN failed--compilation aborted at simple.pl line 16. Mark Wood-Patrick ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------

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From Dancer launch Background Process
by Hugues Max 01 May '13

01 May '13

Hello I would like to launch in background a perl program ( or function who create lot of PDF) from my Dancer APP. and view in web page the log of this program. I've done a small test, ajax part works well, but if my process backgroup is too long with sleep , nothing works, web browser wait... What is the best way to do that ? use backtick ``, system, exec ? create sub or launch external perl program as my $output = qx|perl /util/generation.pl $id &|; print $output; or fork module ? thanks for your advice Hugues. post '/generationpdf' => sub { ... ... background(); } #my test background process sub background { open (LOG,">:encoding(UTF-8)",$PATHPDF."generationpdf.log") || die ("Problème d'ouverture du fichier de log $!"); say LOG "\n################################################"; for (my $i=0;$i<300;$i++) { # sleep 1; say LOG $i; } } AJAX PART ajax '/getloadavg' => sub { my $cmd = "tail ". $PATHPDF. "generationpdf.log"; { timestamp => time, loadavg => `$cmd`, }; TEMPLATE PART <pre>Calcul des PDF: <span id="flog"></span> </pre> <script type="text/javascript"> setInterval(function() { $.getJSON('[% request.uri_base %]/getloadavg', function(response) { var point = [ response.timestamp, response.log ];; $("#timestamp").text(response.timestamp); $("#flog").text(response.flog); }) }, 1000); </script>

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Dancer2 status
by Pedro Melo 29 Apr '13

29 Apr '13

Hi, I've been lurking for the past few months, but I don't have a complete notion on the status of Dancer2. I'm starting two new projects this week, small websites, one a intranet, another a small ecommerce site. I would like to use Dancer for this but I don't know if Dancer2 is ready or not. Also, is dancer-users(a)dancer.pm the new official mailing list for dancer? Bye, -- Pedro Melo @pedromelo http://www.simplicidade.org/ xmpp:melo@simplicidade.org mailto:melo@simplicidade.org

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Looking for examples of using Dancer with javascript frameworks
by Mark Wood-Patrick 29 Apr '13

29 Apr '13

I'm looking for examples of using Dancer with javascript frameworks like angular or ember but doing a web search I did not turn up much anyone have any suggestions or pointers Mark Wood-Patrick ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------

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Automating loading of index.html
by Mark Wood-Patrick 28 Apr '13

28 Apr '13

Is there a way to be able to tell Dancer to load and index.html file automatically if it exists so be able to specify: http://l-sim-27-071:4080/todomvc/architecture-examples/yui rather than http://l-sim-27-071:4080/todomvc/architecture-examples/yui/index.html Mark Wood-Patrick ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------

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getting seg fault when running under the perl debugger
by Mark Wood-Patrick 28 Apr '13

28 Apr '13

Are there any known issues with running under the perl debugger I get a segmentation violation Signal SEGV at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/App.pm line 94 Dancer::App::reload_apps('Dancer::App') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/Handler.pm line 73 Dancer::Handler::handle_request('Dancer::Handler::Standalone=HASH(0x189c648)', 'Dancer::Request=HASH(0x18f2a18)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/Handler.pm line 123 Dancer::Handler::__ANON__[/home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/Handler.pm:124]('HASH(0x18f2d18)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-PSGI-0.14/lib/HTTP/Server/Simple/PSGI.pm line 103 eval {...} called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-PSGI-0.14/lib/HTTP/Server/Simple/PSGI.pm line 103 HTTP::Server::Simple::PSGI::handler('Dancer::Handler::Standalone=HASH(0x189c5a0)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-0.44/lib/HTTP/Server/Simple.pm line 402 HTTP::Server::Simple::__ANON__[/home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-0.44/lib/HTTP/Server/Simple.pm:403]('Dancer::Handler::Standalone::NetServer0') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-0.44/lib/HTTP/Server/Simple.pm line 307 HTTP::Server::Simple::__ANON__[/home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-0.44/lib/HTTP/Server/Simple.pm:314]('Dancer::Handler::Standalone::NetServer0', 'port', 4080) called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/HTTP-Server-Simple-0.44/lib/HTTP/Server/Simple.pm line 271 HTTP::Server::Simple::run('Dancer::Handler::Standalone=HASH(0x189c5a0)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/Handler/Standalone.pm line 36 Dancer::Handler::Standalone::start('Dancer::Handler::Standalone=HASH(0x189c648)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer/Handler.pm line 207 Dancer::Handler::dance('Dancer::Handler::Standalone=HASH(0x189c648)') called at /home/app_perf_catalog/mwoodpatrick/mongodb/PORTool/Perl/Dancer-1.3112/lib/Dancer.pm line 480 Dancer::_start() called at dancer.pl line 128 Aborted (core dumped) Mark Wood-Patrick Performance Infrastructure Lead e-mail: mwoodpatrick(a)nvidia.com<mailto:mwoodpatrick@nvidia.com> Building/Cube: SC B31.3084 Primary Office: please use cell # below (+1 408 486-2757) Cell: 408-627-5025 Fax: 408 486-4757 Mailstop/Mailbox: MS-10 / B307 (\__/) (='.'=) (")_(") ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------

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how to get more diagnostics on Internal Server Error.
by Mark Wood-Patrick 26 Apr '13

26 Apr '13

I'm running with Dancer-1.3112 on CentOS release 5.7 (Final) On starting dancer and running wget http://0.0.0.0:3000 I get: --2013-04-24 03:56:34-- http://0.0.0.0:3000/ Connecting to 0.0.0.0:3000... connected. HTTP request sent, awaiting response... 500 Internal Server Error 2013-04-24 03:56:34 ERROR 500: Internal Server Error. But no other info on what the problem is. I'm probably doing something wrong but how can I get more diagnostics on what the problem is Mark Wood-Patrick ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. -----------------------------------------------------------------------------------

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Getting started with Perl Dancer - new screencast
by Gabor Szabo 24 Apr '13

24 Apr '13

Hi, recently I've started again to publish screencasts, this time solely on my own Perl Maven site. After two very experimental videos, I think this is already reasonably ok to show: http://perlmaven.com/videos/getting-started-with-perl-dancer Given enough feedback I can create a whole series of screencasts for Dancer, but I'd certainly like to get some feedback from you. What subject would you like to be covered? Should this be aimed at Perl developers who start with Dancer or people who are already experienced with Dancer? Should it maybe even assume no, or very little Perl knowledge as well? My plan is to follow the footsteps of railscasts.com and provide some of the videos free of charge and some for paying subscribers only so I can cover my bills. Will there be enough people to make this sustainable? Gabor

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