May 2017 - dancer-users - lists.preshweb.co.uk

How can a fork+system() Dancer app not create zombie processes?
by Shlomi Fish 29 Jun '17

29 Jun '17

Hi all! When running a simple and reduced Dancer 1 application which forks and runs perldoc -f system , I am getting many zombie processes after making requests. This does not happen with https://github.com/shlomif/shlomif-perl-snippets/blob/master/tcp-socket-ser… which does the same thing using IO::Socket and plain TCP. To reproduce, do: hg clone https://shlomif@bitbucket.org/shlomif/app-notifier cd app-notifier hg checkout zombies-processes-bug cd App-Notifier-Service/ And then run “bash run-server.bash” and in a different shell session “bash run-client.bash.” . You can run 'pstree -p' to see the zombies processes. This happens on Mageia v6 x86-64 and Fedora 25 x86-64 with perl-Dancer-1.320.200-2.mga6 . I am quoting a discussion I had on #dancer on irc.perl.org about it. Any further insights about a solution will be welcome. Regards, Shlomi Fish ``` Apr 02 16:47:21 <rindolf> Hi all! My dancer service here (run run-server.bash and then run-client.bash in the App-Notifier-Service directory and note the branch) generates many zombie processes - how can I prevent it from happening? https://bitbucket.org/shlomif/app-notifier/branch/zombies-processes-bug Apr 02 16:54:58 <racke> how do you start the dancer service? Apr 02 16:55:57 <rindolf> racke: perl -I"`pwd`/lib" bin/app.pl --port=6300 Apr 02 16:56:25 <racke> so that is Dancer 1 ? Apr 02 16:56:40 <rindolf> racke: yes, it is Apr 02 16:58:36 <racke> you start only one instance so i might not be able to handle the incoming request Apr 02 16:59:32 <rindolf> racke: it handles most requests fine Apr 02 16:59:36 <racke> better use something like plackup -s Starman --workers=5 Apr 02 17:01:13 <rindolf> racke: what do I need it for? Apr 02 17:01:38 <racke> as I explained before Apr 02 17:01:44 <racke> you need more than one instance Apr 02 17:02:33 <rindolf> racke: see https://metacpan.org/pod/App::Notifier::Service for my use case Apr 02 17:02:38 <rindolf> racke: why? Apr 02 17:03:08 <rindolf> racke: i don't need to handle moer than one request at the time Apr 02 17:03:23 <racke> hm Apr 02 17:03:30 <racke> if you think so Apr 02 17:05:01 <racke> you probably don't handle fork correctly, that is likely to cause your zombies Apr 02 17:05:27 <rindolf> racke: I followed perldoc perlipc Apr 02 17:10:42 <racke> well why not use something like IPC::RUn? Apr 02 17:16:33 <rindolf> racke: 1. I used fork+system - it is enough for my needs, 2. I provided a link to the code - did you take a look? 3. I found IPC::Run buggy when i used it in a different project Apr 02 17:17:22 <rindolf> racke: and also - this is the reduced-to-a-minimum code Apr 02 17:19:23 <racke> yeah I did take a look Apr 02 17:19:49 <rindolf> racke: ok, thanks! Apr 02 17:20:09 <racke> I am not familar with using fork so ... Apr 02 17:20:33 <racke> but it looks like it produces your army of zombies :-) Apr 02 18:01:22 <rindolf> racke: the IO-Socket-INET equivalent does not spawn any zombies - https://github.com/shlomif/shlomif-perl-snippets/blob/master/tcp-socket-ser… Apr 02 18:07:07 <rindolf> http://stackoverflow.com/questions/13614498/forking-to-run-code-in-a-child-… - there is this too ``` -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ My Favourite FOSS - http://www.shlomifish.org/open-source/favourite/ Chuck Norris can end world hunger, but he thinks that hungry people make humanity a more challenging adversary. — http://www.shlomifish.org/humour/bits/facts/Chuck-Norris/ Please reply to list if it's a mailing list post

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Command line change password script (Was: Custom login page with Dancer2::Plugin::Auth::Extensible)
by Nathan Bailey 26 May '17

26 May '17

Hi all, Separate but somewhat related to my previous questions - how can I make a command line script to do a change password, using the DPAE infrastructure? Presumably I will need to use Dancer2? Or can I dig directly into DPAE's set_user_password()? Dancer2::Plugin::Auth::Extensible::Provider::Database->new() wants a 'plugin', and Dancer2::Plugin::Auth::Extensible->new() wants an 'app'; I could pass fake values in but I suspect that's going to break things. How far up the tree do I need to go to be able to say "Use XXX", "XXX->new" and "XXX...->set_user_password"? thanks, Nathan

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DPAE workflow: password reset => change password, rather than temporary password?
by Nathan Bailey 26 May '17

26 May '17

Hi all, I now have Dancer2::Plugin::Auth::Extensible working in our environment. It works great, but I think the 'forgot password' workflow is a little longer than it needs to be. It appears that the 'Forgot password' workflow is: 1. Type in email and request token 2. Get token in email 3. Click the link with the token (in your email) 4. Click 'Reset password' 5. Get a new password 6. Login in with the new password 7. Presumably, change your password It seems that steps 5 and 6 are redundant to me - once we've authenticated the user, I'd like to get them to change their password immediately. Presumably others have already done this, does anyone have some code they'd like to share? thanks! Nathan

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Printing output directly
by Amelia Ireland 23 May '17

23 May '17

Hello Dancers, Is it possible to print web page output directly using Dancer2? I'm using Text::CSV_XS to output DB data as CSV like so: while ( my $row = $sth->fetch ) { $csv->print ( $io, $row ); } where $io is a file handle, socket, etc. At the moment, I'm creating a temp file, writing the data, and then using send_file to dispatch the data. Ideally I'd like to just print it straight to the web output, but (e.g.) setting $io to *STDOUT does not work, and there is no serialiser for csv or plain text. Is there a shortcut that I'm missing? Thanks!

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query parameter parsing and Dancer vs Apache handling
by Amelia Ireland 15 May '17

15 May '17

Hi Dancers, Is it possible to have Dancer selectively handle some routes based on query parameters, and leave others for another script to handle? I'm working with an old site where some URLs with query params of the form main.cgi?param=value&param2=value2&param3=value3 can be handled by Dancer (by redirecting to new pages), but others must be handled by the old site. At present, I have a route set up to parse query params for /main.cgi, and any query params that Dancer can't handle go to the 404 page. Is there are way to let those queries 'pass through' dancer (i.e. not trigger a 404) and be handled by the perl script main.cgi instead? If I set up Apache or my psgi application to send all those queries to main.cgi first, the subset of pages that can be redirected by new pages will just show the old page. Unfortunately I cannot change the content of the old pages to change the URLs. I'd guess I can create Apache redirects for sets of query parameters -- it's pretty easy to specify that only certain combinations of query params are handled by Dancer, and I'm not sure it is as easy a task with Apache. Thanks!

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Custom login page with Dancer2::Plugin::Auth::Extensible
by Nathan Bailey 15 May '17

15 May '17

Per the documentation, http://search.cpan.org/~hornburg/Dancer2-Plugin-Auth-Extensible-0.703/lib/D… in my .yml config, I have: plugins: Auth::Extensible: # Set the view name for a custom login page, defaults to 'login' login_template: login but my login page: get '/login' => sub { ... template 'login', { ... }; }; doesn't seem to get called. I've tried "login_template: /login" but the default login is still getting loaded. Any ideas? thanks! Nathan

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by Stanley Lankford 12 May '17

12 May '17

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TT 'include file if exists'
by Nathan Bailey 01 May '17

01 May '17

Hi all, More of a Template Toolkit question rather than Dancer per se, but is there a better way to load a file only if it exists? >From my Googling around, it appears the only approaches are (a) Try/Catch in TT or (b) include a full <%PERL%> call (which I'm guessing may be a little heavy to do on every page load). I'd like to dynamically include a help file if it exists, otherwise provide a 'No help available for this page' message. Current code looks like this: <% help_file = 'help' _ request.request_uri.remove('\?.*') _ '.tt' %> <% TRY %> <% USE File('/full_unix_path/views/' _ help_file) %> <% INCLUDE $help_file %> <% CATCH File %> '<% help_file %>' doesn't exist: <% error.info %> <% END %> I'm not keen on the fixed path and it seems overkill to have to try/catch if the file exists rather than just load it (and fail silently) or test if it exists and then load. Do people have better patterns for managing inline help? thanks, Nathan

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