trusty (3) Mojolicious::Guides::FAQ.3pm.gz

NAME

       Mojolicious::Guides::FAQ - Frequently Asked Questions

OVERVIEW

       This document contains answers for the most frequently asked questions about Mojolicious.

QUESTIONS

   How does Mojolicious compare to other Perl web frameworks?
       The short answer is "it doesn't", because we interpret the words "web framework" much more literally than
       others. With the emergence of the "real-time web" and new technologies such as "WebSockets", we are
       facing new challenges that go way beyond what commonly used modules like LWP were designed for. Because
       of this, Mojolicious contains a whole new HTTP client/server stack called Mojo, which was heavily
       inspired by the original "LWPng" effort and carefully designed with these new requirements in mind. So
       while some of the higher abstraction layers might look similar to other web frameworks, it actually
       defines a whole new category and could even be the foundation for more advanced ones in the future.

   Why doesn't Mojolicious have any dependencies?
       We are optimizing Mojolicious for user-friendliness and development speed, without compromises. While
       there are no rules in Mojolicious::Guides::Contributing that forbid dependencies, we do currently
       discourage adding non-optional ones in favor of a faster and more painless installation process. And we
       do in fact already use several optional CPAN modules such as EV, IO::Socket::IP, IO::Socket::SSL and
       Plack to provide advanced functionality if they are installed.

   Why reinvent wheels?
       Because we can make them rounder. Components specifically designed for user-friendliness and development
       speed are not easy to come by. We are strong believers of the Perl mantra "There is more than one way to
       do it", and our quest is to develop the best possible solutions for these two criteria.

   What about backwards compatibility?
       In conformance with Mojolicious::Guides::Contributing, we will always deprecate a feature before removing
       or changing it in incompatible ways between major releases. New features can however be marked as
       experimental to explicitly exclude them from these rules. This gives us the necessary freedom to ensure a
       healthy future for Mojolicious. So, as long as you are not using anything marked experimental, untested
       or undocumented, you can always count on backwards compatibility, everything else would be considered a
       bug.

   Why not split up Mojolicious into many smaller distributions?
       Because there are no advantages, it drastically increases maintenance costs and installation times
       without giving us anything in return. It would only make sense if we wanted to pass ownership of a module
       to a new maintainer, which we already have done in the past.

   Which versions of Perl are supported by Mojolicious?
       First of all, you need to be aware that according to the perlpolicy, only the two most recent stable
       release series of Perl are supported by the community and receive bug fixes, which are currently 5.18.x
       and 5.16.x.  Mojolicious follows this model and fully supports these two release series.  In addition we
       will also keep the distribution installable up to a certain legacy version that we deem worthy of
       supporting, but not specifically optimize for it, this is currently 5.10.1.

   What does the error "Maximum message size exceeded" mean?
       To protect your applications from excessively large requests and responses, our HTTP parser has a cap
       after which it will automatically stop accepting new data, and in most cases force the connection to be
       closed. This limit is around "10MB" by default, you can use the MOJO_MAX_MESSAGE_SIZE environment
       variable to change this value.

   What does the error "Maximum line size exceeded" mean?
       This is a very similar protection mechanism to the one described in the previous answer, but a little
       more specific. It limits the maximum length of any "\x0d\x0a" terminated part of a HTTP message, such as
       request line, status line and headers. This limit is around "10KB" by default, you can use the
       MOJO_MAX_LINE_SIZE environment variable to change this value.

   What does the error "Maximum buffer size exceeded" mean?
       This protection mechanism is very similar to those mentioned in the two previous answers. It limits how
       much content the HTTP parser is allowed to buffer when parsing chunked, compressed and multipart
       messages. This limit is around "256KB" by default, you can use the MOJO_MAX_BUFFER_SIZE environment
       variable to change this value.

   What does the error "EV does not work with ithreads" mean?
       The Mojolicious user agent and web servers are based on an event loop that supports multiple reactor
       backends. One of these backends is EV, it is very fast and will be automatically used if installed. On
       Windows however, the "ithreads" based "fork()" emulation can interfere with it, and you may have to use
       the MOJO_REACTOR environment variable to enforce a more portable one.

         MOJO_REACTOR=Mojo::Reactor::Poll

   What does "Your secret passphrase needs to be changed" mean?
       Mojolicious uses secret passphrases for security features such as signed cookies. It defaults to the
       moniker of your application, which is not very secure, so we added this log message as a reminder. You
       can change the passphrase with the attribute "secrets" in Mojolicious.

         app->secrets(['My very secret passphrase.']);

   What does "Nothing has been rendered, expecting delayed response" mean?
       Mojolicious has been designed from the ground up for non-blocking I/O and event loops. So when a new
       request comes in and no response is generated right away, it will assume that this was intentional and
       return control to the web server, which can then handle other requests while waiting for events such as
       timers to finally generate a response.

   What does "Inactivity timeout" mean?
       To protect your applications from denial-of-service attacks, all connections have an inactivity timeout
       which limits how long a connection may be inactive before being closed automatically. It defaults to 20
       seconds for the user agent and 15 seconds for all built-in web servers, and is commonly referred to as
       "inactivity_timeout". This timeout always applies, so you might have to tweak it for applications that
       take a long time to process a request.

   What does "Premature connection close" mean?
       This error message is often related to the one above, and means that the web server closed the connection
       before the user agent could receive the whole response or that the user agent got destroyed, which forces
       all connections to be closed immediately.

   What does "Worker 31842 has no heartbeat, restarting" mean?
       As long as they are accepting new connections, Hypnotoad worker processes send heartbeat messages to the
       manager process at regular intervals, to signal that they are still responsive. A blocking operation such
       as an infinite loop in your application (or active connections after a worker has stopped accepting new
       connections) can prevent this, and will force the affected worker to be restarted after a timeout. This
       "heartbeat_timeout" defaults to 20 seconds and can be extended if your application requires it.

MORE

       You can continue with Mojolicious::Guides now or take a look at the Mojolicious wiki
       <http://github.com/kraih/mojo/wiki>, which contains a lot more documentation and examples by many
       different authors.

SUPPORT

       If you have any questions the documentation might not yet answer, don't hesitate to ask on the mailing-
       list <http://groups.google.com/group/mojolicious> or the official IRC channel "#mojo" on "irc.perl.org".