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".