
=head1 NAME

Mojolicious::Guides::FAQ - Frequently Asked Questions

=head1 OVERVIEW

This document contains the most frequently asked questions about
L<Mojolicious> together with the right answers.

=head1 QUESTIONS

=head2 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
C<real-time web> and new technologies such as C<WebSockets>, we are facing new
challenges that go way beyond what commonly used modules like L<LWP> were
designed for. Because of this, L<Mojolicious> contains a whole new HTTP
client/server stack called L<Mojo>, which was heavily inspired by the original
C<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.

=head2 Why doesn't Mojolicious have any dependencies?

We are optimizing L<Mojolicious> for user-friendliness and development speed,
without compromises. While there are no rules in
L<Mojolicious::Guides::CodingGuidelines> 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 L<EV>, L<IO::Socket::IP>, L<IO::Socket::SSL>,
L<Net::Rendezvous::Publish> and L<Plack> to provide advanced functionality if
they are installed.

=head2 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.

=head2 What about backwards compatibility?

In conformance with L<Mojolicious::Guides::CodingGuidelines>, 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 L<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.

=head2 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.

=head2 Can you add feature XY to the core distribution?

Probably not. While the L<Mojolicious> distribtion covers a wide range of
features, we are rather conservative when it comes to adding new ones. The
most important criteria are outlined in
L<Mojolicious::Guides::CodingGuidelines>. But don't let this discourage you,
it doesn't hurt to open a
L<GitHub issue|https://github.com/kraih/mojo/issues> and ask, just be prepared
that it might not pass the vote. To increase the chances you can also discuss
and refine ideas on the
L<mailing-list|http://groups.google.com/group/mojolicious>.

=head2 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 C<5MB> by default, you can use the C<MOJO_MAX_MESSAGE_SIZE> environment
variable to change this value.

=head2 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 C<\r\n> terminated part of a HTTP message, such as request line, status
line and headers. This limit is around C<10KB> by default, you can use the
C<MOJO_MAX_LINE_SIZE> environment variable to change this value.

=head2 What does "Your secret passphrase needs to be changed!!!" mean?

L<Mojolicious> uses a secret passphrase for security features such as signed
cookies. It defaults to the name 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 L<Mojolicious/"secret">.

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

=head2 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 C<20> seconds for the user
agent and C<15> seconds for all built-in web servers, and is commonly referred
to as C<inactivity_timeout>. This timeout always applies, so you might have to
tweak it for applications that take a long time to process a request.

=head2 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.

=head2 What does "Worker 31842 has no heartbeat, restarting." mean?

Hypnotoad worker processes send heartbeat messages to the manager process in
regular intervals to signal that they are still responsive. A blocking
operation such as an infinite loop in your application can prevent this, and
will force the affected worker to be restarted after a timeout. This
C<heartbeat_timeout> defaults to C<20> seconds and can be extended if your
application requires it.

=head2 I think i have found a bug, what should i do now?

First make sure you are using the latest version of L<Mojolicious>, it is
quite likely that the bug has already been fixed. If that doesn't help,
prepare a test case demonstrating the bug, you are not expected to fix it
yourself, but you'll have to make sure the developers can replicate your
problem. Sending in your whole application generally does more harm than good,
the C<t> directory of this distribution has many good examples for how to do
it right. Writing a test is usually the hardest part of fixing a bug, so the
better your test case the faster it can be fixed. ;)

Once that's done you can contact the developers via
L<GitHub issue|https://github.com/kraih/mojo/issues>.

If you decide to fix the bug yourself, make sure to also take a look at
L<Mojolicious::Guides::CodingGuidelines>.

=head1 MORE

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

=cut
