NAME

NAME
Chouette - REST API Framework

DESCRIPTION
Chouette is a framework for making HTTP services. It is primarily
designed for services that implement REST-like APIs using
"application/json" as input and "application/x-www-form-urlencoded" as
output, although this is somewhat flexible.

Why "chouette"? A backgammon chouette
<http://www.bkgm.com/variants/Chouette.html> is a fast-paced, exciting
game with lots going on at once, kind of like an asynchronous REST API
server. :)

Chouette was extracted from numerous services I have built before, and
its main purpose is to glue together the following of my modules in the
way they were designed to be used:

AnyEvent::Task
Allows us to perform blocking operations without holding up other
requests.

Callback::Frame
Makes exception handling simple and convenient. You can "die"
anywhere and it will only affect the request being currently
handled.

Session::Token
For random identifiers such as session tokens (obviously).

Log::Defer
Structured logging, properly integrated with AnyEvent::Task so your
tasks can log messages into the proper request log contexts.

Note that Chouette also depends on Log::Defer::Viz so
"log-defer-viz" will be available for viewing logs.

Log::File::Rolling
To store the logs in files, and rotate them periodically. Also
maintains a current symlink so you can simply run the following in a
shell and you'll always see the latest logs as you need them:

$ log-defer-viz -F /var/myapi/logs/myapi.current.log

Chouette will always depend on the above modules, so if your app uses
them it is sufficient to depend on "Chouette" alone.

CHOUETTE OBJECT
To start a server, create a "Chouette" object. The constructor accepts a
hash ref with the following parameters. See the "bin/myapi" file below
for a full example.

"config_file"
This path is where the config file will be read from. If this
parameter is not provided then no file will be used.

The file's format is YAML. The only required parameters in the file
are "var_dir" and "listen" (though these can be defaulted with the
"config_defaults" parameter below).

"config_defaults"
This hash is where you provide default config values. These values
can be overridden by the config file.

You can use the config store for values specific to your application
(it is accessible with the "config" method of the context), but here
are the values that "Chouette" itself looks for:

"var_dir" - This directory must exist and be writable. "Chouette"
will use this to store log files and AnyEvent::Task sockets.

"listen" - This is the location the Chouette server will listen on.
Examples: 8080 "127.0.0.1:8080" "unix:/var/myapi/myapi.socket"

"logging.file_prefix" - The prefix for log file names (default is
"app").

"logging.timezone" - Either "gmtime" or "localtime" ("gmtime" is
default, see Log::File::Rolling).

"middleware"
Any array-ref of Plack::Middleware packages. Either strings
representing packages, or an array-ref where the first element is
the package and the rest are the arguments to the middleware.

The strings representing packages can either be prefixed with
"Plack::Middleware::" or not. If not, it will try the package as is
and if that doesn't exist, it will try adding the
"Plack::Middleware::" prefix.

middleware => [
'Plack::Middleware::ContentLength',
'ETag',
['Plack::Middleware::CrossOrigin', origins => '*'],
],

"pre_route"
A package and function that will be called with a context and
callback. If the function determines the request processing should
continue, it should call the callback.

See the "lib/MyAPI/Auth.pm" file below for an example of the
function.

"routes"
Routes are specified when you create the "Chouette" object.

routes => {
'/myapi/resource' => {
POST => 'MyAPI::Resource::create',
GET => 'MyAPI::Resource::get_all',
},

'/myapi/resource/:resource_id' => {
GET => 'MyAPI::Resource::get_by_id',
POST => sub {
my $c = shift;
die "400: can't update ID " . $c->route_params->{resource_id};
},
},
},

For each route, it will try to "require" the package specified, and
obtain the function specified for each HTTP method. If the package
or function doesn't exists, an error will be thrown.

You can use ":name" elements in your routes to extract parameters.
They are accessible via the "route_params" method of the context
(see "lib/MyAPI/Resource.pm" below).

Note that routes are combined with Regexp::Assemble so don't worry
about having lots of routes, it doesn't loop over each one.

See the "bin/myapi" file below for an example.

"tasks"
This is a hash-ref of AnyEvent::Task servers/clients to create.

tasks => {
db => {
pkg => 'LPAPI::Task::DB',
checkout_caching => 1,
client => {
timeout => 20,
},
server => {
hung_worker_timeout => 60,
},
},
},

"checkout_caching" means that if a checkout is obtained and
released, it will be maintained for the duration of the request and
if another checkout for this task is obtained, then the original
will be returned. This is useful for DBI for example, because we
want the authenticate handler to run in the same transaction as the
handler (for both correctness and efficiency reasons).

Additional arguments to AnyEvent::Task::Client and
<AnyEvent::Task::Server> can be passed in via "client" and "server".

See the "bin/myapi" and "lib/MyAPI/Task/PasswordHasher.pm" files for
an example.

"quiet"
If set, suppress the "welcome" message:

===============================================================================

Chouette 0.100

PID = 31713
UID/GIDs = 1000/1000 4 20 24 27 30 46 113 129 1000
Listening on: http://0.0.0.0:8080

Follow log messages:
log-defer-viz -F /var/myapi/logs/myapi.current.log

===============================================================================

After the "Chouette" object is obtained, you should call "serve" or
"run". They are basically the same except "serve" returns whereas "run"
enters the AnyEvent event loop. These are equivalent:

$chouette->run;

and

$chouette->serve;
AE::cv->recv;

CONTEXT
There is a "Chouette::Context" object passed into every handler.
Typically we name it $c. It represents the current request and various
related items.

"respond"
The respond method sends a JSON response, which will be encoded from
the first argument:

$c->respond({ a => 1, b => 2, });

Note: After responding, this method returns and your code continues.
If you call "respond" again, an error will be logged but the second
response will not be sent (it can't be -- the connection is probably
already closed). If you wish to stop processing, you can "die" with
the result from "respond" since it returns a special object for this
purpose:

die $c->respond({ a => 1, });

"respond" takes an optional second argument which is the HTTP
response code (defaults to 200):

$c->respond({ error => "access denied" }, 403);

Note that processing continues here again. If you wish to terminate
the processing right away, prefix with "die" as above, or use the
following shortcut:

die "403: access denied";

If you are happy with the Feersum default message ("Forbidden" in
this case) you can just do:

die 403;

"done"
If you wish to stop processing but not send a response:

$c->done;

You will need to send a response later, usually from an async
callback. Note: If the last reference to the context is destroyed
without a response being sent, a 500 "internal server error"
response will be sent.

You don't need to call "done", you can just "return" from the
handler. "done" is just for convenience if you are deeply nested in
callbacks and don't want to worry about writing a bunch of returning
logic.

"respond_raw"
Similar to "respond" except it doesn't assume JSON encoding:

$c->respond_raw(200, 'text/plain', 'some plain text');

"logger"
Returns the Log::Defer object associated with the request:

$c->logger->info("some stuff is happening");

{
my $timer = $c->logger->timer('doing big_computation');
big_computation();
}

See the Log::Defer docs for more details. For viewing the log
messages, check out Log::Defer::Viz.

"config"
Returns the "config" hash. See the "CHOUETTE OBJECT" section for
details.

"req"
Returns the Plack::Request object created by this request.

my $name = $c->req->parameters->{name};

"res"
You would think this would return a Plack::Response object but this
isn't yet implemented and will instead throw an error.

"generate_token"
Generates a Session::Token random string. The Session::Token
generator is created when the first request comes in so as to avoid
"cold" entropy pool immediately after a reboot (see Session::Token
docs).

"task"
Returns an <AnyEvent::Task> checkout object for the task with the
given name:

$c->task('db')->selectrow_hashref(q{ SELECT * FROM sometable WHERE id = ? },
undef, $id, sub {
my ($dbh, $row) = @_;

die $c->respond($row);
});

See AnyEvent::Task for more details.

EXAMPLE
These files are a complete-ish Chouette application that I have
extracted from a real-world app. Warning: untested!

"bin/myapi"
#!/usr/bin/env perl

use common::sense;

use Chouette;

my $chouette = Chouette->new({
config_file => '/etc/myapi.conf',

config_defaults => {
var_dir => '/var/myapi',
listen => '8080',

logging => {
file_prefix => 'myapi',
timezone => 'localtime',
},
},

middleware => [
'Plack::Middleware::ContentLength',
],

pre_route => 'MyAPI::Auth::authenticate',

routes => {
'/myapi/unauth/login' => {
POST => 'MyAPI::User::login',
},

'/myapi/resource' => {
POST => 'MyAPI::Resource::create',
GET => 'MyAPI::Resource::get_all',
},

'/myapi/resource/:resource_id' => {
GET => 'MyAPI::Resource::get_by_id',
},
},

tasks => {
passwd => {
pkg => 'MyAPI::Task::PasswordHasher',
},
db => {
pkg => 'MyAPI::Task::DB',
checkout_caching => 1, ## so same dbh is used in authenticate and handler
},
},
});

$chouette->run;

"lib/MyAPI/Auth.pm"
package MyAPI::Auth;

use common::sense;

sub authenticate {
my ($c, $cb) = @_;

if ($c->{env}->{PATH_INFO} =~ m{^/myapi/unauth/}) {
return $cb->();
}

my $session = $c->req->parameters->{session};

$c->task('db')->selectrow_hashref(q{ SELECT user_id FROM session WHERE session_token = ? },
undef, $session, sub {
my ($dbh, $row) = @_;

die 403 if !$row;

$c->{user_id} = $row->{user_id};

$cb->();
});
}

1;

"lib/MyAPI/User.pm"
package MyAPI::User;

use common::sense;

sub login {
my $c = shift;

my $username = $c->req->parameters->{username};
my $password = $c->req->parameters->{password};

$c->task('db')->selectrow_hashref(q{ SELECT user_id, password_hashed FROM myuser WHERE username = ? }, undef, $username, sub {
my ($dbh, $row) = @_;

die 403 if !$row;

$c->task('passwd')->verify_password($row->{password_hashed}, $password, sub {
die 403 if !$_[1];

my $session_token = $c->generate_token();

$dbh->do(q{ INSERT INTO session (session_token, user_id) VALUES (?, ?) },
undef, $session_token, $row->{user_id}, sub {

$dbh->commit(sub {
die $c->respond({ sess => $session_token });
});
});
});
});
}

1;

"lib/MyAPI/Resource.pm"
package MyAPI::Auth;

use common::sense;

sub create {
my $c = shift;
die "500 not implemented";
}

sub get_all {
$c->logger->warn("denying access to get_all");
die 403;
}

sub get_by_id {
my $c = shift;
my $resource_id = $c->route_params->{resource_id};
die $c->respond({ resource_id => $resource_id, });
}

1;

"lib/MyAPI/Task/PasswordHasher.pm"
package MyAPI::Task::PasswordHasher;

use common::sense;

use Authen::Passphrase::BlowfishCrypt;
use Encode;

sub new {
my ($class, %args) = @_;

my $self = {};
bless $self, $class;

open($self->{dev_urandom}, '<:raw', '/dev/urandom') || die "open urandom: $!";

setpriority(0, $$, 19); ## renice our process so we don't hold up more important processes

return $self;
}

sub hash_password {
my ($self, $plaintext_passwd) = @_;

read($self->{dev_urandom}, my $salt, 16) == 16 || die "bad read from urandom";

return Authen::Passphrase::BlowfishCrypt->new(cost => 10,
salt => $salt,
passphrase => encode_utf8($plaintext_passwd // ''))
->as_crypt;

}

sub verify_password {
my ($self, $crypted_passwd, $plaintext_passwd) = @_;

return Authen::Passphrase::BlowfishCrypt->from_crypt($crypted_passwd // '')
->match(encode_utf8($plaintext_passwd // ''));
}

1;

"lib/MyAPI/Task/DB.pm"
package MyAPI::Task::DB;

use common::sense;

use AnyEvent::Task::Logger;

use DBI;

sub new {
my $config = shift;

my $dbh = DBI->connect("dbi:Pg:dbname=myapi", '', '', {AutoCommit => 0, RaiseError => 1, PrintError => 0, })
|| die "couldn't connect to db";

return $dbh;
}

sub CHECKOUT_DONE {
my ($dbh) = @_;

$dbh->rollback;
}

1;

SEE ALSO
More documentation can be found in the modules linked in the DESCRIPTION
section.

Chouette github repo <https://github.com/hoytech/Chouette>

AUTHOR
Doug Hoyte, "<[email protected]>"

COPYRIGHT & LICENSE
Copyright 2017 Doug Hoyte.

This module is licensed under the same terms as perl itself.