In part 1 we designed our API using OpenAPI/Swagger. Now it’s time to write some tests and wire it up using Mojolicious::Plugin::OpenAPI. This is a much longer article; buckle up!
If you haven’t already, you’ll need to install Perl. Using Linux or macOS? You’ve already got Perl installed on your system. On Windows? I recommend you install Strawberry Perl as it lets you develop Perl applications using the same tools that our Unix-based brethren use.
(Advanced users may want to investigate using perlbrew, plenv, or berrybrew for managing multiple versions of Perl and installing more recent versions than are included on your system.)
Once you have Perl installed, it’s a simple matter of using either the cpan
or cpanm
tools to install Mojolicious and Mojolicious::Plugin::OpenAPI. The latter will install some dependencies as well. Here’s a transcript of installing cpanm
and the two modules:
% curl -L https://cpanmin.us | perl - App::cpanminus
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 295k 100 295k 0 0 97765 0 0:00:03 0:00:03 --:--:-- 97765
--> Working on App::cpanminus
Fetching http://www.cpan.org/authors/id/M/MI/MIYAGAWA/App-cpanminus-1.7044.tar.gz ... OK
Configuring App-cpanminus-1.7044 ... OK
Building and testing App-cpanminus-1.7044 ... OK
Successfully installed App-cpanminus-1.7044
1 distribution installed
% cpanm Mojolicious Mojolicious::Plugin::OpenAPI
--> Working on Mojolicious
Fetching http://www.cpan.org/authors/id/S/SR/SRI/Mojolicious-9.01.tar.gz ... OK
Configuring Mojolicious-9.01 ... OK
Building and testing Mojolicious-9.01 ... OK
Successfully installed Mojolicious-9.01
--> Working on Mojolicious::Plugin::OpenAPI
Fetching http://www.cpan.org/authors/id/J/JH/JHTHORSEN/Mojolicious-Plugin-OpenAPI-4.00.tar.gz ... OK
Configuring Mojolicious-Plugin-OpenAPI-4.00 ... OK
==> Found dependencies: JSON::Validator
--> Working on JSON::Validator
Fetching http://www.cpan.org/authors/id/J/JH/JHTHORSEN/JSON-Validator-4.14.tar.gz ... OK
Configuring JSON-Validator-4.14 ... OK
==> Found dependencies: YAML::PP, Test::Deep
--> Working on YAML::PP
Fetching http://www.cpan.org/authors/id/T/TI/TINITA/YAML-PP-0.026.tar.gz ... OK
Configuring YAML-PP-0.026 ... OK
==> Found dependencies: Test::Warn, Test::Deep
--> Working on Test::Warn
Fetching http://www.cpan.org/authors/id/B/BI/BIGJ/Test-Warn-0.36.tar.gz ... OK
Configuring Test-Warn-0.36 ... OK
==> Found dependencies: Sub::Uplevel
--> Working on Sub::Uplevel
Fetching http://www.cpan.org/authors/id/D/DA/DAGOLDEN/Sub-Uplevel-0.2800.tar.gz ... OK
Configuring Sub-Uplevel-0.2800 ... OK
Building and testing Sub-Uplevel-0.2800 ... OK
Successfully installed Sub-Uplevel-0.2800
Building and testing Test-Warn-0.36 ... OK
Successfully installed Test-Warn-0.36
--> Working on Test::Deep
Fetching http://www.cpan.org/authors/id/R/RJ/RJBS/Test-Deep-1.130.tar.gz ... OK
Configuring Test-Deep-1.130 ... OK
Building and testing Test-Deep-1.130 ... OK
Successfully installed Test-Deep-1.130
Building and testing YAML-PP-0.026 ... OK
Successfully installed YAML-PP-0.026
Building and testing JSON-Validator-4.14 ... OK
Successfully installed JSON-Validator-4.14
Building and testing Mojolicious-Plugin-OpenAPI-4.00 ... OK
Successfully installed Mojolicious-Plugin-OpenAPI-4.00
7 distributions installed
(The versions listed above may differ as this article gets progressively out of date.)
Next, make a folder somewhere to place our new microservice project. We’ll call it ~/Projects/blog
here, but any place will do as long as you know how to get to it from your text editor and your command line.
After that, go into that directory and use the newly-installed mojo
command to build the basics of our project:
% cd ~/Projects/blog
% mojo generate app Local::Dictionary::Microservice
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/script
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/script/local_dictionary_microservice
[chmod] /Users/mgardner/Projects/blog/local_dictionary_microservice/script/local_dictionary_microservice 744
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/lib/Local/Dictionary
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/lib/Local/Dictionary/Microservice.pm
[exist] /Users/mgardner/Projects/blog/local_dictionary_microservice
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/local-dictionary-microservice.yml
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/lib/Local/Dictionary/Microservice/Controller
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/lib/Local/Dictionary/Microservice/Controller/Example.pm
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/t
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/t/basic.t
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/public
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/public/index.html
[mkdir] /Users/mgardner/Projects/local_dictionary_microservice/templates/layouts
[write] /Users/mgardner/Projects/local_dictionary_microservice/templates/layouts/default.html.ep
[mkdir] /Users/mgardner/Projects/blog/local_dictionary_microservice/templates/example
[write] /Users/mgardner/Projects/blog/local_dictionary_microservice/templates/example/welcome.html.ep
This command builds the scaffolding for our new project. We won’t be using all of it, but it does provide some useful starting points.
(Why did we put Local::
in the beginning of the name? Because nothing you place there will conflict with other modules you install from CPAN.)
Next, put the OpenAPI document we developed in part 1 somewhere in the project. We’ll choose openapi/dictionary_openapi.yml
. Create a folder called openapi
in the project, and then open your text editor and paste the following document into a file called dictionary_openapi.yml
.
openapi: 3.0.3
info:
title: Dictionary
description: The PhoenixTrap.com dictionary microservice
version: 1.0.0
license:
name: Artistic License 2.0
url: https://www.perlfoundation.org/artistic-license-20.html
paths:
/health:
get:
summary: Check if this service is online
x-mojo-to: monitoring#heartbeat
responses:
200:
description: All systems operational
content:
application/json:
schema:
type: object
500:
description: Something is wrong
/word/{word}:
get:
summary: Get the definition of a word
x-mojo-to: word#define
parameters:
- $ref: '#/components/parameters/word'
responses:
200:
description: Found word
content:
application/json:
schema:
type: string
404:
description: Could not find word
post:
summary: Add or replace the definition of a word
x-mojo-to: word#save
parameters:
- $ref: '#/components/parameters/word'
requestBody:
description: Definition of a word
required: true
content:
application/x-www-form-urlencoded:
schema:
type: object
properties:
definition:
type: string
responses:
200:
description: Word saved
delete:
summary: Delete an entry from the dictionary
x-mojo-to: word#remove
parameters:
- $ref: '#/components/parameters/word'
responses:
200:
description: Word deleted
components:
parameters:
word:
description: A word in the dictionary
in: path
name: word
required: true
schema:
type: string
Calling the plugin
Right now all our application does is serve a demonstration page; you can test it by running the following command:
% script/local_dictionary_microservice daemon
[2021-02-28 16:17:09.76863] [74167] [info] Listening at "http://*:3000"
Web application available at http://127.0.0.1:3000
…and then going to that URL on the last line.
After you’ve verified that it works, hold down the Control key and type the letter C in your terminal to stop the script. Edit the lib/Local/Dictionary/Microservice.pm
file in your text editor. Replace it with this:
package Local::Dictionary::Microservice;
use Mojo::Base 'Mojolicious', -signatures;
# This method will run once at server start
sub startup($self) {
# Load configuration from config file
my $config = $self->plugin('NotYAMLConfig');
# Configure the application
$self->secrets( $config->{secrets} );
$self->plugin( OpenAPI => {
url => $self->home
->rel_file('openapi/dictionary_openapi.yml'),
} );
}
1;
Now when you run the script as a daemon, the URL it reports responds with the JSON version of our OpenAPI document. Progress!
Note the $self->plugin()
call towards the end of our class above. That’s the secret sauce that loads our OpenAPI document and tells Mojolicious to create responses from it.
Writing our first tests
Next, we’ll write a couple of test scripts. (Why are we writing tests before actually coding our microservice? Because we’re practicing test-driven development, in which we write our tests first, see that they fail, and then write the code to make them succeed.) Here’s a modified t/basic.t
script that should succeed right off the bat:
use Mojo::Base -strict;
use Test::More;
use Test::Mojo;
my $t = Test::Mojo->new('Local::Dictionary::Microservice');
$t->get_ok('/')->status_is(200)->json_has('/openapi');
done_testing();
Run it with prove
:
% prove -vl t/basic.t
t/basic.t .. [2021-02-28 16:32:54.79287] [74611] [debug] [3kzjyqgi] GET "/"
[2021-02-28 16:32:54.79321] [74611] [debug] [3kzjyqgi] Routing to a callback
[2021-02-28 16:32:54.79536] [74611] [debug] [3kzjyqgi] 200 OK (0.002493s, 401.123/s)
ok 1 - GET /
ok 2 - 200 OK
ok 3 - has value for JSON Pointer "/openapi"
1..3
ok
All tests successful.
Files=1, Tests=3, 0 wallclock secs ( 0.02 usr 0.01 sys + 0.45 cusr 0.07 csys = 0.55 CPU)
Result: PASS
Now for a test that will fail at first. Put this in t/word.t
:
use Mojo::Base -strict;
use Test::More;
use Test::Mojo;
my $t = Test::Mojo->new('Local::Dictionary::Microservice');
$t->post_ok(
'/word/foo' =>
form => { definition => 'A metasyntactic variable' },
)->status_is(200);
done_testing();
And prove
it:
% prove -vl t/word.t
t/word.t .. [2021-02-28 16:48:53.26826] [75751] [debug] [SlDSHWVE] POST "/word/foo"
[2021-02-28 16:48:53.26897] [75751] [debug] [SlDSHWVE] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "save"
[2021-02-28 16:48:53.27278] [75751] [debug] [SlDSHWVE] Template "word/save.html.ep" not found
[2021-02-28 16:48:53.27287] [75751] [debug] [SlDSHWVE] Nothing has been rendered, expecting delayed response
[2021-02-28 16:49:23.27553] [75751] [debug] Inactivity timeout
# Premature connection close
not ok 1 - POST /word/foo
not ok 2 - 200 OK
# Failed test 'POST /word/foo'
# at t/word.t line 8.
# Failed test '200 OK'
# at t/word.t line 8.
# got: undef
# expected: '200'
1..2
# Looks like you failed 2 tests of 2.
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/2 subtests
Test Summary Report
-------------------
t/word.t (Wstat: 512 Tests: 2 Failed: 2)
Failed tests: 1-2
Non-zero exit status: 2
Files=1, Tests=2, 31 wallclock secs ( 0.02 usr 0.01 sys + 0.45 cusr 0.07 csys = 0.55 CPU)
Result: FAIL
Note in the second line of output that Mojolicious tried to route to a controller class at Local::Dictionary::Microservice::Controller::Word
with an action of save
. That’s what our OpenAPI document told it to do with its x-mojo-to: word#save
line.
Adding methods to make the tests pass
Now we’ll write the controller class at lib/Local/Dictionary/Microservice/Controller/Word.pm
:
package Local::Dictionary::Microservice::Controller::Word;
use Mojo::Base 'Mojolicious::Controller', -signatures;
use DB_File;
sub save($self) {
return if not $self->openapi->valid_input;
my ( $word, $definition ) = map { $self->param($_) }
qw(word definition);
tie my %definition, 'DB_File',
$self->app->home->child('definitions.db');
$definition{$word} = $definition;
return $self->render( openapi => {} );
}
1;
The save
method above retrieves the word
and definition
parameters from the URL path and POST data, respectively, and then saves them into a hash that is tie
d to a Berkeley DB file stored in definitions.db
. It then renders an empty response back to the client.
Now run the test:
% prove -vl t/word.t
t/word.t .. [2021-02-28 18:06:33.77551] [78923] [debug] [VV0L-5rU] POST "/word/foo"
[2021-02-28 18:06:33.77623] [78923] [debug] [VV0L-5rU] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "save"
[2021-02-28 18:06:33.77751] [78923] [debug] [VV0L-5rU] 200 OK (0.001994s, 501.505/s)
ok 1 - POST /word/foo
ok 2 - 200 OK
1..2
ok
All tests successful.
Files=1, Tests=2, 0 wallclock secs ( 0.02 usr 0.01 sys + 0.43 cusr 0.07 csys = 0.53 CPU)
Result: PASS
Woohoo, our method works! Let’s add some tests to the same t/word.t
script, underneath the first one:
$t->get_ok('/word/foo')->status_is(200)
->content_is('"A metasyntactic variable"');
$t->delete_ok('/word/foo')->status_is(200);
$t->get_ok('/word/foo')->status_is(404);
Here we’re testing that we get back the definition we saved, that we can delete the definition, and that when we try to retrieve it again we get a 404 Not Found
error.
The test script will fail again, but we can fix that by adding the define
and remove
methods to our controller class in lib/Local/Dictionary/Microservice/Controller/Word.pm
:
sub define($self) {
return if not $self->openapi->valid_input;
my $word = $self->param('word');
tie my %definition, 'DB_File',
$self->app->home->child('definitions.db');
return $self->render( openapi => $definition{$word},
exists $definition{$word} ? () : (status => 404),
);
}
sub remove($self) {
return if not $self->openapi->valid_input;
my $word = $self->param('word');
tie my %definition, 'DB_File',
$self->app->home->child('definitions.db');
delete $definition{$word};
return $self->render( openapi => {} );
}
Run the test script one last time:
% prove -vl t/word.t
t/word.t .. [2021-02-28 18:13:50.82904] [79162] [debug] [7PprxDOz] POST "/word/foo"
[2021-02-28 18:13:50.82978] [79162] [debug] [7PprxDOz] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "save"
[2021-02-28 18:13:50.83225] [79162] [debug] [7PprxDOz] 200 OK (0.003191s, 313.381/s)
ok 1 - POST /word/foo
ok 2 - 200 OK
[2021-02-28 18:13:50.83531] [79162] [debug] [G0qyFA0G] GET "/word/foo"
[2021-02-28 18:13:50.83568] [79162] [debug] [G0qyFA0G] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "define"
[2021-02-28 18:13:50.85745] [79162] [debug] [G0qyFA0G] 200 OK (0.022096s, 45.257/s)
ok 3 - GET /word/foo
ok 4 - 200 OK
ok 5 - exact match for content
[2021-02-28 18:13:50.86182] [79162] [debug] [MoedWcOi] DELETE "/word/foo"
[2021-02-28 18:13:50.86224] [79162] [debug] [MoedWcOi] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "remove"
[2021-02-28 18:13:50.86337] [79162] [debug] [MoedWcOi] 200 OK (0.001535s, 651.466/s)
ok 6 - DELETE /word/foo
ok 7 - 200 OK
[2021-02-28 18:13:50.86662] [79162] [debug] [G2lH8gyw] GET "/word/foo"
[2021-02-28 18:13:50.86684] [79162] [debug] [G2lH8gyw] Routing to controller "Local::Dictionary::Microservice::Controller::Word" and action "define"
[2021-02-28 18:13:50.86964] [79162] [debug] [G2lH8gyw] 404 Not Found (0.002989s, 334.560/s)
ok 8 - GET /word/foo
ok 9 - 404 Not Found
1..9
ok
All tests successful.
Files=1, Tests=9, 0 wallclock secs ( 0.02 usr 0.01 sys + 0.46 cusr 0.10 csys = 0.59 CPU)
Result: PASS
Congratulations! You now have a simple microservice for storing and retrieving definitions of words. You can now write a web front-end in HTML and JavaScript, or perhaps another microservice that consumes this one.
(As an exercise, write the /health
route defined in our OpenAPI document. It calls a heartbeat
method in a controller class named Monitoring
.)
What next?
- You may not want to store your definitions in a DB file in your project; consider making it a configurable option. Or use one of the many modules on CPAN to choose a completely different backend.
- Add methods to list some or all definitions, using hypertext as the engine of application state (HATEOAS) to render links where appropriate.
- Support multiple definitions of the same word, or expand the API to respond with synonyms and antonyms. (Just make sure to increment the version in the OpenAPI document and add some way for clients to specify the version to indicate you’re making a breaking change!)
Did you have any trouble following along? Got stuck on the installation steps or somewhere else? Please leave a comment below and I’ll try to help.