feat(external data): loading currencies

* Added an app in the backend dedicated to the link with external data
* Create a command to update the data
* Support updating data from fixer
* Updated doc accordingly

Almost done #28

backend/base_app/settings/main.py

@@ -63,6 +63,7 @@ INSTALLED_APPS = [
     "rest_framework.authtoken",
     "backend_app",
     "base_app",
+    "external_data",
     "webpack_loader",
     "django_filters",
 ]

backend/external_data/admin.py

+from django.contrib import admin
+
+from external_data.models import ExternalDataUpdateInfo
+
+admin.site.register(ExternalDataUpdateInfo)

backend/external_data/apps.py

+from django.apps import AppConfig
+
+
+class ExternalDataConfig(AppConfig):
+    name = "external_data"

backend/external_data/management/commands/update_external_data.py

+import logging
+import os
+
+import requests
+from django.core.management.base import BaseCommand
+
+from backend_app.models.currency import Currency
+from external_data.models import ExternalDataUpdateInfo
+
+FIXER_API_TOKEN = os.environ["FIXER_API_TOKEN"].strip()
+logger = logging.getLogger("django")
+
+
+class Command(BaseCommand):
+    help = "Command to handle updating remote data"
+
+    def add_arguments(self, parser):
+        subparsers = parser.add_subparsers(
+            title="subcommands", dest="subcommand", required=False
+        )
+        subparsers.add_parser("all", help="(default) Update all external data")
+        subparsers.add_parser("currencies", help="Update currencies from fixer")
+
+    def handle(self, *args, **options):
+        if "subcommand" in options.keys():
+            subcommand = options["subcommand"]
+            if subcommand == "all" or subcommand is None:
+                self.update_all()
+            elif options["subcommand"] == "currencies":
+                self.update_currencies()
+        else:
+            self.update_all()
+
+    @staticmethod
+    def update_all():
+        logger.info("Updating all external data")
+        Command.update_currencies()
+
+    @staticmethod
+    def update_currencies():
+        logger.info("Updating currencies")
+        response = requests.get(
+            "http://data.fixer.io/api/latest?access_key={}".format(FIXER_API_TOKEN)
+        )
+
+        data = response.json()
+
+        if data["success"]:
+            for (code, rate) in response.json()["rates"].items():
+                Currency.objects.update_or_create(
+                    code=code, defaults={"one_EUR_in_this_currency": rate}
+                )
+            ExternalDataUpdateInfo.objects.create(source="fixer")
+            logger.info("Currency update was successful")
+
+        else:
+            logger.error(
+                "Updating currency information from fixer failed, see response from the API below."
+            )
+            logger.error(response.json())

backend/external_data/migrations/0001_initial.py

+# Generated by Django 2.1.7 on 2019-06-01 09:22
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="ExternalDataUpdateInfo",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("timestamp", models.DateTimeField(auto_now=True)),
+                ("source", models.CharField(max_length=50)),
+            ],
+        )
+    ]

backend/external_data/models.py

+from django.db import models
+
+
+class ExternalDataUpdateInfo(models.Model):
+    timestamp = models.DateTimeField(auto_now=True)
+    source = models.CharField(
+        max_length=50
+    )  # Source identifier of the data that was updated

docker-compose.yml

@@ -29,7 +29,7 @@ services:
     networks: [backend-nginx, backend-db]
     environment:
       WAIT_HOSTS: database:5432  # For the 'wait' script, so that we are sure the db is up and running
-    env_file: [./server/envs/db.env, ./server/envs/django.env]
+    env_file: [./server/envs/db.env, ./server/envs/django.env, ./server/envs/external_data.env]
     # Run the django developpement server on image startup.
     command: /bin/sh -c "/wait && cd backend && ./entry.sh && ./manage.py runserver 0.0.0.0:8000 --nostatic"
     # Required that the `database` and `frontend` service are up and running.

documentation/Application/Backend/external_data.md

+External data
+=============
+
+`REX-DRI` interacts with several external services to provide consistent and up-to-date data to the application.
+
+All the fetching of remote data is handled in a dedicated backend app: `external_data`. A command line interface has also been developed. Once connected to the backend app container, run:
+
+```bash
+./manage.py update_external_data --help
+```
+
+```txt
+usage: manage.py update_external_data [-h] [--version] [-v {0,1,2,3}]
+                                      [--settings SETTINGS]
+                                      [--pythonpath PYTHONPATH] [--traceback]
+                                      [--no-color]
+                                      {all,currencies} ...
+
+Command to handle updating remote data
+
+[...]
+
+subcommands:
+  {all,currencies}
+    all                 (default) Update all external data
+    currencies          Update currencies from fixer
+```
+
+
+## Currencies
+
+Currencies exchange rates are taken from [`fixer`](https://fixer.io/). You must provide a consistent API key in `server/envs/external_data.env` to be able to use the service properly.
+
+To trigger un update of currencies, run `./manage.py update_external_data currencies`.
+
+
+## UTC
+
+TODO
+
+## Auto update
+
+TODO

documentation/_sidebar.md

@@ -19,6 +19,7 @@
     * [Data validation](Application/Backend/data_validation.md)
     * [Tags](Application/Backend/tags.md)
     * [API](Application/Backend/API.md)
+    * [External data](Application/Backend/external_data.md)
     * [Tests](Application/Backend/tests.md)
     * [Optimization](Application/Backend/optimization.md)
 

server/docker-compose.prod.yml

@@ -21,7 +21,7 @@ services:
       - ./uwsgi/:/usr/src/uwsgi/:ro
       - django_logs:/var/log/django
       - frontend_logs:/var/log/frontend
-    env_file: [./envs/db.env, ./envs/django.env]
+    env_file: [./envs/db.env, ./envs/django.env, ./envs/external_data.env]
     environment:
       WAIT_HOSTS: database:5432  # For the 'wait' script, so that we are sure the db is up and running
       ENV: PROD  # make sure to be in prod env