REST API

powered by Flask and deployed with Flynn

This guide assumes you already have a running Flynn cluster and have configured the flynn command-line tool. If this is not the case, follow the Installation Guide first to get things set up.

It also assumes you are using the demo.localflynn.com default domain (which is the case if you installed the Vagrant demo environment). If you are using your own domain, substitute demo.localflynn.com with whatever you set CLUSTER_DOMAIN to during the bootstrap process.

Reference: https://flynn.io/docs/basics

Installation

On the development machine, clone the Git repo:

$ git clone https://github.com/lvaylet/rest-api

Inside the cloned repo, create a .env file to store secret credentials as environment variables:

$ cd rest-api
$ cat > .env <<EOF
LMS_TOKEN=...
EXTRA_TOKEN=...
USERNAME=...
EOF

The next step is to create a Flynn application (still inside the cloned repo):

$ flynn create rest-api
Created rest-api

The above command should have added a flynn Git remote:

$ git remote -v
flynn	https://git.demo.localflynn.com/rest-api.git (fetch)
flynn	https://git.demo.localflynn.com/rest-api.git (push)
origin	https://github.com/lvaylet/rest-api.git (fetch)
origin	https://github.com/lvaylet/rest-api.git (push)

The app depends on Redis, so add a database:

$ flynn resource add redis
Created resource b8494c73-f4bb-40f1-be81-1f9fb5e26655 and release b9f8752e-41c9-4bd0-a2dd-1f1cd7c9bbb7.

You can see the configuration for the database that the app will use:

$ flynn env
FLYNN_REDIS=redis-94c2d8b2-f35a-41b2-8e24-8d0074b785c2
REDIS_HOST=leader.redis-94c2d8b2-f35a-41b2-8e24-8d0074b785c2.discoverd
REDIS_PASSWORD=75ada8955fd8503379ca
REDIS_PORT=6379
REDIS_URL=redis://:75ada8955fd8503379ca@leader.redis-94c2d8b2-f35a-41b2-8e24-8d0074b785c2.discoverd:6379

Add environment variables to configure the app or feed credentials:

$ flynn env set FLASK_CONFIG=config.ProductionConfig
Created release cf952afc-8386-4684-85a2-7416b386a92e.
$ flynn env set LMS_TOKEN=<...>
Created release 8accf819-dcc4-4776-ba16-652af979b3ae.

Development

A fully dockerized development environment lets you mimic the production environment, complete with Redis database and hot reloading. You can build the image, run the full stack and display the logs with:

$ docker-compose up --build

Alternatively, you can use the run.py script to start a development server from your IDE (Pycharm, for example) and use debugging features. Do not forget to set the required environment variables (FLASK_CONFIG or LMS_TOKEN, for example). Make sure to provision a Redis server too. The default app configuration points to a local Redis container instantiated with:

$ docker run --name redis-devel -d -p 6379:6379 redis

Deployment

New releases are created by committing changes to Git and pushing those changes to Flynn. Push to the flynn Git remote to build and deploy the application:

$ git push flynn master
Counting objects: 135, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (122/122), done.
Writing objects: 100% (135/135), 21.87 KiB | 1.29 MiB/s, done.
Total 135 (delta 52), reused 0 (delta 0)
-----> Building rest-api...
-----> Python app detected
-----> Installing python-3.6.3
-----> Installing pip
-----> Installing requirements with pip
      Collecting hammock==0.2.4 (from -r /tmp/build/app/requirements.txt (line 1))
      Downloading hammock-0.2.4.tar.gz
      Collecting Flask==0.12.2 (from -r /tmp/build/app/requirements.txt (line 2))
      Downloading Flask-0.12.2-py2.py3-none-any.whl (83kB)
      [...]
      Successfully installed Flask-0.12.2 Flask-Caching-1.3.3 Flask-RESTful-0.3.6 Jinja2-2.10 MarkupSafe-1.0 Werkzeug-0.13 aniso8601-1.3.0 certifi-2017.11.5 chardet-3.0.4 click-6.7 gunicorn-19.7.1 hammock-0.2.4 idna-2.6 itsdangerous-0.24 python-dateutil-2.6.1 pytz-2017.3 redis-2.10.6 requests-2.18.4 six-1.11.0 urllib3-1.22

-----> Discovering process types
      Procfile declares types -> web
-----> Compiled slug size is 37.3 MiB
-----> Creating release...
=====> Scaling initial release to web=1
-----> Waiting for initial web job to start...
=====> Initial web job started
=====> Application deployed
To https://git.demo.localflynn.com/rest-api.git
* [new branch]      master -> master

Now the application is deployed, you can make HTTP requests to it using the default route for the application:

$ curl http://rest-api.demo.localflynn.com/todos
{"todo1": "Remember the milk", "todo2": "Change my brakepads"}

Scale

New applications with a web process type are initially scaled to run one web process, as can be seen with the ps command:

$ flynn ps
ID                                          TYPE  STATE  CREATED         RELEASE
flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d  web   up     45 seconds ago  81d38fd5-d76e-4d2e-8c80-ab5589d5e3a4

Run more web processes using the scale command:

$ flynn scale web=3
scaling web: 1=>3

19:23:33.566 ==> web cf578d05-537a-46b6-b920-2b53065e69ad pending
19:23:33.579 ==> web flynn-cf578d05-537a-46b6-b920-2b53065e69ad starting
19:23:33.579 ==> web fadaf881-37a4-4501-bf95-ba198125f723 pending
19:23:33.617 ==> web flynn-fadaf881-37a4-4501-bf95-ba198125f723 starting
19:23:34.305 ==> web flynn-cf578d05-537a-46b6-b920-2b53065e69ad up
19:23:34.313 ==> web flynn-fadaf881-37a4-4501-bf95-ba198125f723 up

scale completed in 825.052583ms

ps should now show three running processes:

$ flynn ps
ID                                          TYPE  STATE  CREATED         RELEASE
flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d  web   up     59 seconds ago  81d38fd5-d76e-4d2e-8c80-ab5589d5e3a4
flynn-cf578d05-537a-46b6-b920-2b53065e69ad  web   up     5 seconds ago   81d38fd5-d76e-4d2e-8c80-ab5589d5e3a4
flynn-fadaf881-37a4-4501-bf95-ba198125f723  web   up     5 seconds ago   81d38fd5-d76e-4d2e-8c80-ab5589d5e3a4

Repeated HTTP requests should show that the requests are load balanced across those processes and talk to the database.

Logs

You can view the logs (the stdout/stderr streams) of all processes running in the app using the log command:

$ flynn log
2017-12-29T18:22:44.774541Z app[web.flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d]: [2017-12-29 18:22:44 +0000] [12] [INFO] Starting gunicorn 19.7.1
2017-12-29T18:22:44.775368Z app[web.flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d]: [2017-12-29 18:22:44 +0000] [12] [INFO] Listening at: http://0.0.0.0:8080 (12)
2017-12-29T18:22:44.775757Z app[web.flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d]: [2017-12-29 18:22:44 +0000] [12] [INFO] Using worker: sync
2017-12-29T18:22:44.778585Z app[web.flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d]: [2017-12-29 18:22:44 +0000] [25] [INFO] Booting worker with pid: 25
2017-12-29T18:23:11.860960Z app[web.flynn-9a6a75ad-f2ae-497a-b4db-fc3f385dbc7d]: 100.100.23.1 - - [29/Dec/2017:18:23:11 +0000] "GET /todos HTTP/1.1" 200 63 "-" "curl/7.54.0"
2017-12-29T18:23:34.194677Z app[web.flynn-fadaf881-37a4-4501-bf95-ba198125f723]: [2017-12-29 18:23:34 +0000] [15] [INFO] Starting gunicorn 19.7.1
2017-12-29T18:23:34.194723Z app[web.flynn-fadaf881-37a4-4501-bf95-ba198125f723]: [2017-12-29 18:23:34 +0000] [15] [INFO] Listening at: http://0.0.0.0:8080 (15)
2017-12-29T18:23:34.194810Z app[web.flynn-fadaf881-37a4-4501-bf95-ba198125f723]: [2017-12-29 18:23:34 +0000] [15] [INFO] Using worker: sync
2017-12-29T18:23:34.197054Z app[web.flynn-fadaf881-37a4-4501-bf95-ba198125f723]: [2017-12-29 18:23:34 +0000] [27] [INFO] Booting worker with pid: 27
2017-12-29T18:23:34.242027Z app[web.flynn-cf578d05-537a-46b6-b920-2b53065e69ad]: [2017-12-29 18:23:34 +0000] [14] [INFO] Starting gunicorn 19.7.1
2017-12-29T18:23:34.242500Z app[web.flynn-cf578d05-537a-46b6-b920-2b53065e69ad]: [2017-12-29 18:23:34 +0000] [14] [INFO] Listening at: http://0.0.0.0:8080 (14)
2017-12-29T18:23:34.242634Z app[web.flynn-cf578d05-537a-46b6-b920-2b53065e69ad]: [2017-12-29 18:23:34 +0000] [14] [INFO] Using worker: sync
2017-12-29T18:23:34.245652Z app[web.flynn-cf578d05-537a-46b6-b920-2b53065e69ad]: [2017-12-29 18:23:34 +0000] [26] [INFO] Booting worker with pid: 26

lvaylet / my-rest-api