flask-envoy-docker-microservice
A simple tutorial how to setup a Flask microservice using https://www.envoyproxy.io Service mesh and Docker.
MIT License
Flask on Envoy Cluster microservice example
A simple tutorial how to setup a Flask microservice using Envoy Service mesh and Docker.
Running the service
Step 1: Install Docker
Ensure that you have a recent versions of
docker, docker-compose and docker-machine
installed.
Step 2: Setup Docker Machine
Create a new machine which will hold the containers:
$ docker-machine create --driver virtualbox default
$ eval $(docker-machine env default)
Tip Run the bootstrap.sh program to perform the list of steps in one go.
Step 3: Create configuration for Front End Envoy Gateway First create an Envoy config that will act as a Front End proxy server:
$ mkdir gateway
$ touch front-proxy-envoy.json
The configuration is a simple proxy redirect to a backend url:
{
"listeners": [
{
"address": "tcp://0.0.0.0:80",
"filters": [
{
"name": "http_connection_manager",
"config": {
"codec_type": "auto",
"stat_prefix": "ingress_http",
"route_config": {
"virtual_hosts": [
{
"name": "app_backend",
"domains": [
"*"
],
"routes": [
{
"timeout_ms": 0,
"prefix": "/",
"cluster": "app"
}
]
}
]
},
"filters": [
{
"name": "router",
"config": {}
}
]
}
}
]
}
],
"admin": {
"access_log_path": "/dev/null",
"address": "tcp://0.0.0.0:8001"
},
"cluster_manager": {
"clusters": [
{
"name": "app",
"connect_timeout_ms": 250,
"type": "strict_dns",
"lb_type": "round_robin",
"features": "http2",
"hosts": [
{
"url": "tcp://app:80"
}
]
}
]
}
}
Step 4: Add Dockerfile for Front End Envoy Gateway
$ touch DockerFile
$ cat <<EOF > DockerFile
FROM envoyproxy/envoy:latest
RUN apt-get update && apt-get -q install -y \
curl
CMD /usr/local/bin/envoy -c /etc/front-proxy-envoy.json --service-cluster front-proxy
EOF
Step 5: Create configuration for Back End Envoy Proxy Server First create an Envoy config that will act as a Back End proxy server. Make sure you match the listener address to the hosts address of the front-end proxy.
{
"listeners": [
{
"address": "tcp://0.0.0.0:80",
"filters": [
{
"name": "http_connection_manager",
"config": {
"codec_type": "auto",
"stat_prefix": "ingress_http",
"route_config": {
"virtual_hosts": [
{
"name": "app",
"domains": [
"*"
],
"routes": [
{
"timeout_ms": 0,
"prefix": "/",
"cluster": "local_service"
}
]
}
]
},
"filters": [
{
"name": "router",
"config": {}
}
]
}
}
]
}
],
"admin": {
"access_log_path": "/dev/null",
"address": "tcp://0.0.0.0:8001"
},
"cluster_manager": {
"clusters": [
{
"name": "local_service",
"connect_timeout_ms": 250,
"type": "strict_dns",
"lb_type": "round_robin",
"hosts": [
{
"url": "tcp://127.0.0.1:8080"
}
]
}
]
}
}
Step 6: Add Dockerfile for Backend Envoy Gateway
$ touch DockerFile
$ cat <<EOF > DockerFile
FROM envoyproxy/envoy:latest
RUN apt-get update && apt-get -q install -y \
curl \
software-properties-common \
python-software-properties
RUN add-apt-repository ppa:deadsnakes/ppa
RUN apt-get update && apt-get -q install -y \
python3 \
python3-pip
RUN python3 --version && pip3 --version
RUN mkdir /code
COPY . /code
WORKDIR /code
RUN pip3 install -r ./requirements.txt
ADD ./start_service.sh /usr/local/bin/start_service.sh
RUN chmod u+x /usr/local/bin/start_service.sh
ENTRYPOINT /usr/local/bin/start_service.sh
EOF
add also a start up shell for your app
$ touch start_service.sh
$ cat <<EOF > start_service.sh
#!/bin/bash
set -xe
python3 ./app.py & envoy -c /etc/app-service-envoy.json --service-cluster app
EOF
Step 7: Add docker-compose script for setting up all containers
$ touch docker-compose.yml
cat<<EOF > docker-compose.yml
version: '2'
services:
front-envoy:
build:
context: .
dockerfile: gateway/Dockerfile
volumes:
- ./gateway/front-proxy-envoy.json:/etc/front-proxy-envoy.json
networks:
- envoymesh
expose:
- "80"
- "8001"
ports:
- "8000:80"
- "8001:8001"
app:
build:
context: ./app
dockerfile: Dockerfile
volumes:
- ./app/app-service-envoy.json:/etc/app-service-envoy.json
networks:
envoymesh:
aliases:
- app
expose:
- "80"
networks:
envoymesh: {}
EOF
Step 8: Add requirements.txt and flask app Create the basic flask micro-service and add the following code.
$ touch requirements.txt
$ cat<<EOF > requirements.txt
Flask==0.12.2
gunicorn==18.0
python-dotenv==0.7.1
EOF
$ touch app.py
app.py
from flask import Flask
import settings
def init():
""" Create a Flask app. """
server = Flask(__name__)
return server
app = init()
@app.route('/')
def index():
return 'My awesome micro-service'
if __name__ == "__main__":
app.run(
host=settings.API_BIND_HOST,
port=settings.API_BIND_PORT,
debug=settings.DEBUG)
settings.py
"""
Settings file, which is populated from the environment while enforcing common
use-case defaults.
"""
import os
from os.path import join, dirname
from dotenv import load_dotenv
dotenv_path = join(dirname(__file__), '.env')
load_dotenv(dotenv_path)
# OR, the same with increased verbosity:
load_dotenv(dotenv_path, verbose=True)
DEBUG = True
if os.getenv('DEBUG', '').lower() in ['0', 'no', 'false']:
DEBUG = False
API_BIND_HOST = os.getenv('SERVICE_API_HOST', '127.0.0.1')
API_BIND_PORT = int(os.getenv('SERVICE_API_PORT', 8080))
SERVICE_NAME = os.getenv('SERVICE_NAME', 'app')
Step 9: Test the service locally
$ python app.py
* Running on http://127.0.0.1:8080/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 185-774-130
and in another terminal
$ curl http://127.0.0.1:8080/
My awesome micro-service%
Step 10: Start all containers
$ docker-compose up --build -d
$ docker-compose ps
Name Command State Ports
-------------------------------------------------------------------------------------------------------------
app_service_1 /bin/sh -c /usr/local/bin/ ... Up 80/tcp
front-proxy-envoy_1 /bin/sh -c /usr/local/bin/ ... Up 0.0.0.0:8000->80/tcp, 0.0.0.0:8001->8001/tcp
Step 11: Test routing capabilities
You can now send a request to services via the front-envoy.
curl -X GET -v $(docker-machine ip default):8000
* Rebuilt URL to: 0.0.0.0:8000/
* Trying 0.0.0.0...
* TCP_NODELAY set
* Connected to 0.0.0.0 (0.0.0.0) port 8000 (#0)
> GET / HTTP/1.1
> Host: 0.0.0.0:8000
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: text/html; charset=utf-8
< content-length: 24
< server: envoy
< date: Thu, 14 Dec 2017 08:51:39 GMT
< x-envoy-upstream-service-time: 4
<
* Connection #0 to host 0.0.0.0 left intact
My awesome micro-service%
**Step 12: Enjoy your micro-service and have some Beer **
LICENCE
MIT @ Theo Despoudis