envoy-config

###docker-compose
version: '3'
services:
  redis:
    image: "redis:alpine"
    networks:
    - envoymesh
  proxy:
    build:
      context: .
      dockerfile: Dockerfile-envoy
    ports:
    - "8080:80"
    - "8001:8001"
    expose:
    - "80"
    - "8001"
    volumes:
      - ./front-envoy.yaml:/etc/front-envoy.yaml
    networks:
    - envoymesh
  flaskweb:
    build:
      context: .
      dockerfile: Dockerfile-flask
    volumes:
    - .:/code
    ports:
    - "5000:5000"
    expose:
    - "5000"
    depends_on: 
    - redis
    networks:
      envoymesh:
        aliases:
          - flaskservice
networks:
  envoymesh: {}

################################################################################################################

###front-envoy.yaml

static_resources:
  listeners:
  - address:
      socket_address:
        address: 0.0.0.0
        port_value: 80
    filter_chains:
    - filters:
      - name: envoy.http_connection_manager
        config:
          # "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager
          codec_type: auto 
          stat_prefix: ingress_http
          route_config:
            name: local_route
            virtual_hosts:
            - name: flask_backend
              domains: 
              - "*"
              routes:
              - match:
                  prefix: "/flask/home"
                route:
                  cluster: flask
          http_filters:
          - name: envoy.router
            typed_config: {}
  clusters:
  - name: flask
    connect_timeout: 0.25s
    type: strict_dns
    lb_policy: round_robin
    http2_protocol_options: {}
    load_assignment:
      cluster_name: flaskcluster
      endpoints:
      - lb_endpoints:
          - endpoint:
              address:
                socket_address:
                  address: flaskservice
                  port_value: 5000
admin:
  access_log_path: "/dev/null"
  address:
    socket_address:
      address: 0.0.0.0
      port_value: 8001



### Dockerfile-envoy
FROM envoyproxy/envoy:latest

RUN apt-get update && apt-get -q install -y \
    curl
CMD /usr/local/bin/envoy -c /etc/front-envoy.yaml --service-cluster front-proxy

################################################################################################################

###Dockerfile-flask

FROM python:3.4-alpine
ADD . /code
WORKDIR /code
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

################################################################################################################

### requirements.txt
flask
redis

################################################################################################################

### app.py

import time

import redis
from flask import Flask


app = Flask(__name__)
cache = redis.Redis(host='redis', port=6379)


def get_hit_count():
    retries = 5
    while True:
        try:
            return cache.incr('hits')
        except redis.exceptions.ConnectionError as exc:
            if retries == 0:
                raise exc
            retries -= 1
            time.sleep(0.5)


@app.route('/')
def hello():
    count = get_hit_count()
    return 'Hello from Docker! I have been seen {} times.\n'.format(count)

if __name__ == "__main__":
    app.run(host="0.0.0.0", debug=True)