Scaling a web app

A repository for learning how to scale a web application, concentrates over using docker containers over a bridge network for application instances that are being load balanced using the Round Robin algorithm. The application instances interact with a data service and a logging service that run in their separate containers.

Installation

Create subnet

Subnet makes service discovery easier, as all the microservices are gonna run on this subnet, and it will be easier to manually assign ip addresses.

• docker network create --subnet=172.18.0.0/16 scalenet

Building image for the dataservice

• docker build -f .docker/dataservice.dockerfile -t scale/dataservice .

Building image for the loadbalancer

• docker build -f .docker/loadbalancer.dockerfile -t scale/loadbalancer .

Building image for cache service

• docker build -f .docker/cacheservice.dockerfile -t scale/cacheservice .

Building image for log service

• docker build -f .docker/logservice.dockerfile -t scale/logservice .

Building image for web backend

• docker build -f .docker/web.dockerfile -t scale/web .

Create containers

• Containers:

  docker run --name dataservice --ip=172.18.0.10 --net=scalenet -p 4000:4000 --rm -it -d scale/dataservice
  docker run --name loadbalancer --ip=172.18.0.12 --net=scalenet -p 2000:2000 --rm -it -d scale/loadbalancer
  docker run --name cacheservice --ip=172.18.0.13 --net=scalenet -p 5000:5000 --rm -it scale/cacheservice
  docker run --name logservice --ip=172.18.0.14 --net=scalenet -p 6000:6000 --rm -it -v /Users/rahuldhar/log:/log scale/logservice
  docker run --net=scalenet --ip=172.18.0.2 -p3000:3000 --name webtest --rm -it scale/web --dataservice=https://172.18.0.10:4000 --loadbalancer=https://172.18.0.12:2001 --cachingservice=https://172.18.0.13:5000 --logservice=https://172.18.0.14:6000
  

• Check that both the containers are up and running using the below-mentioned commands:

  docker ps
  docker network inspect scalenet
  

The docker network inspect command should show both the containers in the Containers object of the configuration, see the eg below

• An output for docker network inspect scalenet

  Rahuls-MacBook-Pro:scaling-web-app rahuldhar$ docker network inspect scalenet
  [
      {
          "Name": "scalenet",
          "Id": "01f8a6ee533b66b0775b4ad6fb99c825dbafd8aba963459d00fb835940ae9eab",
          "Created": "2019-04-30T19:45:53.380381186Z",
          "Scope": "local",
          "Driver": "bridge",
          "EnableIPv6": false,
          "IPAM": {
              "Driver": "default",
              "Options": {},
              "Config": [
                  {
                      "Subnet": "172.18.0.0/16",
                      "Gateway": "172.18.0.1"
                  }
              ]
          },
          "Internal": false,
          "Attachable": false,
          "Ingress": false,
          "ConfigFrom": {
              "Network": ""
          },
          "ConfigOnly": false,
          "Containers": {
              "a7c1fe39219c3eb41f69ef6965dd8b0911eb69067cc22e8171e30958f47d1cf5": {
                  "Name": "dataservice",
                  "EndpointID": "e3696f2c570ac122526c94e82fe258faa58d58a2f669e513b3c433c8f2b81df2",
                  "MacAddress": "02:42:ac:12:00:0a",
                  "IPv4Address": "172.18.0.10/16",
                  "IPv6Address": ""
              },
              "c7bffd2989d8534671005e43f23b9ad45fc2d67d351a6828c12a049bfceacc6d": {
                  "Name": "webtest",
                  "EndpointID": "000995e02495a6ea1455588af0747a9423bafba6761dddffd7f31513eab1c571",
                  "MacAddress": "02:42:ac:12:00:02",
                  "IPv4Address": "172.18.0.2/16",
                  "IPv6Address": ""
              },
              "f402bfa13e2491a5de1e08af880c80a59ffd2c4919400cf9c9a841f17202925c": {
                  "Name": "loadbalancer",
                  "EndpointID": "b8d56b9813d55ddcac5a12853ccd14ba2b911b4c8609537519b1c56d85904f9e",
                  "MacAddress": "02:42:ac:12:00:0c",
                  "IPv4Address": "172.18.0.12/16",
                  "IPv6Address": ""
              }
          },
          "Options": {},
          "Labels": {}
      }
  ]