# Docker Compose

If we want to setup a complex application with multiple services . A better way to do it is to use docker-compose. With Docker-compose we can create a comfiguration file in YAML format called docker-compose.yml & put together the different services & options specific to runnning them in the file .

\>>simply run docker-compose up command to bring up the entire application stack.

\>>Its only applicable only when we are running all our container on single DOCKER HOST.

![](/files/-MERdYCqIkNACse_eCBb)

<https://github.com/dockersamples/example-voting-app>

This voting app provides two options to choose between a Cat & a Dog.

![](/files/-MERe_vxhetp8noFgaQo)

Now see how we can put this entire stack on Single Docker Sever without using Docker Swarm:

links is used to link used two container together .

links are now depriciated . This is beacuse of the Docker Swarm & some advanced netwroking concepts:

Here we can see that Postgre & Redis already build on Docker registry so instead of pulling pass build option .

\>>>Now Docker compose first build the images then use those images to run conatiners using options that we specified.

version 1 is the original version of docker -compose&#x20;

In version 1 docker-compose attaches all the container to a default bridge network & then use links to enable communication between the containers .

In version 2 , automatically created a dedicated bridge netwrok for the application & then attaches all containers to that new netwrok. All container then comuunicate each other using service names. So there is no need to use links in version 2 of docker compose.

\>>Version 2 introduces depends-on feature&#x20;

\>> Version 3 is similar to version2 execpt it comes up with support of Docker Swarm.

![](/files/-MERkBPI0BBOi07EEF29)

&#x20;Now we have created two networks front-end & back-end:

1\) front-end : a front-end network dedicated for traffic from users generated traffic.

2\) a back-end netwrok dedicated for traffic within the application. We then connect the user facing applications voting-app & result-app with a front-end netwrok & all the components to internal back-end network.

![](/files/-MERlvIDfrIZL9JAuM8p)

Practical Implementation : example-voting-app

<https://github.com/dockersamples/example-voting-app>

\>>First we need to remove our containers that we created manaully in oder to run the application using docker-compose.

&#x20;

![](/files/-MERpkKeXsEii6CJ7P9v)


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