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# nginx-sidecar

A simple nginx reverse proxy side-car, which can be placed in front an application's web container to queue requests and to provide statistics to New Relic about request queuing.

## Requirements

 - The application must be linked (either by Docker `--link` or ECS `links` section) as `app`.

 - The `NGINX_PORT` environment variable should be set to the port nginx should bind to.

 - The `APP_PORT` environment variable should be set to the port that the application is bound to inside the `app` container.

## Example

In your `.hopper/config.yml`:

```yaml

# ...

services:

  web:

    containerDefinitions:

      # Your application container, defined as normal, but without any `portMappings` section:

      app:

        cpu: 1024

        memory: 1024

        essential: true

        command: "exec puma -p 3001 -C config/puma.rb"

      # A separate `containerDefinition` should be added for the nginx side-car.

      # The side-car doesn't care what this is called, but it'll need to match the `process_name`

      # in your app's Terraform, as this is where Hopper expects to find the bound port.

      web:

        # Pin to a specific image of the nginx-sidecar.

        # TODO: Staging vs. production??

        image: 517902663915.dkr.ecr.eu-west-1.amazonaws.com/nginx-sidecar:740797ae4525cceb81625dd70b0035516aaf80ba

        cpu: 128

        memory: 256

        essential: true

        # Link your `app` to this container, so that the nginx sidecar can forward requests.

        # If your app container is named something else (e.g. `appcontainer`), you can use

        # `appcontainer:app` to specify it.

        links:

        - app

        portMappings:

        - containerPort: 3000

        # Specify which port nginx should listen on (should match the `portMappings` above), and

        # which port the `app` is listening on.

        environment:

        - name: NGINX_PORT

          value: '3000'

        - name: APP_PORT

          value: '3001'

  # ...

```

## Future

This relies on the legacy `--link` flag of Docker/ECS and requires the `bridged` networking mode.

We'll want to switch to another way of doing this once we have different networking modes available - this is an ongoing area of research for Production Engineering.