Configuring TAS for VMs to Route Traffic to Apps on Custom Ports

By default, apps only receive requests on port 8080 for both HTTP and TCP routing. Configuring custom app ports allows developers to bring workloads onto TAS for VMs that receive requests on ports other than 8080. Here are some example use cases:

Serving web client requests on one port, and stats and debugging on another
Using TCP protocols that require multiple ports
Running Docker images on TAS for VMs

To use the apps and route_mappings Cloud Controller API endpoints to update the ports so the the app can receive requests, see Procedure.

Flow of a request to an app

The table describes the Network Address Translation that occurs in the data path of a client request:

Port Type	Description	Network Hop
Route port	The port to which a client sends a request	Client to load balancer, load balancer to Gorouter
Back end port	The port on the VM where an application container is hosted, which is unique to the container	Gorouter to Diego Cell
App port	The port on the container, which must match a port on which the app is configured to receive requests	Diego Cell to application container

The following diagram shows an example data path and Network Address Translation for TCP routing:

Traffic flow-diagram for data path and Network Address Translation for TCP routing

For HTTP routing, the route port is always 80 or 443.

Prerequisites

Before you follow the procedure to configure routing to your app on custom ports, you must have:

An app pushed to TAS for VMs that can receive requests on one or more custom ports.
Routes for which you want traffic forwarded to your app on custom ports, which are mapped to the app.

If your app receives requests on two ports, and you want clients to be able to send requests to both of them, create two routes. These routes can be from HTTP or TCP domains.

Procedure

In the following procedure, use API endpoints to map the routes to your app on the ports it uses to receive requests. For more information about routes, see Routes and Domains.

To configure your app to receive HTTP or TCP requests on custom ports:

Run:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of your app.
From the output, record:
- Under guid, the global unique identifier (GUID) of your app.
- Under type, the process type your app uses.
Retrieve the GUIDs of the routes for your app by running one of these commands, depending on whether your app uses HTTP or TCP routes:
- For HTTP routes, run:
```
cf curl /v3/apps/APP-GUID/routes?hosts=ROUTE-HOSTNAME
```
  Where:
  - APP-GUID is the GUID of your app that you recorded in an earlier step.
  - ROUTE-HOSTNAME is the subdomain of the domain associated with the route. For example, in the route example-app.shared-domain.example.com, the host name is example-app.
- For TCP routes, run:
```
cf curl /v3/apps/APP-GUID/routes?port=PORT
```
  Where:
  - APP-GUID is the GUID of your app that you recorded in an earlier step.
  - PORT is the port to which the TCP route sends requests.
From the output, record the GUIDs of the routes for your app.
For each route, update the ports to which it sends requests by running:
```
cf curl -X PATCH /v3/routes/ROUTE-GUID/destinations -d '{
"destinations": [
    {
      "app": {
        "guid": "APP-GUID",
        "process": {
          "type": "PROCESS-TYPE"
        }
      },
      "port": PORT,
      "protocol": "PROTOCOL"
    }
  ]
}'
```
Where:
- APP-GUID is the GUID of your app that you recorded in an earlier step.
- ROUTE-GUID is the GUID of a route that you recorded in an earlier step.
- PORT is a custom port on which your app is configured to receive requests.
- PROTOCOL is the protocol that the route uses. For HTTP routes, this value is either http1 or http2. For TCP routes, this value is tcp.
- PROCESS-TYPE is the value of type that you recorded in an earlier step. This value is usually web.
Caution This API call removes all destinations for a route and replaces them with the destinations you provide in the API request.

Additional resources

For more information about making requests to the Cloud Controller API (CAPI) apps endpoints, see the CAPI V3 documentation.