Using Dynamic Variables for Configuration

Mesh enables usage of dynamic values in the configuration setup. Usage is done with curly braces, e.g. {context.headers['x-my-api-token']}.

env variables

All variables available on your env could be used as configuration variables. For example, setting a base URL could be done as follows:

sources:
  - name: MyGraphQLApi
    handler:
      graphql:
        endpoint: '{env.BASE_URL}/graphql'

Runtime variables

In addition to environment variables, Mesh also supports runtime variables. These variables can be devided into two groups:

Operation Specific

Those are variables that are available only for a specific operation:

‘args’ Variables

Enables usage of operation arguments as variables. In the following example we define an argument for the subreddit field and use it in the path of the operation:

  ...
      jsonSchema:
        baseUrl: https://www.reddit.com/
        operations:
          - type: Query
            field: subreddit
            path: "/r/{args.subreddit}.json"
            method: GET
            responseSample: https://www.reddit.com/r/AskReddit.json
            responseTypeName: Subreddit
            argTypeMap:
              subreddit:
                type: string

‘root’ variables

Enables usage of the root entity as a variable. For a reference, you can see the federation example, using the user.id as a variable.

Runtime Globally

This variables are available for all operations:

‘context’ variable

Enables usage of the Mesh runtime context as a variable. If Mesh runs as a gateway, the context variable will contain the headers and cookies of the request. If Mesh runs as a standalone server, the context variable will contain the headers and cookies of the request, as well as the req and res objects.

In the following example we use the accessToken cookie as an auth token:

sources:
  - name: Microsoft Graph
    handler:
      odata:
        endpoint: https://graph.microsoft.com/v1.0/
        batch: json
        operationHeaders:
          Authorization: 'Bearer {context.cookies.accessToken}'

If Mesh is initialized with a context object, it will be available as a variable as well. Other than that, some handler-dependent context properties might be available.