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In Optic, a task is a way to manually configure traffic capture for your project, often against a local target. It is very flexible in that it can take a command to start your project, and inboundURL and targetUrl to define the downstream and upstream proxy URLs. You won't need to use all of these parameters: which ones you choose will depend on how you want to capture your traffic. If you want to point Optic at a remote host with no other configuration, consider environments instead.

What kind of information does Optic require in a task configuration?#

api run starts a local proxy and may also start your API project. Optic needs to know where it should listen for traffic, how it will reach your API (either by starting it or knowing where to send traffic), and if it depends on other Optic tasks to already be running (such as when running tests).


api exec normally takes the start command on the command line. To share an exec configuration with your team, define a task with only a command parameter. Any task with only a command parameter can be run with api run, and will be treated as if it was run with api exec. That is, it will start a service to capture traffic from the Optic middleware.

What parameters are available when configuring a task?#

There are four parameters available when configuring a task. No task configuration requires all four:

  • inboundURL: Where will Optic listen for incoming traffic? We recommend starting this on the port your project usually starts on, as Optic will provide an environment variable, PORT, for the application to start on. That way, no changes need to be made to your local workflow. This is required for all tasks except api exec tasks.
  • command: How Optic can start your API project.
    • Optic will provide the PORT enviornment variable to the application at startup.
    • If this is the only parameter present, it is treated as an api exec task.
    • This parameter is optional when defining both inboundURL and targetUrl, as these provide Optic the information it needs to proxy to your project if it is already running.
  • targetUrl: Where Optic will point traffic, if Optic will not be starting the application with command.
    • This is only required when setting up a proxy manually. Otherwise, Optic would start your application with command, pass it an environment variable PORT, and expect it to listen on localhost:PORT.
  • useTask: If this run task is starting tests or other processes that expect your service to be running, you can start them with another task and use the useTask parameter to depend on it.
    • The base task definition (the task named in useTask) should work to intercept traffic to your application.
    • When using useTask, the only other parameter to supply is command which will define the tests/other command to run.

What are some examples of how I'd define my tasks?#

Intercept traffic to my project, which normally listens on port 8080
name: "todo-js"tasks:  start:    # Starts a node server on $PORT (provided by Optic at runtime). Optic will listen for traffic on port 8080.    # To run this task: api run start    command: node server.js --watch db.json --routes routes.json --port $PORT    inboundUrl: http://localhost:8080
Set up a manual proxy to a service that runs separately
name: "todo-js"tasks:  start:    # Expects your API project to run on localhost:8080. Optic will listen on localhost:3001 and forward traffic.    # Make sure your clients all use localhost:3001, Optic's inbound proxy port, so traffic is captured.    # To run this task: api run start    targetUrl: http://localhost:8080    inboundUrl: http://localhost:3001
Run tests against my API project through Optic
name: "todo-js"tasks:  start:    command: node server.js --watch db.json --routes routes.json --port $PORT    inboundUrl: http://localhost:8080  tests:    # Runs a collection of Postman tests (using newman). Newman should send traffic to port 8080, Optic's inbound port.    # This uses the start task to spin up the application first, then sends test traffic through Optic.    command: newman run tests.postman_collection.json --environment local.postman_environment.json    useTask: start
Define an exec task to share with my team
name: "todo-js"tasks:  start:    # Starts the node server. This assumes it is already integrated with Optic midleware.    # Optic will start a service to receive traffic from the middleware.    # To run this task, the following are equivalent:    #   - api run start     #   - api exec node server.js --watch db.json --routes routes.json --port $PORT    command: node server.js --watch db.json --routes routes.json --port $PORT