Cohttp + Lwt

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1. Define your task

Your task definition is where you’ll perform your tasks, such as sending emails, processing files, or moving data between systems.

With Mergent, tasks are defined by HTTP request handlers inside your application.

open Lwt.Infix
open Cohttp
open Cohttp_lwt_unix

let perform_task () =
  (* This is where you'll perform your task.
     For now, we'll just log it. *)
  Lwt_io.printf "Performing task: %s\n"

let server =
  let callback _conn req _body =
    let uri = req |> Request.uri |> Uri.to_string in
    match Uri.path (Request.uri req) with
    | "/api/tasks" -> begin
        perform_task () >>= fun () ->
        Server.respond_string ~status:`OK ~body:"" ()
      end
    | _ ->
        Server.respond_string ~status:`Not_found ~body:"Route not found" ()
  in
  Server.create ~mode:(`TCP (`Port 3000)) (Server.make ~callback ())

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2. Get your handler’s URL

Before you can run your task, your handler must be accessible from the internet.

To do this, you can use a tool like ngrok, or deploy your application to a platform like Vercel or Render.

For more information, see our guide to localhost dev & webhooks.

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3. Create your first task

Once your task handler is reachable via a URL, you can create your first task. Go to the Mergent Tasks Dashboard and click the Create button.

In this step, you’ll set the Request URL to your task handler’s URL. You’ll also provide the required parameters (in the request body) for your handler to carry out the task.

Click Create to queue the task. Once the task executes, you should see the related log in your console, indicating a successful run. 🎊

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4. Next Steps

At this point, you have a few options:

Use cron schedules to create tasks on a recurring basis

Create your first schedule by clicking Create in the Schedules Dashboard.

Your schedule will now create tasks using the cron schedule you provided. 🎊

Create tasks using OCaml and Cohttp + Lwt

1. Obtain your API keys

Mergent authenticates all requests using project API keys.

API keys can be obtained from the Project Settings screen in the Dashboard.

2. Create your task

Create a task whenever you need to. For example, you might create a task any time a user signs up.

Use the URL of the task definition you’d like to run.

open Lwt.Infix
open Cohttp
open Cohttp_lwt_unix

let create_task () =
  (* set the Mergent API key *)
  let api_key = "..." in

  (* create a task that will run in 5 minutes *)
  (* the URL should be set to the URL of your task handler *)
  let headers = Header.init_with "Authorization" ("Bearer " ^ api_key) in
  let body = `String "{ \"request\": { \"url\": \"...\", \"body\": \"Hello, world!\" }, \"delay\": \"PT5M\" }" in
  Client.post ~headers ~body (Uri.of_string "https://api.mergent.co/v2/tasks") >>= fun (resp, body) ->
  let code = resp |> Response.status |> Code.code_of_status in
  body |> Cohttp_lwt.Body.to_string >|= fun body ->
  Lwt_io.printf "Response: %d\n%s\n" code body

You can now create a task any time you’d like to perform some work in the background. 🎊

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