iron hook

You're looking at a simple plug-in webhook service for your Golang application.

It's agnostic of your wider architectural choices and doesnt make too many assumptions about your application.

It persists state like registered endpoints and all sent notifications to a database controlled by the Gorm ORM, but the database can be as simpe as an in-memory sqlite if you don't require persistence between processes.

How it works

The service runs around two structs: WebhookEndpoint and a WebhookNotification.

You can create the service like this:

service, err := ironhook.NewWebhookService(nil)

Then we can create a new WebhookEndpoint like this:

e := ironhook.WebhookEndpoint{
    URL: "http://localhost:8080"
}

endpoint := service.Create(e)

At first, the endpoint is Unverified, but we can fix that quickly by Verifying it:

verified_endpoint, err := service.Verify(endpoint)

You may want to persist the UUID of this endpoint to be able to reference it in the future

endpoint_id := verified_endpoint.UUID // save to your database

And with that out of the way, we can send notifications

uuid_trace := uuid.Must(uuid.NewV4())

notification := ironhook.NewNotification(
    event: uuid_trace,
    topic: "Batch processing #1 complete",
    body: "All batches have been processed"
)

err := service.Notify(verified_endpoint, notification)

Returning customer

If you want to send another notification to the same endpoint, the starting point will be the UUID of the endpoint.

endpoint_id := verified_endpoint.UUID // or read from your DB

With that, we can create a new notification and send it in one go:

endpoint := ironhook.WebhookEndpoint{
    UUID: endpoint_id,
}

notification := ironhook.NewNotification(
    event: uuid_trace,
    topic: "Batch processing #2 complete",
    body: "All batches have been processed"
)

err := service.Notify(endpoint, notification)

Verification

Every Endpoint has to be verified before it can be used for notifications.

The verification process is relatively simple and best shown with an example.

Given an endpoint like this:

webhooks.example.com

A verification request will be sent to

webhooks.example.com/verification

with an id query parameter cointaining a uuid identifier of the endpoint, like this: id=6551e000-947a-40a4-948d-18d01e3660d4

Putting it together, a request like this will be made:

webhooks.example.com/verification?id=6551e000-947a-40a4-948d-18d01e3660d4

And in response to this request, we expect to see the uuid as body of the response.

In Golang, one of the simpler approaches to the verification would be something like this:

func VerificationHandler(w http.ResponseWriter, r *http.Request) {

    qID, ok := r.URL.Query()["id"]
    
    if !ok || len(qID[0]) < 1 {
		fmt.Fprintf(w, "URL Parameter <id> is missing")
		return
	}
    
    fmt.Fprint(w, qID[0])
}

Which you can also see in the examples section: _examples/receiver/http_handlers.go

Configuration

Database

By default, if no environment variables are specified, the service will persist state to an in-memory sqlite database.

If you want to have it stored in a file, you might want to specify the below:

HOOK_DB_DSN=webhooks.db

Available database engine options are:

• postgres
  • cockroach
• mysql
• sqlserver
• sqlite

Naturally, you can use databases like cockroachdb since they may be compatible with one of the supported engines. In this example, cockroachdb is compatible with postgres.

In order to specify an engine you can use:

HOOK_DB_ENGINE=postgres

And specify the connection string for it:

HOOK_DB_DSN=postgres://postgres:123456@localhost:5432/mywebapp

Logging

The service uses zap for logging, at the moment, you can configure the logging level:

HOOK_LOG_LEVEL=warn

By default, info level is used.

If you specify an unsupported log level, the configuration will default to info.

HTTP Client

You can also tell ironhook to use your pre-configured http client if the default isn't what you're after.

http_client = &http.Client{
    Timeout: time.Second * 3,
}
service, err := ironhook.NewWebhookService(http_client)

The above is also the default configuration.