Receive events from Vanus with CloudEvents SDK

The following document will teach you how to build a simple consumer to consume events from Vanus.

Operations

Prerequisites

To consume events from Vanus, you must meet the following prerequisites:

1. Have a running Vanus cluster.
2. Have vsctl.
3. Have created a subscription in Vanus. Please refer to this section of Manage Subscriptions to create a subscription.

We also provide an interactive Kubernetes environment to simply deploy and try Vanus in your browser.

Example code gitgit

package main

import (
    "context"
    "fmt"
    "net"

    ce "github.com/cloudevents/sdk-go/v2"
)

func main() {
    ctx := context.Background()
    // step 1: Create a tcp listener
    ls, err := net.Listen("tcp", ":6789")
    if err != nil {
        panic(fmt.Sprintf("failed to listen, err: %s\n", err.Error()))
    }

    // step 2: Create a cloudevents client
    ceClient, err := ce.NewClientHTTP(ce.WithListener(ls))
    if err != nil {
        panic(fmt.Sprintf("failed to init cloudevents client, err: %s", err.Error()))
    }

    fmt.Println("start event receiver")
    // step 3: Start the receiver and do business logic
    err = ceClient.StartReceiver(ctx, func(event ce.Event) {
        fmt.Printf("received an event: %s\n", event.String())
    })
    if err != nil {
        panic(fmt.Sprintf("failed to start cloudevents receiver, err: %s\n", err.Error()))
    }
}

Note: Vanus must communicate with the consumer.

Send an event to Vanus

Send an event to the Eventbus

~ > vsctl event put quick-start \
  --data-format plain \
  --data "Hello Vanus" \
  --id "1" \
  --source "quick-start" \
  --type "examples"

Expected results

listen 0.0.0.0:6789...
received an event: Context Attributes,
  specversion: 1.0
  type: examples
  source: quick-start
  id: 34d3e285-0329-4c6c-9e80-5b3bbcf7cd6f
  time: 2022-09-21T02:08:42.893778582Z
  datacontenttype: text/plain
Extensions,
  xvanuseventbus: quick-start
  xvanusstime: 2022-09-21T02:08:42.894Z
Data,
  Hello Vanus