How can we actually see the event from Beacon

[MisiakGeo]

Hello, I have this piece of code. I trying to see block events from beacon chain. The test case does not show exactly how can I see and navigate within the event json.

	doneChn := make(chan struct{})
	errChn := make(chan error)
	//eventChn := make(chan *apiv1.Event)
	go func() {
		spew.Dump("Start listening for blocks")

		for {
			err = client.(eth2Client.EventsProvider).Events(ctx, []string{"block"}, func(event *apiv1.Event) {
				spew.Dump(event)
			})
			if err != nil {
				errChn <- err
			}

			select {
			case err := <-errChn:
				spew.Dump(err)
			case <-doneChn:
				// case incoming := <-eventChn:
				// 	spew.Dump("New event arrived: ")
				// 	spew.Dump(incoming)
				// Update global slot to be available to all services  (TODO)
			}
		}
	}()

Is there a way to fetch the event data?

[mcdee]

Where you have spew.Dump(event) you need to cast the event data, e.g. data := event.Data.(*api.BlockEvent) then you can access the individual fields.

[MisiakGeo]

Is the foor loop required? If it is, do I need to create ctx everytime?

[mcdee]

You don't need that for loop. I'm not 100% sure what you are trying to achieve, but here is a full example:

package main

import (
        "context"
        "fmt"
        "os"
        "os/signal"
        "syscall"
        "time"

        consensusclient "github.com/attestantio/go-eth2-client"
        apiv1 "github.com/attestantio/go-eth2-client/api/v1"
        "github.com/attestantio/go-eth2-client/http"
        "github.com/rs/zerolog"
)

func main() {
        ctx, cancel := context.WithCancel(context.Background())

        client, err := http.New(ctx,
                http.WithLogLevel(zerolog.Disabled),
                http.WithAddress("http://localhost:5052"),
        )
        if err != nil {
                panic(err)
        }

        blockHandlers := []func(context.Context, *apiv1.BlockEvent){
                handler1,
                handler2,
        }

        handler := func(event *apiv1.Event) {
                for _, blockHandler := range blockHandlers {
                        go blockHandler(ctx, event.Data.(*apiv1.BlockEvent))
                }
        }

        if err := client.(consensusclient.EventsProvider).Events(ctx, []string{"block"}, handler); err != nil {
                panic(err)
        }

        // Wait for a signal or error.
        sigCh := make(chan os.Signal, 1)
        signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM, os.Interrupt)
        for {
                sig := <-sigCh
                if sig == syscall.SIGINT || sig == syscall.SIGTERM || sig == os.Interrupt || sig == os.Kill {
                        break
                }
        }

        // Shut down the connection cleanly.
        cancel()
        time.Sleep(100 * time.Millisecond)
}

func handler1(ctx context.Context, block *apiv1.BlockEvent) {
        fmt.Fprintf(os.Stdout, "Handler 1 received event for slot %d\n", block.Slot)
}

func handler2(ctx context.Context, block *apiv1.BlockEvent) {
        fmt.Fprintf(os.Stdout, "Handler 2 received event for slot %d\n", block.Slot)
}

You would need to decide how to create your list of handlers (and they could just be a list of channels if you prefer) but something close the above is likely what you're looking for.

[MisiakGeo]

Thabk you very much. I do want to create a listener to listen for live block events and slot numbers.

[MisiakGeo]

@mcdee Thank you very much. Indeed the code is working. There was an issue with events.go where when I used a quicknode url with token in it https://methodical-billowing-dew.quiknode.pro/<token>, the line where the callURL was created callURL := s.base.ResolveReference(reference).String(), results in a url without the token https://methodical-billowing-dew.quiknode.pro, thus the call to the url was silent failed, due to absent of error returned in .Dial . I resolved it using this line instead callURL := fmt.Sprintf("%s/%s", s.base.String(), reference)

[mcdee]

Thank you for letting me know of this issue, it has been fixed in the latest master.