Read Alertmanager NFLOG

main.go

package main

import (
	"errors"
	"flag"
	"fmt"
	"io"
	"os"

	"github.com/gogo/protobuf/jsonpb"
	pb "github.com/prometheus/alertmanager/nflog/nflogpb"

	"github.com/matttproud/golang_protobuf_extensions/pbutil"
)

type state map[string]*pb.MeshEntry

// stateKey returns a string key for a log entry consisting of the group key
// and receiver.
func stateKey(k string, r *pb.Receiver) string {
	return fmt.Sprintf("%s:%s", k, receiverKey(r))
}
func receiverKey(r *pb.Receiver) string {
	return fmt.Sprintf("%s/%s/%d", r.GroupName, r.Integration, r.Idx)
}

func main() {
	flag.Parse()
	r, err := os.Open(flag.Arg(0))
	if err != nil {
		panic(err)
	}
	s, err := decodeState(r)
	if err != nil {
		panic(err)
	}
	for entry, mesh := range s {
		m := &jsonpb.Marshaler{
			Indent: "  ",
		}
		os.Stdout.Write([]byte(fmt.Sprintf("Entry: %s\n", entry)))
		m.Marshal(os.Stdout, mesh)
		os.Stdout.Write([]byte("\n"))
	}
}
func decodeState(r io.Reader) (state, error) {
	st := state{}
	for {
		var e pb.MeshEntry
		_, err := pbutil.ReadDelimited(r, &e)
		if err == nil {
			if e.Entry == nil || e.Entry.Receiver == nil {
				return nil, errors.New("oops")
			}
			st[stateKey(string(e.Entry.GroupKey), e.Entry.Receiver)] = &e
			continue
		}
		if err == io.EOF {
			break
		}
		return nil, err
	}
	return st, nil

}

Thanks for this piece of code!

One improvement, if you dump the result as JSON, the output will be sorted and consistent which can be handy if debugging Alertmanager cluster and comparing nflogs of multiple instances for example

enc := json.NewEncoder(os.Stdout)
enc.SetIndent("", "  ")
enc.Encode(s)