Metrics Code Review for OP SIG meeting by ChatGPT

Development
1

This Go code sets up an HTTP server that exposes metrics for monitoring purposes using Prometheus. Let’s break down the code step by step:

package main

import (
	"flag"
	"log"
	"net/http"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/collectors"
	"github.com/prometheus/client_golang/prometheus/promhttp"

	"github.com/ignition-pillar/go-zdk/client"
	"github.com/ignition-pillar/go-zdk/zdk"
)

type metrics struct {
	syncCurrentHeight     prometheus.Gauge
	syncTargetHeight      prometheus.Gauge
	networkConnectedPeers    prometheus.Gauge
}

func NewMetrics(reg prometheus.Registerer) *metrics {
	m := &metrics{
		syncCurrentHeight: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name:       "znnd_sync_current",
				Help:       "Znnd Sync Current.",
			},
		),
		syncTargetHeight: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name:       "znnd_sync_target",
				Help:       "Znnd Sync Target.",
			},
		),
		networkConnectedPeers: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name:       "znnd_network_peers",
				Help:       "Znnd Network Peers.",
			},
		),
	}
	reg.MustRegister(m.syncCurrentHeight)
	reg.MustRegister(m.syncTargetHeight)
	reg.MustRegister(m.networkConnectedPeers)
	return m
}

func main() {
	var (
		addr              = flag.String("listen-address", ":8080", "The address to listen on for HTTP requests.")
		rpca              = flag.String("rpc-address", "https://my.hc1node.com:35997", "todo")
	)

	flag.Parse()

	rpc, err := client.NewClient(*rpca)
	if err != nil {
		log.Fatalln(err)
	}
	log.Println("Connected to", *rpca)
	z := zdk.NewZdk(rpc)

	reg := prometheus.NewRegistry()

	m := NewMetrics(reg)
	reg.MustRegister(collectors.NewBuildInfoCollector())

	go func() {
		for {
			// todo error handling
			v, _ := z.Stats.SyncInfo()
			m.syncTargetHeight.Set(float64(v.TargetHeight))
			m.syncCurrentHeight.Set(float64(v.CurrentHeight))
			time.Sleep(10 * time.Second)
		}
	}()
	go func() {
		for {
			v, _ := z.Stats.NetworkInfo()
			m.networkConnectedPeers.Set(float64(v.NumPeers))
			time.Sleep(10 * time.Second)
		}
	}()


	http.Handle("/metrics", promhttp.HandlerFor(
		reg,
		promhttp.HandlerOpts{
			EnableOpenMetrics: true,
			Registry: reg,
		},
	))
	log.Fatal(http.ListenAndServe(*addr, nil))
}

1. Imports and Dependencies

  • flag, log, net/http, time – Standard Go libraries for command-line flag parsing, logging, HTTP server setup, and time manipulation.
  • github.com/prometheus/client_golang/prometheus and prometheus/promhttp – Prometheus packages for creating metrics and serving them via HTTP.
  • github.com/ignition-pillar/go-zdk/client and go-zdk/zdk – Custom packages used for interacting with Zenon Network (denoted by zdk), which provides RPC (Remote Procedure Call) methods.

2. Defining Metrics Structure

type metrics struct {
	syncCurrentHeight     prometheus.Gauge
	syncTargetHeight      prometheus.Gauge
	networkConnectedPeers prometheus.Gauge
}
  • This structure (metrics) defines three Prometheus metrics:
    • syncCurrentHeight: Represents the current height of blockchain synchronization.
    • syncTargetHeight: Represents the target height of synchronization.
    • networkConnectedPeers: Represents the number of peers connected in the network.
  • These are Gauge types, which means they represent numerical values that can go up or down.

3. Creating New Metrics (NewMetrics function)

func NewMetrics(reg prometheus.Registerer) *metrics {
	// Define each metric with a name and help string.
	m := &metrics{
		syncCurrentHeight: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name: "znnd_sync_current",
				Help: "Znnd Sync Current.",
			},
		),
		syncTargetHeight: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name: "znnd_sync_target",
				Help: "Znnd Sync Target.",
			},
		),
		networkConnectedPeers: prometheus.NewGauge(
			prometheus.GaugeOpts{
				Name: "znnd_network_peers",
				Help: "Znnd Network Peers.",
			},
		),
	}
	// Register each metric with Prometheus.
	reg.MustRegister(m.syncCurrentHeight)
	reg.MustRegister(m.syncTargetHeight)
	reg.MustRegister(m.networkConnectedPeers)
	return m
}
  • The NewMetrics function takes a prometheus.Registerer as an argument to register the metrics with Prometheus.
  • It initializes each metric with appropriate labels and registers them to make them available for monitoring.

4. Main Function

Command Line Arguments

var (
	addr = flag.String("listen-address", ":8080", "The address to listen on for HTTP requests.")
	rpca = flag.String("rpc-address", "https://my.hc1node.com:35997", "todo")
)
  • The flag package is used to define command-line flags:
    • listen-address: The address where the HTTP server will be listening for incoming requests.
    • rpc-address: The RPC endpoint to connect to the Zenon Network node.

Client Setup

rpc, err := client.NewClient(*rpca)
if err != nil {
	log.Fatalln(err)
}
log.Println("Connected to", *rpca)
z := zdk.NewZdk(rpc)
  • It establishes a connection with the Zenon RPC node using the address provided.
  • A NewClient function from the client package is used to create an RPC client.
  • If an error occurs during connection, it will log the error and terminate the program (log.Fatalln).
  • The RPC client is then wrapped by zdk.NewZdk to use the higher-level Zenon API.

Prometheus Registry and Metric Registration

reg := prometheus.NewRegistry()
m := NewMetrics(reg)
reg.MustRegister(collectors.NewBuildInfoCollector())
  • A custom Prometheus registry (reg) is created.
  • The NewMetrics function is called to register the custom metrics.
  • The NewBuildInfoCollector() is also registered, which provides metadata such as Go version and build details.

5. Metrics Collection Goroutines

Sync Information Collector

go func() {
	for {
		// todo error handling
		v, _ := z.Stats.SyncInfo()
		m.syncTargetHeight.Set(float64(v.TargetHeight))
		m.syncCurrentHeight.Set(float64(v.CurrentHeight))
		time.Sleep(10 * time.Second)
	}
}()
  • A goroutine (go func() { ... }()) is used to collect synchronization information from the Zenon node every 10 seconds.
  • z.Stats.SyncInfo() retrieves the sync information (TargetHeight and CurrentHeight) and updates the corresponding metrics.
  • The time.Sleep(10 * time.Second) ensures the metrics are updated at regular intervals.
  • Note that error handling is not implemented here (// todo error handling).

Network Info Collector

go func() {
	for {
		v, _ := z.Stats.NetworkInfo()
		m.networkConnectedPeers.Set(float64(v.NumPeers))
		time.Sleep(10 * time.Second)
	}
}()
  • Another goroutine is used to collect the network information, specifically the number of peers (NumPeers).
  • This metric is updated every 10 seconds.

6. HTTP Metrics Endpoint

http.Handle("/metrics", promhttp.HandlerFor(
	reg,
	promhttp.HandlerOpts{
		EnableOpenMetrics: true,
		Registry:          reg,
	},
))
log.Fatal(http.ListenAndServe(*addr, nil))
  • The HTTP server is set up to handle /metrics endpoint requests.
  • promhttp.HandlerFor(reg, ...) is used to serve the metrics collected by the custom registry (reg) in the OpenMetrics format.
  • The server listens on the address provided by the addr flag (e.g., :8080).
  • If there is an issue with starting the server, log.Fatal will log the error and stop the program.

Summary

This code provides a Prometheus metrics exporter for monitoring the state of a Zenon node by collecting:

  • Sync Target Height: The target block height for synchronization.
  • Sync Current Height: The current block height of synchronization.
  • Connected Peers: Number of peers connected to the network.

Two separate goroutines are used to periodically update these metrics from the Zenon node, and an HTTP server serves these metrics at /metrics, which can be scraped by Prometheus.

2

@georgezgeorgez Should we track the rate at which blocks are produced in case one hangs and we need to trouble shoot it?

3

We can derive that metric by changes in targetHeight right?

4

Right. If this runs every 10 seconds it will get all of them and we can calculate the time. For some reason I was thinking we could have 2 momentums in within 10 seconds (and miss one), but I assume that is impossible / unlikely.

5

Every 5 minutes, 5 * 60 = 300 seconds, 30 pillars are elected and assigned momentums to produce every 300/30 = 10 seconds.

1 Like