From e2c626bb8a8b9eb7f496efd1123d58db066c050f Mon Sep 17 00:00:00 2001
From: Aditya Maru <adityamaru@gmail.com>
Date: Tue, 26 Nov 2024 12:25:41 -0500
Subject: [PATCH] cmd: add liveness reporter to ping our backend

---
 cmd/liveness_reporter.go | 82 ++++++++++++++++++++++++++++++++++++++++
 cmd/server.go            | 12 ++++++
 2 files changed, 94 insertions(+)
 create mode 100644 cmd/liveness_reporter.go

diff --git a/cmd/liveness_reporter.go b/cmd/liveness_reporter.go
new file mode 100644
index 0000000..cda7b5e
--- /dev/null
+++ b/cmd/liveness_reporter.go
@@ -0,0 +1,82 @@
+package cmd
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"math/rand"
+	"net/http"
+	"time"
+)
+
+type LivenessReporter struct {
+	client            http.Client
+	backendEndpoint   string
+	backendAdminToken string
+	ip                string
+	region            string
+}
+
+func (r *LivenessReporter) Report(ctx context.Context) {
+	requestBody := struct {
+		IP     string `json:"ip"`
+		Region string `json:"region"`
+	}{
+		IP:     r.ip,
+		Region: r.region,
+	}
+	jsonBody, err := json.Marshal(requestBody)
+	if err != nil {
+		fmt.Printf("failed to marshal request body: %v\n", err)
+		return
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fmt.Sprintf("%s/staticip/liveness", r.backendEndpoint), bytes.NewBuffer(jsonBody))
+	if err != nil {
+		fmt.Printf("failed to create request: %v\n", err)
+		return
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", r.backendAdminToken))
+
+	resp, err := r.client.Do(req)
+	if err != nil {
+		fmt.Printf("failed to send request: %v\n", err)
+		return
+	}
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			fmt.Printf("failed to close response body: %v\n", err)
+		}
+	}()
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
+		fmt.Printf("error reporting liveness: unexpected status code: %d\n", resp.StatusCode)
+	}
+}
+
+const (
+	minLivenessReportInterval = 1500 * time.Millisecond
+	maxLivenessReportInterval = 2 * time.Second
+)
+
+func (r *LivenessReporter) Start(ctx context.Context) {
+	go func() {
+		ticker := time.NewTicker(r.randomInterval())
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ticker.C:
+				r.Report(ctx)
+				ticker.Reset(r.randomInterval())
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+}
+
+func (r *LivenessReporter) randomInterval() time.Duration {
+	return time.Duration(rand.Int63n(int64(maxLivenessReportInterval-minLivenessReportInterval))) + minLivenessReportInterval
+}
diff --git a/cmd/server.go b/cmd/server.go
index 2cf3b87..71dda5d 100644
--- a/cmd/server.go
+++ b/cmd/server.go
@@ -4,7 +4,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net/http"
 	"net/netip"
+	"os"
 	"os/signal"
 	"strconv"
 	"syscall"
@@ -115,6 +117,16 @@ func runServer(cmd *cobra.Command, args []string) error {
 	defer sm.Wait()
 	defer done()
 
+	// Start the liveness reporter.
+	livenessReporter := &LivenessReporter{
+		client:            http.Client{Timeout: 5 * time.Second},
+		ip:                serverCmdArgs.ip[0],
+		region:            serverCmdArgs.region,
+		backendEndpoint:   os.Getenv("BACKEND_ENDPOINT"),
+		backendAdminToken: os.Getenv("BACKEND_ADMIN_TOKEN"),
+	}
+	livenessReporter.Start(ctx)
+
 	for _, ipStr := range serverCmdArgs.ip {
 		ip, err := netip.ParseAddr(ipStr)
 		if err != nil || !ip.Is4() {