cmd/devp2p: avoid exceeding cloudflare record quota

etclabscore/discv4-dns-lists#323

This patch modifies the deployment
pattern by deleting one stale record
before creating a new record, rather
than leaving all the stales to be deleted
at the end.

Date: 2023-12-07 08:24:07-07:00
Signed-off-by: meows <b5c6@protonmail.com>

cmd/devp2p/dns_cloudflare.go

@@ -125,16 +125,41 @@ func (c *cloudflareClient) uploadRecords(name string, records map[string]string)
 		}
 		existing[strings.ToLower(entry.Name)] = entry
 	}
+	// if the record exists on cloudflare, but is not in our local records, it is stale
+	stales := make(map[string]cloudflare.DNSRecord)
+	for path, entry := range existing {
+		if _, ok := records[path]; !ok {
+			stales[path] = entry
+		}
+	}
+	// firstCloudflareRecord is a helper function returning the first path:record value from a path:DNSRecord map.
+	firstCloudflareRecord := func(cfPathRecordMap map[string]cloudflare.DNSRecord) (string, cloudflare.DNSRecord) {
+		for path, entry := range cfPathRecordMap {
+			return path, entry
+		}
+		return "", cloudflare.DNSRecord{}
+	}
 
 	// Iterate over the new records and inject anything missing.
 	log.Info("Updating DNS entries")
 	created := 0
 	updated := 0
 	skipped := 0
+	deleted := 0
 	for path, val := range records {
 		old, exists := existing[path]
 		if !exists {
-			// Entry is unknown, push a new one to Cloudflare.
+			// Entry is unknown, push a new one to Cloudflare after removing first stale record, if any.
+			// We delete any one stale record before creating a new one to avoid exceeding the Cloudflare
+			// record quota.
+			if path, entry := firstCloudflareRecord(stales); path != "" {
+				log.Debug(fmt.Sprintf("Deleting %s = %q", path, entry.Content))
+				deleted++
+				if err := c.DeleteDNSRecord(context.Background(), c.zoneID, entry.ID); err != nil {
+					return fmt.Errorf("failed to delete %s: %v", path, err)
+				}
+				delete(stales, path)
+			}
 			log.Debug(fmt.Sprintf("Creating %s = %q", path, val))
 			created++
 			ttl := rootTTL
@@ -157,21 +182,17 @@ func (c *cloudflareClient) uploadRecords(name string, records map[string]string)
 			return fmt.Errorf("failed to publish %s: %v", path, err)
 		}
 	}
-	log.Info("Updated DNS entries", "new", created, "updated", updated, "untouched", skipped)
-	// Iterate over the old records and delete anything stale.
-	deleted := 0
+	log.Info("Updated DNS entries", "new", created, "updated", updated, "untouched", skipped, "deleted", deleted)
+	// Iterate over the old records and delete anything left stale.
+	deleted = 0
 	log.Info("Deleting stale DNS entries")
-	for path, entry := range existing {
-		if _, ok := records[path]; ok {
-			continue
-		}
-		// Stale entry, nuke it.
+	for path, entry := range stales {
 		log.Debug(fmt.Sprintf("Deleting %s = %q", path, entry.Content))
 		deleted++
 		if err := c.DeleteDNSRecord(context.Background(), c.zoneID, entry.ID); err != nil {
 			return fmt.Errorf("failed to delete %s: %v", path, err)
 		}
 	}
-	log.Info("Deleted stale DNS entries", "count", deleted)
+	log.Info("Deleted remaining stale DNS entries", "count", deleted)
 	return nil
 }