Fix service monitor connection leak

services.go

@@ -74,6 +74,20 @@ type ServiceHistoryPoint struct {
 	LatencyMS float64 `json:"latencyMs"`
 }
 
+var serviceHTTPTransport = &http.Transport{
+	Proxy:                 http.ProxyFromEnvironment,
+	DialContext:           (&net.Dialer{Timeout: 10 * time.Second, KeepAlive: 30 * time.Second}).DialContext,
+	ForceAttemptHTTP2:     true,
+	MaxIdleConns:          32,
+	MaxIdleConnsPerHost:   2,
+	IdleConnTimeout:       30 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: time.Second,
+	TLSClientConfig:       &tls.Config{InsecureSkipVerify: true, MinVersion: tls.VersionTLS12},
+}
+
+var serviceHTTPClient = &http.Client{Transport: serviceHTTPTransport}
+
 func (s *Store) Services() ([]MonitoredService, error) {
 	rows, err := s.db.Query(`SELECT id,name,url,local_address,check_type,expected_code,expected_text,timeout_seconds,enabled FROM services ORDER BY id`)
 	if err != nil {
@@ -296,14 +310,12 @@ func checkServiceEndpoint(v MonitoredService, kind, label, target string) Servic
 			st.Error = strings.TrimSpace(string(out))
 		}
 	default:
-		tr := &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true, MinVersion: tls.VersionTLS12}}
-		client := &http.Client{Transport: tr, Timeout: time.Duration(v.TimeoutSeconds) * time.Second}
 		req, err := http.NewRequestWithContext(ctx, http.MethodGet, target, nil)
 		if err != nil {
 			st.Error = err.Error()
 			break
 		}
-		resp, err := client.Do(req)
+		resp, err := serviceHTTPClient.Do(req)
 		if err != nil {
 			st.Error = err.Error()
 		} else {