Altered auto-reconnection attempt logic to comply with part 4 of the OCPP2.0.1 standard

ws/network_test.go

@@ -120,7 +120,8 @@ func (s *NetworkTestSuite) TestClientConnectionFailedTimeout() {
 func (s *NetworkTestSuite) TestClientAutoReconnect() {
 	t := s.T()
 	// Set timeouts for test
-	s.client.timeoutConfig.ReconnectBackoff = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffWaitMinimum = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffRandomRange = 1 // seconds
 	// Setup
 	serverOnDisconnected := make(chan bool, 1)
 	clientOnDisconnected := make(chan bool, 1)
@@ -147,7 +148,7 @@ func (s *NetworkTestSuite) TestClientAutoReconnect() {
 		clientOnDisconnected <- true
 	})
 	s.client.SetReconnectedHandler(func() {
-		time.Sleep(50 * time.Millisecond) // Make sure we reconnected after backoff
+		time.Sleep(time.Duration(s.client.timeoutConfig.RetryBackOffRandomRange)*time.Second + 50*time.Millisecond) // Make sure we reconnected after backoff
 		reconnected <- true
 	})
 	// Connect client
@@ -172,7 +173,7 @@ func (s *NetworkTestSuite) TestClientAutoReconnect() {
 	elapsed := time.Since(start)
 	assert.True(t, result)
 	assert.True(t, s.client.IsConnected())
-	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.ReconnectBackoff.Milliseconds())
+	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.RetryBackOffWaitMinimum.Milliseconds())
 	// Cleanup
 	s.client.SetDisconnectedHandler(func(err error) {
 		assert.Nil(t, err)
@@ -191,7 +192,8 @@ func (s *NetworkTestSuite) TestClientPongTimeout() {
 	// Server will close connection
 	s.client.timeoutConfig.PongWait = 2 * time.Second
 	s.client.timeoutConfig.PingPeriod = (s.client.timeoutConfig.PongWait * 5) / 10
-	s.client.timeoutConfig.ReconnectBackoff = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffWaitMinimum = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffWaitMinimum = 0 // remove randomness
 	s.server.timeoutConfig.PingWait = (s.client.timeoutConfig.PongWait * 7) / 10
 	// Setup
 	serverOnDisconnected := make(chan bool, 1)
@@ -246,7 +248,7 @@ func (s *NetworkTestSuite) TestClientPongTimeout() {
 	result = <-reconnected
 	require.True(t, result)
 	elapsed := time.Since(startTimeout)
-	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.ReconnectBackoff.Milliseconds())
+	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.RetryBackOffWaitMinimum.Milliseconds())
 	// Cleanup
 	s.client.SetDisconnectedHandler(nil)
 	s.client.Stop()
@@ -258,7 +260,8 @@ func (s *NetworkTestSuite) TestClientReadTimeout() {
 	// Set timeouts for test
 	s.client.timeoutConfig.PongWait = 2 * time.Second
 	s.client.timeoutConfig.PingPeriod = (s.client.timeoutConfig.PongWait * 7) / 10
-	s.client.timeoutConfig.ReconnectBackoff = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffWaitMinimum = 1 * time.Second
+	s.client.timeoutConfig.RetryBackOffRandomRange = 0 // remove randomness
 	s.server.timeoutConfig.PingWait = s.client.timeoutConfig.PongWait
 	// Setup
 	serverOnDisconnected := make(chan bool, 1)
@@ -317,7 +320,7 @@ func (s *NetworkTestSuite) TestClientReadTimeout() {
 	result = <-reconnected
 	require.True(t, result)
 	elapsed := time.Since(startTimeout)
-	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.ReconnectBackoff.Milliseconds())
+	assert.GreaterOrEqual(t, elapsed.Milliseconds(), s.client.timeoutConfig.RetryBackOffWaitMinimum.Milliseconds())
 	// Cleanup
 	s.client.SetDisconnectedHandler(nil)
 	s.client.Stop()

ws/websocket.go

@@ -10,6 +10,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io"
+	"math/rand"
 	"net"
 	"net/http"
 	"net/url"
@@ -33,10 +34,19 @@ const (
 	defaultPingPeriod = (defaultPongWait * 9) / 10
 	// Time allowed for the initial handshake to complete.
 	defaultHandshakeTimeout = 30 * time.Second
-	// The base delay to be used for automatic reconnection. Will double for every attempt up to maxReconnectionDelay.
-	defaultReconnectBackoff = 5 * time.Second
-	// Default maximum reconnection delay for websockets
-	defaultReconnectMaxBackoff = 2 * time.Minute
+	// When the Charging Station is reconnecting, after a connection loss, it will use this variable for the amount of time
+	// it will double the previous back-off time. When the maximum number of increments is reached, the Charging
+	// Station keeps connecting with the same back-off time.
+	defaultRetryBackOffRepeatTimes = 5
+	// When the Charging Station is reconnecting, after a connection loss, it will use this variable as the maximum value
+	// for the random part of the back-off time. It will add a new random value to every increasing back-off time,
+	// including the first connection attempt (with this maximum), for the amount of times it will double the previous
+	// back-off time. When the maximum number of increments is reached, the Charging Station will keep connecting
+	// with the same back-off time.
+	defaultRetryBackOffRandomRange = 15 // seconds
+	// When the Charging Station is reconnecting, after a connection loss, it will use this variable as the minimum backoff
+	// time, the first time it tries to reconnect.
+	defaultRetryBackOffWaitMinimum = 10 * time.Second
 )
 
 // The internal verbose logger
@@ -76,25 +86,27 @@ func NewServerTimeoutConfig() ServerTimeoutConfig {
 // To set a custom configuration, refer to the client's SetTimeoutConfig method.
 // If no configuration is passed, a default configuration is generated via the NewClientTimeoutConfig function.
 type ClientTimeoutConfig struct {
-	WriteWait           time.Duration
-	HandshakeTimeout    time.Duration
-	PongWait            time.Duration
-	PingPeriod          time.Duration
-	ReconnectBackoff    time.Duration
-	ReconnectMaxBackoff time.Duration
+	WriteWait               time.Duration
+	HandshakeTimeout        time.Duration
+	PongWait                time.Duration
+	PingPeriod              time.Duration
+	RetryBackOffRepeatTimes int
+	RetryBackOffRandomRange int
+	RetryBackOffWaitMinimum time.Duration
 }
 
 // NewClientTimeoutConfig creates a default timeout configuration for a websocket endpoint.
 //
 // You may change fields arbitrarily and pass the struct to a SetTimeoutConfig method.
 func NewClientTimeoutConfig() ClientTimeoutConfig {
 	return ClientTimeoutConfig{
-		WriteWait:           defaultWriteWait,
-		HandshakeTimeout:    defaultHandshakeTimeout,
-		PongWait:            defaultPongWait,
-		PingPeriod:          defaultPingPeriod,
-		ReconnectBackoff:    defaultReconnectBackoff,
-		ReconnectMaxBackoff: defaultReconnectMaxBackoff,
+		WriteWait:               defaultWriteWait,
+		HandshakeTimeout:        defaultHandshakeTimeout,
+		PongWait:                defaultPongWait,
+		PingPeriod:              defaultPingPeriod,
+		RetryBackOffRepeatTimes: defaultRetryBackOffRepeatTimes,
+		RetryBackOffRandomRange: defaultRetryBackOffRandomRange,
+		RetryBackOffWaitMinimum: defaultRetryBackOffWaitMinimum,
 	}
 }
 
@@ -973,7 +985,8 @@ func (client *Client) cleanup() {
 
 func (client *Client) handleReconnection() {
 	log.Info("started automatic reconnection handler")
-	delay := client.timeoutConfig.ReconnectBackoff
+	delay := client.timeoutConfig.RetryBackOffWaitMinimum + time.Duration(rand.Intn(client.timeoutConfig.RetryBackOffRandomRange+1))*time.Second
+	reconnectionAttempts := 1
 	for {
 		// Wait before reconnecting
 		select {
@@ -992,11 +1005,13 @@ func (client *Client) handleReconnection() {
 			return
 		}
 		client.error(fmt.Errorf("reconnection failed: %w", err))
-		// Re-connection failed, double the delay
-		delay *= 2
-		if delay >= client.timeoutConfig.ReconnectMaxBackoff {
-			delay = client.timeoutConfig.ReconnectMaxBackoff
+
+		if reconnectionAttempts < client.timeoutConfig.RetryBackOffRepeatTimes {
+			// Re-connection failed, double the delay
+			delay *= 2
+			delay += time.Duration(rand.Intn(client.timeoutConfig.RetryBackOffRandomRange+1)) * time.Second
 		}
+		reconnectionAttempts += 1
 	}
 }