Merge pull request #657 from ably/feature/realtime-fallbacks

[ECO-4327] Feature - realtime fallbacks

README.md

@@ -450,8 +450,6 @@ See [jwt auth issue](https://github.com/ably/ably-go/issues/569) for more detail
 - Inband reauthentication is not supported; expiring tokens will trigger a disconnection and resume of a realtime
   connection. See [server initiated auth](https://github.com/ably/ably-go/issues/228) for more details.
 
-- Realtime connection failure handling is partially implemented. See [host fallback](https://github.com/ably/ably-go/issues/225) for more details.
-
 - Channel suspended state is partially implemented. See [suspended channel state](https://github.com/ably/ably-go/issues/568).
 
 - Realtime Ping function is not implemented.

ably/error.go

@@ -147,6 +147,17 @@ func errFromUnprocessableBody(resp *http.Response) error {
 	return &ErrorInfo{Code: ErrBadRequest, StatusCode: resp.StatusCode, err: err}
 }
 
+func isTimeoutOrDnsErr(err error) bool {
+	var netErr net.Error
+	if errors.As(err, &netErr) {
+		if netErr.Timeout() { // RSC15l2
+			return true
+		}
+	}
+	var dnsErr *net.DNSError
+	return errors.As(err, &dnsErr) // RSC15l1
+}
+
 func checkValidHTTPResponse(resp *http.Response) error {
 	type errorBody struct {
 		Error errorInfo `json:"error,omitempty" codec:"error,omitempty"`

ably/export_test.go

@@ -36,10 +36,6 @@ func (opts *clientOptions) RestURL() string {
 	return opts.restURL()
 }
 
-func (opts *clientOptions) RealtimeURL() string {
-	return opts.realtimeURL()
-}
-
 func (c *REST) Post(ctx context.Context, path string, in, out interface{}) (*http.Response, error) {
 	return c.post(ctx, path, in, out)
 }
@@ -93,6 +89,10 @@ func (c *REST) GetCachedFallbackHost() string {
 	return c.hostCache.get()
 }
 
+func (c *REST) ActiveRealtimeHost() string {
+	return c.activeRealtimeHost
+}
+
 func (c *RealtimeChannel) GetChannelSerial() string {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
@@ -121,6 +121,10 @@ func (opts *clientOptions) GetFallbackRetryTimeout() time.Duration {
 	return opts.fallbackRetryTimeout()
 }
 
+func (opts *clientOptions) HasActiveInternetConnection() bool {
+	return opts.hasActiveInternetConnection()
+}
+
 func NewErrorInfo(code ErrorCode, err error) *ErrorInfo {
 	return newError(code, err)
 }
@@ -222,6 +226,10 @@ func (c *Connection) SetKey(key string) {
 	c.key = key
 }
 
+func (r *Realtime) Rest() *REST {
+	return r.rest
+}
+
 func (c *RealtimePresence) Members() map[string]*PresenceMessage {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
@@ -272,6 +280,11 @@ type DurationFromMsecs = durationFromMsecs
 type ProtoErrorInfo = errorInfo
 type ProtoFlag = protoFlag
 type ProtocolMessage = protocolMessage
+type WebsocketErr = websocketErr
+
+func (w *WebsocketErr) HttpResp() *http.Response {
+	return w.resp
+}
 
 const (
 	DefaultCipherKeyLength = defaultCipherKeyLength

ably/options.go

@@ -1,9 +1,11 @@
 package ably
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -28,6 +30,10 @@ const (
 	Port           = 80
 	TLSPort        = 443
 	maxMessageSize = 65536 // 64kb, default value TO3l8
+
+	// RTN17c
+	internetCheckUrl = "https://internet-up.ably-realtime.com/is-the-internet-up.txt"
+	internetCheckOk  = "yes"
 )
 
 var defaultOptions = clientOptions{
@@ -482,10 +488,10 @@ func (opts *clientOptions) restURL() (restUrl string) {
 	return "https://" + baseUrl
 }
 
-func (opts *clientOptions) realtimeURL() (realtimeUrl string) {
-	baseUrl := opts.getRealtimeHost()
+func (opts *clientOptions) realtimeURL(realtimeHost string) (realtimeUrl string) {
+	baseUrl := realtimeHost
 	_, _, err := net.SplitHostPort(baseUrl)
-	if err != nil { // set port if not set in baseUrl
+	if err != nil { // set port if not set in provided realtimeHost
 		port, _ := opts.activePort()
 		baseUrl = net.JoinHostPort(baseUrl, strconv.Itoa(port))
 	}
@@ -595,6 +601,20 @@ func (opts *clientOptions) idempotentRESTPublishing() bool {
 	return opts.IdempotentRESTPublishing
 }
 
+// RTN17c
+func (opts *clientOptions) hasActiveInternetConnection() bool {
+	res, err := opts.httpclient().Get(internetCheckUrl)
+	if err != nil || res.StatusCode != 200 {
+		return false
+	}
+	defer res.Body.Close()
+	data, err := io.ReadAll(res.Body)
+	if err != nil {
+		return false
+	}
+	return bytes.Contains(data, []byte(internetCheckOk))
+}
+
 type ScopeParams struct {
 	Start time.Time
 	End   time.Time

ably/options_test.go

@@ -14,31 +14,32 @@ import (
 )
 
 func TestDefaultFallbacks_RSC15h(t *testing.T) {
-	t.Run("with env should return environment fallback hosts", func(t *testing.T) {
-		expectedFallBackHosts := []string{
-			"a.ably-realtime.com",
-			"b.ably-realtime.com",
-			"c.ably-realtime.com",
-			"d.ably-realtime.com",
-			"e.ably-realtime.com",
-		}
-		hosts := ably.DefaultFallbackHosts()
-		assert.Equal(t, expectedFallBackHosts, hosts)
-	})
+	expectedFallBackHosts := []string{
+		"a.ably-realtime.com",
+		"b.ably-realtime.com",
+		"c.ably-realtime.com",
+		"d.ably-realtime.com",
+		"e.ably-realtime.com",
+	}
+	hosts := ably.DefaultFallbackHosts()
+	assert.Equal(t, expectedFallBackHosts, hosts)
 }
 
 func TestEnvFallbackHosts_RSC15i(t *testing.T) {
-	t.Run("with env should return environment fallback hosts", func(t *testing.T) {
-		expectedFallBackHosts := []string{
-			"sandbox-a-fallback.ably-realtime.com",
-			"sandbox-b-fallback.ably-realtime.com",
-			"sandbox-c-fallback.ably-realtime.com",
-			"sandbox-d-fallback.ably-realtime.com",
-			"sandbox-e-fallback.ably-realtime.com",
-		}
-		hosts := ably.GetEnvFallbackHosts("sandbox")
-		assert.Equal(t, expectedFallBackHosts, hosts)
-	})
+	expectedFallBackHosts := []string{
+		"sandbox-a-fallback.ably-realtime.com",
+		"sandbox-b-fallback.ably-realtime.com",
+		"sandbox-c-fallback.ably-realtime.com",
+		"sandbox-d-fallback.ably-realtime.com",
+		"sandbox-e-fallback.ably-realtime.com",
+	}
+	hosts := ably.GetEnvFallbackHosts("sandbox")
+	assert.Equal(t, expectedFallBackHosts, hosts)
+}
+
+func TestInternetConnectionCheck_RTN17c(t *testing.T) {
+	clientOptions := ably.NewClientOptions()
+	assert.True(t, clientOptions.HasActiveInternetConnection())
 }
 
 func TestFallbackHosts_RSC15b(t *testing.T) {