Flush host when network connectivity changes

4 files changed, 31 insertions, 3 deletions

diff --git a/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.h b/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.h
index 2fae410331..8d5c1b3e68 100644
--- a/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.h
+++ b/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.h
@@ -73,5 +73,6 @@
  * Only one handler is active at a time, so if this method is called again before the previous
  * handler has been called, it might never be called at all (or yes, if it has already been queued).
  */
-- (void)handleLossWithHandler:(nonnull void (^)())handler;
+- (void)handleLossWithHandler:(void (^)())handler
+      wifiStatusChangeHandler:(void (^)())wifiStatusChangeHandler;
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.m b/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.m
index b4061bd5ef..d736c5e6b0 100644
--- a/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.m
+++ b/src/objective-c/GRPCClient/private/GRPCConnectivityMonitor.m
@@ -120,6 +120,7 @@ static void PassFlagsToContextInfoBlock(SCNetworkReachabilityRef target,
 
 @implementation GRPCConnectivityMonitor {
   SCNetworkReachabilityRef _reachabilityRef;
+  GRPCReachabilityFlags *_previousReachabilityFlags;
 }
 
 - (nullable instancetype)initWithReachability:(nullable SCNetworkReachabilityRef)reachability {
@@ -129,6 +130,13 @@ static void PassFlagsToContextInfoBlock(SCNetworkReachabilityRef target,
   if ((self = [super init])) {
     _reachabilityRef = CFRetain(reachability);
     _queue = dispatch_get_main_queue();
+    SCNetworkReachabilityFlags flags;
+    if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags)) {
+      _previousReachabilityFlags =
+          [[GRPCReachabilityFlags alloc] initWithFlags:flags];
+    } else {
+      _previousReachabilityFlags = 0;
+    }
   }
   return self;
 }
@@ -149,11 +157,16 @@ static void PassFlagsToContextInfoBlock(SCNetworkReachabilityRef target,
   return returnValue;
 }
 
-- (void)handleLossWithHandler:(void (^)())handler {
+- (void)handleLossWithHandler:(void (^)())handler
+      wifiStatusChangeHandler:(nonnull void (^)())wifiStatusChangeHandler {
   [self startListeningWithHandler:^(GRPCReachabilityFlags *flags) {
-    if (!flags.isHostReachable) {
+    if (!flags.reachable && handler) {
       handler();
+    } else if (flags.isWWAN ^ _previousReachabilityFlags.isWWAN &&
+               wifiStatusChangeHandler) {
+      wifiStatusChangeHandler();
     }
+    _previousReachabilityFlags = flags;
   }];
 }
 
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.m b/src/objective-c/GRPCClient/private/GRPCHost.m
index f8634b448e..ee6045653e 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.m
+++ b/src/objective-c/GRPCClient/private/GRPCHost.m
@@ -43,6 +43,7 @@
 
 #import "GRPCChannel.h"
 #import "GRPCCompletionQueue.h"
+#import "GRPCConnectivityMonitor.h"
 #import "NSDictionary+GRPC.h"
 
 NS_ASSUME_NONNULL_BEGIN
@@ -52,6 +53,7 @@ NS_ASSUME_NONNULL_BEGIN
 #define GRPC_OBJC_VERSION_STRING @"1.0.0"
 
 static NSMutableDictionary *kHostCache;
+static GRPCConnectivityMonitor *connectivityMonitor = nil;
 
 @implementation GRPCHost {
   // TODO(mlumish): Investigate whether caching channels with strong links is a good idea.
@@ -98,6 +100,16 @@ static NSMutableDictionary *kHostCache;
       _address = address;
       _secure = YES;
       kHostCache[address] = self;
+
+      if (!connectivityMonitor) {
+        connectivityMonitor =
+            [GRPCConnectivityMonitor monitorWithHost:hostURL.host];
+        void (^handler)() = ^{
+          [GRPCHost flushChannelCache];
+        };
+        [connectivityMonitor handleLossWithHandler:handler
+                           wifiStatusChangeHandler:handler];
+      }
     }
   }
   return self;
@@ -110,6 +122,7 @@ static NSMutableDictionary *kHostCache;
                                                     BOOL * _Nonnull stop) {
       [host disconnect];
     }];
+    connectivityMonitor = nil;
   }
 }
 
diff --git a/src/objective-c/GRPCClient/private/GRPCReachabilityFlagNames.xmacro.h b/src/objective-c/GRPCClient/private/GRPCReachabilityFlagNames.xmacro.h
index 4b92504b55..1c907877a0 100644
--- a/src/objective-c/GRPCClient/private/GRPCReachabilityFlagNames.xmacro.h
+++ b/src/objective-c/GRPCClient/private/GRPCReachabilityFlagNames.xmacro.h
@@ -65,3 +65,4 @@ GRPC_XMACRO_ITEM(interventionRequired, InterventionRequired)
 GRPC_XMACRO_ITEM(connectionOnDemand, ConnectionOnDemand)
 GRPC_XMACRO_ITEM(isLocalAddress, IsLocalAddress)
 GRPC_XMACRO_ITEM(isDirect, IsDirect)
+GRPC_XMACRO_ITEM(isWWAN, IsWWAN)