Timeout and backoff

src/objective-c/GRPCClient/GRPCCall+ChannelArg.h

@@ -60,4 +60,14 @@ typedef NS_ENUM(NSInteger, GRPCCompressAlgorithm) {
  * immediately returned to the application layer. */
 + (void)enableRetry:(BOOL)enabled forHost:(nonnull NSString *)host;
 
+/** Set channel connection timeout and backoff parameters. All parameters are positive integers in
+ * milliseconds. Set a parameter to 0 to make gRPC use default value for that parameter.
+ *
+ * Refer to gRPC's doc at https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md for the
+ * details of each parameter. */
++ (void)setMinConnectTimeout:(unsigned int)timeout
+              initialBackoff:(unsigned int)initialBackoff
+                  maxBackoff:(unsigned int)maxBackoff
+                     forHost:(nonnull NSString *)host;
+
 @end

src/objective-c/GRPCClient/GRPCCall+ChannelArg.m

@@ -69,4 +69,14 @@
   hostConfig.retryEnabled = enabled;
 }
 
++ (void)setMinConnectTimeout:(unsigned int)timeout
+              initialBackoff:(unsigned int)initialBackoff
+                  maxBackoff:(unsigned int)maxBackoff
+                     forHost:(nonnull NSString *)host {
+  GRPCHost *hostConfig = [GRPCHost hostWithAddress:host];
+  hostConfig.minConnectTimeout = timeout;
+  hostConfig.initialConnectBackoff = initialBackoff;
+  hostConfig.maxConnectBackoff = maxBackoff;
+}
+
 @end

src/objective-c/GRPCClient/private/GRPCHost.h

@@ -40,6 +40,10 @@ struct grpc_channel_credentials;
 @property(nonatomic) id logContext;
 @property(nonatomic) BOOL retryEnabled;
 
+@property(nonatomic) unsigned int minConnectTimeout;
+@property(nonatomic) unsigned int initialConnectBackoff;
+@property(nonatomic) unsigned int maxConnectBackoff;
+
 /** The following properties should only be modified for testing: */
 
 @property(nonatomic, getter=isSecure) BOOL secure;

src/objective-c/GRPCClient/private/GRPCHost.m

@@ -245,6 +245,16 @@ static NSMutableDictionary *kHostCache;
     args[@GRPC_ARG_ENABLE_RETRIES] = [NSNumber numberWithInt:0];
   }
 
+  if (_minConnectTimeout > 0) {
+    args[@GRPC_ARG_MIN_RECONNECT_BACKOFF_MS] = [NSNumber numberWithInt:_minConnectTimeout];
+  }
+  if (_initialConnectBackoff > 0) {
+    args[@GRPC_ARG_INITIAL_RECONNECT_BACKOFF_MS] = [NSNumber numberWithInt:_initialConnectBackoff];
+  }
+  if (_maxConnectBackoff > 0) {
+    args[@GRPC_ARG_MAX_RECONNECT_BACKOFF_MS] = [NSNumber numberWithInt:_maxConnectBackoff];
+  }
+
   return args;
 }