Merge pull request #15838 from muxi/objc-channel-args

Surface more channel args on gRPC iOS

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

@@ -55,4 +55,19 @@ typedef NS_ENUM(NSInteger, GRPCCompressAlgorithm) {
                          timeout:(int)timeout
                          forHost:(nonnull NSString *)host;
 
+/** Enable/Disable automatic retry of gRPC calls on the channel. If automatic retry is enabled, the
+ * retry is controlled by server's service config. If automatic retry is disabled, failed calls are
+ * 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

@@ -64,4 +64,19 @@
   hostConfig.keepaliveTimeout = timeout;
 }
 
++ (void)enableRetry:(BOOL)enabled forHost:(nonnull NSString *)host {
+  GRPCHost *hostConfig = [GRPCHost hostWithAddress:host];
+  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

@@ -38,6 +38,11 @@ struct grpc_channel_credentials;
 @property(nonatomic) int keepaliveInterval;
 @property(nonatomic) int keepaliveTimeout;
 @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: */
 

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

@@ -85,6 +85,7 @@ static NSMutableDictionary *kHostCache;
       _secure = YES;
       kHostCache[address] = self;
       _compressAlgorithm = GRPC_COMPRESS_NONE;
+      _retryEnabled = YES;
     }
 #ifndef GRPC_CFSTREAM
     [GRPCConnectivityMonitor registerObserver:self selector:@selector(connectivityChange:)];
@@ -240,6 +241,20 @@ static NSMutableDictionary *kHostCache;
     args[@GRPC_ARG_DISABLE_CLIENT_AUTHORITY_FILTER] = [NSNumber numberWithInt:1];
   }
 
+  if (_retryEnabled == NO) {
+    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;
 }
 

src/objective-c/tests/GRPCClientTests.m

@@ -548,4 +548,47 @@ static GRPCProtoMethod *kFullDuplexCallMethod;
   [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
 }
 
+- (void)testTimeoutBackoffWithTimeout:(double)timeout Backoff:(double)backoff {
+  const double maxConnectTime = timeout > backoff ? timeout : backoff;
+  const double kMargin = 0.1;
+
+  __weak XCTestExpectation *completion = [self expectationWithDescription:@"Timeout in a second."];
+  NSString *const kDummyAddress = [NSString stringWithFormat:@"8.8.8.8:1"];
+  GRPCCall *call = [[GRPCCall alloc] initWithHost:kDummyAddress
+                                             path:@""
+                                   requestsWriter:[GRXWriter writerWithValue:[NSData data]]];
+  [GRPCCall setMinConnectTimeout:timeout * 1000
+                  initialBackoff:backoff * 1000
+                      maxBackoff:0
+                         forHost:kDummyAddress];
+  NSDate *startTime = [NSDate date];
+  id<GRXWriteable> responsesWriteable = [[GRXWriteable alloc] initWithValueHandler:^(id value) {
+    XCTAssert(NO, @"Received message. Should not reach here");
+  }
+      completionHandler:^(NSError *errorOrNil) {
+        XCTAssertNotNil(errorOrNil, @"Finished with no error");
+        // The call must fail before maxConnectTime. However there is no lower bound on the time
+        // taken for connection. A shorter time happens when connection is actively refused
+        // by 8.8.8.8:1 before maxConnectTime elapsed.
+        XCTAssertLessThan([[NSDate date] timeIntervalSinceDate:startTime],
+                          maxConnectTime + kMargin);
+        [completion fulfill];
+      }];
+
+  [call startWithWriteable:responsesWriteable];
+
+  [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
+}
+
+// The numbers of the following three tests are selected to be smaller than the default values of
+// initial backoff (1s) and min_connect_timeout (20s), so that if they fail we know the default
+// values fail to be overridden by the channel args.
+- (void)testTimeoutBackoff2 {
+  [self testTimeoutBackoffWithTimeout:0.7 Backoff:0.3];
+}
+
+- (void)testTimeoutBackoff3 {
+  [self testTimeoutBackoffWithTimeout:0.3 Backoff:0.7];
+}
+
 @end