Merge pull request #9247 from muxi/packet-coalescing-objc

Packet Coalescing - ObjC

src/objective-c/GRPCClient/GRPCCall.m

@@ -36,6 +36,7 @@
 #include <grpc/grpc.h>
 #include <grpc/support/time.h>
 #import <RxLibrary/GRXConcurrentWriteable.h>
+#import <RxLibrary/GRXImmediateSingleWriter.h>
 
 #import "private/GRPCConnectivityMonitor.h"
 #import "private/GRPCHost.h"
@@ -45,6 +46,11 @@
 #import "private/NSDictionary+GRPC.h"
 #import "private/NSError+GRPC.h"
 
+// At most 6 ops can be in an op batch for a client: SEND_INITIAL_METADATA,
+// SEND_MESSAGE, SEND_CLOSE_FROM_CLIENT, RECV_INITIAL_METADATA, RECV_MESSAGE,
+// and RECV_STATUS_ON_CLIENT.
+NSInteger kMaxClientBatch = 6;
+
 NSString * const kGRPCHeadersKey = @"io.grpc.HeadersKey";
 NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
 static NSMutableDictionary *callFlags;
@@ -100,6 +106,13 @@ static NSMutableDictionary *callFlags;
   GRPCCall *_retainSelf;
 
   GRPCRequestHeaders *_requestHeaders;
+
+  // In the case that the call is a unary call (i.e. the writer to GRPCCall is of type
+  // GRXImmediateSingleWriter), GRPCCall will delay sending ops (not send them to C core
+  // immediately) and buffer them into a batch _unaryOpBatch. The batch is sent to C core when
+  // the SendClose op is added.
+  BOOL _unaryCall;
+  NSMutableArray *_unaryOpBatch;
 }
 
 @synthesize state = _state;
@@ -157,6 +170,11 @@ static NSMutableDictionary *callFlags;
     _requestWriter = requestWriter;
 
     _requestHeaders = [[GRPCRequestHeaders alloc] initWithCall:self];
+
+    if ([requestWriter isKindOfClass:[GRXImmediateSingleWriter class]]) {
+      _unaryCall = YES;
+      _unaryOpBatch = [NSMutableArray arrayWithCapacity:kMaxClientBatch];
+    }
   }
   return self;
 }
@@ -165,6 +183,9 @@ static NSMutableDictionary *callFlags;
 
 - (void)finishWithError:(NSError *)errorOrNil {
   @synchronized(self) {
+    if (_state == GRXWriterStateFinished) {
+      return;
+    }
     _state = GRXWriterStateFinished;
   }
 
@@ -254,15 +275,22 @@ static NSMutableDictionary *callFlags;
 
 - (void)sendHeaders:(NSDictionary *)headers {
   // TODO(jcanizales): Add error handlers for async failures
-  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMetadata alloc] initWithMetadata:headers
-                                                                                  flags:[GRPCCall callFlagsForHost:_host path:_path]
-                                                                                handler:nil]]];
+  GRPCOpSendMetadata *op = [[GRPCOpSendMetadata alloc] initWithMetadata:headers
+                                                                  flags:[GRPCCall callFlagsForHost:_host path:_path]
+                                                                handler:nil];  // No clean-up needed after SEND_INITIAL_METADATA
+  if (!_unaryCall) {
+    [_wrappedCall startBatchWithOperations:@[op]];
+  } else {
+    [_unaryOpBatch addObject:op];
+  }
 }
 
 #pragma mark GRXWriteable implementation
 
 // Only called from the call queue. The error handler will be called from the
 // network queue if the write didn't succeed.
+// If the call is a unary call, parameter \a errorHandler will be ignored and
+// the error handler of GRPCOpSendClose will be executed in case of error.
 - (void)writeMessage:(NSData *)message withErrorHandler:(void (^)())errorHandler {
 
   __weak GRPCCall *weakSelf = self;
@@ -275,9 +303,17 @@ static NSMutableDictionary *callFlags;
       }
     }
   };
-  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMessage alloc] initWithMessage:message
-                                                                              handler:resumingHandler]]
-                            errorHandler:errorHandler];
+
+  GRPCOpSendMessage *op = [[GRPCOpSendMessage alloc] initWithMessage:message
+                                                             handler:resumingHandler];
+  if (!_unaryCall) {
+    [_wrappedCall startBatchWithOperations:@[op]
+                              errorHandler:errorHandler];
+  } else {
+    // Ignored errorHandler since it is the same as the one for GRPCOpSendClose.
+    // TODO (mxyan): unify the error handlers of all Ops into a single closure.
+    [_unaryOpBatch addObject:op];
+  }
 }
 
 - (void)writeValue:(id)value {
@@ -302,8 +338,14 @@ static NSMutableDictionary *callFlags;
 // Only called from the call queue. The error handler will be called from the
 // network queue if the requests stream couldn't be closed successfully.
 - (void)finishRequestWithErrorHandler:(void (^)())errorHandler {
-  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendClose alloc] init]]
-                            errorHandler:errorHandler];
+  if (!_unaryCall) {
+    [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendClose alloc] init]]
+                              errorHandler:errorHandler];
+  } else {
+    [_unaryOpBatch addObject:[[GRPCOpSendClose alloc] init]];
+    [_wrappedCall startBatchWithOperations:_unaryOpBatch
+                              errorHandler:errorHandler];
+  }
 }
 
 - (void)writesFinishedWithError:(NSError *)errorOrNil {

src/objective-c/GRPCClient/internal_testing/GRPCCall+InternalTests.h

@@ -0,0 +1,61 @@
+/*
+ *
+ * Copyright 2017, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifdef GRPC_TEST_OBJC
+
+#import "../GRPCCall.h"
+
+/**
+ * Methods used for gRPC internal tests. DO NOT USE.
+ */
+@interface GRPCCall (InternalTests)
+
+/**
+ * Enables logging of op batches. Memory consumption increases as more ops are logged.
+ *
+ * This function is for internal testing of gRPC only. It is not part of gRPC's public interface.
+ * Do not use in production. To enable, set the preprocessor flag GRPC_TEST_OBJC.
+ */
++ (void)enableOpBatchLog:(BOOL)enabled;
+
+/**
+ * Obtain the logged op batches. Invoking this method will clean the log.
+ *
+ * This function is for internal testing of gRPC only. It is not part of gRPC's public interface.
+ * Do not use in production. To enable, set the preprocessor flag GRPC_TEST_OBJC.
+ */
++ (NSArray *)obtainAndCleanOpBatchLog;
+
+@end
+
+#endif

src/objective-c/GRPCClient/internal_testing/GRPCCall+InternalTests.m

@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2017, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifdef GRPC_TEST_OBJC
+
+#import "GRPCCall+InternalTests.h"
+
+#import "../private/GRPCOpBatchLog.h"
+
+@implementation GRPCCall (InternalTests)
+
++ (void)enableOpBatchLog:(BOOL)enabled {
+  [GRPCOpBatchLog enableOpBatchLog:enabled];
+}
+
++ (NSArray *)obtainAndCleanOpBatchLog {
+  return [GRPCOpBatchLog obtainAndCleanOpBatchLog];
+}
+
+@end
+
+#endif

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

@@ -0,0 +1,59 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+
+#ifdef GRPC_TEST_OBJC
+
+/**
+ * Logs the op batches of a client. Used for testing.
+ */
+@interface GRPCOpBatchLog : NSObject
+
+/**
+ * Enables logging of op batches. Memory consumption increases as more ops are logged.
+ */
++ (void)enableOpBatchLog:(BOOL)enabled;
+
+/**
+ * Add an op batch to log.
+ */
++ (void)addOpBatchToLog:(NSArray *)batch;
+
+/**
+ * Obtain the logged op batches. Invoking this method will clean the log.
+ */
++ (NSArray *)obtainAndCleanOpBatchLog;
+
+@end
+
+#endif

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

@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifdef GRPC_TEST_OBJC
+
+#import "GRPCOpBatchLog.h"
+
+static NSMutableArray *opBatchLog = nil;
+
+@implementation GRPCOpBatchLog
+
++ (void)enableOpBatchLog:(BOOL)enabled {
+  @synchronized (opBatchLog) {
+    if (enabled) {
+      if (!opBatchLog) {
+        opBatchLog = [NSMutableArray array];
+      }
+    } else {
+      if (opBatchLog) {
+        opBatchLog = nil;
+      }
+    }
+  }
+}
+
++ (void)addOpBatchToLog:(NSArray *)batch {
+  @synchronized (opBatchLog) {
+    [opBatchLog addObject:batch];
+  }
+}
+
++ (NSArray *)obtainAndCleanOpBatchLog {
+  @synchronized (opBatchLog) {
+    NSArray *out = opBatchLog;
+    opBatchLog = [NSMutableArray array];
+    return out;
+  }
+}
+
+@end
+
+#endif

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

@@ -44,6 +44,8 @@
 #import "NSData+GRPC.h"
 #import "NSError+GRPC.h"
 
+#import "GRPCOpBatchLog.h"
+
 @implementation GRPCOperation {
 @protected
   // Most operation subclasses don't set any flags in the grpc_op, and rely on the flag member being
@@ -274,6 +276,12 @@
 }
 
 - (void)startBatchWithOperations:(NSArray *)operations errorHandler:(void (^)())errorHandler {
+  // Keep logs of op batches when we are running tests. Disabled when in production for improved
+  // performance.
+#ifdef GRPC_TEST_OBJC
+  [GRPCOpBatchLog addOpBatchToLog:operations];
+#endif
+
   size_t nops = operations.count;
   grpc_op *ops_array = gpr_malloc(nops * sizeof(grpc_op));
   size_t i = 0;

src/objective-c/RxLibrary/GRXImmediateSingleWriter.h

@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "GRXImmediateWriter.h"
+
+/**
+ * Utility to construct GRXWriter instances from values that are immediately available when
+ * required.
+ */
+@interface GRXImmediateSingleWriter : GRXImmediateWriter
+
+/**
+ * Returns a writer that sends the passed value to its writeable and then finishes (releasing the
+ * value).
+ */
++ (GRXWriter *)writerWithValue:(id)value;
+
+@end

src/objective-c/RxLibrary/GRXImmediateSingleWriter.m

@@ -0,0 +1,89 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRXImmediateSingleWriter.h"
+
+@implementation GRXImmediateSingleWriter {
+  id _value;
+  id<GRXWriteable> _writeable;
+}
+
+@synthesize state = _state;
+
+- (instancetype)initWithValue:(id)value {
+  if (self = [super init]) {
+    _value = value;
+    _state = GRXWriterStateNotStarted;
+  }
+  return self;
+}
+
++ (GRXWriter *)writerWithValue:(id)value {
+  return [[self alloc] initWithValue:value];
+}
+
+- (void)startWithWriteable:(id<GRXWriteable>)writeable {
+  _state = GRXWriterStateStarted;
+  _writeable = writeable;
+  [writeable writeValue:_value];
+  [self finish];
+}
+
+- (void)finish {
+  _state = GRXWriterStateFinished;
+  _value = nil;
+  id<GRXWriteable> writeable = _writeable;
+  _writeable = nil;
+  [writeable writesFinishedWithError:nil];
+}
+
+// Overwrite the setter to disallow manual state transition. The getter
+// of _state is synthesized.
+- (void)setState:(GRXWriterState)newState {
+  // Manual state transition is not allowed
+  return;
+}
+
+// Overrides [requestWriter(Transformations):map:] for Protocol Buffers
+// encoding.
+// We need the return value of this map to be a GRXImmediateSingleWriter but
+// the original \a map function returns a new Writer of another type. So we
+// need to override this function here.
+- (GRXWriter *)map:(id (^)(id))map {
+  // Since _value is available when creating the object, we can simply
+  // apply the map and store the output.
+  _value = map(_value);
+  return self;
+}
+
+@end

src/objective-c/RxLibrary/GRXWriter+Immediate.m

@@ -34,6 +34,7 @@
 #import "GRXWriter+Immediate.h"
 
 #import "GRXImmediateWriter.h"
+#import "GRXImmediateSingleWriter.h"
 
 @implementation GRXWriter (Immediate)
 
@@ -50,7 +51,7 @@
 }
 
 + (instancetype)writerWithValue:(id)value {
-  return [GRXImmediateWriter writerWithValue:value];
+  return [GRXImmediateSingleWriter writerWithValue:value];
 }
 
 + (instancetype)writerWithError:(NSError *)error {

src/objective-c/tests/GRPCClientTests.m

@@ -38,6 +38,7 @@
 #import <GRPCClient/GRPCCall+ChannelArg.h>
 #import <GRPCClient/GRPCCall+OAuth2.h>
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
 #import <ProtoRPC/ProtoMethod.h>
 #import <RemoteTest/Messages.pbobjc.h>
 #import <RxLibrary/GRXWriteable.h>

src/objective-c/tests/InteropTests.m

@@ -38,6 +38,7 @@
 #import <Cronet/Cronet.h>
 #import <GRPCClient/GRPCCall+ChannelArg.h>
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
 #import <GRPCClient/GRPCCall+Cronet.h>
 #import <ProtoRPC/ProtoRPC.h>
 #import <RemoteTest/Messages.pbobjc.h>
@@ -45,6 +46,8 @@
 #import <RemoteTest/Test.pbrpc.h>
 #import <RxLibrary/GRXBufferedPipe.h>
 #import <RxLibrary/GRXWriter+Immediate.h>
+#import <grpc/support/log.h>
+#import <grpc/grpc.h>
 
 #define TEST_TIMEOUT 32
 
@@ -97,15 +100,6 @@
   return 0;
 }
 
-+ (void)setUp {
-#ifdef GRPC_COMPILE_WITH_CRONET
-  // Cronet setup
-  [Cronet setHttp2Enabled:YES];
-  [Cronet start];
-  [GRPCCall useCronetWithEngine:[Cronet getGlobalEngine]];
-#endif
-}
-
 - (void)setUp {
   self.continueAfterFailure = NO;
 
@@ -155,6 +149,44 @@
   [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
 }
 
+- (void)testPacketCoalescing {
+  XCTAssertNotNil(self.class.host);
+  __weak XCTestExpectation *expectation = [self expectationWithDescription:@"LargeUnary"];
+
+  RMTSimpleRequest *request = [RMTSimpleRequest message];
+  request.responseType = RMTPayloadType_Compressable;
+  request.responseSize = 10;
+  request.payload.body = [NSMutableData dataWithLength:10];
+
+  [GRPCCall enableOpBatchLog:YES];
+  [_service unaryCallWithRequest:request handler:^(RMTSimpleResponse *response, NSError *error) {
+    XCTAssertNil(error, @"Finished with unexpected error: %@", error);
+
+    RMTSimpleResponse *expectedResponse = [RMTSimpleResponse message];
+    expectedResponse.payload.type = RMTPayloadType_Compressable;
+    expectedResponse.payload.body = [NSMutableData dataWithLength:10];
+    XCTAssertEqualObjects(response, expectedResponse);
+
+    // The test is a success if there is a batch of exactly 3 ops (SEND_INITIAL_METADATA,
+    // SEND_MESSAGE, SEND_CLOSE_FROM_CLIENT). Without packet coalescing each batch of ops contains
+    // only one op.
+    NSArray *opBatches = [GRPCCall obtainAndCleanOpBatchLog];
+    const NSInteger kExpectedOpBatchSize = 3;
+    for (NSObject *o in opBatches) {
+      if ([o isKindOfClass:[NSArray class]]) {
+        NSArray *batch = (NSArray *)o;
+        if ([batch count] == kExpectedOpBatchSize) {
+          [expectation fulfill];
+          break;
+        }
+      }
+    }
+  }];
+
+  [self waitForExpectationsWithTimeout:16 handler:nil];
+  [GRPCCall enableOpBatchLog:NO];
+}
+
 - (void)test4MBResponsesAreAccepted {
   XCTAssertNotNil(self.class.host);
   __weak XCTestExpectation *expectation = [self expectationWithDescription:@"MaxResponseSize"];

src/objective-c/tests/InteropTestsLocalCleartext.m

@@ -32,6 +32,7 @@
  */
 
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
 
 #import "InteropTests.h"
 

src/objective-c/tests/InteropTestsLocalSSL.m

@@ -32,6 +32,7 @@
  */
 
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
 
 #import "InteropTests.h"
 

src/objective-c/tests/InteropTestsRemote.m

@@ -32,6 +32,7 @@
  */
 
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
 
 #import "InteropTests.h"
 

src/objective-c/tests/InteropTestsRemoteWithCronet/InteropTestsRemoteWithCronet.m

@@ -32,6 +32,10 @@
  */
 
 #import <GRPCClient/GRPCCall+Tests.h>
+#import <GRPCClient/internal_testing/GRPCCall+InternalTests.h>
+
+#import <Cronet/Cronet.h>
+#import <GRPCClient/GRPCCall+Cronet.h>
 
 #import "InteropTests.h"
 

src/objective-c/tests/Podfile

@@ -97,15 +97,20 @@ post_install do |installer|
         # GPR_UNREACHABLE_CODE causes "Control may reach end of non-void
         # function" warning
         config.build_settings['GCC_WARN_ABOUT_RETURN_TYPE'] = 'NO'
+        config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] = '$(inherited) COCOAPODS=1 GRPC_CRONET_WITH_PACKET_COALESCING=1'
       end
     end
 
     # Activate Cronet for the dedicated build configuration 'Cronet', which will be used solely by
     # the test target 'InteropTestsRemoteWithCronet'
+    # Activate GRPCCall+InternalTests functions for the dedicated build configuration 'Test', which will
+    # be used by all test targets using it.
     if target.name == 'gRPC'
       target.build_configurations.each do |config|
         if config.name == 'Cronet'
-          config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] = '$(inherited) COCOAPODS=1 GRPC_COMPILE_WITH_CRONET=1'
+          config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] = '$(inherited) COCOAPODS=1 GRPC_COMPILE_WITH_CRONET=1 GRPC_TEST_OBJC=1'
+        elsif config.name == 'Test'
+          config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] = '$(inherited) COCOAPODS=1 GRPC_TEST_OBJC=1'
         end
       end
     end

src/objective-c/tests/Tests.xcodeproj/project.pbxproj

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@@ -162,15 +164,22 @@
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+		6793C9D019CB268C5BB491A2 /* Pods-CoreCronetEnd2EndTests.test.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-CoreCronetEnd2EndTests.test.xcconfig"; path = "Pods/Target Support Files/Pods-CoreCronetEnd2EndTests/Pods-CoreCronetEnd2EndTests.test.xcconfig"; sourceTree = "<group>"; };
+		781089FAE980F51F88A3BE0B /* Pods-RxLibraryUnitTests.test.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-RxLibraryUnitTests.test.xcconfig"; path = "Pods/Target Support Files/Pods-RxLibraryUnitTests/Pods-RxLibraryUnitTests.test.xcconfig"; sourceTree = "<group>"; };
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 			name = Pods;
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@@ -1237,6 +1255,210 @@
 /* End PBXTargetDependency section */
 
 /* Begin XCBuildConfiguration section */
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+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
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+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
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+				);
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+					"GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1",
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+				ENABLE_TESTABILITY = YES;
+				INFOPLIST_FILE = CronetUnitTests/Info.plist;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.3;
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
+				PRODUCT_BUNDLE_IDENTIFIER = io.grpc.CronetUnitTests;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				USER_HEADER_SEARCH_PATHS = "\"${PODS_ROOT}/../../../..\" $(inherited)";
+			};
+			name = Test;
+		};
 		5E8A5DAC1D3840B4000F8BC4 /* Debug */ = {
 			isa = XCBuildConfiguration;
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@@ -1407,6 +1629,12 @@
 			buildSettings = {
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				ENABLE_TESTABILITY = YES;
+				GCC_PREPROCESSOR_DEFINITIONS = (
+					"$(inherited)",
+					"COCOAPODS=1",
+					"$(inherited)",
+					"GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1",
+				);
 				INFOPLIST_FILE = Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
@@ -1471,10 +1699,10 @@
 				GCC_PREPROCESSOR_DEFINITIONS = (
 					"$(inherited)",
 					"COCOAPODS=1",
-					"$(inherited)",
 					"GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1",
 					"GRPC_COMPILE_WITH_CRONET=1",
 					"GRPC_CRONET_WITH_PACKET_COALESCING=1",
+					"GRPC_TEST_OBJC=1",
 				);
 				INFOPLIST_FILE = InteropTestsRemoteWithCronet/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.3;
@@ -1495,7 +1723,6 @@
 				GCC_PREPROCESSOR_DEFINITIONS = (
 					"$(inherited)",
 					"COCOAPODS=1",
-					"$(inherited)",
 					"GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1",
 				);
 				INFOPLIST_FILE = InteropTestsRemoteWithCronet/Info.plist;
@@ -1770,6 +1997,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				5E8A5DAC1D3840B4000F8BC4 /* Debug */,
+				5E12289F1E4D400F00E8504F /* Test */,
 				5EC3C7A71D4FC18C000330E2 /* Cronet */,
 				5E8A5DAD1D3840B4000F8BC4 /* Release */,
 			);
@@ -1780,6 +2008,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				5EAD6D2C1E27047400002378 /* Debug */,
+				5E1228A11E4D400F00E8504F /* Test */,
 				5EAD6D2D1E27047400002378 /* Cronet */,
 				5EAD6D2E1E27047400002378 /* Release */,
 			);
@@ -1790,6 +2019,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				5EE84BF91D4717E40050C6CC /* Debug */,
+				5E1228A01E4D400F00E8504F /* Test */,
 				5EC3C7A81D4FC18C000330E2 /* Cronet */,
 				5EE84BFA1D4717E40050C6CC /* Release */,
 			);
@@ -1800,6 +2030,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				63423F4E1B150A5F006CF63C /* Debug */,
+				5E12289A1E4D400F00E8504F /* Test */,
 				5EC3C7A21D4FC18C000330E2 /* Cronet */,
 				63423F4F1B150A5F006CF63C /* Release */,
 			);
@@ -1810,6 +2041,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				635697D91B14FC11007A7283 /* Debug */,
+				5E1228981E4D400F00E8504F /* Test */,
 				5EC3C7A01D4FC18C000330E2 /* Cronet */,
 				635697DA1B14FC11007A7283 /* Release */,
 			);
@@ -1820,6 +2052,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				635697DC1B14FC11007A7283 /* Debug */,
+				5E1228991E4D400F00E8504F /* Test */,
 				5EC3C7A11D4FC18C000330E2 /* Cronet */,
 				635697DD1B14FC11007A7283 /* Release */,
 			);
@@ -1830,6 +2063,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				63DC841C1BE15179000708E8 /* Debug */,
+				5E12289B1E4D400F00E8504F /* Test */,
 				5EC3C7A31D4FC18C000330E2 /* Cronet */,
 				63DC841D1BE15179000708E8 /* Release */,
 			);
@@ -1840,6 +2074,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				63DC842C1BE15267000708E8 /* Debug */,
+				5E12289C1E4D400F00E8504F /* Test */,
 				5EC3C7A41D4FC18C000330E2 /* Cronet */,
 				63DC842D1BE15267000708E8 /* Release */,
 			);
@@ -1850,6 +2085,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				63DC843D1BE15294000708E8 /* Debug */,
+				5E12289D1E4D400F00E8504F /* Test */,
 				5EC3C7A51D4FC18C000330E2 /* Cronet */,
 				63DC843E1BE15294000708E8 /* Release */,
 			);
@@ -1860,6 +2096,7 @@
 			isa = XCConfigurationList;
 			buildConfigurations = (
 				63DC844C1BE152B5000708E8 /* Debug */,
+				5E12289E1E4D400F00E8504F /* Test */,
 				5EC3C7A61D4FC18C000330E2 /* Cronet */,
 				63DC844D1BE152B5000708E8 /* Release */,
 			);

src/objective-c/tests/Tests.xcodeproj/xcshareddata/xcschemes/AllTests.xcscheme

@@ -23,7 +23,7 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
@@ -63,7 +63,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
@@ -101,7 +101,7 @@
       </MacroExpansion>
    </ProfileAction>
    <AnalyzeAction
-      buildConfiguration = "Debug">
+      buildConfiguration = "Test">
    </AnalyzeAction>
    <ArchiveAction
       buildConfiguration = "Release"

src/objective-c/tests/Tests.xcodeproj/xcshareddata/xcschemes/InteropTestsLocalCleartext.xcscheme

@@ -23,7 +23,7 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
@@ -54,7 +54,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
@@ -92,7 +92,7 @@
       </MacroExpansion>
    </ProfileAction>
    <AnalyzeAction
-      buildConfiguration = "Debug">
+      buildConfiguration = "Test">
    </AnalyzeAction>
    <ArchiveAction
       buildConfiguration = "Release"

src/objective-c/tests/Tests.xcodeproj/xcshareddata/xcschemes/InteropTestsLocalSSL.xcscheme

@@ -23,7 +23,7 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
@@ -57,7 +57,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
@@ -86,7 +86,7 @@
       debugDocumentVersioning = "YES">
    </ProfileAction>
    <AnalyzeAction
-      buildConfiguration = "Debug">
+      buildConfiguration = "Test">
    </AnalyzeAction>
    <ArchiveAction
       buildConfiguration = "Release"

src/objective-c/tests/Tests.xcodeproj/xcshareddata/xcschemes/InteropTestsRemote.xcscheme

@@ -23,7 +23,7 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
@@ -57,7 +57,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
@@ -86,7 +86,7 @@
       debugDocumentVersioning = "YES">
    </ProfileAction>
    <AnalyzeAction
-      buildConfiguration = "Debug">
+      buildConfiguration = "Test">
    </AnalyzeAction>
    <ArchiveAction
       buildConfiguration = "Release"