[binder] Handle outbound flow control (#27243)

src/core/ext/transport/binder/transport/binder_stream.h

@@ -51,7 +51,6 @@ struct grpc_binder_stream {
       : t(t),
         refcount(refcount),
         arena(arena),
-        seq(0),
         tx_code(tx_code),
         is_client(is_client) {
     // TODO(waynetu): Should this be protected?
@@ -74,13 +73,11 @@ struct grpc_binder_stream {
   }
 
   int GetTxCode() const { return tx_code; }
-  int GetThenIncSeq() { return seq++; }
 
   grpc_binder_transport* t;
   grpc_stream_refcount* refcount;
   grpc_core::Arena* arena;
   grpc_core::ManualConstructor<grpc_core::SliceBufferByteStream> sbs;
-  int seq;
   int tx_code;
   bool is_client;
   bool is_closed = false;

src/core/ext/transport/binder/transport/binder_transport.cc

@@ -324,8 +324,7 @@ static void perform_stream_op_locked(void* stream_op,
     if (!gbs->is_client) {
       // Send trailing metadata to inform the other end about the cancellation,
       // regardless if we'd already done that or not.
-      grpc_binder::Transaction cancel_tx(gbs->GetTxCode(), gbs->GetThenIncSeq(),
-                                         gbt->is_client);
+      grpc_binder::Transaction cancel_tx(gbs->GetTxCode(), gbt->is_client);
       cancel_tx.SetSuffix(grpc_binder::Metadata{});
       cancel_tx.SetStatus(1);
       absl::Status status = gbt->wire_writer->RpcCall(cancel_tx);
@@ -368,20 +367,13 @@ static void perform_stream_op_locked(void* stream_op,
     return;
   }
 
-  std::unique_ptr<grpc_binder::Transaction> tx;
   int tx_code = gbs->tx_code;
+  grpc_binder::Transaction tx(tx_code, gbt->is_client);
 
-  if (op->send_initial_metadata || op->send_message ||
-      op->send_trailing_metadata) {
-    // Only increment sequence number when there's a send operation.
-    tx = absl::make_unique<grpc_binder::Transaction>(
-        /*tx_code=*/tx_code, /*seq_num=*/gbs->GetThenIncSeq(), gbt->is_client);
-  }
   if (op->send_initial_metadata) {
     gpr_log(GPR_INFO, "send_initial_metadata");
     grpc_binder::Metadata init_md;
     auto batch = op->payload->send_initial_metadata.send_initial_metadata;
-    GPR_ASSERT(tx);
 
     for (grpc_linked_mdelem* md = batch->list.head; md != nullptr;
          md = md->next) {
@@ -399,12 +391,12 @@ static void perform_stream_op_locked(void* stream_op,
 
         // Only client send method ref.
         GPR_ASSERT(gbt->is_client);
-        tx->SetMethodRef(path);
+        tx.SetMethodRef(path);
       } else {
         init_md.emplace_back(std::string(key), std::string(value));
       }
     }
-    tx->SetPrefix(init_md);
+    tx.SetPrefix(init_md);
   }
   if (op->send_message) {
     gpr_log(GPR_INFO, "send_message");
@@ -426,8 +418,7 @@ static void perform_stream_op_locked(void* stream_op,
       grpc_slice_unref_internal(message_slice);
     }
     gpr_log(GPR_INFO, "message_data = %s", message_data.c_str());
-    GPR_ASSERT(tx);
-    tx->SetData(message_data);
+    tx.SetData(message_data);
     // TODO(b/192369787): Are we supposed to reset here to avoid
     // use-after-free issue in call.cc?
     op->payload->send_message.send_message.reset();
@@ -437,7 +428,6 @@ static void perform_stream_op_locked(void* stream_op,
     gpr_log(GPR_INFO, "send_trailing_metadata");
     auto batch = op->payload->send_trailing_metadata.send_trailing_metadata;
     grpc_binder::Metadata trailing_metadata;
-    GPR_ASSERT(tx);
 
     for (grpc_linked_mdelem* md = batch->list.head; md != nullptr;
          md = md->next) {
@@ -447,7 +437,7 @@ static void perform_stream_op_locked(void* stream_op,
       if (grpc_slice_eq(GRPC_MDKEY(md->md), GRPC_MDSTR_GRPC_STATUS)) {
         int status = grpc_get_status_code_from_metadata(md->md);
         gpr_log(GPR_INFO, "send trailing metadata status = %d", status);
-        tx->SetStatus(status);
+        tx.SetStatus(status);
       } else {
         absl::string_view key =
             grpc_core::StringViewFromSlice(GRPC_MDKEY(md->md));
@@ -460,7 +450,7 @@ static void perform_stream_op_locked(void* stream_op,
     }
     // TODO(mingcl): Will we ever has key-value pair here? According to
     // wireformat client suffix data is always empty.
-    tx->SetSuffix(trailing_metadata);
+    tx.SetSuffix(trailing_metadata);
   }
   if (op->recv_initial_metadata) {
     gpr_log(GPR_INFO, "recv_initial_metadata");
@@ -540,8 +530,12 @@ static void perform_stream_op_locked(void* stream_op,
   }
   // Only send transaction when there's a send op presented.
   absl::Status status = absl::OkStatus();
-  if (tx) {
-    status = gbt->wire_writer->RpcCall(*tx);
+  if (op->send_initial_metadata || op->send_message ||
+      op->send_trailing_metadata) {
+    // TODO(waynetu): RpcCall() is doing a lot of work (including waiting for
+    // acknowledgements from the other side). Consider delaying this operation
+    // with combiner.
+    status = gbt->wire_writer->RpcCall(tx);
     if (!gbs->is_client && op->send_trailing_metadata) {
       gbs->trailing_metadata_sent = true;
       // According to transport explaineer - "Server extra: This op shouldn't

src/core/ext/transport/binder/wire_format/BUILD

@@ -86,6 +86,7 @@ grpc_cc_library(
     srcs = ["wire_writer.cc"],
     hdrs = ["wire_writer.h"],
     external_deps = [
+        "absl/container:flat_hash_map",
         "absl/strings",
     ],
     deps = [

src/core/ext/transport/binder/wire_format/transaction.h

@@ -39,8 +39,8 @@ using Metadata = std::vector<std::pair<std::string, std::string>>;
 
 class Transaction {
  public:
-  Transaction(int tx_code, int seq_num, bool is_client)
-      : tx_code_(tx_code), seq_num_(seq_num), is_client_(is_client) {}
+  Transaction(int tx_code, bool is_client)
+      : tx_code_(tx_code), is_client_(is_client) {}
   // TODO(mingcl): Consider using string_view
   void SetPrefix(Metadata prefix_metadata) {
     prefix_metadata_ = prefix_metadata;
@@ -77,7 +77,6 @@ class Transaction {
   bool IsClient() const { return is_client_; }
   bool IsServer() const { return !is_client_; }
   int GetTxCode() const { return tx_code_; }
-  int GetSeqNum() const { return seq_num_; }
   int GetFlags() const { return flags_; }
 
   absl::string_view GetMethodRef() const { return method_ref_; }
@@ -88,7 +87,6 @@ class Transaction {
 
  private:
   int tx_code_;
-  int seq_num_;
   bool is_client_;
   Metadata prefix_metadata_;
   Metadata suffix_metadata_;

src/core/ext/transport/binder/wire_format/wire_reader_impl.cc

@@ -202,9 +202,11 @@ absl::Status WireReaderImpl::ProcessTransaction(transaction_code_t code,
       return absl::UnimplementedError("SHUTDOWN_TRANSPORT");
     }
     case BinderTransportTxCode::ACKNOWLEDGE_BYTES: {
-      int num_bytes = -1;
-      RETURN_IF_ERROR(parcel->ReadInt32(&num_bytes));
-      gpr_log(GPR_INFO, "received acknowledge bytes = %d", num_bytes);
+      int64_t num_bytes = -1;
+      RETURN_IF_ERROR(parcel->ReadInt64(&num_bytes));
+      gpr_log(GPR_INFO, "received acknowledge bytes = %lld",
+              static_cast<long long>(num_bytes));
+      wire_writer_->OnAckReceived(num_bytes);
       break;
     }
     case BinderTransportTxCode::PING: {
@@ -259,7 +261,8 @@ absl::Status WireReaderImpl::ProcessStreamingTransaction(
     }
   }
   if ((num_incoming_bytes_ - num_acknowledged_bytes_) >= kFlowControlAckBytes) {
-    absl::Status ack_status = wire_writer_->Ack(num_incoming_bytes_);
+    GPR_ASSERT(wire_writer_);
+    absl::Status ack_status = wire_writer_->SendAck(num_incoming_bytes_);
     if (status.ok()) {
       status = ack_status;
     }
@@ -339,6 +342,7 @@ absl::Status WireReaderImpl::ProcessStreamingTransactionImpl(
     }
     gpr_log(GPR_INFO, "msg_data = %s", msg_data.c_str());
     message_buffer_[code] += msg_data;
+    // TODO(waynetu): This should be parcel->GetDataSize().
     num_incoming_bytes_ += count;
     if ((flags & kFlagMessageDataIsPartial) == 0) {
       std::string s = std::move(message_buffer_[code]);

src/core/ext/transport/binder/wire_format/wire_writer.cc

@@ -30,18 +30,8 @@ namespace grpc_binder {
 WireWriterImpl::WireWriterImpl(std::unique_ptr<Binder> binder)
     : binder_(std::move(binder)) {}
 
-absl::Status WireWriterImpl::RpcCall(const Transaction& tx) {
-  // TODO(mingcl): check tx_code <= last call id
-  grpc_core::MutexLock lock(&mu_);
-  GPR_ASSERT(tx.GetTxCode() >= kFirstCallId);
-  RETURN_IF_ERROR(binder_->PrepareTransaction());
-  WritableParcel* parcel = binder_->GetWritableParcel();
-  {
-    //  fill parcel
-    RETURN_IF_ERROR(parcel->WriteInt32(tx.GetFlags()));
-    RETURN_IF_ERROR(parcel->WriteInt32(tx.GetSeqNum()));
-    if (tx.GetFlags() & kFlagPrefix) {
-      // prefix set
+absl::Status WireWriterImpl::WriteInitialMetadata(const Transaction& tx,
+                                                  WritableParcel* parcel) {
   if (tx.IsClient()) {
     // Only client sends method ref.
     RETURN_IF_ERROR(parcel->WriteString(tx.GetMethodRef()));
@@ -51,11 +41,11 @@ absl::Status WireWriterImpl::RpcCall(const Transaction& tx) {
     RETURN_IF_ERROR(parcel->WriteByteArrayWithLength(md.first));
     RETURN_IF_ERROR(parcel->WriteByteArrayWithLength(md.second));
   }
-    }
-    if (tx.GetFlags() & kFlagMessageData) {
-      RETURN_IF_ERROR(parcel->WriteByteArrayWithLength(tx.GetMessageData()));
-    }
-    if (tx.GetFlags() & kFlagSuffix) {
+  return absl::OkStatus();
+}
+
+absl::Status WireWriterImpl::WriteTrailingMetadata(const Transaction& tx,
+                                                   WritableParcel* parcel) {
   if (tx.IsServer()) {
     if (tx.GetFlags() & kFlagStatusDescription) {
       RETURN_IF_ERROR(parcel->WriteString(tx.GetStatusDesc()));
@@ -71,14 +61,111 @@ absl::Status WireWriterImpl::RpcCall(const Transaction& tx) {
       gpr_log(GPR_ERROR, "Got non-empty suffix metadata from client.");
     }
   }
+  return absl::OkStatus();
+}
+
+const int64_t WireWriterImpl::kBlockSize = 16 * 1024;
+const int64_t WireWriterImpl::kFlowControlWindowSize = 128 * 1024;
+
+bool WireWriterImpl::CanBeSentInOneTransaction(const Transaction& tx) const {
+  return (tx.GetFlags() & kFlagMessageData) == 0 ||
+         tx.GetMessageData().size() <= kBlockSize;
+}
+
+absl::Status WireWriterImpl::RpcCallFastPath(const Transaction& tx) {
+  int& seq = seq_num_[tx.GetTxCode()];
+  // Fast path: send data in one transaction.
+  RETURN_IF_ERROR(binder_->PrepareTransaction());
+  WritableParcel* parcel = binder_->GetWritableParcel();
+  RETURN_IF_ERROR(parcel->WriteInt32(tx.GetFlags()));
+  RETURN_IF_ERROR(parcel->WriteInt32(seq++));
+  if (tx.GetFlags() & kFlagPrefix) {
+    RETURN_IF_ERROR(WriteInitialMetadata(tx, parcel));
+  }
+  if (tx.GetFlags() & kFlagMessageData) {
+    RETURN_IF_ERROR(parcel->WriteByteArrayWithLength(tx.GetMessageData()));
   }
+  if (tx.GetFlags() & kFlagSuffix) {
+    RETURN_IF_ERROR(WriteTrailingMetadata(tx, parcel));
   }
   // FIXME(waynetu): Construct BinderTransportTxCode from an arbitrary integer
   // is an undefined behavior.
   return binder_->Transact(BinderTransportTxCode(tx.GetTxCode()));
 }
 
-absl::Status WireWriterImpl::Ack(int64_t num_bytes) {
+bool WireWriterImpl::WaitForAcknowledgement() {
+  if (num_outgoing_bytes_ < num_acknowledged_bytes_ + kFlowControlWindowSize) {
+    return true;
+  }
+  absl::Time deadline = absl::Now() + absl::Seconds(1);
+  do {
+    if (cv_.WaitWithDeadline(&mu_, deadline)) {
+      return false;
+    }
+    if (absl::Now() >= deadline) {
+      return false;
+    }
+  } while (num_outgoing_bytes_ >=
+           num_acknowledged_bytes_ + kFlowControlWindowSize);
+  return true;
+}
+
+absl::Status WireWriterImpl::RpcCall(const Transaction& tx) {
+  // TODO(mingcl): check tx_code <= last call id
+  grpc_core::MutexLock lock(&mu_);
+  GPR_ASSERT(tx.GetTxCode() >= kFirstCallId);
+  if (CanBeSentInOneTransaction(tx)) {
+    return RpcCallFastPath(tx);
+  }
+  // Slow path: the message data is too large to fit in one transaction.
+  int& seq = seq_num_[tx.GetTxCode()];
+  int original_flags = tx.GetFlags();
+  GPR_ASSERT(original_flags & kFlagMessageData);
+  absl::string_view data = tx.GetMessageData();
+  size_t bytes_sent = 0;
+  while (bytes_sent < data.size()) {
+    if (!WaitForAcknowledgement()) {
+      return absl::InternalError("Timeout waiting for acknowledgement");
+    }
+    RETURN_IF_ERROR(binder_->PrepareTransaction());
+    WritableParcel* parcel = binder_->GetWritableParcel();
+    size_t size =
+        std::min(static_cast<size_t>(kBlockSize), data.size() - bytes_sent);
+    int flags = kFlagMessageData;
+    if (bytes_sent == 0) {
+      // This is the first transaction. Include initial metadata if there's any.
+      if (original_flags & kFlagPrefix) {
+        flags |= kFlagPrefix;
+      }
+    }
+    if (bytes_sent + kBlockSize >= data.size()) {
+      // This is the last transaction. Include trailing metadata if there's any.
+      if (original_flags & kFlagSuffix) {
+        flags |= kFlagSuffix;
+      }
+    } else {
+      // There are more messages to send.
+      flags |= kFlagMessageDataIsPartial;
+    }
+    RETURN_IF_ERROR(parcel->WriteInt32(flags));
+    RETURN_IF_ERROR(parcel->WriteInt32(seq++));
+    if (flags & kFlagPrefix) {
+      RETURN_IF_ERROR(WriteInitialMetadata(tx, parcel));
+    }
+    RETURN_IF_ERROR(
+        parcel->WriteByteArrayWithLength(data.substr(bytes_sent, size)));
+    if (flags & kFlagSuffix) {
+      RETURN_IF_ERROR(WriteTrailingMetadata(tx, parcel));
+    }
+    RETURN_IF_ERROR(binder_->Transact(BinderTransportTxCode(tx.GetTxCode())));
+    bytes_sent += size;
+    // TODO(waynetu): This should be parcel->GetDataSize().
+    num_outgoing_bytes_ += size;
+  }
+  return absl::OkStatus();
+}
+
+absl::Status WireWriterImpl::SendAck(int64_t num_bytes) {
   grpc_core::MutexLock lock(&mu_);
   RETURN_IF_ERROR(binder_->PrepareTransaction());
   WritableParcel* parcel = binder_->GetWritableParcel();
@@ -86,4 +173,10 @@ absl::Status WireWriterImpl::Ack(int64_t num_bytes) {
   return binder_->Transact(BinderTransportTxCode::ACKNOWLEDGE_BYTES);
 }
 
+void WireWriterImpl::OnAckReceived(int64_t num_bytes) {
+  grpc_core::MutexLock lock(&mu_);
+  num_acknowledged_bytes_ = std::max(num_acknowledged_bytes_, num_bytes);
+  cv_.Signal();
+}
+
 }  // namespace grpc_binder

src/core/ext/transport/binder/wire_format/wire_writer.h

@@ -20,7 +20,7 @@
 #include <string>
 #include <vector>
 
-#include <grpc/support/log.h>
+#include "absl/container/flat_hash_map.h"
 
 #include "src/core/ext/transport/binder/wire_format/binder.h"
 #include "src/core/ext/transport/binder/wire_format/transaction.h"
@@ -32,18 +32,51 @@ class WireWriter {
  public:
   virtual ~WireWriter() = default;
   virtual absl::Status RpcCall(const Transaction& call) = 0;
-  virtual absl::Status Ack(int64_t num_bytes) = 0;
+  virtual absl::Status SendAck(int64_t num_bytes) = 0;
+  virtual void OnAckReceived(int64_t num_bytes) = 0;
 };
 
 class WireWriterImpl : public WireWriter {
  public:
   explicit WireWriterImpl(std::unique_ptr<Binder> binder);
   absl::Status RpcCall(const Transaction& tx) override;
-  absl::Status Ack(int64_t num_bytes) override;
+  absl::Status SendAck(int64_t num_bytes) override;
+  void OnAckReceived(int64_t num_bytes) override;
+
+  // Split long message into chunks of size 16k. This doesn't necessarily have
+  // to be the same as the flow control acknowledgement size, but it should not
+  // exceed 128k.
+  static const int64_t kBlockSize;
+  // Flow control allows sending at most 128k between acknowledgements.
+  static const int64_t kFlowControlWindowSize;
 
  private:
+  absl::Status WriteInitialMetadata(const Transaction& tx,
+                                    WritableParcel* parcel)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);
+  absl::Status WriteTrailingMetadata(const Transaction& tx,
+                                     WritableParcel* parcel)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);
+
+  bool CanBeSentInOneTransaction(const Transaction& tx) const;
+  absl::Status RpcCallFastPath(const Transaction& tx)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);
+
+  // Wait for acknowledgement from the other side for a while (the timeout is
+  // currently set to 10ms for debugability). Returns true if we are able to
+  // proceed, and false otherwise.
+  //
+  // TODO(waynetu): Currently, RpcCall() will fail if we are blocked for 10ms.
+  // In the future, we should queue the transactions and release them later when
+  // acknowledgement comes.
+  bool WaitForAcknowledgement() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);
+
   grpc_core::Mutex mu_;
+  grpc_core::CondVar cv_;
   std::unique_ptr<Binder> binder_ ABSL_GUARDED_BY(mu_);
+  absl::flat_hash_map<int, int> seq_num_ ABSL_GUARDED_BY(mu_);
+  int64_t num_outgoing_bytes_ ABSL_GUARDED_BY(mu_) = 0;
+  int64_t num_acknowledged_bytes_ ABSL_GUARDED_BY(mu_) = 0;
 };
 
 }  // namespace grpc_binder

test/core/transport/binder/binder_transport_test.cc

@@ -332,74 +332,12 @@ TEST_F(BinderTransportTest, TransactionIdIncrement) {
   grpc_binder_stream* gbs0 = InitNewBinderStream();
   EXPECT_EQ(gbs0->t, GetBinderTransport());
   EXPECT_EQ(gbs0->tx_code, kFirstCallId);
-  EXPECT_EQ(gbs0->seq, 0);
   grpc_binder_stream* gbs1 = InitNewBinderStream();
   EXPECT_EQ(gbs1->t, GetBinderTransport());
   EXPECT_EQ(gbs1->tx_code, kFirstCallId + 1);
-  EXPECT_EQ(gbs1->seq, 0);
   grpc_binder_stream* gbs2 = InitNewBinderStream();
   EXPECT_EQ(gbs2->t, GetBinderTransport());
   EXPECT_EQ(gbs2->tx_code, kFirstCallId + 2);
-  EXPECT_EQ(gbs2->seq, 0);
-}
-
-TEST_F(BinderTransportTest, SeqNumIncrement) {
-  grpc_core::ExecCtx exec_ctx;
-  grpc_binder_stream* gbs = InitNewBinderStream();
-  EXPECT_EQ(gbs->t, GetBinderTransport());
-  EXPECT_EQ(gbs->tx_code, kFirstCallId);
-  // A simple batch that contains only "send_initial_metadata"
-  grpc_transport_stream_op_batch op{};
-  grpc_transport_stream_op_batch_payload payload(nullptr);
-  op.payload = &payload;
-  MakeSendInitialMetadata send_initial_metadata(kDefaultMetadata, "", &op);
-  EXPECT_EQ(gbs->seq, 0);
-  PerformStreamOp(gbs, &op);
-  grpc_core::ExecCtx::Get()->Flush();
-  EXPECT_EQ(gbs->tx_code, kFirstCallId);
-  EXPECT_EQ(gbs->seq, 1);
-  PerformStreamOp(gbs, &op);
-  grpc_core::ExecCtx::Get()->Flush();
-  EXPECT_EQ(gbs->tx_code, kFirstCallId);
-  EXPECT_EQ(gbs->seq, 2);
-}
-
-TEST_F(BinderTransportTest, SeqNumNotIncrementWithoutSend) {
-  grpc_core::ExecCtx exec_ctx;
-  {
-    grpc_binder_stream* gbs = InitNewBinderStream();
-    EXPECT_EQ(gbs->t, GetBinderTransport());
-    EXPECT_EQ(gbs->tx_code, kFirstCallId);
-    // No-op batch.
-    grpc_transport_stream_op_batch op{};
-    EXPECT_EQ(gbs->seq, 0);
-    PerformStreamOp(gbs, &op);
-    grpc_core::ExecCtx::Get()->Flush();
-    EXPECT_EQ(gbs->tx_code, kFirstCallId);
-    EXPECT_EQ(gbs->seq, 0);
-  }
-  {
-    grpc_binder_stream* gbs = InitNewBinderStream();
-    EXPECT_EQ(gbs->t, GetBinderTransport());
-    EXPECT_EQ(gbs->tx_code, kFirstCallId + 1);
-    // Batch with only receiving operations.
-    grpc_transport_stream_op_batch op{};
-    grpc_transport_stream_op_batch_payload payload(nullptr);
-    op.payload = &payload;
-    MakeRecvInitialMetadata recv_initial_metadata(&op);
-    EXPECT_EQ(gbs->seq, 0);
-    PerformStreamOp(gbs, &op);
-    EXPECT_EQ(gbs->tx_code, kFirstCallId + 1);
-    EXPECT_EQ(gbs->seq, 0);
-
-    // Just to trigger the callback.
-    auto* gbt = reinterpret_cast<grpc_binder_transport*>(transport_);
-    gbt->transport_stream_receiver->NotifyRecvInitialMetadata(gbs->tx_code,
-                                                              kDefaultMetadata);
-    PerformStreamOp(gbs, &op);
-    grpc_core::ExecCtx::Get()->Flush();
-    recv_initial_metadata.notification.WaitForNotification();
-  }
 }
 
 TEST_F(BinderTransportTest, PerformSendInitialMetadata) {

test/core/transport/binder/end2end/end2end_binder_transport_test.cc

@@ -293,6 +293,25 @@ TEST_P(End2EndBinderTransportTest, BiDirStreamingCallThroughFakeBinderChannel) {
   server->Shutdown();
 }
 
+TEST_P(End2EndBinderTransportTest, LargeMessage) {
+  grpc::ChannelArguments args;
+  grpc::ServerBuilder builder;
+  end2end_testing::EchoServer service;
+  builder.RegisterService(&service);
+  std::unique_ptr<grpc::Server> server = builder.BuildAndStart();
+  std::shared_ptr<grpc::Channel> channel = BinderChannel(server.get(), args);
+  std::unique_ptr<EchoService::Stub> stub = EchoService::NewStub(channel);
+  grpc::ClientContext context;
+  EchoRequest request;
+  EchoResponse response;
+  request.set_text(std::string(1000000, 'a'));
+  grpc::Status status = stub->EchoUnaryCall(&context, request, &response);
+  EXPECT_TRUE(status.ok());
+  EXPECT_EQ(response.text(), std::string(1000000, 'a'));
+
+  server->Shutdown();
+}
+
 INSTANTIATE_TEST_SUITE_P(
     End2EndBinderTransportTestWithDifferentDelayTimes,
     End2EndBinderTransportTest,

test/core/transport/binder/mock_objects.h

@@ -88,7 +88,8 @@ class MockTransactionReceiver : public TransactionReceiver {
 class MockWireWriter : public WireWriter {
  public:
   MOCK_METHOD(absl::Status, RpcCall, (const Transaction&), (override));
-  MOCK_METHOD(absl::Status, Ack, (int64_t), (override));
+  MOCK_METHOD(absl::Status, SendAck, (int64_t), (override));
+  MOCK_METHOD(void, OnAckReceived, (int64_t), (override));
 };
 
 class MockTransportStreamReceiver : public TransportStreamReceiver {

test/core/transport/binder/wire_writer_test.cc

@@ -30,7 +30,8 @@ using ::testing::Return;
 using ::testing::StrictMock;
 
 MATCHER_P(StrEqInt8Ptr, target, "") {
-  return std::string(reinterpret_cast<const char*>(arg)) == target;
+  return std::string(reinterpret_cast<const char*>(arg), target.size()) ==
+         target;
 }
 
 TEST(WireWriterTest, RpcCall) {
@@ -53,7 +54,6 @@ TEST(WireWriterTest, RpcCall) {
 
   ::testing::InSequence sequence;
   int sequence_number = 0;
-  int tx_code = kFirstCallId;
 
   {
     // flag
@@ -61,18 +61,18 @@ TEST(WireWriterTest, RpcCall) {
     // sequence number
     EXPECT_CALL(mock_writable_parcel, WriteInt32(sequence_number));
 
-    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(tx_code)));
+    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(kFirstCallId)));
 
-    Transaction tx(tx_code, sequence_number, /*is_client=*/true);
+    Transaction tx(kFirstCallId, /*is_client=*/true);
     EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
     sequence_number++;
-    tx_code++;
   }
   {
     // flag
     EXPECT_CALL(mock_writable_parcel, WriteInt32(kFlagPrefix));
-    // sequence number
-    EXPECT_CALL(mock_writable_parcel, WriteInt32(sequence_number));
+    // sequence number. This is another stream so the sequence number starts
+    // with 0.
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(0));
 
     EXPECT_CALL(mock_writable_parcel,
                 WriteString(absl::string_view("/example/method/ref")));
@@ -96,12 +96,10 @@ TEST(WireWriterTest, RpcCall) {
     EXPECT_CALL(mock_binder_ref,
                 Transact(BinderTransportTxCode(kFirstCallId + 1)));
 
-    Transaction tx(kFirstCallId + 1, 1, /*is_client=*/true);
+    Transaction tx(kFirstCallId + 1, /*is_client=*/true);
     tx.SetPrefix(kMetadata);
     tx.SetMethodRef("/example/method/ref");
     EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
-    sequence_number++;
-    tx_code++;
   }
   {
     // flag
@@ -110,11 +108,12 @@ TEST(WireWriterTest, RpcCall) {
     EXPECT_CALL(mock_writable_parcel, WriteInt32(sequence_number));
 
     ExpectWriteByteArray("data");
-    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(tx_code)));
+    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(kFirstCallId)));
 
-    Transaction tx(tx_code, sequence_number, /*is_client=*/true);
+    Transaction tx(kFirstCallId, /*is_client=*/true);
     tx.SetData("data");
     EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
+    sequence_number++;
   }
   {
     // flag
@@ -122,13 +121,12 @@ TEST(WireWriterTest, RpcCall) {
     // sequence number
     EXPECT_CALL(mock_writable_parcel, WriteInt32(sequence_number));
 
-    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(tx_code)));
+    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(kFirstCallId)));
 
-    Transaction tx(tx_code, sequence_number, /*is_client=*/true);
+    Transaction tx(kFirstCallId, /*is_client=*/true);
     tx.SetSuffix({});
     EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
     sequence_number++;
-    tx_code++;
   }
   {
     // flag
@@ -159,9 +157,9 @@ TEST(WireWriterTest, RpcCall) {
     // Empty message data
     ExpectWriteByteArray("");
 
-    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(tx_code)));
+    EXPECT_CALL(mock_binder_ref, Transact(BinderTransportTxCode(kFirstCallId)));
 
-    Transaction tx(tx_code, sequence_number, /*is_client=*/true);
+    Transaction tx(kFirstCallId, /*is_client=*/true);
     // TODO(waynetu): Implement a helper function that automatically creates
     // EXPECT_CALL based on the tx object.
     tx.SetPrefix(kMetadata);
@@ -170,7 +168,68 @@ TEST(WireWriterTest, RpcCall) {
     tx.SetSuffix({});
     EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
     sequence_number++;
-    tx_code++;
+  }
+
+  // Really large message
+  {
+    EXPECT_CALL(mock_writable_parcel,
+                WriteInt32(kFlagMessageData | kFlagMessageDataIsPartial));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(0));
+    ExpectWriteByteArray(std::string(WireWriterImpl::kBlockSize, 'a'));
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 2)));
+
+    EXPECT_CALL(mock_writable_parcel,
+                WriteInt32(kFlagMessageData | kFlagMessageDataIsPartial));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(1));
+    ExpectWriteByteArray(std::string(WireWriterImpl::kBlockSize, 'a'));
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 2)));
+
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(kFlagMessageData));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(2));
+    ExpectWriteByteArray("a");
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 2)));
+
+    // Use a new stream.
+    Transaction tx(kFirstCallId + 2, /*is_client=*/true);
+    tx.SetData(std::string(2 * WireWriterImpl::kBlockSize + 1, 'a'));
+    EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
+  }
+  // Really large message with metadata
+  {
+    EXPECT_CALL(
+        mock_writable_parcel,
+        WriteInt32(kFlagPrefix | kFlagMessageData | kFlagMessageDataIsPartial));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(0));
+    EXPECT_CALL(mock_writable_parcel, WriteString(absl::string_view("123")));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(0));
+    ExpectWriteByteArray(std::string(WireWriterImpl::kBlockSize, 'a'));
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 3)));
+
+    EXPECT_CALL(mock_writable_parcel,
+                WriteInt32(kFlagMessageData | kFlagMessageDataIsPartial));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(1));
+    ExpectWriteByteArray(std::string(WireWriterImpl::kBlockSize, 'a'));
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 3)));
+
+    EXPECT_CALL(mock_writable_parcel,
+                WriteInt32(kFlagMessageData | kFlagSuffix));
+    EXPECT_CALL(mock_writable_parcel, WriteInt32(2));
+    ExpectWriteByteArray("a");
+    EXPECT_CALL(mock_binder_ref,
+                Transact(BinderTransportTxCode(kFirstCallId + 3)));
+
+    // Use a new stream.
+    Transaction tx(kFirstCallId + 3, /*is_client=*/true);
+    tx.SetPrefix({});
+    tx.SetMethodRef("123");
+    tx.SetData(std::string(2 * WireWriterImpl::kBlockSize + 1, 'a'));
+    tx.SetSuffix({});
+    EXPECT_TRUE(wire_writer.RpcCall(tx).ok());
   }
 }