pytorch/torch/csrc/distributed/rpc/tensorpipe_agent.cpp

#include <torch/csrc/distributed/rpc/tensorpipe_agent.h>

#ifdef USE_TENSORPIPE

#include <limits>
#include <tuple>
#include <utility>

#include <fmt/format.h>
C10_DIAGNOSTIC_PUSH_AND_IGNORED_IF_DEFINED("-Wdeprecated")
#include <tensorpipe/tensorpipe.h>
C10_DIAGNOSTIC_POP()

#include <torch/csrc/distributed/rpc/agent_utils.h>
#include <torch/csrc/distributed/rpc/tensorpipe_utils.h>
#include <torch/csrc/distributed/rpc/utils.h>

#include <c10/core/StreamGuard.h>
#include <c10/util/irange.h>

namespace torch::distributed::rpc {

namespace {

// An environment variable along the lines of GLOO_ and NCCL_SOCKET_IFNAME that
// allows the user to specify a device to bind to, instead of binding to the
// address that the hostname resolves to.
const std::string kSocketIfnameEnvVar = "TP_SOCKET_IFNAME";
const std::string kDefaultUvAddress = "127.0.0.1";

const std::string kGilAverageWaitTime = "agent.gil_average_wait_time_us";
const std::string kThreadPoolSize = "agent.thread_pool_size";
const std::string kNumIdleThreads = "agent.num_idle_threads";
const std::string kClientActiveCalls = "agent.client_active_calls";
const std::string kServerActiveCalls = "agent.server_active_calls";
const std::string kServerActiveAsyncCalls = "agent.server_active_async_calls";

std::vector<c10::Device> getDevicesForTensors(
    const std::vector<torch::Tensor>& tensors,
    const DeviceMap& deviceMap,
    const std::string& remoteName) {
  // If the deviceMap is overridden, use that instead.
  const auto errStr = c10::str(
      "TensorPipe RPC backend only supports CPU tensors by default, please "
      "move your tensors to CPU before sending them over RPC, or call "
      "`set_device_map` on `TensorPipeRpcBackendOptions` to explicitly "
      "configure device mapping. ",
      "Request device mapping is not available for destination ",
      remoteName);
  std::vector<c10::Device> devices;
  devices.reserve(tensors.size());
  bool hasMappedDevice = false;
  for (const auto& t : tensors) {
    if (t.device().is_cpu()) {
      const auto deviceIter = deviceMap.find(c10::kCPU);
      if (deviceIter == deviceMap.end()) {
        devices.emplace_back(c10::kCPU);
      } else {
        devices.emplace_back(deviceIter->second);
        hasMappedDevice = true;
      }
    } else {
      const auto deviceIter = deviceMap.find(t.device());
      TORCH_CHECK(
          deviceIter != deviceMap.end(),
          errStr,
          " for device ",
          t.device(),
          " but received a tensor on that device.");
      devices.push_back(deviceIter->second);
      hasMappedDevice = true;
    }
  }
  if (!hasMappedDevice) {
    devices.clear();
  }
  return devices;
}

std::vector<c10::Stream> getStreamsFromPoolForDevices(
    const std::vector<c10::Device>& devices) {
  if (devices.empty()) {
    return {};
  }
  c10::impl::VirtualGuardImpl impl(devices[0].type());
  std::vector<c10::Stream> streams;
  streams.reserve(devices.size());
  for (const c10::Device& device : devices) {
    TORCH_INTERNAL_ASSERT(device.type() == impl.type());
    streams.push_back(impl.getStreamFromGlobalPool(device));
  }
  return streams;
}

std::vector<c10::Stream> getCurrentStreamsForDevices(
    const std::vector<c10::Device>& devices) {
  if (devices.empty()) {
    return {};
  }
  c10::impl::VirtualGuardImpl impl(devices[0].type());
  std::vector<c10::Stream> streams;
  streams.reserve(devices.size());
  for (const c10::Device& device : devices) {
    TORCH_INTERNAL_ASSERT(device.type() == impl.type());
    streams.push_back(impl.getStream(device));
  }
  return streams;
}

std::vector<c10::Device> getDevicesOfTensors(
    const std::vector<torch::Tensor>& tensors) {
  std::optional<c10::impl::VirtualGuardImpl> impl;
  size_t deviceCount = 0;
  std::vector<bool> indexBitset;
  for (const torch::Tensor& tensor : tensors) {
    if (!tensor.is_cpu()) {
      c10::Device device = tensor.device();
      if (!impl.has_value()) {
        impl.emplace(device.type());
        indexBitset.resize(impl->deviceCount());
      }
      TORCH_INTERNAL_ASSERT(device.type() == impl->type());
      TORCH_INTERNAL_ASSERT(device.has_index());
      if (!indexBitset[device.index()]) {
        deviceCount++;
        indexBitset[device.index()] = true;
      }
    }
  }
  std::vector<c10::Device> devices;
  devices.reserve(deviceCount);
  for (const auto idx : c10::irange(indexBitset.size())) {
    if (indexBitset[idx]) {
      // NOLINTNEXTLINE(bugprone-unchecked-optional-access)
      devices.emplace_back(impl->type(), static_cast<c10::DeviceIndex>(idx));
    }
  }
  return devices;
}

void makeStreamsWaitOnOthers(
    const std::vector<c10::Stream>& consumers,
    const std::vector<c10::Stream>& producers) {
  for (const c10::Stream& producer : producers) {
    const c10::Stream& consumer =
        getStreamForDevice(consumers, producer.device());
    c10::Event event(producer.device_type());
    event.record(producer);
    event.block(consumer);
  }
}

} // namespace

C10_DEFINE_REGISTRY_WITHOUT_WARNING(
    TensorPipeTransportRegistry,
    TransportRegistration)

C10_DEFINE_REGISTRY_WITHOUT_WARNING(
    TensorPipeChannelRegistry,
    ChannelRegistration)

const std::string& TensorPipeAgent::guessAddress() {
  static const std::string uvAddress = []() {
    auto ifnameEnv = c10::utils::get_env(kSocketIfnameEnvVar.c_str());
    if (ifnameEnv.has_value()) {
      auto [error, result] =
          tensorpipe::transport::uv::lookupAddrForIface(ifnameEnv.value());
      if (error) {
        LOG(WARNING) << "Failed to look up the IP address for interface "
                     << ifnameEnv.value() << " (" << error.what()
                     << "), defaulting to " << kDefaultUvAddress;
        return kDefaultUvAddress;
      }
      return result;
    }
    auto [error, result] = tensorpipe::transport::uv::lookupAddrForHostname();
    if (error) {
      LOG(WARNING) << "Failed to look up the IP address for the hostname ("
                   << error.what() << "), defaulting to " << kDefaultUvAddress;
      return kDefaultUvAddress;
    }
    return result;
  }();
  return uvAddress;
}

namespace {

std::unique_ptr<TransportRegistration> makeUvTransport() {
  auto context = tensorpipe::transport::uv::create();
  std::string address = TensorPipeAgent::guessAddress();
  return std::make_unique<TransportRegistration>(TransportRegistration{
      std::move(context), kUvTransportPriority, std::move(address)});
}

// The UV transport is implemented using standard TCP connections. It leverages
// libuv (https://github.com/libuv/libuv) in order to be cross-platform.
C10_REGISTER_CREATOR(TensorPipeTransportRegistry, uv, makeUvTransport)

#if TENSORPIPE_HAS_SHM_TRANSPORT

std::unique_ptr<TransportRegistration> makeShmTransport() {
  auto context = tensorpipe::transport::shm::create();
  return std::make_unique<TransportRegistration>(
      TransportRegistration{std::move(context), kShmTransportPriority, ""});
}

// The SHM implements connections using ringbuffers residing in anonymous shared
// memory (plus UNIX domain sockets to bootstrap the connection and exchange
// file descriptors). It is Linux-only due to some advanced features (O_TMPFILE,
// eventfd, ...).
C10_REGISTER_CREATOR(TensorPipeTransportRegistry, shm, makeShmTransport)

#endif // TENSORPIPE_HAS_SHM_TRANSPORT

#if TENSORPIPE_HAS_IBV_TRANSPORT

std::unique_ptr<TransportRegistration> makeIbvTransport() {
  auto context = tensorpipe::transport::ibv::create();
  std::string address = TensorPipeAgent::guessAddress();
  return std::make_unique<TransportRegistration>(TransportRegistration{
      std::move(context), kIbvTransportPriority, std::move(address)});
}

// The IBV transport sends data across using an InfiniBand queue pair, locally
// copying data to and from a staging buffer (registered with libibverbs) and
// issuing a RDMA write for transferring data across machines (plus a send for
// acknowledging it). It bootstraps using a standard TCP connection to exchange
// setup information. It is Linux-only.
C10_REGISTER_CREATOR(TensorPipeTransportRegistry, ibv, makeIbvTransport)

#endif // TENSORPIPE_HAS_IBV_TRANSPORT

std::unique_ptr<ChannelRegistration> makeBasicChannel() {
  auto context = tensorpipe::channel::basic::create();
  return std::make_unique<ChannelRegistration>(
      ChannelRegistration{std::move(context), kBasicChannelPriority});
}

// The basic channel is just a straightforward adapter wrapper that allows any
// transport to be used as a channel.
C10_REGISTER_CREATOR(TensorPipeChannelRegistry, basic, makeBasicChannel)

#if TENSORPIPE_HAS_CMA_CHANNEL

std::unique_ptr<ChannelRegistration> makeCmaChannel() {
  auto context = tensorpipe::channel::cma::create();
  return std::make_unique<ChannelRegistration>(
      ChannelRegistration{std::move(context), kCmaChannelPriority});
}

// The CMA channel uses the Linux cross-memory attach syscalls (process_vm_readv
// and _writev), which allow one process to access the private memory of another
// process (as long as they belong to the same user and other security
// constraints are satisfied). It does, more or less, what GDB does when it's
// attached to a running process.
C10_REGISTER_CREATOR(TensorPipeChannelRegistry, cma, makeCmaChannel)

#endif // TENSORPIPE_HAS_CMA_CHANNEL

constexpr static int kNumUvThreads = 16;

std::unique_ptr<ChannelRegistration> makeMultiplexedUvChannel() {
  std::vector<std::shared_ptr<tensorpipe::transport::Context>> contexts;
  contexts.reserve(kNumUvThreads);
  std::vector<std::shared_ptr<tensorpipe::transport::Listener>> listeners;
  listeners.reserve(kNumUvThreads);
  for ([[maybe_unused]] const auto laneIdx : c10::irange(kNumUvThreads)) {
    auto context = tensorpipe::transport::uv::create();
    const std::string& address = TensorPipeAgent::guessAddress();
    contexts.push_back(std::move(context));
    listeners.push_back(contexts.back()->listen(address));
  }
  auto context = tensorpipe::channel::mpt::create(
      std::move(contexts), std::move(listeners));
  return std::make_unique<ChannelRegistration>(
      ChannelRegistration{std::move(context), kMultiplexedUvChannelPriority});
}

// The multiplexed UV channel encapsulates multiple UV transports (each with its
// own event loop thread). Each channel will, in turn, contain multiple UV
// connections, one for each of those contexts. When sending a tensor, its data
// is split in equal chunks and each chunks is sent on a different connection
// and thus driven by a different thread. This is needed to reach very high
// bandwidths.
C10_REGISTER_CREATOR(
    TensorPipeChannelRegistry,
    mpt_uv,
    makeMultiplexedUvChannel)

} // namespace

//////////////////////////  MetricsTracker  /////////////////////////////////

TensorPipeAgent::TimeSeriesMetricsTracker::TimeSeriesMetricsTracker(
    uint64_t currentSum,
    uint64_t currentCount)
    : currentSum_(currentSum), currentCount_(currentCount) {}

void TensorPipeAgent::TimeSeriesMetricsTracker::addData(uint64_t dataPoint) {
  currentSum_ += dataPoint;
  ++currentCount_;
}

float TensorPipeAgent::TimeSeriesMetricsTracker::computeAverage() const {
  return currentCount_ == 0 ? 0
                            : static_cast<float>(
                                  static_cast<double>(currentSum_) /
                                  static_cast<double>(currentCount_));
}

////////////////////////  TensorpipeRpcAgent  /////////////////////////////////

void TensorPipeAgent::removeFromTimeoutMap(uint64_t messageId) {
  // Remove entry from timeoutMap_.
  {
    std::unique_lock<std::mutex> lock(timeoutMapMutex_);
    auto it = messageIdToTimeout_.find(messageId);
    if (it == messageIdToTimeout_.end()) {
      // Already removed from the map by pollTimeoutRpcs(), no need to
      // process further.
      return;
    }

    auto& expirationTime = it->second;

    auto& timedOutFuturesVector = timeoutMap_[expirationTime];
    for (auto it = timedOutFuturesVector.begin();
         it != timedOutFuturesVector.end();
         it++) {
      if (it->messageId == messageId) {
        it = timedOutFuturesVector.erase(it);
        break;
      }
    }

    if (timedOutFuturesVector.empty()) {
      timeoutMap_.erase(expirationTime);
    }

    // Remove from messageId to timeout map as well.
    messageIdToTimeout_.erase(messageId);
  }
}

void TensorPipeAgent::prepareNames(bool isStaticGroup) {
  std::unordered_map<std::string, worker_id_t> nameToId;
  if (isStaticGroup) {
    nameToId = collectNames(
        rankToNameStore_, workerInfo_.id_, workerInfo_.name_, worldSize_);
  } else {
    nameToId = collectCurrentNames(
        rankToNameStore_, workerInfo_.id_, workerInfo_.name_);
  }

  for (const auto& entry : nameToId) {
    const auto& workerName = entry.first;
    const auto& workerId = entry.second;
    workerIdToInfo_.emplace(workerId, WorkerInfo(workerName, workerId));
    workerNameToInfo_.emplace(workerName, WorkerInfo(workerName, workerId));
  }
}

void TensorPipeAgent::checkAndSetStaticGroup(
    const c10::intrusive_ptr<::c10d::Store>& store) {
  std::string isStaticGroupKey("rpcIsStaticGroup");

  std::string isStaticGroupStr = isStaticGroup_ ? "true" : "false";
  std::vector<uint8_t> isStaticGroupVec(
      (uint8_t*)isStaticGroupStr.c_str(),
      (uint8_t*)isStaticGroupStr.c_str() + isStaticGroupStr.length());
  std::vector<uint8_t> returnedVec;
  returnedVec = store->compareSet(
      isStaticGroupKey, std::vector<uint8_t>(), isStaticGroupVec);
  std::string returnedVal = std::string(returnedVec.begin(), returnedVec.end());
  // In both cases, the returned value should be the value of isStaticGroupStr,
  // otherwise there is a discrepancy with initialization among one of the
  // members
  TORCH_CHECK(
      returnedVal == isStaticGroupStr,
      fmt::format(
          "RPC group mixes statically and dynamically initialized members which is not supported. ",
          "Static group property is initialized as {} and is trying to be set as {} ",
          isStaticGroup_,
          returnedVal));
}

TensorPipeAgent::TensorPipeAgent(
    const c10::intrusive_ptr<::c10d::Store>& store,
    std::string selfName,
    worker_id_t selfId,
    std::optional<int> worldSize,
    TensorPipeRpcBackendOptions opts,
    std::unordered_map<std::string, DeviceMap> reverseDeviceMaps,
    std::vector<c10::Device> devices,
    std::unique_ptr<RequestCallback> cb)
    : RpcAgent(
          WorkerInfo(std::move(selfName), selfId),
          std::move(cb),
          std::chrono::milliseconds(
              static_cast<long>(opts.rpcTimeoutSeconds * kSecToMsConversion))),
      isStaticGroup_(worldSize.has_value()),
      store_(store),
      opts_(std::move(opts)),
      reverseDeviceMaps_(std::move(reverseDeviceMaps)),
      devices_(std::move(devices)),
      threadPool_(opts_.numWorkerThreads),
      context_(std::make_shared<tensorpipe::Context>(
          tensorpipe::ContextOptions().name(workerInfo_.name_))),
      rankToNameStore_("names", store),
      nameToAddressStore_("addrs", store),
      shutdownStore_("shutdown", store) {
  if (isStaticGroup_) {
    worldSize_ = worldSize.value();
  }

  // check the static group attribute against store
  checkAndSetStaticGroup(store);

  // collect worker names
  prepareNames(isStaticGroup_);

  // Initialize the time-series metrics tracking map
  timeSeriesMetrics_.emplace(kGilAverageWaitTime, TimeSeriesMetricsTracker());
}

TensorPipeAgent::~TensorPipeAgent() {
  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " is being destroyed";
  shutdown();
}

void TensorPipeAgent::startImpl() {
  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " is starting";

  std::vector<std::string> addresses;
  int64_t lowestPriority = std::numeric_limits<int64_t>::max();
  std::string lowestPriorityTransport;

  // Register transports
  for (auto& key : TensorPipeTransportRegistry()->Keys()) {
    int64_t priority = -1;
    if (opts_.transports.has_value()) {
      auto iter =
          std::find(opts_.transports->begin(), opts_.transports->end(), key);
      if (iter == opts_.transports->end()) {
        continue;
      }
      // Assign priorities in reverse order of occurrence in the vector, so that
      // a transport that comes before another receives a higher priority.
      priority = static_cast<std::ptrdiff_t>(opts_.transports->size()) - 1 -
          (iter - opts_.transports->begin());
    }
    std::unique_ptr<TransportRegistration> reg =
        TensorPipeTransportRegistry()->Create(key);
    if (!reg->transport->isViable()) {
      continue;
    }
    if (priority == -1) {
      priority = reg->priority;
    }
    if (priority < lowestPriority) {
      lowestPriority = priority;
      lowestPriorityTransport = key;
    }
    addresses.push_back(c10::str(key, "://", reg->address));
    context_->registerTransport(priority, key, reg->transport);
  }

  // Register channels
  for (auto& key : TensorPipeChannelRegistry()->Keys()) {
    int64_t priority = -1;
    if (opts_.channels.has_value()) {
      auto iter =
          std::find(opts_.channels->begin(), opts_.channels->end(), key);
      if (iter == opts_.channels->end()) {
        continue;
      }
      // Assign priorities in reverse order of occurrence in the vector, so
      // that a channel that comes before another receives a higher priority.
      priority = static_cast<std::ptrdiff_t>(opts_.channels->size()) - 1 -
          (iter - opts_.channels->begin());
    }
    std::unique_ptr<ChannelRegistration> reg =
        TensorPipeChannelRegistry()->Create(key);
    if (!reg->channel->isViable()) {
      continue;
    }
    if (priority == -1) {
      priority = reg->priority;
    }
    context_->registerChannel(priority, key, reg->channel);
  }

  listener_ = context_->listen(addresses);

  // Store our own url.
  const auto address = listener_->url(lowestPriorityTransport);
  nameToAddressStore_.set(workerInfo_.name_, address);

  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " is using address "
          << address;

  for (const auto& p : workerNameToInfo_) {
    const auto& name = p.first;
    auto nodeAddrData = nameToAddressStore_.get(name);
    auto nodeAddrStr = std::string(
        reinterpret_cast<const char*>(nodeAddrData.data()),
        nodeAddrData.size());
    workerNameToURL_.insert({name, nodeAddrStr});
  }

  // Start the Timeout Thread
  timeoutThread_ = std::thread(&TensorPipeAgent::pollTimeoutRpcs, this);

  listener_->accept([this](
                        const tensorpipe::Error& error,
                        std::shared_ptr<tensorpipe::Pipe> pipe) {
    onListenerAccepted(error, pipe);
  });
}

void TensorPipeAgent::onListenerAccepted(
    const tensorpipe::Error& error,
    std::shared_ptr<tensorpipe::Pipe>& pipe) {
  if (error) {
    if (error.isOfType<tensorpipe::ListenerClosedError>() &&
        !rpcAgentRunning_.load()) {
      // This is expected.
    } else {
      LOG(WARNING) << "RPC agent for " << workerInfo_.name_
                   << " encountered error when accepting incoming pipe: "
                   << error.what();
    }
    return;
  }

  // Accept the next connection request
  listener_->accept([this](
                        const tensorpipe::Error& error,
                        std::shared_ptr<tensorpipe::Pipe> pipe) {
    onListenerAccepted(error, pipe);
  });

  VLOG(1) << "RPC agent for " << workerInfo_.name_
          << " accepted incoming pipe from " << pipe->getRemoteName();

  // Arm for server read
  respond(pipe);
}

void TensorPipeAgent::pipeRead(
    const std::shared_ptr<tensorpipe::Pipe>& pipe,
    std::function<void(
        const tensorpipe::Error&,
        c10::intrusive_ptr<Message>,
        std::vector<c10::Stream>)> fn) noexcept {
  pipe->readDescriptor([this, fn{std::move(fn)}, pipe](
                           const tensorpipe::Error& error,
                           tensorpipe::Descriptor tpDescriptor) mutable {
    if (error) {
      fn(error, c10::intrusive_ptr<Message>(), {});
      return;
    }

    std::vector<c10::Stream> streams;
    {
      GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
      streams = getStreamsFromPoolForDevices(devices_);
    }
    auto [tpAllocation, tpBuffers] = tensorpipeAllocate(tpDescriptor, streams);

    pipe->read(
        std::move(tpAllocation),
        [tpDescriptor{std::move(tpDescriptor)},
         tpBuffers{
             std::make_shared<TensorpipeReadBuffers>(std::move(tpBuffers))},
         fn{std::move(fn)},
         streams{std::move(streams)}](const tensorpipe::Error& error) mutable {
          if (error) {
            fn(error, c10::intrusive_ptr<Message>(), {});
            return;
          }

          // FIXME This does some unpickling, which could be a bit expensive:
          // perhaps it would be best to perform it inside the worker threads?
          c10::intrusive_ptr<Message> rpcMessage =
              tensorpipeDeserialize(tpDescriptor, std::move(*tpBuffers));

          fn(error, std::move(rpcMessage), std::move(streams));
        });
  });
}

void TensorPipeAgent::pipeWrite(
    const std::shared_ptr<tensorpipe::Pipe>& pipe,
    const c10::intrusive_ptr<Message>& rpcMessage,
    std::vector<c10::Device>&& devices,
    std::vector<c10::Stream> streams,
    std::function<void(const tensorpipe::Error&)> fn) noexcept {
  auto [tpMessage, tpBuffers] =
      tensorpipeSerialize(rpcMessage, std::move(devices), streams);

  pipe->write(
      std::move(tpMessage),
      [tpBuffers{
           std::make_shared<TensorpipeWriteBuffers>(std::move(tpBuffers))},
       fn{std::move(fn)},
       streams{std::move(streams)}](const tensorpipe::Error& error) {
        fn(error);
      });
}

void TensorPipeAgent::sendCompletedResponseMessage(
    std::shared_ptr<tensorpipe::Pipe>& pipe,
    JitFuture& futureResponseMessage,
    uint64_t messageId,
    std::vector<c10::Stream> streams) {
  if (!rpcAgentRunning_.load()) {
    LOG(WARNING) << "RPC agent for " << workerInfo_.name_
                 << " won't send response to request #" << messageId << " to "
                 << pipe->getRemoteName() << ", as the agent is shutting down";
    return;
  }

  VLOG(1) << "RPC agent for " << workerInfo_.name_
          << " is sending response to request #" << messageId << " to "
          << pipe->getRemoteName();

  if (!futureResponseMessage.hasError()) {
    c10::intrusive_ptr<Message> responseMessage =
        futureResponseMessage.value().toCustomClass<Message>();
    responseMessage->setId(static_cast<int64_t>(messageId));

    std::vector<c10::Device> devices;
    try {
      devices = getDevicesForRemote(pipe->getRemoteName(), *responseMessage);
    } catch (const std::exception& e) {
      responseMessage =
          createExceptionResponse(e.what(), static_cast<int64_t>(messageId));
    }

    for (const auto& tensor : responseMessage->tensors()) {
      const auto device = tensor.device();
      if (!device.is_cpu()) {
        GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
        if (std::find(devices_.begin(), devices_.end(), device) ==
            devices_.end()) {
          std::ostringstream oss;
          std::copy(
              devices_.begin(),
              devices_.end(),
              std::ostream_iterator<c10::Device>(oss, ", "));
          responseMessage = createExceptionResponse(
              c10::str(
                  "RPC detected that a user-function output tensor on device ",
                  device,
                  ". This device is not one of the input tensor devices: ",
                  oss.str(),
                  "which is not yet supported. Please file a feature request "
                  "issue in PyTorch GitHub repo."),
              static_cast<int64_t>(messageId));
          break;
        }
      }
    }

    pipeWrite(
        pipe,
        responseMessage,
        std::move(devices),
        std::move(streams),
        [this, pipe, messageId](const tensorpipe::Error& error) {
          if (error) {
            LOG(WARNING)
                << "RPC agent for " << workerInfo_.name_
                << " encountered error when sending response to request #"
                << messageId << " to " << pipe->getRemoteName() << ": "
                << error.what();
            return;
          }

          VLOG(1) << "RPC agent for " << workerInfo_.name_
                  << " done sending response to request #" << messageId
                  << " to " << pipe->getRemoteName();
        });
  } else {
    pipeWrite(
        pipe,
        createExceptionResponse(
            futureResponseMessage.tryRetrieveErrorMessage(),
            static_cast<int64_t>(messageId)),
        /* devices */ {},
        std::move(streams),
        [this, pipe, messageId](const tensorpipe::Error& error) {
          if (error) {
            LOG(WARNING)
                << "RPC agent for " << workerInfo_.name_
                << " encountered error when sending response to request #"
                << messageId << " to " << pipe->getRemoteName() << ": "
                << error.what();
            return;
          }

          VLOG(1) << "RPC agent for " << workerInfo_.name_
                  << " done sending response to request #" << messageId
                  << " to " << pipe->getRemoteName();
        });
  }
}

void TensorPipeAgent::respond(std::shared_ptr<tensorpipe::Pipe>& pipe) {
  pipeRead(
      pipe,
      [this, pipe](
          const tensorpipe::Error& error,
          c10::intrusive_ptr<Message> requestMessage,
          std::vector<c10::Stream> streams) mutable {
        if (error) {
          if (shuttingDown_) {
            // This is expected.
          } else {
            LOG(WARNING)
                << "RPC agent for " << workerInfo_.name_
                << " encountered error when reading incoming request from "
                << pipe->getRemoteName() << ": " << error.what();
          }
          return;
        }

        // Arm for next read
        respond(pipe);

        uint64_t messageId = requestMessage->id();
        increaseCallCount(serverActiveCalls_);

        VLOG(1) << "RPC agent for " << workerInfo_.name_
                << " received request #" << messageId << " from "
                << pipe->getRemoteName();

        // Defer user RPC UDF run to thread pool
        threadPool_.run([this,
                         pipe,
                         messageId,
                         requestMessage{std::move(requestMessage)},
                         streams{std::move(streams)}]() mutable {
          VLOG(1) << "RPC agent for " << workerInfo_.name_
                  << " is running request #" << messageId << " from "
                  << pipe->getRemoteName() << " in thread pool";

          c10::intrusive_ptr<JitFuture> futureResponseMessage;
          try {
            // Instead of creating a MultiStreamGuard here, the ctx is passed
            // to the callback and the MultiStreamGuard is created there,
            // because subsequent processing can switch threads due to 1)
            // waiting for RRef arguments to become ready 2) async_execution.
            // Besides, the `ctx` also needs to be propagated to
            // `process***Call` methods to synchronize CUDA streams there
            // to make sure that we fetch the correct value from `to_here()`
            // call.
            futureResponseMessage =
                cb_->operator()(*requestMessage, std::move(streams));
          } catch (const std::exception& /* unused */) {
            futureResponseMessage =
                c10::make_intrusive<JitFuture>(at::AnyClassType::get());
            futureResponseMessage->setError(std::current_exception());
          }

          increaseCallCount(serverActiveAsyncCalls_);
          futureResponseMessage->addCallback(
              [this, pipe, messageId](
                  JitFuture& futureResponseMessage) mutable {
                decreaseCallCount(serverActiveCalls_);
                decreaseCallCount(serverActiveAsyncCalls_);
                auto streams = getCurrentStreamsForDevices(
                    futureResponseMessage.devices());
                sendCompletedResponseMessage(
                    pipe, futureResponseMessage, messageId, std::move(streams));
              });

          VLOG(1) << "RPC agent for " << workerInfo_.name_
                  << " done running request #" << messageId << " from "
                  << pipe->getRemoteName() << " in thread pool";
        });
      });
}

c10::intrusive_ptr<JitFuture> TensorPipeAgent::send(
    const WorkerInfo& toWorkerInfo,
    c10::intrusive_ptr<Message> requestMessage,
    const float rpcTimeoutSeconds,
    const DeviceMap& deviceMap) {
  TORCH_CHECK(
      requestMessage->isRequest(),
      "TensorPipeAgent::send(..) is only for sending requests.");

  if (!rpcAgentRunning_.load()) {
    auto err = c10::str(
        "Node ",
        RpcAgent::getWorkerInfo().id_,
        "tried to send() a message of type ",
        requestMessage->type(),
        " but RPC is no longer running on this node.");
    TORCH_CHECK(false, err);
  }

  const auto& url = findWorkerURL(toWorkerInfo);

  decltype(connectedPipes_)::iterator it;
  {
    std::unique_lock<std::mutex> lock(connectedPipesMutex_);

    // See if we already have a connection to this address or not
    it = connectedPipes_.find(toWorkerInfo.id_);
    if (it == connectedPipes_.end()) {
      // An instance of ClientPipe cannot be copied or moved as it contains a
      // mutex, and to force in-place construction in GCC 5 we need piecewise
      // construction in order to work around an issue.
      it = connectedPipes_
               .emplace(
                   std::piecewise_construct,
                   std::forward_as_tuple(toWorkerInfo.id_),
                   std::forward_as_tuple(context_->connect(
                       url,
                       tensorpipe::PipeOptions().remoteName(
                           toWorkerInfo.name_))))
               .first;
    }
  }
  ClientPipe& clientPipe = it->second;

  std::shared_ptr<torch::distributed::rpc::TensorPipeAgent::AtomicJitFuture>
      futureResponseMessage;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    futureResponseMessage = std::make_shared<AtomicJitFuture>(devices_);
  }
  uint64_t messageId = nextMessageID_++;
  requestMessage->setId(static_cast<int64_t>(messageId));

  {
    std::unique_lock<std::mutex> lock(clientPipe.mutex_);
    clientPipe.pendingResponseMessage_[messageId] = futureResponseMessage;
  }

  // Get devices for tensors in the request message. This can throw if device
  // maps are not configured properly for this request.
  std::vector<c10::Device> devices;
  if (deviceMap.empty()) {
    devices =
        getDevicesForRemote(clientPipe.pipe_->getRemoteName(), *requestMessage);
  } else {
    // If deviceMap is specified, use that instead.
    devices = getDevicesForTensors(
        requestMessage->tensors(),
        deviceMap,
        clientPipe.pipe_->getRemoteName());
  }

  futureResponseMessage->jitFuture->addCallback(
      [this](JitFuture& /* unused */) {
        TORCH_INTERNAL_ASSERT(
            this->threadPool_.inThreadPool(),
            "Future marked complete from outside the thread pool");
      });

  increaseCallCount(clientActiveCalls_);
  // Use the default RPC timeout if no timeout is specified for this send call
  auto timeout = rpcTimeoutSeconds == kUnsetRpcTimeout
      ? getRpcTimeout()
      : std::chrono::milliseconds(
            static_cast<int>(rpcTimeoutSeconds * kSecToMsConversion));

  // We only add to the timeoutMap_ if the timeout is not 0. Per our
  // documentation, a user-provided timeout of 0 indicates the RPC should never
  // expire (infinite timeout), so there is no need to track it in the
  // timeoutMap_.
  steady_clock_time_point expirationTime;
  if (timeout.count() != 0) {
    // Compute the expiration time for this message based on the timeout
    expirationTime = computeRpcMessageExpiryTime(timeout);

    // Add the Future to the right vector in the timeoutMap_
    {
      std::unique_lock<std::mutex> lock(timeoutMapMutex_);
      auto& timeoutFuturesVector = timeoutMap_[expirationTime];
      messageIdToTimeout_.emplace(messageId, expirationTime);
      timeoutFuturesVector.emplace_back(
          messageId, futureResponseMessage, timeout);
    }
    timeoutThreadCV_.notify_one();
  }

  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " is sending request #"
          << messageId << " to " << clientPipe.pipe_->getRemoteName();

  std::vector<c10::Stream> streams;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    streams = getStreamsFromPoolForDevices(devices_);
  }
  makeStreamsWaitOnOthers(
      streams,
      getCurrentStreamsForDevices(
          getDevicesOfTensors(requestMessage->tensors())));
  pipeWrite(
      clientPipe.pipe_,
      requestMessage,
      std::move(devices),
      std::move(streams),
      [this, &clientPipe, messageId](const tensorpipe::Error& error) mutable {
        if (error) {
          if (error.isOfType<tensorpipe::PipeClosedError>() &&
              !rpcAgentRunning_.load()) {
            // This is expected.
          } else {
            LOG(WARNING) << "RPC agent for " << workerInfo_.name_
                         << " encountered error when sending outgoing request #"
                         << messageId << " to "
                         << clientPipe.pipe_->getRemoteName() << ": "
                         << error.what();
          }
          handleClientError(clientPipe, error);
          return;
        }

        VLOG(1) << "RPC agent for " << workerInfo_.name_ << " sent request #"
                << messageId << " to " << clientPipe.pipe_->getRemoteName();

        pipeRead(
            clientPipe.pipe_,
            [this, &clientPipe](
                const tensorpipe::Error& error,
                c10::intrusive_ptr<Message> responseMessage,
                std::vector<c10::Stream> streams) {
              if (error) {
                if (error.isOfType<tensorpipe::PipeClosedError>() &&
                    !rpcAgentRunning_.load()) {
                  // This is expected.
                } else {
                  LOG(WARNING)
                      << "RPC agent for " << workerInfo_.name_
                      << " encountered error when reading incoming response from "
                      << clientPipe.pipe_->getRemoteName() << ": "
                      << error.what();
                }
                handleClientError(clientPipe, error);
                return;
              }

              // Identify future response message by message ID
              uint64_t messageId = responseMessage->id();

              VLOG(1) << "RPC agent for " << workerInfo_.name_
                      << " received response #" << messageId << " from "
                      << clientPipe.pipe_->getRemoteName();

              std::shared_ptr<AtomicJitFuture> futureResponseMessage;
              {
                std::lock_guard<std::mutex> lock(clientPipe.mutex_);
                // A read error will lead all following callbacks to be
                // invoked with error, and shouldn't reach here.
                TORCH_INTERNAL_ASSERT(
                    !clientPipe.inError_, "Shouldn't be in error state");
                auto it = clientPipe.pendingResponseMessage_.find(messageId);
                TORCH_INTERNAL_ASSERT(
                    it != clientPipe.pendingResponseMessage_.end(),
                    "message ID ",
                    messageId,
                    " is not recognized");
                futureResponseMessage = std::move(it->second);
                clientPipe.pendingResponseMessage_.erase(it);
              }

              // Remove entry from timeoutMap_.
              removeFromTimeoutMap(messageId);

              if (responseMessage->type() == MessageType::EXCEPTION) {
                markFutureWithError(
                    std::move(futureResponseMessage),
                    std::string(
                        responseMessage->payload().begin(),
                        responseMessage->payload().end()));
              } else {
                markFutureAsComplete(
                    std::move(futureResponseMessage),
                    std::move(responseMessage),
                    std::move(streams));
              }
            });
      });

  return futureResponseMessage->jitFuture;
}

void TensorPipeAgent::handleClientError(
    ClientPipe& clientPipe,
    const tensorpipe::Error& error) {
  // When an error occurs on a pipe all pending operations will be aborted and
  // all callbacks invoked with error, hence we immediately flush all future
  // messages belonging to this pipe.
  decltype(clientPipe.pendingResponseMessage_) pendingMsgs;
  {
    std::lock_guard<std::mutex> lock(clientPipe.mutex_);
    std::swap(clientPipe.pendingResponseMessage_, pendingMsgs);
    clientPipe.inError_ = true;
  }
  std::string errorMsg = error.what();
  for (auto& p : pendingMsgs) {
    markFutureWithError(std::move(p.second), errorMsg);

    // Remove entry from timeoutMap_.
    removeFromTimeoutMap(p.first);
  }
}

void TensorPipeAgent::pollTimeoutRpcs() {
  while (rpcAgentRunning_.load()) {
    std::unique_lock<std::mutex> lock(timeoutMapMutex_);

    // We sleep until the earliest expiring RPC in the timeoutMap_. We must
    // also ensure that we sleep while the map is empty, and we exit sleeping
    // if the RPC Agent has been shutdown.
    for (;;) {
      if (!rpcAgentRunning_.load()) {
        return;
      }

      if (!timeoutMap_.empty()) {
        steady_clock_time_point earliestTimeout = timeoutMap_.begin()->first;
        if (std::chrono::steady_clock::now() >= earliestTimeout) {
          break;
        }
        timeoutThreadCV_.wait_until(lock, earliestTimeout);
      } else {
        timeoutThreadCV_.wait(lock);
      }
    }

    // Move all these futures to a separate vector so we can process them
    // outside the lock.
    std::vector<TimeoutMessageMetadata> timedOutFutures =
        std::move(timeoutMap_.begin()->second);

    // We can safely remove this key from the timeoutMap_ since all these
    // futures will be processed.
    timeoutMap_.erase(timeoutMap_.begin());

    for (auto& timeoutMetadata : timedOutFutures) {
      // Remove from messageIdToTimeout map.
      messageIdToTimeout_.erase(timeoutMetadata.messageId);
    }
    lock.unlock();

    // Set an error on futures added to the timedOutFutures vector. We do this
    // outside the lock to prevent potential lock-order-inversions by callbacks
    // triggered by the setError call.
    for (auto& timeoutMetadata : timedOutFutures) {
      std::string errorMsg =
          fmt::format(kRpcTimeoutErrorStr, timeoutMetadata.timeout.count());
      auto err = makeRPCError(errorMsg, RPCErrorType::TIMEOUT);
      markFutureWithError(
          std::move(timeoutMetadata.responseFuture), std::move(err));
    }
  }
}

void TensorPipeAgent::leaveGroup() {
  std::unique_lock<std::mutex> lock(callCountMutex_);
  // local worker ActiveCallCount is 0 at this point and we will shutdown
  // (any future calls will be dropped)
  callCountCV_.wait(lock, [this] { return clientActiveCalls_ == 0; });

  // Remove this agent's WorkerInfo from store
  removeCurrentName(rankToNameStore_, workerInfo_.id_, workerInfo_.name_);

  // Set internal variable to be used during destructor
  shuttingDown_ = true;
}

// TODO: Remove join()
void TensorPipeAgent::join(bool shutdown, float /* unused */) {
  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " is joining";
  if (!isStaticGroup_) {
    leaveGroup();
    return;
  }

  // This method behaves like a barrier, as it can only return once all workers
  // have no more requests pending, including "nested" requests (triggered from
  // within the remote code of another call) and "follow-up" requests (triggered
  // from the callback of a future).
  while (true) {
    {
      std::unique_lock<std::mutex> lock(callCountMutex_);
      // It is enough to wait for there to be no more active client calls, since
      // each server call corresponds to a client call for some other worker.
      callCountCV_.wait(lock, [this] { return clientActiveCalls_ == 0; });

      // We'd like to immediately proceed with the allreduce, but it's a call
      // that may block for some time, as it waits for other workers to also
      // complete all their active client calls. While we call allreduce we must
      // hold the mutex, or else the count we send to other workers may get
      // stale (e.g., if some nested call happens in the meantime). But we can't
      // hold the lock for an indeterminately long time, as that would block
      // other operations (e.g., send). Thus we must release the lock and only
      // re-acquire it when all workers are ready to proceed with the allreduce.
      // We perform this synchronization using a barrier.
    }
    VLOG(1) << "RPC agent for " << workerInfo_.name_
            << " completed all client calls and is entering a barrier";
    syncCallCount(shutdownStore_, worldSize_);
    {
      std::unique_lock<std::mutex> lock(callCountMutex_);
      // At this point, the count may have become non-zero again. We can't wait
      // for those calls to complete as other workers are waiting for us in the
      // allreduce and we would block them. Thus we send our count even if it is
      // non-zero and if anyone (be it us or another worker) has a non-zero
      // count we'll just do another round.
      VLOG(1) << "RPC agent for " << workerInfo_.name_
              << " exited the barrier and found " << clientActiveCalls_
              << " active client calls";
      int totalClientActiveCalls =
          syncCallCount(shutdownStore_, worldSize_, clientActiveCalls_);
      VLOG(1) << "RPC agent for " << workerInfo_.name_
              << " completed sync call counts and got a total of "
              << totalClientActiveCalls
              << " active client calls across all workers";
      if (totalClientActiveCalls == 0) {
        if (shutdown) {
          shuttingDown_ = true;
          syncCallCount(shutdownStore_, worldSize_);
        }
        break;
      }
    }
  }
  VLOG(1) << "RPC agent for " << workerInfo_.name_ << " done joining";
}

void TensorPipeAgent::shutdownImpl() {
  // FIXME Isn't it too verbose for a library to print logs in normal operation?
  LOG(INFO) << "RPC agent for " << workerInfo_.name_ << " is shutting down";

  // Join the Timeout Thread
  timeoutThreadCV_.notify_one();
  if (timeoutThread_.joinable()) {
    timeoutThread_.join();
  }
  VLOG(1) << "RPC agent for " << workerInfo_.name_
          << " done waiting for timeout thread to join";

  // This will close all the pipes and listeners, invoke all callbacks with
  // errors, turn down the I/O event loops and wait for everything to terminate.
  context_->join();
  VLOG(1) << "RPC agent for " << workerInfo_.name_
          << " done waiting for TensorPipe context to join";

  // NOTE: We need to call waitWorkComplete in the end after we have shutdown
  // all listeners for Tensorpipe. This is to drain any already accepted work
  // in the ThreadPool. If this is done before we shutdown the listeners,
  // additional work could be added after this call and before we shutdown
  // listeners. This work would continue executing in the threadpool and might
  // cause issues during shutdown of the system.
  threadPool_.waitWorkComplete();
  VLOG(1) << "RPC agent for " << workerInfo_.name_
          << " done waiting for thread pool to complete work";
}

const WorkerInfo& TensorPipeAgent::getWorkerInfo(
    const std::string& workerName) const {
  std::unordered_map<std::string, WorkerInfo>::const_iterator it;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    it = workerNameToInfo_.find(workerName);
  }
  TORCH_CHECK(
      it != workerNameToInfo_.end(),
      fmt::format(
          "name:{},rank:{} could not find destination name {}",
          workerInfo_.name_,
          workerInfo_.id_,
          workerName));
  return it->second;
}

const WorkerInfo& TensorPipeAgent::getWorkerInfo(worker_id_t workerId) const {
  std::unordered_map<worker_id_t, WorkerInfo>::const_iterator it;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    it = workerIdToInfo_.find(workerId);
  }
  TORCH_CHECK(
      it != workerIdToInfo_.end(),
      fmt::format(
          "name:{},rank:{} could not find destination id {}",
          workerInfo_.name_,
          workerInfo_.id_,
          workerId));
  return it->second;
}

std::vector<WorkerInfo> TensorPipeAgent::getWorkerInfos() const {
  std::vector<WorkerInfo> workerInfos;
  workerInfos.reserve(workerNameToInfo_.size());
  for (auto& item : workerNameToInfo_) {
    workerInfos.emplace_back(item.second);
  }
  return workerInfos;
}

const std::string& TensorPipeAgent::findWorkerURL(
    const WorkerInfo& worker) const {
  std::unordered_map<std::string, std::string>::const_iterator it;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    it = workerNameToURL_.find(worker.name_);
  }
  TORCH_CHECK(
      it != workerNameToURL_.end(),
      fmt::format(
          "name:{},rank:{} could not find destination url for name {}",
          workerInfo_.name_,
          workerInfo_.id_,
          worker.name_));
  return it->second;
}

void TensorPipeAgent::updateGroupMembership(
    const WorkerInfo& workerInfo,
    const std::vector<c10::Device>& devices,
    const std::unordered_map<std::string, DeviceMap>& reverseDeviceMaps,
    bool isJoin) {
  std::string name = workerInfo.name_;
  worker_id_t id = workerInfo.id_;
  // Rank with workerInfo is joining the group, update internal mappings
  if (isJoin) {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    workerIdToInfo_.emplace(id, workerInfo);
    workerNameToInfo_.emplace(name, workerInfo);

    // TODO: we should get nodeAddrStr in the joining process, then pass in as
    // an argument rather than getting from store each time
    auto nodeAddrData = nameToAddressStore_.get(name);
    auto nodeAddrStr = std::string(
        reinterpret_cast<const char*>(nodeAddrData.data()),
        nodeAddrData.size());
    workerNameToURL_.insert({name, nodeAddrStr});

    for (const auto& it : reverseDeviceMaps) {
      if (reverseDeviceMaps_.find(it.first) == reverseDeviceMaps_.end()) {
        reverseDeviceMaps_[it.first] = it.second;
      }
    }
    // TODO: clean up mutex for devices_ usage
    // Add devices that have not been added yet
    for (const auto& it : devices) {
      if (std::find(devices_.begin(), devices_.end(), it) == devices_.end()) {
        devices_.push_back(it);
      }
    }
  } else {
    workerIdToInfo_.erase(id);
    workerNameToInfo_.erase(name);
    workerNameToURL_.erase(name);

    // remove reverse device maps that are no longer used
    for (auto it = reverseDeviceMaps_.begin();
         it != reverseDeviceMaps_.end();) {
      if (reverseDeviceMaps.find(it->first) == reverseDeviceMaps.end()) {
        it = reverseDeviceMaps_.erase(it);
      } else {
        it++;
      }
    }

    // remove devices that are no longer used
    for (auto it = devices_.begin(); it != devices_.end();) {
      if (std::find(devices.begin(), devices.end(), *it) == devices.end()) {
        it = devices_.erase(it);
      } else {
        it++;
      }
    }
  }
}
std::unordered_map<std::string, std::string> TensorPipeAgent::getMetrics() {
  std::unordered_map<std::string, std::string> metrics;
  metrics[kThreadPoolSize] = std::to_string(threadPool_.size());
  metrics[kNumIdleThreads] = std::to_string(threadPool_.numAvailable());
  {
    std::unique_lock<std::mutex> lock(callCountMutex_);
    metrics[kClientActiveCalls] = std::to_string(clientActiveCalls_);
    metrics[kServerActiveCalls] = std::to_string(serverActiveCalls_);
    metrics[kServerActiveAsyncCalls] = std::to_string(serverActiveAsyncCalls_);
  }
  if (isGILProfilingEnabled()) {
    {
      std::unique_lock<std::mutex> lock(metricsMutex_);
      // Include the averages for each time series metric. This is just the GIL
      // Wait Time for now.
      auto averageGilWaitTime =
          timeSeriesMetrics_[kGilAverageWaitTime].computeAverage();
      lock.unlock();
      metrics[kGilAverageWaitTime] = std::to_string(averageGilWaitTime);
    }
  }

  return metrics;
}

void TensorPipeAgent::addGilWaitTime(
    const std::chrono::microseconds gilWaitTime) {
  std::lock_guard<std::mutex> lock(metricsMutex_);
  timeSeriesMetrics_[kGilAverageWaitTime].addData(gilWaitTime.count());
}

TensorPipeAgent::NetworkDataDict TensorPipeAgent::getNetworkData() {
  std::lock_guard<std::mutex> lock(networkDataMutex_);
  return networkData_;
}

NetworkSourceInfo TensorPipeAgent::getNetworkSourceInfo() {
  NetworkSourceInfo info = {
      RpcAgent::getWorkerInfo().id_,
      nameToAddressStore_.get(RpcAgent::getWorkerInfo().name_)};

  return info;
}

void TensorPipeAgent::trackNetworkData(
    uint64_t requestSize,
    uint64_t responseSize,
    const std::string& destWorkerName) {
  std::lock_guard<std::mutex> lock(networkDataMutex_);
  networkData_[destWorkerName].numCalls++;
  networkData_[destWorkerName].totalSentBytes += requestSize;
  networkData_[destWorkerName].totalRecvBytes += responseSize;
}

void TensorPipeAgent::trackNetworkError(
    uint64_t requestSize,
    const std::string& destWorkerName) {
  std::lock_guard<std::mutex> lock(networkDataMutex_);
  networkData_[destWorkerName].numCalls++;
  networkData_[destWorkerName].totalSentBytes += requestSize;
  networkData_[destWorkerName].totalErrors++;
}

void TensorPipeAgent::increaseCallCount(int32_t& count) {
  {
    std::unique_lock<std::mutex> lock(callCountMutex_);
    ++count;
  }
  callCountCV_.notify_all();
}

void TensorPipeAgent::decreaseCallCount(int32_t& count) {
  {
    std::unique_lock<std::mutex> lock(callCountMutex_);
    --count;
  }
  callCountCV_.notify_all();
}

void TensorPipeAgent::markFutureAsComplete(
    std::shared_ptr<AtomicJitFuture> atomicFuture,
    c10::intrusive_ptr<Message> message,
    std::vector<c10::Stream> streams) {
  if (!atomicFuture->isComplete.test_and_set()) {
    // Completing the future will run its callbacks, which could execute
    // arbitrary user code. To prevent blocking or stalling the TensorPipe event
    // loops, we defer this to a worker thread.
    threadPool_.run([this,
                     atomicFuture{std::move(atomicFuture)},
                     message{std::move(message)},
                     streams{std::move(streams)}]() mutable {
      c10::MultiStreamGuard guard(streams);
      std::vector<c10::weak_intrusive_ptr<c10::StorageImpl>> storages =
          message->getStorages();
      atomicFuture->jitFuture->markCompleted(
          std::move(message), std::move(storages));
      // The future's callbacks may schedule further RPCs, increasing the count.
      // Thus we must decrease it after completing the future, otherwise it may
      // briefly dip to zero and trick join into thinking all work is done.
      decreaseCallCount(clientActiveCalls_);
    });
  }
}

void TensorPipeAgent::markFutureWithError(
    std::shared_ptr<AtomicJitFuture> atomicFuture,
    std::string errorMsg) {
  if (!atomicFuture->isComplete.test_and_set()) {
    // Completing the future will run its callbacks, which could execute
    // arbitrary user code. To prevent blocking or stalling the TensorPipe event
    // loops, we defer this to a worker thread.
    threadPool_.run([this,
                     atomicFuture{std::move(atomicFuture)},
                     errorMsg{std::move(errorMsg)}]() mutable {
      atomicFuture->jitFuture->setError(
          std::make_exception_ptr(std::runtime_error(errorMsg)));
      // The future's callbacks may schedule further RPCs, increasing the count.
      // Thus we must decrease it after completing the future, otherwise it may
      // briefly dip to zero and trick join into thinking all work is done.
      decreaseCallCount(clientActiveCalls_);
    });
  }
}

std::vector<c10::Device> TensorPipeAgent::getDevicesForRemote(
    const std::string& remoteName,
    const Message& message) const {
  std::unordered_map<std::string, DeviceMap> deviceMaps;
  {
    GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
    deviceMaps = message.isRequest() ? opts_.deviceMaps : reverseDeviceMaps_;
  }

  const auto errStr = c10::str(
      "TensorPipe RPC backend only supports CPU tensors by default, please "
      "move your tensors to CPU before sending them over RPC, or call "
      "`set_device_map` on `TensorPipeRpcBackendOptions` to explicitly "
      "configure device mapping. ",
      message.isRequest() ? "Request" : "Response",
      " device mapping is not available for destination ",
      remoteName);

  const auto& iter = deviceMaps.find(remoteName);
  if (iter == deviceMaps.end()) {
    for (const auto& t : message.tensors()) {
      TORCH_CHECK(
          t.device().is_cpu(),
          errStr,
          ", but found tensor on device: ",
          t.device());
    }
    return {};
  } else {
    return getDevicesForTensors(message.tensors(), iter->second, errStr);
  }
}

DeviceMap TensorPipeAgent::getDeviceMap(const WorkerInfo& dst) const {
  auto it = opts_.deviceMaps.find(dst.name_);
  if (it == opts_.deviceMaps.end()) {
    return {};
  }
  return it->second;
}

const c10::intrusive_ptr<::c10d::Store> TensorPipeAgent::getStore() const {
  return store_;
}

TensorPipeRpcBackendOptions TensorPipeAgent::getBackendOptions() const {
  return opts_;
}

const std::vector<c10::Device>& TensorPipeAgent::getDevices() const {
  GroupMembershipLockGuard guard(groupMembershipMutex_, isStaticGroup_);
  return devices_;
}

size_t TensorPipeAgent::timeoutMapSize() {
  std::unique_lock<std::mutex> lock(timeoutMapMutex_);
  return timeoutMap_.size();
}

size_t TensorPipeAgent::numPendingResponses() {
  std::unique_lock<std::mutex> lock(callCountMutex_);
  return clientActiveCalls_;
}

size_t TensorPipeAgent::messageIdToTimeoutMapSize() {
  std::unique_lock<std::mutex> lock(timeoutMapMutex_);
  return messageIdToTimeout_.size();
}

} // namespace torch::distributed::rpc

#endif // USE_TENSORPIPE