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[fix][client] Fix data race on the close counter of ClientImpl #626

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[fix][client] Fix data race on the close counter of ClientImpl #626

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12 changes: 8 additions & 4 deletions lib/ClientImpl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -856,7 +856,8 @@ void ClientImpl::closeAsync(const CloseCallback& callback) {
auto producers = producers_.move();
auto consumers = consumers_.move();

SharedInt numberOfOpenHandlers = std::make_shared<int>(producers.size() + consumers.size());
SharedInt numberOfOpenHandlers =
std::make_shared<std::atomic<int>>(static_cast<int>(producers.size() + consumers.size()));
LOG_INFO("Closing Pulsar client with " << producers.size() << " producers and " << consumers.size()
<< " consumers");

Expand Down Expand Up @@ -896,10 +897,13 @@ void ClientImpl::handleClose(Result result, const SharedInt& numberOfOpenHandler
<< expected << ". This means multiple errors have occurred while closing the client");
}

if (*numberOfOpenHandlers > 0) {
--(*numberOfOpenHandlers);
// Decrement the counter atomically and let only the call that observes it reaching zero proceed,
// otherwise concurrent close callbacks may race on the counter and both (or neither) shut down.
int remaining = numberOfOpenHandlers->load(std::memory_order_acquire);
while (remaining > 0 && !numberOfOpenHandlers->compare_exchange_weak(remaining, remaining - 1,
std::memory_order_acq_rel)) {
}
if (*numberOfOpenHandlers == 0) {
if (remaining <= 1) {
std::unique_lock lock(mutex_);
if (state_ == Closed) {
LOG_DEBUG("Client is already shutting down, possible race condition in handleClose");
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2 changes: 1 addition & 1 deletion lib/ClientImpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -232,7 +232,7 @@ class ClientImpl : public std::enable_shared_from_this<ClientImpl> {
void handleConsumerCreated(Result result, const ConsumerImplBaseWeakPtr& consumerWeakPtr,
const SubscribeV2Callback& callback, const ConsumerImplBasePtr& consumer);

typedef std::shared_ptr<int> SharedInt;
typedef std::shared_ptr<std::atomic<int>> SharedInt;

void handleClose(Result result, const SharedInt& remaining, const ResultCallback& callback);

Expand Down