Copilot commented on code in PR #538:
URL: https://github.com/apache/pulsar-client-cpp/pull/538#discussion_r2764151322
##########
lib/MultiTopicsConsumerImpl.cc:
##########
@@ -847,48 +847,44 @@ void
MultiTopicsConsumerImpl::getBrokerConsumerStatsAsync(const BrokerConsumerSt
Lock lock(mutex_);
MultiTopicsBrokerConsumerStatsPtr statsPtr =
std::make_shared<MultiTopicsBrokerConsumerStatsImpl>(numberTopicPartitions_->load());
- LatchPtr latchPtr =
std::make_shared<Latch>(numberTopicPartitions_->load());
+ auto latchPtr =
std::make_shared<std::atomic_size_t>(numberTopicPartitions_->load());
lock.unlock();
size_t i = 0;
- consumers_.forEachValue([this, &latchPtr, &statsPtr, &i, callback](const
ConsumerImplPtr& consumer) {
- size_t index = i++;
- auto weakSelf = weak_from_this();
- consumer->getBrokerConsumerStatsAsync([this, weakSelf, latchPtr,
statsPtr, index, callback](
- Result result, const
BrokerConsumerStats& stats) {
- auto self = weakSelf.lock();
- if (self) {
- handleGetConsumerStats(result, stats, latchPtr, statsPtr,
index, callback);
- }
+ auto failedResult = std::make_shared<std::atomic<Result>>(ResultOk);
+ consumers_.forEachValue(
+ [this, &latchPtr, &statsPtr, &i, callback, &failedResult](const
ConsumerImplPtr& consumer) {
+ size_t index = i++;
+ auto weakSelf = weak_from_this();
+ consumer->getBrokerConsumerStatsAsync(
+ [this, weakSelf, latchPtr, statsPtr, index, callback,
failedResult](
+ Result result, const BrokerConsumerStats& stats) {
+ auto self = weakSelf.lock();
+ if (!self) {
+ return;
+ }
+ if (result == ResultOk) {
+ std::lock_guard<std::mutex> lock{mutex_};
+ statsPtr->add(stats, index);
+ } else {
+ failedResult->store(result, std::memory_order_release);
+ }
+ if (--*latchPtr == 0) {
+ if (failedResult->load(std::memory_order_acquire) ==
ResultOk) {
+ callback(ResultOk, BrokerConsumerStats{statsPtr});
+ } else {
+ // Fail the whole operation if any of the
consumers failed
+ callback(result, {});
Review Comment:
The callback is using the local `result` parameter instead of the stored
`failedResult`. This means if multiple consumers fail and the last callback to
execute (when latch reaches 0) happens to be from a successful consumer, it
will incorrectly report success. The callback should use
`failedResult->load(std::memory_order_acquire)` to report the actual failure
that was stored earlier.
```suggestion
callback(failedResult->load(std::memory_order_acquire), {});
```
##########
lib/MultiTopicsConsumerImpl.cc:
##########
@@ -847,48 +847,44 @@ void
MultiTopicsConsumerImpl::getBrokerConsumerStatsAsync(const BrokerConsumerSt
Lock lock(mutex_);
MultiTopicsBrokerConsumerStatsPtr statsPtr =
std::make_shared<MultiTopicsBrokerConsumerStatsImpl>(numberTopicPartitions_->load());
- LatchPtr latchPtr =
std::make_shared<Latch>(numberTopicPartitions_->load());
+ auto latchPtr =
std::make_shared<std::atomic_size_t>(numberTopicPartitions_->load());
lock.unlock();
size_t i = 0;
- consumers_.forEachValue([this, &latchPtr, &statsPtr, &i, callback](const
ConsumerImplPtr& consumer) {
- size_t index = i++;
- auto weakSelf = weak_from_this();
- consumer->getBrokerConsumerStatsAsync([this, weakSelf, latchPtr,
statsPtr, index, callback](
- Result result, const
BrokerConsumerStats& stats) {
- auto self = weakSelf.lock();
- if (self) {
- handleGetConsumerStats(result, stats, latchPtr, statsPtr,
index, callback);
- }
+ auto failedResult = std::make_shared<std::atomic<Result>>(ResultOk);
+ consumers_.forEachValue(
+ [this, &latchPtr, &statsPtr, &i, callback, &failedResult](const
ConsumerImplPtr& consumer) {
+ size_t index = i++;
+ auto weakSelf = weak_from_this();
+ consumer->getBrokerConsumerStatsAsync(
+ [this, weakSelf, latchPtr, statsPtr, index, callback,
failedResult](
+ Result result, const BrokerConsumerStats& stats) {
+ auto self = weakSelf.lock();
+ if (!self) {
+ return;
+ }
+ if (result == ResultOk) {
+ std::lock_guard<std::mutex> lock{mutex_};
+ statsPtr->add(stats, index);
+ } else {
+ failedResult->store(result, std::memory_order_release);
+ }
+ if (--*latchPtr == 0) {
+ if (failedResult->load(std::memory_order_acquire) ==
ResultOk) {
+ callback(ResultOk, BrokerConsumerStats{statsPtr});
+ } else {
+ // Fail the whole operation if any of the
consumers failed
+ callback(result, {});
Review Comment:
If multiple consumers fail concurrently, each failure will overwrite the
previous one stored in `failedResult`. This means the final error code reported
to the caller is non-deterministic and depends on which failure's store
operation executes last. Consider using compare_exchange to only store the
first failure, which would provide more predictable behavior.
```suggestion
// Only store the first failure result to make the
reported error deterministic
Result expected = ResultOk;
failedResult->compare_exchange_strong(expected,
result, std::memory_order_acq_rel);
}
if (--*latchPtr == 0) {
Result finalResult =
failedResult->load(std::memory_order_acquire);
if (finalResult == ResultOk) {
callback(ResultOk,
BrokerConsumerStats{statsPtr});
} else {
// Fail the whole operation if any of the
consumers failed
callback(finalResult, {});
```
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