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[fix][client] Fix data races on the random generators of generateRandomName and ConnectionPool #627

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[fix][client] Fix data races on the random generators of generateRandomName and ConnectionPool #627

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7 changes: 4 additions & 3 deletions lib/ClientImpl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -78,11 +78,12 @@ void invokeLegacyCallback(const std::function<void(Result, T)>& callback,

static const char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
static std::uniform_int_distribution<> hexDigitsDist(0, sizeof(hexDigits) - 1);
static std::mt19937 randomEngine =
std::mt19937(std::chrono::high_resolution_clock::now().time_since_epoch().count());

std::string generateRandomName() {
// Called concurrently by all the clients of the process, so the generator state must not be shared.
thread_local std::uniform_int_distribution<> hexDigitsDist(0, sizeof(hexDigits) - 1);
thread_local std::mt19937 randomEngine(std::random_device{}());

const int randomNameLength = 10;

std::string randomName;
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7 changes: 6 additions & 1 deletion lib/ConnectionPool.h
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,11 @@ class PULSAR_PUBLIC ConnectionPool {
return getConnectionAsync(address, address);
}

size_t generateRandomIndex() { return randomDistribution_(randomEngine_); }
size_t generateRandomIndex() {
// Handlers are created concurrently from the caller and executor threads.
std::lock_guard<std::mutex> lock(randomMutex_);
return randomDistribution_(randomEngine_);
}

private:
const AtomicSharedPtr<ServiceInfo>& serviceInfo_;
Expand All @@ -110,6 +114,7 @@ class PULSAR_PUBLIC ConnectionPool {

std::uniform_int_distribution<> randomDistribution_;
std::mt19937 randomEngine_;
std::mutex randomMutex_;

auto releaseConnections() {
decltype(pool_) pool;
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