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Fix a race condition on the session pointer in PartitionAwarePolicy #4

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Fix a race condition on the session pointer in PartitionAwarePolicy #4

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10 changes: 6 additions & 4 deletions src/load_balancing.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,16 +18,18 @@
namespace cass {

ControlConnection* LoadBalancingPolicy::control_connection() {
return session_ == NULL ? NULL : session_->control_connection();
auto* session = session_.load(std::memory_order_acquire);
return session ? session->control_connection() : nullptr;
}

const Metadata* LoadBalancingPolicy::metadata() const {
const Session* s = session_; // const cast
return s == NULL ? NULL : &s->metadata();
const auto* session = session_.load(std::memory_order_acquire);
return session ? &session->metadata() : nullptr;
}

const TokenMap* LoadBalancingPolicy::token_map() const {
return session_ == NULL ? NULL : session_->token_map();
auto* session = session_.load(std::memory_order_acquire);
return session ? session->token_map() : nullptr;
}

} // namespace cass
6 changes: 4 additions & 2 deletions src/load_balancing.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
#include <list>
#include <set>
#include <string>
#include <atomic>

#include <uv.h>

Expand Down Expand Up @@ -82,7 +83,7 @@ class LoadBalancingPolicy : public Host::StateListener, public RefCounted<LoadBa
typedef SharedRefPtr<LoadBalancingPolicy> Ptr;

LoadBalancingPolicy()
: RefCounted<LoadBalancingPolicy>(), session_(NULL) {}
: RefCounted<LoadBalancingPolicy>() {}

virtual ~LoadBalancingPolicy() {}

Expand Down Expand Up @@ -112,7 +113,8 @@ class LoadBalancingPolicy : public Host::StateListener, public RefCounted<LoadBa
const Metadata* metadata() const;
const TokenMap* token_map() const;

Session* session_;
private:
std::atomic<Session*> session_{nullptr};
};


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5 changes: 3 additions & 2 deletions src/partition_aware_policy.cpp
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Expand Up @@ -202,7 +202,8 @@ QueryPlan* PartitionAwarePolicy::new_query_plan(const std::string& keyspace,
RequestHandler* request_handler) {
QueryPlan* const child_plan = child_policy_->new_query_plan(keyspace, request_handler);

if (request_handler == NULL || request_handler->request() == NULL || metadata() == NULL) {
auto* metadata = this->metadata();
if (request_handler == NULL || request_handler->request() == NULL || metadata == NULL) {
LOG_TRACE("Request or metadata is not available - child policy will be used");
return child_plan;
}
Expand All @@ -215,7 +216,7 @@ QueryPlan* PartitionAwarePolicy::new_query_plan(const std::string& keyspace,
return child_plan;
}

const Metadata::SchemaSnapshot schema = metadata()->schema_snapshot(
const Metadata::SchemaSnapshot schema = metadata->schema_snapshot(
CASS_HIGHEST_SUPPORTED_PROTOCOL_VERSION, VersionNumber(3, 0, 0));
const TableSplitMetadata::MapPtr& partitions = schema.get_partitions();

Expand Down