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fix race between speculating read timer and request completion

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Speculating timer may expire after request is complete, but before a
continuation that cancels it runs. In this case the timer should not
initiate additional request and just do nothing instead.
This commit is contained in:
Gleb Natapov
2015-08-30 18:04:12 +03:00
committed by Avi Kivity
parent 2ef5816996
commit 5bb37bc92e
1 changed files with 10 additions and 5 deletions
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15
service/storage_proxy.cc
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@@ -1302,6 +1302,9 @@ public:
void add_wait_targets(size_t targets_count) {
_targets_count += targets_count;
}
bool is_completed() {
return _digest_results.size() == _targets_count;
}
};
class data_read_resolver : public abstract_read_resolver {
@@ -1595,11 +1598,13 @@ public:
using abstract_read_executor::abstract_read_executor;
virtual future<> make_requests(digest_resolver_ptr resolver) {
_speculate_timer.set_callback([this, resolver] {
resolver->add_wait_targets(1); // we send one more request so wait for it too
future<> f = resolver->has_data() ?
make_digest_requests(resolver, _targets.end() - 1, _targets.end()) :
make_data_requests(resolver, _targets.end() - 1, _targets.end());
f.finally([exec = shared_from_this()]{});
if (!resolver->is_completed()) { // at the time the callback runs request may be completed already
resolver->add_wait_targets(1); // we send one more request so wait for it too
future<> f = resolver->has_data() ?
make_digest_requests(resolver, _targets.end() - 1, _targets.end()) :
make_data_requests(resolver, _targets.end() - 1, _targets.end());
f.finally([exec = shared_from_this()]{});
}
});
// FIXME: the timeout should come from previous latency statistics for a partition
auto timeout = std::chrono::high_resolution_clock::now() + std::chrono::milliseconds(get_local_storage_proxy().get_db().local().get_config().read_request_timeout_in_ms()/2);