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lwt: sleep a random amount of time when retrying CAS

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Sleep a random interval between 0 and 100 ms before retrying CAS.
Reuse sleep function, make the distribution object thread local.
This commit is contained in:
Konstantin Osipov
2019-10-23 00:10:12 +03:00
parent 0674fab05c
commit 203eb3eccc
1 changed files with 9 additions and 7 deletions
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16
service/storage_proxy.cc
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@@ -685,13 +685,17 @@ public:
}
};
static future<std::optional<paxos_response_handler::ballot_and_contention>> sleep_and_restart() {
static future<> sleep_approx_50ms() {
static thread_local std::default_random_engine re{std::random_device{}()};
std::uniform_int_distribution<> dist(0, 100);
return sleep(std::chrono::milliseconds(dist(re))).then([] {
static thread_local std::uniform_int_distribution<> dist(0, 100);
return seastar::sleep(std::chrono::milliseconds(dist(re)));
}
static future<std::optional<paxos_response_handler::ballot_and_contention>> sleep_and_restart() {
return sleep_approx_50ms().then([] {
return std::optional<paxos_response_handler::ballot_and_contention>(); // continue
});
};
}
/**
* Begin a Paxos session by sending a prepare request and completing any in-progress requests seen in the replies.
@@ -3970,9 +3974,7 @@ future<bool> storage_proxy::cas(schema_ptr schema, shared_ptr<cas_request> reque
handler->id());
tracing::trace(handler->tr_state, "PAXOS proposal not accepted (pre-empted by a higher ballot)");
++contentions;
return seastar::sleep(100ms).then([] {
return std::optional<bool>();
});
return sleep_approx_50ms().then([] { return std::optional<bool>(); });
});
});
});