102 lines
2.7 KiB
C++
102 lines
2.7 KiB
C++
/*
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* Copyright 2015-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#pragma once
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#include <seastar/core/future.hh>
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#include <seastar/core/gate.hh>
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#include <seastar/core/shared_ptr.hh>
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#include "seastarx.hh"
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namespace utils {
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// Synchronizer which allows to track and wait for asynchronous operations
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// which were in progress at the time of wait initiation.
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class phased_barrier {
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public:
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using phase_type = uint64_t;
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private:
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using gate = seastar::named_gate;
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sstring _name;
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lw_shared_ptr<gate> _gate;
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phase_type _phase;
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public:
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explicit phased_barrier(sstring name)
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: _name(std::move(name))
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, _gate(make_lw_shared<gate>(_name))
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, _phase(0)
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{ }
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phased_barrier(phased_barrier&&) = default;
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phased_barrier& operator=(phased_barrier&&) = default;
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class operation {
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lw_shared_ptr<gate> _gate;
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public:
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operation() : _gate() {}
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operation(lw_shared_ptr<gate> g) : _gate(std::move(g)) {}
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operation(const operation&) = delete;
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operation(operation&&) = default;
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operation& operator=(operation&& o) noexcept {
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if (this != &o) {
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this->~operation();
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new (this) operation(std::move(o));
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}
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return *this;
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}
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~operation() {
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if (_gate) {
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_gate->leave();
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}
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}
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};
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// Starts new operation. The operation ends when the "operation" object is destroyed.
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// The operation may last longer than the life time of the phased_barrier.
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operation start() {
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_gate->enter();
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return { _gate };
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}
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future<> close() noexcept {
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return _gate->close();
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}
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bool is_closed() const noexcept {
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return _gate->is_closed();
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}
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// Starts a new phase and waits for all operations started in any of the earlier phases.
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// It is fine to start multiple awaits in parallel.
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// Cannot fail.
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future<> advance_and_await() noexcept {
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if (!operations_in_progress()) {
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++_phase;
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return make_ready_future();
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}
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auto new_gate = [this] {
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seastar::memory::scoped_critical_alloc_section _;
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return make_lw_shared<gate>(_name);
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}();
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++_phase;
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auto old_gate = std::exchange(_gate, std::move(new_gate));
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return old_gate->close().then([old_gate, op = start()] {});
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}
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// Returns current phase number. The smallest value returned is 0.
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phase_type phase() const {
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return _phase;
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}
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// Number of operations in current phase.
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size_t operations_in_progress() const {
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return _gate->get_count();
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}
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};
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}
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