wehub-resource-sync
91 lines
2.2 KiB
C++
91 lines
2.2 KiB
C++
// SPDX-License-Identifier: Apache-2.0
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#pragma once
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#include <atomic>
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#include <chrono>
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#include <cstdint>
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namespace lmcache {
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namespace storage_manager {
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/**
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* @brief A thread-safe lock with TTL (Time-To-Live) support.
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*
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* This lock maintains a counter that can be incremented (lock) and decremented
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* (unlock). The lock also has a TTL mechanism - if the TTL expires, the lock
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* is considered unlocked regardless of the counter value.
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*
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* Thread Safety:
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* - All operations are thread-safe using atomic operations.
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* - lock() and unlock() use memory_order_seq_cst for full synchronization.
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* - is_locked() uses memory_order_acquire for visibility guarantees.
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*/
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class TTLLock {
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public:
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/**
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* @brief Construct a new TTLLock with the specified TTL duration.
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*
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* @param ttl_second The TTL duration in seconds. Default is 300 seconds.
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*/
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explicit TTLLock(uint32_t ttl_second = 300);
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/**
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* @brief Increment the lock counter by 1 and update the TTL.
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*
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* If the previous TTL has expired, the counter is reset to 1.
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* Otherwise, the counter is incremented by 1.
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* The TTL is always refreshed to the current time + TTL duration.
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*/
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void lock();
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/**
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* @brief Decrement the lock counter by 1.
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*
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* The counter will not go below 0.
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*/
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void unlock();
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/**
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* @brief Check if the lock is currently held.
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*
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* The lock is considered held if:
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* 1. The counter is greater than 0, AND
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* 2. The TTL has not expired.
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*
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* @return true if the lock is held, false otherwise.
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*/
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bool is_locked() const;
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/**
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* @brief Reset the lock to initial state (counter = 0, TTL expired).
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*/
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void reset();
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private:
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using Clock = std::chrono::steady_clock;
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using TimePoint = std::chrono::time_point<Clock>;
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/**
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* @brief Get the current timestamp in milliseconds since epoch.
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*/
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static int64_t now_ms();
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/**
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* @brief Convert TimePoint to milliseconds since epoch.
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*/
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static int64_t to_ms(const TimePoint& tp);
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// The lock counter
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std::atomic<int64_t> counter_;
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// The expiration time in milliseconds since steady_clock epoch
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std::atomic<int64_t> expiration_ms_;
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// The TTL duration in milliseconds
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const int64_t ttl_ms_;
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};
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} // namespace storage_manager
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} // namespace lmcache
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