mirror of https://gitee.com/bigwinds/arangodb
107 lines
3.8 KiB
C++
107 lines
3.8 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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////////////////////////////////////////////////////////////////////////////////
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#include <stddef.h>
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#include <atomic>
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#include "ticks.h"
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#include "Basics/HybridLogicalClock.h"
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#include "Cluster/ServerState.h"
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using namespace arangodb;
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using namespace arangodb::basics;
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/// @brief current tick identifier (48 bit)
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static std::atomic<uint64_t> CurrentTick(0);
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/// @brief a hybrid logical clock
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static HybridLogicalClock hybridLogicalClock;
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/// @brief create a new tick, using a hybrid logical clock
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TRI_voc_tick_t TRI_HybridLogicalClock() {
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return hybridLogicalClock.getTimeStamp();
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}
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/// @brief create a new tick, using a hybrid logical clock, this variant
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/// is supposed to be called when a time stamp is received in network
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/// communications.
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TRI_voc_tick_t TRI_HybridLogicalClock(TRI_voc_tick_t received) {
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return hybridLogicalClock.getTimeStamp(received);
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}
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/// @brief create a new tick
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TRI_voc_tick_t TRI_NewTickServer() { return ++CurrentTick; }
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/// @brief updates the tick counter, with lock
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void TRI_UpdateTickServer(TRI_voc_tick_t tick) {
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TRI_voc_tick_t t = tick;
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auto expected = CurrentTick.load(std::memory_order_relaxed);
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// only update global tick if less than the specified value...
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while (expected < t && !CurrentTick.compare_exchange_weak(expected, t, std::memory_order_release,
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std::memory_order_relaxed)) {
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expected = CurrentTick.load(std::memory_order_relaxed);
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}
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}
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/// @brief returns the current tick counter
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TRI_voc_tick_t TRI_CurrentTickServer() { return CurrentTick; }
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/// @brief generates a new tick which also encodes this server's id
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TRI_voc_tick_t TRI_NewServerSpecificTick() {
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static constexpr uint64_t LowerMask{0x000000FFFFFFFFFF};
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static constexpr uint64_t UpperMask{0xFFFFFF0000000000};
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static constexpr size_t UpperShift{40};
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uint64_t lower = TRI_NewTickServer() & LowerMask;
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uint64_t upper =
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(static_cast<uint64_t>(ServerState::instance()->getShortId()) << UpperShift) & UpperMask;
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uint64_t tick = (upper | lower);
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return static_cast<TRI_voc_tick_t>(tick);
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}
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/// @brief generates a new tick which also encodes this server's id, and is
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/// congruent to 0 modulo 4
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TRI_voc_tick_t TRI_NewServerSpecificTickMod4() {
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static constexpr uint64_t LowerMask{0x000000FFFFFFFFFC};
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static constexpr uint64_t UpperMask{0xFFFFFF0000000000};
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static constexpr size_t LowerShift{2};
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static constexpr size_t UpperShift{40};
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const uint64_t lower = (TRI_NewTickServer() << LowerShift) & LowerMask;
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const uint64_t upper =
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(static_cast<uint64_t>(ServerState::instance()->getShortId()) << UpperShift) & UpperMask;
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return static_cast<TRI_voc_tick_t>(upper | lower);
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}
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/// @brief extracts the server id from a server-specific tick
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uint32_t TRI_ExtractServerIdFromTick(TRI_voc_tick_t tick) {
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static constexpr uint64_t Mask{0x0000000000FFFFFF};
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static constexpr size_t Shift{40};
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uint32_t shortId = static_cast<uint32_t>((tick >> Shift) & Mask);
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return shortId;
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}
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