| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License. |
| #pragma once |
| |
| #include <cstdint> |
| #include <string> |
| |
| #include "kudu/clock/clock.h" |
| #include "kudu/common/common.pb.h" |
| #include "kudu/common/timestamp.h" |
| #include "kudu/gutil/atomicops.h" |
| #include "kudu/gutil/ref_counted.h" |
| #include "kudu/util/metrics.h" |
| #include "kudu/util/status.h" |
| |
| namespace kudu { |
| |
| class MonoTime; |
| |
| namespace clock { |
| |
| // An implementation of Clock that behaves as a plain Lamport Clock. |
| // In a single node, single tablet, setting this generates exactly the |
| // same Timestamp sequence as the original MvccManager did, but it can be |
| // updated to make sure replicas generate new timestamps on becoming leader. |
| // This can be used as a deterministic timestamp generator that has the same |
| // consistency properties as a HybridTime clock. |
| // |
| // The Wait* methods are unavailable in this implementation and will |
| // return Status::ServiceUnavailable(). |
| // |
| // NOTE: this class is thread safe. |
| class LogicalClock : public Clock { |
| public: |
| // Create logical clock starting with the given timestamp. |
| explicit LogicalClock(const Timestamp& timestamp, |
| const scoped_refptr<MetricEntity>& metric_entity = {}); |
| |
| Status Init() override { return Status::OK(); } |
| |
| Timestamp Now() override; |
| |
| // In the logical clock this call is equivalent to Now(); |
| Timestamp NowLatest() override; |
| |
| Status Update(const Timestamp& to_update) override; |
| |
| // The Wait*() functions are not available for this clock. |
| Status WaitUntilAfter(const Timestamp& then, |
| const MonoTime& deadline) override; |
| Status WaitUntilAfterLocally(const Timestamp& then, |
| const MonoTime& deadline) override; |
| |
| bool IsAfter(Timestamp t) override; |
| |
| std::string Stringify(Timestamp timestamp) override; |
| |
| // Used to get the timestamp without incrementing the logical component. |
| // Mostly used for tests/metrics. |
| uint64_t GetCurrentTime(); |
| |
| // Logical clock doesn't support COMMIT_WAIT. |
| bool SupportsExternalConsistencyMode(ExternalConsistencyMode mode) const override { |
| return mode != COMMIT_WAIT; |
| } |
| |
| private: |
| base::subtle::Atomic64 now_; |
| |
| FunctionGaugeDetacher metric_detacher_; |
| }; |
| |
| } // namespace clock |
| } // namespace kudu |