// 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 <stdint.h>

#include <atomic>

#include <condition_variable>

#include <mutex>

namespace doris {

/*

    This class is used to control compaction permission. To some extent, it can be used to control memory consumption.

    "permits" should be applied before a compaction task can execute. When the sum of "permites" held by executing

    compaction tasks reaches a threshold, subsequent compaction task will be no longer allowed, until some "permits"

    are released by some finished compaction tasks. "compaction score" for tablet is used as "permits" here.

*/

class CompactionPermitLimiter {

public:

    CompactionPermitLimiter();

    virtual ~CompactionPermitLimiter() {}

    void request(int64_t permits);

    void release(int64_t permits);

    int64_t usage() const { return _used_permits.load(std::memory_order_relaxed); }

private:

    // sum of "permits" held by executing compaction tasks currently

    std::atomic<int64_t> _used_permits;

    std::mutex _permits_mutex;

    std::condition_variable _permits_cv;

};

} // namespace doris