YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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// under the License.

//

// The following only applies to changes made to this file as part of YugaByte development.

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// Portions Copyright (c) YugaByte, Inc.

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// Licensed 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

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// http://www.apache.org/licenses/LICENSE-2.0

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#ifndef YB_TABLET_MAINTENANCE_MANAGER_H

#define YB_TABLET_MAINTENANCE_MANAGER_H

#include <stdint.h>

#include <condition_variable>

#include <map>

#include <memory>

#include <set>

#include <string>

#include <vector>

#include "yb/gutil/macros.h"

#include "yb/gutil/thread_annotations.h"

#include "yb/tablet/tablet.pb.h"

#include "yb/util/condition_variable.h"

#include "yb/util/monotime.h"

#include "yb/util/mutex.h"

#include "yb/util/threadpool.h"

namespace yb {

template<class T>

class AtomicGauge;

class Histogram;

class MaintenanceManager;

class MemTracker;

class MaintenanceOpStats {

 public:

  MaintenanceOpStats();

  // Zero all stats. They are invalid until the first setter is called.

  void Clear();

  bool runnable() const {

    DCHECK(valid_);

    return runnable_;

  }

  void set_runnable(bool runnable) {

    UpdateLastModified();

    runnable_ = runnable;

  }

  uint64_t ram_anchored() const {

    DCHECK(valid_);

    return ram_anchored_;

  }

  void set_ram_anchored(uint64_t ram_anchored) {

    UpdateLastModified();

    ram_anchored_ = ram_anchored;

  }

  int64_t logs_retained_bytes() const {

    DCHECK(valid_);

    return logs_retained_bytes_;

  }

  void set_logs_retained_bytes(int64_t logs_retained_bytes) {

    UpdateLastModified();

    logs_retained_bytes_ = logs_retained_bytes;

  }

  double perf_improvement() const {

    DCHECK(valid_);

    return perf_improvement_;

  }

  void set_perf_improvement(double perf_improvement) {

    UpdateLastModified();

    perf_improvement_ = perf_improvement;

  }

  const MonoTime& last_modified() const {

    DCHECK(valid_);

    return last_modified_;

  }

  bool valid() const {

    return valid_;

  }

 private:

  void UpdateLastModified() {

    valid_ = true;

    last_modified_ = MonoTime::Now();

  }

  // True if these stats are valid.

  bool valid_;

  // True if this op can be run now.

  bool runnable_;

  // The approximate amount of memory that not doing this operation keeps

  // around.  This number is used to decide when to start freeing memory, so it

  // should be fairly accurate.  May be 0.

  uint64_t ram_anchored_;

  // The approximate amount of disk space that not doing this operation keeps us from GCing from

  // the logs. May be 0.

  int64_t logs_retained_bytes_;

  // The estimated performance improvement-- how good it is to do this on some

  // absolute scale (yet TBD).

  double perf_improvement_;

  // The last time that the stats were modified.

  MonoTime last_modified_;

};

class ScopedMaintenanceOpRun;

// MaintenanceOp objects represent background operations that the

// MaintenanceManager can schedule.  Once a MaintenanceOp is registered, the

// manager will periodically poll it for statistics.  The registrant is

// responsible for managing the memory associated with the MaintenanceOp object.

// Op objects should be unregistered before being de-allocated.

class MaintenanceOp {

 public:

  friend class MaintenanceManager;

  // General indicator of how much IO the Op will use.

  enum IOUsage {

    LOW_IO_USAGE, // Low impact operations like removing a file, updating metadata.

    HIGH_IO_USAGE // Everything else.

  };

  explicit MaintenanceOp(std::string name, IOUsage io_usage);

  virtual ~MaintenanceOp();

  // Unregister this op, if it is currently registered.

  void Unregister();

  // Update the op statistics.  This will be called every scheduling period

  // (about a few times a second), so it should not be too expensive.  It's

  // possible for the returned statistics to be invalid; the caller should

  // call MaintenanceOpStats::valid() before using them.  This will be run

  // under the MaintenanceManager lock.

  virtual void UpdateStats(MaintenanceOpStats* stats) = 0;

  // Prepare to perform the operation.  This will be run without holding the

  // maintenance manager lock.  It should be short, since it is run from the

  // context of the maintenance op scheduler thread rather than a worker thread.

  // If this returns false, we will abort the operation.

  virtual bool Prepare() = 0;

  // Perform the operation.  This will be run without holding the maintenance

  // manager lock, and may take a long time.

  virtual void Perform() = 0;

  // Returns the histogram for this op that tracks duration. Cannot be NULL.

  virtual scoped_refptr<Histogram> DurationHistogram() const = 0;

  // Returns the gauge for this op that tracks when this op is running. Cannot be NULL.

  virtual scoped_refptr<AtomicGauge<uint32_t> > RunningGauge() const = 0;

  uint32_t running() { return running_; }

  std::string name() const { return name_; }

  IOUsage io_usage() const { return io_usage_; }

 private:

  friend class ScopedMaintenanceOpRun;

  // The name of the operation.  Op names must be unique.

  const std::string name_;

  // The number of times that this op is currently running.

  uint32_t running_ = 0;

  // Condition variable which the UnregisterOp function can wait on.

  //

  // Note: 'cond_' is used with the MaintenanceManager's mutex. As such,

  // it only exists when the op is registered.

  std::condition_variable cond_;

  // The MaintenanceManager with which this op is registered, or null

  // if it is not registered.

  std::shared_ptr<MaintenanceManager> manager_;

  IOUsage io_usage_;

  DISALLOW_COPY_AND_ASSIGN(MaintenanceOp);

};

struct MaintenanceOpComparator {

  bool operator() (const MaintenanceOp* lhs,

                   const MaintenanceOp* rhs) const {

    return lhs->name().compare(rhs->name()) < 0;

  }

};

// Holds the information regarding a recently completed operation.

struct CompletedOp {

  std::string name;

  MonoDelta duration;

  MonoTime start_mono_time;

};

// The MaintenanceManager manages the scheduling of background operations such

// as flushes or compactions.  It runs these operations in the background, in a

// thread pool.  It uses information provided in MaintenanceOpStats objects to

// decide which operations, if any, to run.

class MaintenanceManager : public std::enable_shared_from_this<MaintenanceManager> {

 public:

  struct Options {

    int32_t num_threads;

    int32_t polling_interval_ms;

    uint32_t history_size;

    std::shared_ptr<MemTracker> parent_mem_tracker;

  };

  explicit MaintenanceManager(const Options& options);

  ~MaintenanceManager();

  CHECKED_STATUS Init();

  void Shutdown();

  // Register an op with the manager.

  void RegisterOp(MaintenanceOp* op);

  // Unregister an op with the manager.

  // If the Op is currently running, it will not be interrupted.  However, this

  // function will block until the Op is finished.

  void UnregisterOp(MaintenanceOp* op);

  void GetMaintenanceManagerStatusDump(tablet::MaintenanceManagerStatusPB* out_pb);

  static const Options DEFAULT_OPTIONS;

 private:

  friend class ScopedMaintenanceOpRun;

  FRIEND_TEST(MaintenanceManagerTest, TestLogRetentionPrioritization);

  typedef std::map<MaintenanceOp*, MaintenanceOpStats, MaintenanceOpComparator> OpMapTy;

  void RunSchedulerThread();

  // find the best op, or null if there is nothing we want to run

  MaintenanceOp* FindBestOp() REQUIRES(mutex_);

  void LaunchOp(const ScopedMaintenanceOpRun& op);

  std::mutex mutex_;

  const int32_t num_threads_;

  const int32_t polling_interval_ms_;

  const std::shared_ptr<MemTracker> parent_mem_tracker_;

  OpMapTy ops_ GUARDED_BY(mutex_); // registered operations

  scoped_refptr<yb::Thread> monitor_thread_;

  std::unique_ptr<ThreadPool> thread_pool_;

  std::condition_variable cond_;

  bool shutdown_ GUARDED_BY(mutex_) = false;

  uint64_t running_ops_ = 0;

  // Vector used as a circular buffer for recently completed ops. Elements need to be added at

  // the completed_ops_count_ % the vector's size and then the count needs to be incremented.

  std::vector<CompletedOp> completed_ops_ GUARDED_BY(mutex_);

  int64_t completed_ops_count_ GUARDED_BY(mutex_) = 0;

  DISALLOW_COPY_AND_ASSIGN(MaintenanceManager);

};

class ScopedMaintenanceOpRun {

 public:

  explicit ScopedMaintenanceOpRun(MaintenanceOp* op);

  ScopedMaintenanceOpRun(const ScopedMaintenanceOpRun& rhs);

  void operator=(const ScopedMaintenanceOpRun& rhs);

  ScopedMaintenanceOpRun(ScopedMaintenanceOpRun&& rhs);

  void operator=(ScopedMaintenanceOpRun&& rhs);

  ~ScopedMaintenanceOpRun();

  void Reset();

  MaintenanceOp* get() const;

 private:

  void Assign(MaintenanceOp* op);

  MaintenanceOp* op_;

};

} // namespace yb

#endif // YB_TABLET_MAINTENANCE_MANAGER_H