// Copyright (c) 2013, Facebook, Inc.  All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.

#ifndef STORAGE_ROCKSDB_INCLUDE_STATISTICS_H_
#define STORAGE_ROCKSDB_INCLUDE_STATISTICS_H_

#include <atomic>
#include <cstddef>
#include <cstdint>
#include <string>
#include <memory>
#include <vector>

namespace rocksdb {

/**
 * Keep adding ticker's here.
 *  1. Any ticker should be added before TICKER_ENUM_MAX.
 *  2. Add a readable string in TickersNameMap below for the newly added ticker.
 */
enum Tickers {
  // total block cache misses
  // REQUIRES: BLOCK_CACHE_MISS == BLOCK_CACHE_INDEX_MISS +
  //                               BLOCK_CACHE_FILTER_MISS +
  //                               BLOCK_CACHE_DATA_MISS;
  BLOCK_CACHE_MISS,
  // total block cache hit
  // REQUIRES: BLOCK_CACHE_HIT == BLOCK_CACHE_INDEX_HIT +
  //                              BLOCK_CACHE_FILTER_HIT +
  //                              BLOCK_CACHE_DATA_HIT;
  BLOCK_CACHE_HIT,
  // # of blocks added to block cache.
  BLOCK_CACHE_ADD,
  // # of times cache miss when accessing index block from block cache.
  BLOCK_CACHE_INDEX_MISS,
  // # of times cache hit when accessing index block from block cache.
  BLOCK_CACHE_INDEX_HIT,
  // # of times cache miss when accessing filter block from block cache.
  BLOCK_CACHE_FILTER_MISS,
  // # of times cache hit when accessing filter block from block cache.
  BLOCK_CACHE_FILTER_HIT,
  // # of times cache miss when accessing data block from block cache.
  BLOCK_CACHE_DATA_MISS,
  // # of times cache hit when accessing data block from block cache.
  BLOCK_CACHE_DATA_HIT,
  // # of times bloom filter has avoided file reads.
  BLOOM_FILTER_USEFUL,

  // # of memtable hits.
  MEMTABLE_HIT,
  // # of memtable misses.
  MEMTABLE_MISS,

  /**
   * COMPACTION_KEY_DROP_* count the reasons for key drop during compaction
   * There are 3 reasons currently.
   */
  COMPACTION_KEY_DROP_NEWER_ENTRY, // key was written with a newer value.
  COMPACTION_KEY_DROP_OBSOLETE, // The key is obsolete.
  COMPACTION_KEY_DROP_USER, // user compaction function has dropped the key.

  // Number of keys written to the database via the Put and Write call's
  NUMBER_KEYS_WRITTEN,
  // Number of Keys read,
  NUMBER_KEYS_READ,
  // Number keys updated, if inplace update is enabled
  NUMBER_KEYS_UPDATED,
  // Bytes written / read
  BYTES_WRITTEN,
  BYTES_READ,
  NO_FILE_CLOSES,
  NO_FILE_OPENS,
  NO_FILE_ERRORS,
  // Time system had to wait to do LO-L1 compactions
  STALL_L0_SLOWDOWN_MICROS,
  // Time system had to wait to move memtable to L1.
  STALL_MEMTABLE_COMPACTION_MICROS,
  // write throttle because of too many files in L0
  STALL_L0_NUM_FILES_MICROS,
  RATE_LIMIT_DELAY_MILLIS,

  NO_ITERATORS, // number of iterators currently open

  // Number of MultiGet calls, keys read, and bytes read
  NUMBER_MULTIGET_CALLS,
  NUMBER_MULTIGET_KEYS_READ,
  NUMBER_MULTIGET_BYTES_READ,

  // Number of deletes records that were not required to be
  // written to storage because key does not exist
  NUMBER_FILTERED_DELETES,
  NUMBER_MERGE_FAILURES,
  SEQUENCE_NUMBER,

  // number of times bloom was checked before creating iterator on a
  // file, and the number of times the check was useful in avoiding
  // iterator creation (and thus likely IOPs).
  BLOOM_FILTER_PREFIX_CHECKED,
  BLOOM_FILTER_PREFIX_USEFUL,

  // Number of times we had to reseek inside an iteration to skip
  // over large number of keys with same userkey.
  NUMBER_OF_RESEEKS_IN_ITERATION,

  // Record the number of calls to GetUpadtesSince. Useful to keep track of
  // transaction log iterator refreshes
  GET_UPDATES_SINCE_CALLS,

  BLOCK_CACHE_COMPRESSED_MISS, // miss in the compressed block cache
  BLOCK_CACHE_COMPRESSED_HIT,  // hit in the compressed block cache

  TICKER_ENUM_MAX
};

// The order of items listed in  Tickers should be the same as
// the order listed in TickersNameMap
const std::vector<std::pair<Tickers, std::string>> TickersNameMap = {
  { BLOCK_CACHE_MISS,                 "rocksdb.block.cache.miss"             },
  { BLOCK_CACHE_HIT,                  "rocksdb.block.cache.hit"              },
  { BLOCK_CACHE_ADD,                  "rocksdb.block.cache.add"              },
  { BLOCK_CACHE_INDEX_MISS,           "rocksdb.block.cache.index.miss"       },
  { BLOCK_CACHE_INDEX_HIT,            "rocksdb.block.cache.index.hit"        },
  { BLOCK_CACHE_FILTER_MISS,          "rocksdb.block.cache.filter.miss"      },
  { BLOCK_CACHE_FILTER_HIT,           "rocksdb.block.cache.filter.hit"       },
  { BLOCK_CACHE_DATA_MISS,            "rocksdb.block.cache.data.miss"        },
  { BLOCK_CACHE_DATA_HIT,             "rocksdb.block.cache.data.hit"         },
  { BLOOM_FILTER_USEFUL,              "rocksdb.bloom.filter.useful"          },
  { MEMTABLE_HIT,                     "rocksdb.memtable.hit"                 },
  { MEMTABLE_MISS,                    "rocksdb.memtable.miss"                },
  { COMPACTION_KEY_DROP_NEWER_ENTRY,  "rocksdb.compaction.key.drop.new"      },
  { COMPACTION_KEY_DROP_OBSOLETE,     "rocksdb.compaction.key.drop.obsolete" },
  { COMPACTION_KEY_DROP_USER,         "rocksdb.compaction.key.drop.user"     },
  { NUMBER_KEYS_WRITTEN,              "rocksdb.number.keys.written"          },
  { NUMBER_KEYS_READ,                 "rocksdb.number.keys.read"             },
  { NUMBER_KEYS_UPDATED,              "rocksdb.number.keys.updated"          },
  { BYTES_WRITTEN,                    "rocksdb.bytes.written"                },
  { BYTES_READ,                       "rocksdb.bytes.read"                   },
  { NO_FILE_CLOSES,                   "rocksdb.no.file.closes"               },
  { NO_FILE_OPENS,                    "rocksdb.no.file.opens"                },
  { NO_FILE_ERRORS,                   "rocksdb.no.file.errors"               },
  { STALL_L0_SLOWDOWN_MICROS,         "rocksdb.l0.slowdown.micros"           },
  { STALL_MEMTABLE_COMPACTION_MICROS, "rocksdb.memtable.compaction.micros"   },
  { STALL_L0_NUM_FILES_MICROS,        "rocksdb.l0.num.files.stall.micros"    },
  { RATE_LIMIT_DELAY_MILLIS,          "rocksdb.rate.limit.delay.millis"      },
  { NO_ITERATORS,                     "rocksdb.num.iterators"                },
  { NUMBER_MULTIGET_CALLS,            "rocksdb.number.multiget.get"          },
  { NUMBER_MULTIGET_KEYS_READ,        "rocksdb.number.multiget.keys.read"    },
  { NUMBER_MULTIGET_BYTES_READ,       "rocksdb.number.multiget.bytes.read"   },
  { NUMBER_FILTERED_DELETES,          "rocksdb.number.deletes.filtered"      },
  { NUMBER_MERGE_FAILURES,            "rocksdb.number.merge.failures"        },
  { SEQUENCE_NUMBER,                  "rocksdb.sequence.number"              },
  { BLOOM_FILTER_PREFIX_CHECKED,      "rocksdb.bloom.filter.prefix.checked"  },
  { BLOOM_FILTER_PREFIX_USEFUL,       "rocksdb.bloom.filter.prefix.useful"   },
  { NUMBER_OF_RESEEKS_IN_ITERATION,   "rocksdb.number.reseeks.iteration"     },
  { GET_UPDATES_SINCE_CALLS,          "rocksdb.getupdatessince.calls"        },
  { BLOCK_CACHE_COMPRESSED_MISS,      "rocksdb.block.cachecompressed.miss"   },
  { BLOCK_CACHE_COMPRESSED_HIT,       "rocksdb.block.cachecompressed.hit"    },
};

/**
 * Keep adding histogram's here.
 * Any histogram whould have value less than HISTOGRAM_ENUM_MAX
 * Add a new Histogram by assigning it the current value of HISTOGRAM_ENUM_MAX
 * Add a string representation in HistogramsNameMap below
 * And increment HISTOGRAM_ENUM_MAX
 */
enum Histograms {
  DB_GET,
  DB_WRITE,
  COMPACTION_TIME,
  TABLE_SYNC_MICROS,
  COMPACTION_OUTFILE_SYNC_MICROS,
  WAL_FILE_SYNC_MICROS,
  MANIFEST_FILE_SYNC_MICROS,
  // TIME SPENT IN IO DURING TABLE OPEN
  TABLE_OPEN_IO_MICROS,
  DB_MULTIGET,
  READ_BLOCK_COMPACTION_MICROS,
  READ_BLOCK_GET_MICROS,
  WRITE_RAW_BLOCK_MICROS,

  STALL_L0_SLOWDOWN_COUNT,
  STALL_MEMTABLE_COMPACTION_COUNT,
  STALL_L0_NUM_FILES_COUNT,
  HARD_RATE_LIMIT_DELAY_COUNT,
  SOFT_RATE_LIMIT_DELAY_COUNT,
  NUM_FILES_IN_SINGLE_COMPACTION,
  HISTOGRAM_ENUM_MAX,
};

const std::vector<std::pair<Histograms, std::string>> HistogramsNameMap = {
  { DB_GET, "rocksdb.db.get.micros" },
  { DB_WRITE, "rocksdb.db.write.micros" },
  { COMPACTION_TIME, "rocksdb.compaction.times.micros" },
  { TABLE_SYNC_MICROS, "rocksdb.table.sync.micros" },
  { COMPACTION_OUTFILE_SYNC_MICROS, "rocksdb.compaction.outfile.sync.micros" },
  { WAL_FILE_SYNC_MICROS, "rocksdb.wal.file.sync.micros" },
  { MANIFEST_FILE_SYNC_MICROS, "rocksdb.manifest.file.sync.micros" },
  { TABLE_OPEN_IO_MICROS, "rocksdb.table.open.io.micros" },
  { DB_MULTIGET, "rocksdb.db.multiget.micros" },
  { READ_BLOCK_COMPACTION_MICROS, "rocksdb.read.block.compaction.micros" },
  { READ_BLOCK_GET_MICROS, "rocksdb.read.block.get.micros" },
  { WRITE_RAW_BLOCK_MICROS, "rocksdb.write.raw.block.micros" },
  { STALL_L0_SLOWDOWN_COUNT, "rocksdb.l0.slowdown.count"},
  { STALL_MEMTABLE_COMPACTION_COUNT, "rocksdb.memtable.compaction.count"},
  { STALL_L0_NUM_FILES_COUNT, "rocksdb.num.files.stall.count"},
  { HARD_RATE_LIMIT_DELAY_COUNT, "rocksdb.hard.rate.limit.delay.count"},
  { SOFT_RATE_LIMIT_DELAY_COUNT, "rocksdb.soft.rate.limit.delay.count"},
  { NUM_FILES_IN_SINGLE_COMPACTION, "rocksdb.numfiles.in.singlecompaction" },
};

struct HistogramData {
  double median;
  double percentile95;
  double percentile99;
  double average;
  double standard_deviation;
};


class Histogram {
 public:
  // clear's the histogram
  virtual void Clear() = 0;
  virtual ~Histogram();
  // Add a value to be recorded in the histogram.
  virtual void Add(uint64_t value) = 0;

  virtual std::string ToString() const = 0;

  // Get statistics
  virtual double Median() const = 0;
  virtual double Percentile(double p) const = 0;
  virtual double Average() const = 0;
  virtual double StandardDeviation() const = 0;
  virtual void Data(HistogramData * const data) const = 0;

};

/**
 * A dumb ticker which keeps incrementing through its life time.
 * Thread safe. Locking managed by implementation of this interface.
 */
class Ticker {
 public:
  Ticker() : count_(0) { }

  inline void setTickerCount(uint64_t count) {
    count_ = count;
  }

  inline void recordTick(int64_t count = 1) {
    count_ += count;
  }

  inline uint64_t getCount() {
    return count_;
  }

 private:
  std::atomic_uint_fast64_t count_;
};

// Analyze the performance of a db
class Statistics {
 public:
  virtual long getTickerCount(Tickers tickerType) = 0;
  virtual void recordTick(Tickers tickerType, uint64_t count = 0) = 0;
  virtual void setTickerCount(Tickers tickerType, uint64_t count) = 0;
  virtual void measureTime(Histograms histogramType, uint64_t time) = 0;

  virtual void histogramData(Histograms type, HistogramData* const data) = 0;
  // String representation of the statistic object.
  std::string ToString();
};

// Create a concrete DBStatistics object
std::shared_ptr<Statistics> CreateDBStatistics();

}  // namespace rocksdb

#endif  // STORAGE_ROCKSDB_INCLUDE_STATISTICS_H_