Class: RedisInt64Autoincrement

Inherits:
Object
  • Object
show all
Defined in:
lib/redis_int64_autoincrement.rb

Defined Under Namespace

Modules: Version

Constant Summary collapse

REDIS_KEY_TTL_SECONDS =

Why 50 seconds? Easy to debug and more than enouth for sync time delta shift. You can use 10 or 5 seconds - and all must working normal too. 50seconds was chosen by me without any explanation. Just took this value, i do not know why.

50
MAX_BUFFER_BITS_CNT =

Do not use all 64 bits - in this case signed Int64 can be less than result uid

63
TIMESTAMP_BITS_CNT =

34bits for 150+ years more than enougth

34.freeze
TIMESTAMP_MICROSECONDS_BITS_CNT =

0..999_999 - require 20bits

20.freeze
INCREMENTED_ID_BITS_CNT =

7bits for 0..127 INCREMENTED_UINT8_ID

7.freeze
SERVER_ID_BITS_CNT = 
2.freeze
TIMESTAMP_SECONDS_SHIFT_LEFT_CNT =

So in result: 34 + 20 + 7 + 2 = 63bits(MAX_BUFFER_BITS_CNT).

(TIMESTAMP_MICROSECONDS_BITS_CNT + INCREMENTED_ID_BITS_CNT + SERVER_ID_BITS_CNT).freeze
TIMESTAMP_MICROSECONDS_SHIFT_LEFT_CNT =

9 bits

(INCREMENTED_ID_BITS_CNT + SERVER_ID_BITS_CNT).freeze
INCREMENTED_ID_MAX_VAL =

1111111b=127

((1 << INCREMENTED_ID_BITS_CNT) - 1).freeze
UINT63_MAX_VAL =

2^63 = 9223372036854775808

9223372036854775808
LIB_FIRST_VAL =

First id was generated 23.12.2023 at ~17:30 (Kiev +2:00)

914476352027817480
VERSION = 
Version::STRING

Class Method Summary collapse

Class Method Details

.generate(redis, namespace = 'default', options = {}) ⇒ Object 



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# File 'lib/redis_int64_autoincrement.rb', line 33

def generate(redis, namespace = 'default', options = {})
  server_id = options[:server_id] || 0
  time_redis = options[:time_redis] || redis
  raise("Wrong server_id[#{server_id}]. Allow only 0..3 server_id") unless server_id.between?(0, 3)
  time_arr = time_redis.time
  raise("Wrong time type[#{time_arr.inspect}]") unless time_arr.count.eql?(2)
  unix_seconds = time_arr.first.to_i
  first_part = unix_seconds << TIMESTAMP_SECONDS_SHIFT_LEFT_CNT

  microseconds = time_arr[1].to_i
  raise("Wrong microseconds [#{microseconds}]") unless microseconds.between?(0, 999_999)
  second_part = microseconds << TIMESTAMP_MICROSECONDS_SHIFT_LEFT_CNT

  key = "ai64:#{namespace}:#{unix_seconds}:#{microseconds}"
  incremented_val = redis.incrby(key, 1)
  redis.expire(key, REDIS_KEY_TTL_SECONDS)
  raise("Wrong incremented_val [#{incremented_val}]") unless incremented_val.between?(0, INCREMENTED_ID_MAX_VAL)
  third_part = incremented_val << SERVER_ID_BITS_CNT
  result = ((first_part | second_part) | third_part) | server_id
  raise("Wrong result[#{result}]") unless result.between?(LIB_FIRST_VAL, UINT63_MAX_VAL)
  result
end