SeqNo Generator

a distributed sequence number generator based on MySQL.

Why?

Need a human call number on some cases(Restaurant etc...).

MySQL schema

CREATE TABLE `seqno_generator` (
  `id` bigint(18) NOT NULL AUTO_INCREMENT,
  `logic_id` char(32) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `prefix` char(32) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `last_id` bigint(18) DEFAULT NULL,
  `created_at` datetime DEFAULT NULL,
  `updated_at` datetime DEFAULT NULL,
  `deleted_at` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uni` (`logic_id`,`prefix`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

Examples

    
    //Open a gorm instance
    db, err := gorm.Open("mysql", "root:root@tcp(mysql:3306)/xxx?parseTime=true")
	if err != nil {
		b.Fatal(err)
	}
    
	seqno := NewSeqNoGenerator(db, "test-logic-id").
		PrefixFormat("2006-01-02").
		Step(1).
		Locker(NewRedisLocker(
		&redis.Pool{
			MaxIdle:     5,
			IdleTimeout: 30 * time.Second,
			Dial: func() (redis.Conn, error) {
				return redis.Dial("tcp", "redis:6379")
			},
		},
	))
	num,err := seqno.Next()

Options

Logic ID

Logic ID represents a concrete business logic(like order,user).

Step

Incremental step. default is 1

StartWith

Starting number. default is 1

PrefixFormat

date time format. default is empty. it's mean always use same increment queue. if set PrefixFormat to 2006-01-02, it's mean go to zero once a day.

Locker

locker is a distributed locker interface. already have redis & ETCD implementation on standard library.

Technical Model

1. Lock currently logic id.
2. Insert or Update New Value to MySQL(depend feature DUPLICATE KEY UPDATE ).
3. get last id.
4. Unlock logic id.

2 locker call and 2 MySQL call on a full flow.

ITS ON DEVELOPING STAGE,DONT USE IT ON PRODUCTION.