CosIdGenerator

CosIdGenerator generates time-ordered string IDs for very large clusters. Its 80-bit layout leaves 20 bits for the machine id, about a million instances in one namespace, where a 63-bit Snowflake ID has room for 1024.

Layout

timestamp (44 bits) + machine id (20 bits) + sequence (16 bits) = 80 bits

• Timestamp: milliseconds since the Unix epoch.
• Machine id: leased like a Snowflake machine id, see Machine ID, with cosid.generator.machine-bit bits (20 by default). Give the generator its own cosid.generator.namespace: an instance holds one machine id per namespace, and one leased for 20 bits may not fit a 10-bit Snowflake layout in the same namespace.
• Sequence: 65,536 IDs per millisecond per instance, restarting past half its range like the Snowflake sequence.

The ID is the three parts encoded as fixed-width strings, so IDs sort as strings in the order they were generated, and the parts can be parsed back (getStateParser().asState(id)).

Type	Encoding	Length	Characters per part
RADIX62 (default)	0-9A-Za-z	15 characters	timestamp 8 + machine id 4 + sequence 3
RADIX36	0-9A-Z	17 characters	timestamp 9 + machine id 4 + sequence 4
FRIENDLY	yyyyMMddHHmmssSSS-machineId-sequence	variable	readable, in cosid.generator.zone-id

Radix-62 IDs are case sensitive: store them in a case-sensitive (binary) column.

Properties

• Time-ordered: increasing per instance, trend increasing across instances.
• Local: generation needs no store call after the machine id is leased.
• Short: 15 characters, against 36 for a UUID string.

CosIdGenerator is a StringIdGenerator: it has no long form, so it cannot fill a long field or serve as the share generator.

Configuration

cosid:
  namespace: ${spring.application.name}
  machine:
    enabled: true
    distributor:
      type: redis
  generator:
    enabled: true

The starter registers a CosIdGenerator bean, which is also registered in the IdGeneratorProvider as cosid. Annotate a String field with @CosId("cosid") to fill it with this generator. See the CosIdGenerator configuration.