Generate XIDs, ObjectIds and Snowflakes

xid() generates XIDs: seconds since 1970, a 3-byte machine id, a 2-byte process id and a 3-byte counter. The reference derives the machine id from the host name through MD5; zuid draws three random bytes once per session instead, and machine takes the reference's bytes when they matter. The process id is R's, masked to 16 bits. The counter starts at a random value once per session and increments, wrapping at 2^24.

Usage

xid(n = 1, machine = NULL, process = Sys.getpid(), random = NULL, time = NULL)

objectid(n = 1, random = NULL, time = NULL)

snowflake(n = 1, layout, worker, time = NULL, rollback = c("error", "reset"))

Arguments

n

The number of UUIDs.

machine

For xid(), three raw bytes, or NULL for the session's random ones.

process

For xid(), the process id, Sys.getpid() by default.

random

NULL, or for reproducible values: 6 bytes for xid() (machine, then the counter's start) and 8 for objectid() (the random value, then the counter's start), used for this call only.

time

NULL for the current time, or a POSIXct (or a double of milliseconds since 1970) of length 1 or n.

layout

An id_layout().

worker

The node fields' values: one number when the layout has one node field, else a named list, such as list(datacenter = 1, worker = 7).

rollback

For snowflake(), what to do when the clock (or time) runs back further than the tolerance: "error" or "reset".

Value

A zuid vector of n values.

Details

objectid() generates BSON ObjectIds: seconds, a 5-byte random value drawn once per session, and a 3-byte counter started at a random value.

snowflake() generates Snowflakes under a layout. worker sets every node field, since duplicate node ids across machines are what Snowflake exists to prevent and only the caller can rule them out. The sequence starts at zero each tick and increments within it; when it overflows, generation moves to the next tick. One sequence serves every node value of a layout, so values for different workers interleave without repeats. A clock back by up to the option zuid.clock_tolerance (seconds, 0.01 by default) keeps the last tick. Further back, rollback = "error" raises zuid_clock_error, and rollback = "reset" restarts the layout's generator at the new time, which may repeat values made before.

Examples

xid(2)
#> <zuid_xid[2]>
#> [1] dbmsbt8vvbp1j5ht3ncg dbmsbt8vvbp1j5ht3nd0
objectid(2)
#> <zuid_objectid[2]>
#> [1] 6aedc5f5e751c00b902c9e70 6aedc5f5e751c00b902c9e71
snowflake(2, id_layout("twitter"), list(datacenter = 1, worker = 7))
#> <zuid_snowflake[2]>
#> [1] 2118679813110788096 2118679813110788097