Lexicographically sortable, 128-bit identifier with 48-bit timestamp and 80 random bits. Canonically encoded as a 26 character string, as opposed to the 36 character UUID.
Original implementation and spec: https://github.com/alizain/ulid/
UUID can be suboptimal for many uses-cases because:
- It isn't the most character efficient way of encoding 128 bits of randomness
- UUID v1/v2 is impractical in many environments, as it requires access to a unique, stable MAC address
- UUID v3/v5 requires a unique seed and produces randomly distributed IDs, which can cause fragmentation in many data structures
- UUID v4 provides no other information than randomness which can cause fragmentation in many data structures
Instead, herein is proposed ULID:
- 128-bit compatibility with UUID
- 1.21e+24 unique ULIDs per millisecond
- Lexicographically sortable!
- Canonically encoded as a 26 character string, as opposed to the 36 character UUID
- Uses Crockford's base32 for better efficiency and readability (5 bits per character)
- Case insensitive
- No special characters (URL safe)
A simple usage example:
module Main where
import Data.ULID
main :: IO ()
main = do
-- Derive a ULID using the current time and default random number generator
ulid1 <- getULID
print ulid1
-- Derive a ULID using a specified time and default random number generator
ulid2 <- getULIDTime 1469918176.385 -- POSIX Time, specified to the millisecond
print ulid2As per the spec, it is also possible to use a cryptographically-secure random number generator to contribute the randomness. However, the programmer must manage the generator on their own. Example:
module Main where
import Data.ULID
import qualified Crypto.Random as CR
import qualified Data.ULID.Random as UR
import qualified Data.ULID.TimeStamp as TS
main :: IO ()
main = do
-- This default instantiation may not be sufficiently secure, see the docs
-- https://hackage.haskell.org/package/crypto-api-0.13.2/docs/Crypto-Random.html
g <- (CR.newGenIO :: IO CR.SystemRandom)
-- Generate time stamp from current time
t <- TS.getULIDTimeStamp
let ulid3 = case UR.mkCryptoULIDRandom g of
Left err -> error $ show err
Right (rnd, g2) -> ULID t rnd -- use g2, etc, to continue generating secure ULIDs
print ulid3stack test
stack bench
Running 1 benchmarks...
Benchmark ulid-bench: RUNNING...
217,868 op/s generate
Benchmark ulid-bench: FINISH