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[ruby/securerandom] Add support for UUID version 7
Although the specification for UUIDv7 is still in draft, the UUIDv7 algorithm has been relatively stable as it progresses to completion. Version 7 UUIDs can be very useful, because they are lexographically sortable, which can improve e.g: database index locality. See section 6.10 of the draft specification for further explanation: https://datatracker.ietf.org/doc/draft-ietf-uuidrev-rfc4122bis/ The specification allows up to 12 bits of extra timestamp precision, to make UUID generation closer to monotonically increasing. This provides between 1ms and ~240ns of timestamp precision. At the cost of some code complexity and a small performance penalty, a kwarg may specify any arbitrary precision between 0 and 12 extra bits. Any stronger guarantees of monotonicity have considerably larger tradeoffs, so nothing more is implemented. This limitation is documented. Ruby issue: https://bugs.ruby-lang.org/issues/19735 https://github.com/ruby/securerandom/commit/34ed1a2ec3
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nick evans
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@ -174,6 +174,125 @@ module Random::Formatter
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"%08x-%04x-%04x-%04x-%04x%08x" % ary
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end
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alias uuid_v4 uuid
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# Generate a random v7 UUID (Universally Unique IDentifier).
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#
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# require 'random/formatter'
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#
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# Random.uuid_v7 # => "0188d4c3-1311-7f96-85c7-242a7aa58f1e"
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# Random.uuid_v7 # => "0188d4c3-16fe-744f-86af-38fa04c62bb5"
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# Random.uuid_v7 # => "0188d4c3-1af8-764f-b049-c204ce0afa23"
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# Random.uuid_v7 # => "0188d4c3-1e74-7085-b14f-ef6415dc6f31"
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# # |<--sorted-->| |<----- random ---->|
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#
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# # or
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# prng = Random.new
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# prng.uuid_v7 # => "0188ca51-5e72-7950-a11d-def7ff977c98"
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#
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# The version 7 UUID starts with the least significant 48 bits of a 64 bit
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# Unix timestamp (milliseconds since the epoch) and fills the remaining bits
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# with random data, excluding the version and variant bits.
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#
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# This allows version 7 UUIDs to be sorted by creation time. Time ordered
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# UUIDs can be used for better database index locality of newly inserted
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# records, which may have a significant performance benefit compared to random
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# data inserts.
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#
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# The result contains 74 random bits (9.25 random bytes).
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#
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# Note that this method cannot be made reproducable with Kernel#srand, which
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# can only affect the random bits. The sorted bits will still be based on
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# Process.clock_gettime.
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#
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# See draft-ietf-uuidrev-rfc4122bis[https://datatracker.ietf.org/doc/draft-ietf-uuidrev-rfc4122bis/]
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# for details of UUIDv7.
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#
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# ==== Monotonicity
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#
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# UUIDv7 has millisecond precision by default, so multiple UUIDs created
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# within the same millisecond are not issued in monotonically increasing
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# order. To create UUIDs that are time-ordered with sub-millisecond
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# precision, up to 12 bits of additional timestamp may added with
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# +extra_timestamp_bits+. The extra timestamp precision comes at the expense
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# of random bits. Setting <tt>extra_timestamp_bits: 12</tt> provides ~244ns
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# of precision, but only 62 random bits (7.75 random bytes).
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#
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# prng = Random.new
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# Array.new(4) { prng.uuid_v7(extra_timestamp_bits: 12) }
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# # =>
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# ["0188d4c7-13da-74f9-8b53-22a786ffdd5a",
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# "0188d4c7-13da-753b-83a5-7fb9b2afaeea",
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# "0188d4c7-13da-754a-88ea-ac0baeedd8db",
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# "0188d4c7-13da-7557-83e1-7cad9cda0d8d"]
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# # |<--- sorted --->| |<-- random --->|
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#
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# Array.new(4) { prng.uuid_v7(extra_timestamp_bits: 8) }
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# # =>
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# ["0188d4c7-3333-7a95-850a-de6edb858f7e",
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# "0188d4c7-3333-7ae8-842e-bc3a8b7d0cf9", # <- out of order
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# "0188d4c7-3333-7ae2-995a-9f135dc44ead", # <- out of order
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# "0188d4c7-3333-7af9-87c3-8f612edac82e"]
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# # |<--- sorted -->||<---- random --->|
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#
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# Any rollbacks of the system clock will break monotonicity. UUIDv7 is based
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# on UTC, which excludes leap seconds and can rollback the clock. To avoid
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# this, the system clock can synchronize with an NTP server configured to use
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# a "leap smear" approach. NTP or PTP will also be needed to synchronize
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# across distributed nodes.
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#
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# Counters and other mechanisms for stronger guarantees of monotonicity are
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# not implemented. Applications with stricter requirements should follow
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# {Section 6.2}[https://www.ietf.org/archive/id/draft-ietf-uuidrev-rfc4122bis-07.html#monotonicity_counters]
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# of the specification.
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#
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def uuid_v7(extra_timestamp_bits: 0)
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case (extra_timestamp_bits = Integer(extra_timestamp_bits))
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when 0 # min timestamp precision
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ms = Process.clock_gettime(Process::CLOCK_REALTIME, :millisecond)
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rand = random_bytes(10)
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rand.setbyte(0, rand.getbyte(0) & 0x0f | 0x70) # version
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rand.setbyte(2, rand.getbyte(2) & 0x3f | 0x80) # variant
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"%08x-%04x-%s" % [
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(ms & 0x0000_ffff_ffff_0000) >> 16,
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(ms & 0x0000_0000_0000_ffff),
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rand.unpack("H4H4H12").join("-")
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]
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when 12 # max timestamp precision
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ms, ns = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
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.divmod(1_000_000)
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extra_bits = ns * 4096 / 1_000_000
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rand = random_bytes(8)
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rand.setbyte(0, rand.getbyte(0) & 0x3f | 0x80) # variant
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"%08x-%04x-7%03x-%s" % [
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(ms & 0x0000_ffff_ffff_0000) >> 16,
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(ms & 0x0000_0000_0000_ffff),
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extra_bits,
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rand.unpack("H4H12").join("-")
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]
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when (0..12) # the generic version is slower than the special cases above
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rand_a, rand_b1, rand_b2, rand_b3 = random_bytes(10).unpack("nnnN")
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rand_mask_bits = 12 - extra_timestamp_bits
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ms, ns = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
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.divmod(1_000_000)
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"%08x-%04x-%04x-%04x-%04x%08x" % [
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(ms & 0x0000_ffff_ffff_0000) >> 16,
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(ms & 0x0000_0000_0000_ffff),
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0x7000 |
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((ns * (1 << extra_timestamp_bits) / 1_000_000) << rand_mask_bits) |
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rand_a & ((1 << rand_mask_bits) - 1),
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0x8000 | (rand_b1 & 0x3fff),
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rand_b2,
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rand_b3
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]
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else
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raise ArgumentError, "extra_timestamp_bits must be in 0..12"
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end
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end
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private def gen_random(n)
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self.bytes(n)
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end
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@ -75,6 +75,54 @@ module Random::Formatter
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assert_match(/\A\h{8}-\h{4}-\h{4}-\h{4}-\h{12}\z/, uuid)
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end
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def test_uuid_v7(extra_timestamp_bits)
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t1 = current_uuid7_time
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uuid = @it.uuid_v7
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t3 = current_uuid7_time
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assert_match(/\A\h{8}-\h{4}-7\h{3}-[89ab]\h{3}-\h{12}\z/, uuid)
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t2 = get_uuid7_time(uuid)
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assert_operator(t1, :<=, t2)
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assert_operator(t2, :<=, t3)
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end
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def test_uuid_v7_extra_timestamp_bits
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0.upto(12) do |extra_timestamp_bits|
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t1 = current_uuid7_time extra_timestamp_bits: extra_timestamp_bits
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uuid = @it.uuid_v7 extra_timestamp_bits: extra_timestamp_bits
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t3 = current_uuid7_time extra_timestamp_bits: extra_timestamp_bits
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assert_match(/\A\h{8}-\h{4}-7\h{3}-[89ab]\h{3}-\h{12}\z/, uuid)
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t2 = get_uuid7_time uuid, extra_timestamp_bits: extra_timestamp_bits
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assert_operator(t1, :<=, t2)
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assert_operator(t2, :<=, t3)
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end
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end
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# It would be nice to simply use Time#floor here. But that is problematic
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# due to the difference between decimal vs binary fractions.
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def current_uuid7_time(extra_timestamp_bits: 0)
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denominator = (1 << extra_timestamp_bits).to_r
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Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
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.then {|ns| ((ns / 1_000_000r) * denominator).floor / denominator }
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.then {|ms| Time.at(ms / 1000r, in: "+00:00") }
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end
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def get_uuid7_time(uuid, extra_timestamp_bits: 0)
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denominator = (1 << extra_timestamp_bits) * 1000r
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extra_chars = extra_timestamp_bits / 4
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last_char_bits = extra_timestamp_bits % 4
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extra_chars += 1 if last_char_bits != 0
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timestamp_re = /\A(\h{8})-(\h{4})-7(\h{#{extra_chars}})/
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timestamp_chars = uuid.match(timestamp_re).captures.join
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timestamp = timestamp_chars.to_i(16)
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timestamp >>= 4 - last_char_bits unless last_char_bits == 0
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timestamp /= denominator
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Time.at timestamp, in: "+00:00"
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end
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def test_alphanumeric
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65.times do |n|
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an = @it.alphanumeric(n)
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