dnm: playing with ulids

go.mod

@@ -215,6 +215,7 @@ require (
 	github.com/nicolai86/scaleway-sdk v1.10.2-0.20180628010248-798f60e20bb2 // indirect
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/oklog/run v1.0.1-0.20180308005104-6934b124db28 // indirect
+	github.com/oklog/ulid/v2 v2.0.2 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.0.2 // indirect
 	github.com/opencontainers/selinux v1.8.2 // indirect

go.sum

@@ -981,7 +981,10 @@ github.com/nxadm/tail v1.4.8/go.mod h1:+ncqLTQzXmGhMZNUePPaPqPvBxHAIsmXswZKocGu+
 github.com/oklog/run v1.0.0/go.mod h1:dlhp/R75TPv97u0XWUtDeV/lRKWPKSdTuV0TZvrmrQA=
 github.com/oklog/run v1.0.1-0.20180308005104-6934b124db28 h1:R9vmquWCeGmxTHUVnTQJrU4oPlgEn9+x48nwXSqkIKg=
 github.com/oklog/run v1.0.1-0.20180308005104-6934b124db28/go.mod h1:dlhp/R75TPv97u0XWUtDeV/lRKWPKSdTuV0TZvrmrQA=
+github.com/oklog/ulid v1.3.1 h1:EGfNDEx6MqHz8B3uNV6QAib1UR2Lm97sHi3ocA6ESJ4=
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
+github.com/oklog/ulid/v2 v2.0.2 h1:r4fFzBm+bv0wNKNh5eXTwU7i85y5x+uwkxCUTNVQqLc=
+github.com/oklog/ulid/v2 v2.0.2/go.mod h1:mtBL0Qe/0HAx6/a4Z30qxVIAL1eQDweXq5lxOEiwQ68=
 github.com/olekukonko/tablewriter v0.0.0-20170122224234-a0225b3f23b5/go.mod h1:vsDQFd/mU46D+Z4whnwzcISnGGzXWMclvtLoiIKAKIo=
 github.com/onsi/ginkgo v0.0.0-20151202141238-7f8ab55aaf3b/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/ginkgo v0.0.0-20170829012221-11459a886d9c/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
@@ -1038,6 +1041,7 @@ github.com/packethost/packngo v0.1.1-0.20180711074735-b9cb5096f54c/go.mod h1:otz
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pascaldekloe/goe v0.1.0 h1:cBOtyMzM9HTpWjXfbbunk26uA6nG3a8n06Wieeh0MwY=
 github.com/pascaldekloe/goe v0.1.0/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
+github.com/pborman/getopt v0.0.0-20170112200414-7148bc3a4c30/go.mod h1:85jBQOZwpVEaDAr341tbn15RS4fCAsIst0qp7i8ex1o=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pelletier/go-toml v1.8.1/go.mod h1:T2/BmBdy8dvIRq1a/8aqjN41wvWlN4lrapLU/GW4pbc=
 github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=

lib/ids/common.go

+package ids
+
+func Head(id string) string {
+	return id[0:4]
+}
+
+func Tail(id string) string {
+	return id[len(id)-4:]
+}

lib/ids/ulids.go

+package ids
+
+import (
+	"crypto/rand"
+	"fmt"
+	"time"
+
+	"github.com/hashicorp/go-uuid"
+	"oss.indeed.com/go/libtime"
+)
+
+// NewULID creates a new pseudo-ULID based on the ulid/spec. The output format
+// is that of a UUID rather than the compact form of a ULID.
+//
+// Specification of ULID:
+// https://github.com/ulid/spec
+//
+// This implementation *does not* guarantee monotonic increasing IDs within the
+// same millisecond.
+//
+// This implementation *is* safe to use across goroutines.
+func NewULID() string {
+	b := make([]byte, 16)
+
+	// first 6 bytes are based on timestamp
+	ms := libtime.ToMilliseconds(time.Now().UTC())
+	b[0] = byte(ms >> 40)
+	b[1] = byte(ms >> 32)
+	b[2] = byte(ms >> 24)
+	b[3] = byte(ms >> 16)
+	b[4] = byte(ms >> 8)
+	b[5] = byte(ms)
+
+	// last 10 bytes are based on true random
+	n, rndErr := rand.Read(b[6:])
+	if rndErr != nil {
+		panic(fmt.Errorf("failed to generate ulid: %v", rndErr))
+	}
+	if n != 10 {
+		panic("failed to generate ulid: not enough random bytes")
+	}
+
+	// we like our ULIDs formatted as UUIDs
+	s, fmtErr := uuid.FormatUUID(b)
+	if fmtErr != nil {
+		panic(fmt.Errorf("failed to format ulid as uuid: %v", fmtErr))
+	}
+
+	return s
+}

lib/ids/ulids_test.go

+package ids
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func Test_NewULID(t *testing.T) {
+
+	// create 10 ULIDs quickly; the first few bytes should be the same
+	// and the last few bytes should be completely random
+	var ulids [10]string
+	for i := 0; i < 10; i++ {
+		ulids[i] = NewULID()
+		time.Sleep(1*time.Millisecond + 1)
+		fmt.Println(ulids[i])
+	}
+
+}

lib/ids/uuids.go

+package ids
+
+import (
+	"github.com/hashicorp/go-uuid"
+)
+
+type UUID = string
+
+func NewUUID() UUID {
+	id, err := uuid.GenerateUUID()
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+func ShortUUID(id UUID) string {
+	return NewUUID()[0:4]
+}