tsweb: change RequestID format to have a date in it

So we can locate them in logs more easily.

Updates tailscale/corp#24721

Change-Id: Ia766c75608050dde7edc99835979a6e9bb328df2
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/derper/depaware.txt

@@ -27,7 +27,6 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
    L    github.com/google/nftables/expr                              from github.com/google/nftables+
    L    github.com/google/nftables/internal/parseexprfunc            from github.com/google/nftables+
    L    github.com/google/nftables/xt                                from github.com/google/nftables/expr+
-        github.com/google/uuid                                       from tailscale.com/util/fastuuid
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
    L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/netmon
@@ -152,7 +151,6 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
      💣 tailscale.com/util/deephash                                  from tailscale.com/util/syspolicy/setting
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/hostinfo+
-        tailscale.com/util/fastuuid                                  from tailscale.com/tsweb
      💣 tailscale.com/util/hashx                                     from tailscale.com/util/deephash
         tailscale.com/util/httpm                                     from tailscale.com/client/tailscale
         tailscale.com/util/lineiter                                  from tailscale.com/hostinfo+
@@ -160,6 +158,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/util/mak                                       from tailscale.com/health+
         tailscale.com/util/multierr                                  from tailscale.com/health+
         tailscale.com/util/nocasemaps                                from tailscale.com/types/ipproto
+        tailscale.com/util/rands                                     from tailscale.com/tsweb
         tailscale.com/util/set                                       from tailscale.com/derp+
         tailscale.com/util/singleflight                              from tailscale.com/net/dnscache
         tailscale.com/util/slicesx                                   from tailscale.com/cmd/derper+
@@ -244,7 +243,6 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         crypto/tls                                                   from golang.org/x/crypto/acme+
         crypto/x509                                                  from crypto/tls+
         crypto/x509/pkix                                             from crypto/x509+
-        database/sql/driver                                          from github.com/google/uuid
         embed                                                        from crypto/internal/nistec+
         encoding                                                     from encoding/json+
         encoding/asn1                                                from crypto/x509+
@@ -276,7 +274,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from github.com/mdlayher/netlink+
-        math/rand/v2                                                 from tailscale.com/util/fastuuid+
+        math/rand/v2                                                 from internal/concurrent+
         mime                                                         from github.com/prometheus/common/expfmt+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart

cmd/derper/derper_test.go

@@ -109,6 +109,7 @@ func TestDeps(t *testing.T) {
 			"gvisor.dev/gvisor/pkg/tcpip/header": "https://github.com/tailscale/tailscale/issues/9756",
 			"tailscale.com/net/packet":           "not needed in derper",
 			"github.com/gaissmai/bart":           "not needed in derper",
+			"database/sql/driver":                "not needed in derper", // previously came in via github.com/google/uuid
 		},
 	}.Check(t)
 }

cmd/stund/depaware.txt

@@ -8,7 +8,6 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         github.com/go-json-experiment/json/internal/jsonopts         from github.com/go-json-experiment/json+
         github.com/go-json-experiment/json/internal/jsonwire         from github.com/go-json-experiment/json+
         github.com/go-json-experiment/json/jsontext                  from github.com/go-json-experiment/json+
-        github.com/google/uuid                                       from tailscale.com/util/fastuuid
      💣 github.com/prometheus/client_golang/prometheus               from tailscale.com/tsweb/promvarz
         github.com/prometheus/client_golang/prometheus/internal      from github.com/prometheus/client_golang/prometheus
         github.com/prometheus/client_model/go                        from github.com/prometheus/client_golang/prometheus+
@@ -74,9 +73,9 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/util/ctxkey                                    from tailscale.com/tsweb+
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/tailcfg
-        tailscale.com/util/fastuuid                                  from tailscale.com/tsweb
         tailscale.com/util/lineiter                                  from tailscale.com/version/distro
         tailscale.com/util/nocasemaps                                from tailscale.com/types/ipproto
+        tailscale.com/util/rands                                     from tailscale.com/tsweb
         tailscale.com/util/slicesx                                   from tailscale.com/tailcfg
         tailscale.com/util/vizerror                                  from tailscale.com/tailcfg+
         tailscale.com/version                                        from tailscale.com/envknob+
@@ -133,7 +132,6 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         crypto/tls                                                   from net/http+
         crypto/x509                                                  from crypto/tls
         crypto/x509/pkix                                             from crypto/x509
-        database/sql/driver                                          from github.com/google/uuid
         embed                                                        from crypto/internal/nistec+
         encoding                                                     from encoding/json+
         encoding/asn1                                                from crypto/x509+
@@ -164,7 +162,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from math/big+
-        math/rand/v2                                                 from tailscale.com/util/fastuuid+
+        math/rand/v2                                                 from internal/concurrent+
         mime                                                         from github.com/prometheus/common/expfmt+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart

tsweb/request_id.go

@@ -6,9 +6,10 @@ package tsweb
 import (
 	"context"
 	"net/http"
+	"time"
 
 	"tailscale.com/util/ctxkey"
-	"tailscale.com/util/fastuuid"
+	"tailscale.com/util/rands"
 )
 
 // RequestID is an opaque identifier for a HTTP request, used to correlate
@@ -41,10 +42,12 @@ const RequestIDHeader = "X-Tailscale-Request-Id"
 
 // GenerateRequestID generates a new request ID with the current format.
 func GenerateRequestID() RequestID {
-	// REQ-1 indicates the version of the RequestID pattern. It is
-	// currently arbitrary but allows for forward compatible
-	// transitions if needed.
-	return RequestID("REQ-1" + fastuuid.NewUUID().String())
+	// Return a string of the form "REQ-<VersionByte><...>"
+	// Previously we returned "REQ-1<UUIDString>".
+	// Now we return "REQ-2" version, where the "2" doubles as the year 2YYY
+	// in a leading date.
+	now := time.Now().UTC()
+	return RequestID("REQ-" + now.Format("20060102150405") + rands.HexString(16))
 }
 
 // SetRequestID is an HTTP middleware that injects a RequestID in the

tsweb/tsweb_test.go

@@ -1307,6 +1307,28 @@ func TestBucket(t *testing.T) {
 	}
 }
 
+func TestGenerateRequestID(t *testing.T) {
+	t0 := time.Now()
+	got := GenerateRequestID()
+	t.Logf("Got: %q", got)
+	if !strings.HasPrefix(string(got), "REQ-2") {
+		t.Errorf("expect REQ-2 prefix; got %q", got)
+	}
+	const wantLen = len("REQ-2024112022140896f8ead3d3f3be27")
+	if len(got) != wantLen {
+		t.Fatalf("len = %d; want %d", len(got), wantLen)
+	}
+	d := got[len("REQ-"):][:14]
+	timeBack, err := time.Parse("20060102150405", string(d))
+	if err != nil {
+		t.Fatalf("parsing time back: %v", err)
+	}
+	elapsed := timeBack.Sub(t0)
+	if elapsed > 3*time.Second { // allow for slow github actions runners :)
+		t.Fatalf("time back was %v; want within 3s", elapsed)
+	}
+}
+
 func ExampleMiddlewareStack() {
 	// setHeader returns a middleware that sets header k = vs.
 	setHeader := func(k string, vs ...string) Middleware {