roachpb: print observed timestamps in txn

Split out from #143270.

Epic: none

Release note: None

Author: tbg

pkg/kv/kvpb/errors_test.go

@@ -171,6 +171,8 @@ func TestErrorRedaction(t *testing.T) {
 			hlc.ClockTimestamp{WallTime: 1, Logical: 2},
 		))
 		txn := roachpb.MakeTransaction("foo", roachpb.Key("bar"), isolation.Serializable, 1, hlc.Timestamp{WallTime: 1}, 1, 99, 0, false /* omitInRangefeeds */)
+		txn.UpdateObservedTimestamp(1, hlc.ClockTimestamp{WallTime: 111, Logical: 1})
+		txn.UpdateObservedTimestamp(2, hlc.ClockTimestamp{WallTime: 222, Logical: 2})
 		txn.ID = uuid.Nil
 		txn.Priority = 1234
 		wrappedPErr.UnexposedTxn = &txn
@@ -180,7 +182,7 @@ func TestErrorRedaction(t *testing.T) {
 		var s redact.StringBuilder
 		s.Print(r)
 		act := s.RedactableString().Redact()
-		const exp = "ReadWithinUncertaintyIntervalError: read at time 0.000000001,0 encountered previous write with future timestamp 0.000000002,0 (local=0.000000001,2) within uncertainty interval `t <= (local=0.000000002,2, global=0.000000003,0)`; observed timestamps: [{12 0.000000004,0}]: \"foo\" meta={id=00000000 key=‹×› iso=Serializable pri=0.00005746 epo=0 ts=0.000000001,0 min=0.000000001,0 seq=0} lock=true stat=PENDING rts=0.000000001,0 wto=false gul=0.000000002,0"
+		const exp = "ReadWithinUncertaintyIntervalError: read at time 0.000000001,0 encountered previous write with future timestamp 0.000000002,0 (local=0.000000001,2) within uncertainty interval `t <= (local=0.000000002,2, global=0.000000003,0)`; observed timestamps: [{12 0.000000004,0}]: \"foo\" meta={id=00000000 key=‹×› iso=Serializable pri=0.00005746 epo=0 ts=0.000000001,0 min=0.000000001,0 seq=0} lock=true stat=PENDING rts=0.000000001,0 wto=false gul=0.000000002,0 obs={[email protected],1 [email protected],2}"
 		require.Equal(t, exp, string(act))
 	})
 

pkg/roachpb/data.go

@@ -1554,6 +1554,29 @@ func (t Transaction) SafeFormat(w redact.SafePrinter, _ rune) {
 	}
 	w.Printf("meta={%s} lock=%t stat=%s rts=%s wto=%t gul=%s",
 		t.TxnMeta, t.IsLocking(), t.Status, t.ReadTimestamp, t.WriteTooOld, t.GlobalUncertaintyLimit)
+
+	// Print observed timestamps (limited to 5 for readability).
+	if obsCount := len(t.ObservedTimestamps); obsCount > 0 {
+		w.Printf(" obs={")
+		limit := obsCount
+		if limit > 5 {
+			limit = 5
+		}
+
+		for i := 0; i < limit; i++ {
+			if i > 0 {
+				w.Printf(" ")
+			}
+			obs := t.ObservedTimestamps[i]
+			w.Printf("n%d@%s", obs.NodeID, obs.Timestamp)
+		}
+
+		if obsCount > 5 {
+			w.Printf(", ...")
+		}
+		w.Printf("}")
+	}
+
 	if ni := len(t.LockSpans); t.Status != PENDING && ni > 0 {
 		w.Printf(" int=%d", ni)
 	}