Extra test case and better error message for ambiguous config

nomad/structs/structs.go

@@ -2904,6 +2904,7 @@ func (r *ReschedulePolicy) Validate() error {
 		if r.Unlimited {
 			multierror.Append(&mErr, fmt.Errorf("Reschedule Policy with Attempts = %v, Interval = %v, "+
 				"and Unlimited = %v is ambiguous", r.Attempts, r.Interval, r.Unlimited))
+			multierror.Append(&mErr, errors.New("If Attempts >0, Unlimited cannot also be set to true"))
 		}
 	}
 
@@ -5686,6 +5687,7 @@ func (a *Allocation) RescheduleEligible(reschedulePolicy *ReschedulePolicy, fail
 	if reschedulePolicy.Unlimited {
 		return true
 	}
+	// Early return true if there are no attempts yet and the number of allowed attempts is > 0
 	if (a.RescheduleTracker == nil || len(a.RescheduleTracker.Events) == 0) && attempts > 0 {
 		return true
 	}

nomad/structs/structs_test.go

@@ -2226,7 +2226,7 @@ func TestReschedulePolicy_Validate(t *testing.T) {
 			},
 		},
 		{
-			desc: "Ambiguous Unlimited config",
+			desc: "Ambiguous Unlimited config, has both attempts and unlimited set",
 			ReschedulePolicy: &ReschedulePolicy{
 				Attempts:      1,
 				Unlimited:     true,
@@ -2252,6 +2252,15 @@ func TestReschedulePolicy_Validate(t *testing.T) {
 				fmt.Errorf("Max Delay cannot be less than %v (got %v)", ReschedulePolicyMinDelay, 0*time.Second),
 			},
 		},
+		{
+			desc: "Valid Unlimited config",
+			ReschedulePolicy: &ReschedulePolicy{
+				Unlimited:     true,
+				DelayFunction: "exponential",
+				Delay:         5 * time.Second,
+				MaxDelay:      1 * time.Hour,
+			},
+		},
 	}
 
 	for _, tc := range testCases {