Fixes auto revert to check if the job's spec has changed before reverting. This prevents infinite reverting when reverting to a job version that was previously stable, but not so after attempting a revert.

nomad/deploymentwatcher/deployment_watcher.go

@@ -371,7 +371,13 @@ func (w *deploymentWatcher) watch() {
 				// Description should include that the job is being rolled back to
 				// version N
 				if j != nil {
-					desc = structs.DeploymentStatusDescriptionRollback(desc, j.Version)
+					// only revert if job being changed has a different spec
+					if w.j.SpecChanged(j) {
+						desc = structs.DeploymentStatusDescriptionRollback(desc, j.Version)
+					} else {
+						desc = structs.DeploymentStatusDescriptionRollbackFailed(desc, j.Version, w.j.Version)
+						j = nil
+					}
 				} else {
 					desc = structs.DeploymentStatusDescriptionNoRollbackTarget(desc)
 				}

nomad/structs/structs.go

@@ -4322,6 +4322,12 @@ func DeploymentStatusDescriptionRollback(baseDescription string, jobVersion uint
 	return fmt.Sprintf("%s - rolling back to job version %d", baseDescription, jobVersion)
 }
 
+// DeploymentStatusDescriptionRollbackFailed is used to get the status description of
+// a deployment when rolling back to an older job is not possible because it has the same specification
+func DeploymentStatusDescriptionRollbackFailed(baseDescription string, jobVersion uint64, jobVersionOld uint64) string {
+	return fmt.Sprintf("%s - rolling back to job version %d failed because it had the same specification as job version %d ", baseDescription, jobVersion, jobVersionOld)
+}
+
 // DeploymentStatusDescriptionNoRollbackTarget is used to get the status description of
 // a deployment when there is no target to rollback to but autorevet is desired.
 func DeploymentStatusDescriptionNoRollbackTarget(baseDescription string) string {