enh: alter db replica return quickly, operation executed asynchronously

source/dnode/mnode/impl/src/mndDb.c

@@ -825,7 +825,13 @@ static int32_t mndProcessAlterDbReq(SRpcMsg *pReq) {
   dbObj.cfgVersion++;
   dbObj.updateTime = taosGetTimestampMs();
   code = mndAlterDb(pMnode, pReq, pDb, &dbObj);
-  if (code == 0) code = TSDB_CODE_ACTION_IN_PROGRESS;
+
+  if (dbObj.cfg.replications != pDb->cfg.replications) {
+    // return quickly, operation executed asynchronously
+    mInfo("db:%s, alter db replica from %d to %d", pDb->name, pDb->cfg.replications, dbObj.cfg.replications);
+  } else {
+    if (code == 0) code = TSDB_CODE_ACTION_IN_PROGRESS;
+  }
 
 _OVER:
   if (code != 0 && code != TSDB_CODE_ACTION_IN_PROGRESS) {

tests/script/tsim/db/alter_replica_13.sim

@@ -116,6 +116,25 @@ endi
 
 print ============= step4: alter database
 sql alter database db replica 3
+$wt = 0
+stepwt1:
+ 	$wt = $wt + 1
+ 	sleep 1000
+ 	if $wt == 200 then
+ 	  print ====> dnode not ready!
+ 		return -1
+ 	endi
+sql show transactions
+if $rows != 0 then
+  print wait 1 seconds to alter
+  goto stepwt1
+endi
+
+sql show db.vgroups
+print ---> $data00 $data01 $data02 $data03 $data04 $data05 $data06 $data07 $data08 $data09
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data16 $data27 $data28 $data29
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data26 $data37 $data38 $data39
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data36 $data47 $data48 $data49
 
 $leaderIndex = 0
 

tests/script/tsim/db/alter_replica_31.sim

@@ -148,6 +148,26 @@ endi
 
 print ============= step3: alter database
 sql alter database db replica 1
+wt = 0
+ stepwt1:
+ 	$wt = $wt + 1
+ 	sleep 1000
+ 	if $wt == 200 then
+ 	  print ====> dnode not ready!
+ 		return -1
+ 	endi
+sql show transactions
+if $rows != 0 then
+  print wait 1 seconds to alter
+  goto stepwt1
+endi
+
+sql show db.vgroups
+print ---> $data00 $data01 $data02 $data03 $data04 $data05 $data06 $data07 $data08 $data09
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data16 $data27 $data28 $data29
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data26 $data37 $data38 $data39
+print ---> $data10 $data11 $data12 $data13 $data14 $data15 $data36 $data47 $data48 $data49
+
 $hasleader = 0
 
 $x = 0