[TD-4081]<fix>: fix vnode dropping

src/vnode/src/vnodeMain.c

@@ -124,8 +124,6 @@ int32_t vnodeDrop(int32_t vgId) {
   vInfo("vgId:%d, vnode will be dropped, refCount:%d pVnode:%p", pVnode->vgId, pVnode->refCount, pVnode);
   pVnode->dropped = 1;
 
-  // remove from hash, so new messages wont be consumed
-  vnodeRemoveFromHash(pVnode);
   vnodeRelease(pVnode);
   vnodeCleanupInMWorker(pVnode);
 

src/vnode/src/vnodeMgmt.c

@@ -118,6 +118,8 @@ void vnodeRelease(void *vparam) {
       tsem_post(&pVnode->sem);
     }
   } else {
+    vnodeRemoveFromHash(pVnode);
+
     vDebug("vgId:%d, vnode will be destroyed, refCount:%d pVnode:%p", pVnode->vgId, refCount, pVnode);
     vnodeDestroyInMWorker(pVnode);
     int32_t count = taosHashGetSize(tsVnodesHash);

src/vnode/src/vnodeRead.c

@@ -117,14 +117,18 @@ static SVReadMsg *vnodeBuildVReadMsg(SVnodeObj *pVnode, void *pCont, int32_t con
 }
 
 int32_t vnodeWriteToRQueue(void *vparam, void *pCont, int32_t contLen, int8_t qtype, void *rparam) {
+  SVnodeObj *pVnode = vparam;
+
+  if (pVnode->dropped) {
+    return TSDB_CODE_VND_INVALID_VGROUP_ID;
+  }
+
   SVReadMsg *pRead = vnodeBuildVReadMsg(vparam, pCont, contLen, qtype, rparam);
   if (pRead == NULL) {
     assert(terrno != 0);
     return terrno;
   }
 
-  SVnodeObj *pVnode = vparam;
-
   int32_t code = vnodeCheckRead(pVnode);
   if (code != TSDB_CODE_SUCCESS) {
     taosFreeQitem(pRead);

src/vnode/src/vnodeWrite.c

@@ -386,4 +386,6 @@ void vnodeWaitWriteCompleted(SVnodeObj *pVnode) {
     vTrace("vgId:%d, queued wmsg num:%d", pVnode->vgId, pVnode->queuedWMsg);
     taosMsleep(10);
   }
+
+  taosMsleep(1000 * 3);
 }