refactor async to offload common code to client

Former-commit-id: 9a7547bfaa0ceff76e604262913fb11a64c627d8

src/server.cpp

@@ -4952,6 +4952,26 @@ bool client::postFunction(std::function<void(client *)> fn, bool fLock) {
     }, fLock) == AE_OK;
 }
 
+void client::asyncCommand(std::function<void()> &&preFn, std::function<void()> &&mainFn, std::function<void()> &&postFn) {
+    aeEventLoop *el = serverTL->el;
+    blockClient(this, BLOCKED_ASYNC);
+    g_pserver->asyncworkqueue->AddWorkFunction([el, this, preFn, mainFn, postFn] {
+        preFn();
+        aePostFunction(el, [this, mainFn, postFn] {
+            aeReleaseLock();
+            std::unique_lock<decltype(this->lock)> lock(this->lock);
+            AeLocker locker;
+            locker.arm(this);
+            unblockClient(this);
+            mainFn();
+            locker.disarm();
+            lock.unlock();
+            postFn();
+            aeAcquireLock();
+        });
+    });
+}
+
 /* ====================== Error lookup and execution ===================== */
 
 void incrementErrorCount(const char *fullerr, size_t namelen) {

src/server.h

@@ -1661,6 +1661,7 @@ struct client {
     // post a function from a non-client thread to run on its client thread
     bool postFunction(std::function<void(client *)> fn, bool fLock = true);
     size_t argv_len_sum() const;
+    void asyncCommand(std::function<void()> &&preFn, std::function<void()> &&mainFn, std::function<void()> &&postFn);
 };
 
 struct saveparam {

src/t_string.cpp

@@ -526,27 +526,21 @@ void getrangeCommand(client *c) {
 
 void mgetCommand(client *c) {
     // Do async version for large number of arguments
-    if (c->argc > 100) {
+    if (c->argc > 1) {
         const redisDbPersistentDataSnapshot *snapshot = nullptr;
         if (!(c->flags & (CLIENT_MULTI | CLIENT_BLOCKED)))
             snapshot = c->db->createSnapshot(c->mvccCheckpoint, false /* fOptional */);
         if (snapshot != nullptr) {
             list *keys = listCreate();
-            aeEventLoop *el = serverTL->el;
-            blockClient(c, BLOCKED_ASYNC);
             redisDb *db = c->db;
-            g_pserver->asyncworkqueue->AddWorkFunction([el, c, keys, snapshot, db] {
+            c->asyncCommand(
+            [c, keys] {
                 for (int j = 1; j < c->argc; j++) {
                     incrRefCount(c->argv[j]);
                     listAddNodeTail(keys, c->argv[j]);
                 }
-                aePostFunction(el, [c, keys, snapshot, db] {
-                    aeReleaseLock();
-                    std::unique_lock<decltype(c->lock)> lock(c->lock);
-                    AeLocker locker;
-                    locker.arm(c);
-                    unblockClient(c);
-
+            }, 
+            [c, keys, snapshot] {
                 addReplyArrayLen(c,listLength(keys));
                 listNode *ln = listFirst(keys);
                 while (ln != nullptr) {
@@ -558,15 +552,13 @@ void mgetCommand(client *c) {
                     }
                     ln = ln->next;
                 }
-
-                    locker.disarm();
-                    lock.unlock();
+            }, 
+            [keys, snapshot, db] {
                 db->endSnapshotAsync(snapshot);
                 listSetFreeMethod(keys,decrRefCountVoid);
                 listRelease(keys);
-                    aeAcquireLock();
-                });
-            });
+            }
+            );
             return;
         }
     }