add async to hget and fix bug where a command can hold a key from main db without lock

Former-commit-id: b0b8f426fda7cdabd3898a2d0b38d0fae47d1e69

src/db.cpp

@@ -206,7 +206,7 @@ robj_roptr lookupKeyRead(redisDb *db, robj *key) {
     serverAssert(GlobalLocksAcquired());
     return lookupKeyReadWithFlags(db,key,LOOKUP_NONE);
 }
-robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint) {
+robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint, AeLocker &locker) {
     robj_roptr o;
 
     if (aeThreadOwnsLock()) {
@@ -217,7 +217,6 @@ robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint) {
             return nullptr;
         int idb = db->id;
         if (serverTL->rgdbSnapshot[idb] == nullptr || serverTL->rgdbSnapshot[idb]->mvccCheckpoint() < mvccCheckpoint) {
-            AeLocker locker;
             locker.arm(serverTL->current_client);
             if (serverTL->rgdbSnapshot[idb] != nullptr) {
                 db->endSnapshot(serverTL->rgdbSnapshot[idb]);
@@ -230,6 +229,9 @@ robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint) {
                 o = lookupKeyReadWithFlags(db,key,LOOKUP_NONE);
                 serverTL->disable_async_commands = true; // don't try this again
             }
+            else {
+                locker.disarm();
+            }
         }
         if (serverTL->rgdbSnapshot[idb] != nullptr) {
             o = serverTL->rgdbSnapshot[idb]->find_cached_threadsafe(szFromObj(key)).val();
@@ -263,7 +265,12 @@ static void SentReplyOnKeyMiss(client *c, robj *reply){
     }
 }
 robj_roptr lookupKeyReadOrReply(client *c, robj *key, robj *reply) {
-    robj_roptr o = lookupKeyRead(c->db, key, c->mvccCheckpoint);
+    robj_roptr o = lookupKeyRead(c->db, key);
+    if (!o) SentReplyOnKeyMiss(c, reply);
+    return o;
+}
+robj_roptr lookupKeyReadOrReply(client *c, robj *key, robj *reply, AeLocker &locker) {
+    robj_roptr o = lookupKeyRead(c->db, key, c->mvccCheckpoint, locker);
     if (!o) SentReplyOnKeyMiss(c, reply);
     return o;
 }

src/server.cpp

@@ -599,7 +599,7 @@ struct redisCommand redisCommandTable[] = {
      0,NULL,1,1,1,0,0,0},
 
     {"hget",hgetCommand,3,
-     "read-only fast @hash",
+     "read-only fast async @hash",
      0,NULL,1,1,1,0,0,0},
 
     {"hmset",hsetCommand,-4,

src/server.h

@@ -3363,6 +3363,7 @@ int rewriteConfig(char *path, int force_all);
 void initConfigValues();
 
 /* db.c -- Keyspace access API */
+class AeLocker;
 int removeExpire(redisDb *db, robj *key);
 int removeSubkeyExpire(redisDb *db, robj *key, robj *subkey);
 void propagateExpire(redisDb *db, robj *key, int lazy);
@@ -3370,10 +3371,11 @@ void propagateSubkeyExpire(redisDb *db, int type, robj *key, robj *subkey);
 int expireIfNeeded(redisDb *db, robj *key);
 void setExpire(client *c, redisDb *db, robj *key, robj *subkey, long long when);
 void setExpire(client *c, redisDb *db, robj *key, expireEntry &&entry);
-robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint);
+robj_roptr lookupKeyRead(redisDb *db, robj *key, uint64_t mvccCheckpoint, AeLocker &locker);
 robj_roptr lookupKeyRead(redisDb *db, robj *key);
 int checkAlreadyExpired(long long when);
 robj *lookupKeyWrite(redisDb *db, robj *key);
+robj_roptr lookupKeyReadOrReply(client *c, robj *key, robj *reply, AeLocker &locker);
 robj_roptr lookupKeyReadOrReply(client *c, robj *key, robj *reply);
 robj *lookupKeyWriteOrReply(client *c, robj *key, robj *reply);
 robj_roptr lookupKeyReadWithFlags(redisDb *db, robj *key, int flags);

src/t_hash.cpp

@@ -28,6 +28,7 @@
  */
 
 #include "server.h"
+#include "aelocker.h"
 #include <math.h>
 
 /*-----------------------------------------------------------------------------
@@ -799,8 +800,8 @@ static void addHashFieldToReply(client *c, robj_roptr o, sds field) {
 
 void hgetCommand(client *c) {
     robj_roptr o;
-
+    AeLocker locker;
-    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp])) == nullptr ||
+    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp], locker)) == nullptr ||
         checkType(c,o,OBJ_HASH)) return;
 
     addHashFieldToReply(c, o, szFromObj(c->argv[2]));
@@ -809,10 +810,11 @@ void hgetCommand(client *c) {
 void hmgetCommand(client *c) {
     robj_roptr o;
     int i;
+    AeLocker locker;
 
     /* Don't abort when the key cannot be found. Non-existing keys are empty
      * hashes, where HMGET should respond with a series of null bulks. */
-    o = lookupKeyRead(c->db, c->argv[1], c->mvccCheckpoint);
+    o = lookupKeyRead(c->db, c->argv[1], c->mvccCheckpoint, locker);
     if (checkType(c,o,OBJ_HASH)) return;
 
     addReplyArrayLen(c, c->argc-2);
@@ -889,10 +891,11 @@ void genericHgetallCommand(client *c, int flags) {
     robj_roptr o;
     hashTypeIterator *hi;
     int length, count = 0;
+    AeLocker locker;
 
     robj *emptyResp = (flags & OBJ_HASH_KEY && flags & OBJ_HASH_VALUE) ?
         shared.emptymap[c->resp] : shared.emptyarray;
-    if ((o = lookupKeyReadOrReply(c,c->argv[1],emptyResp))
+    if ((o = lookupKeyReadOrReply(c,c->argv[1],emptyResp,locker))
         == nullptr || checkType(c,o,OBJ_HASH)) return;
 
     /* We return a map if the user requested keys and values, like in the
@@ -946,9 +949,10 @@ void hexistsCommand(client *c) {
 void hscanCommand(client *c) {
     robj_roptr o;
     unsigned long cursor;
+    AeLocker locker;
 
     if (parseScanCursorOrReply(c,c->argv[2],&cursor) == C_ERR) return;
-    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptyscan)) == nullptr ||
+    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptyscan,locker)) == nullptr ||
         checkType(c,o,OBJ_HASH)) return;
     scanGenericCommand(c,o,cursor);
 }

src/t_string.cpp

@@ -285,8 +285,9 @@ void psetexCommand(client *c) {
 
 int getGenericCommand(client *c) {
     robj_roptr o;
+    AeLocker locker;
 
-    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp])) == nullptr)
+    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp],locker)) == nullptr)
         return C_OK;
 
     if (checkType(c,o,OBJ_STRING)) {
@@ -525,9 +526,10 @@ void getrangeCommand(client *c) {
 }
 
 void mgetCommand(client *c) {
+    AeLocker locker;
     addReplyArrayLen(c,c->argc-1);
     for (int i = 1; i < c->argc; i++) {
-        robj_roptr o = lookupKeyRead(c->db,c->argv[i],c->mvccCheckpoint);
+        robj_roptr o = lookupKeyRead(c->db,c->argv[i],c->mvccCheckpoint,locker);
         if (o == nullptr || o->type != OBJ_STRING) {
             addReplyNull(c);
         } else {