diskstore bug fixing and negative cache proper implementation

src/db.c

@@ -93,9 +93,7 @@ int dbAdd(redisDb *db, robj *key, robj *val) {
     } else {
         sds copy = sdsdup(key->ptr);
         dictAdd(db->dict, copy, val);
-        if (server.ds_enabled) {
+        if (server.ds_enabled) cacheSetKeyMayExist(db,key);
-            /* FIXME: remove entry from negative cache */
-        }
         return REDIS_OK;
     }
 }
@@ -106,15 +104,18 @@ int dbAdd(redisDb *db, robj *key, robj *val) {
  * On update (key already existed) 0 is returned. Otherwise 1. */
 int dbReplace(redisDb *db, robj *key, robj *val) {
     robj *oldval;
+    int retval;
 
     if ((oldval = dictFetchValue(db->dict,key->ptr)) == NULL) {
         sds copy = sdsdup(key->ptr);
         dictAdd(db->dict, copy, val);
-        return 1;
+        retval = 1;
     } else {
         dictReplace(db->dict, key->ptr, val);
-        return 0;
+        retval = 0;
     }
+    if (server.ds_enabled) cacheSetKeyMayExist(db,key);
+    return retval;
 }
 
 int dbExists(redisDb *db, robj *key) {
@@ -152,10 +153,10 @@ int dbDelete(redisDb *db, robj *key) {
     /* If diskstore is enabled make sure to awake waiting clients for this key
      * as it is not really useful to wait for a key already deleted to be
      * loaded from disk. */
-    if (server.ds_enabled) handleClientsBlockedOnSwappedKey(db,key);
+    if (server.ds_enabled) {
-
+        handleClientsBlockedOnSwappedKey(db,key);
-    /* FIXME: we should mark this key as non existing on disk in the negative
+        cacheSetKeyDoesNotExist(db,key);
-     * cache. */
+    }
 
     /* Deleting an entry from the expires dict will not free the sds of
      * the key, because it is shared with the main dictionary. */

src/diskstore.c

@@ -298,7 +298,7 @@ void dsFlushOneDir(char *path, int dbid) {
             id[len] = '\0';
             if (atoi(id) != dbid) continue; /* skip this file */
         }
-        if (unlink(path) == -1) {
+        if (unlink(dp->d_name) == -1) {
             redisLog(REDIS_WARNING,
                 "Can't unlink %s: %s", path, strerror(errno));
             redisPanic("Unrecoverable Disk store errore. Existing.");

src/dscache.c

@@ -245,10 +245,10 @@ int cacheFreeOneEntry(void) {
         }
     }
     if (best == NULL) {
-        /* FIXME: If there are objects marked as DS_DIRTY or DS_SAVING
+        /* FIXME: If there are objects that are in the write queue
-         * let's wait for this objects to be clear and retry...
+         * so we can't delete them we should block here, at the cost of
-         *
+         * slowness as the object cache memory limit is considered 
-         * Object cache vm limit is considered an hard limit. */
+         * n hard limit. */
         return REDIS_ERR;
     }
     key = dictGetEntryKey(best);
@@ -306,6 +306,38 @@ void cacheSetKeyDoesNotExist(redisDb *db, robj *key) {
     }
 }
 
+/* Remove one entry from negative cache using approximated LRU. */
+int negativeCacheEvictOneEntry(void) {
+    struct dictEntry *de;
+    robj *best = NULL;
+    redisDb *best_db = NULL;
+    time_t time, best_time = 0;
+    int j;
+
+    for (j = 0; j < server.dbnum; j++) {
+        redisDb *db = server.db+j;
+        int i;
+
+        if (dictSize(db->io_negcache) == 0) continue;
+        for (i = 0; i < 3; i++) {
+            de = dictGetRandomKey(db->io_negcache);
+            time = (time_t) dictGetEntryVal(de);
+
+            if (best == NULL || time < best_time) {
+                best = dictGetEntryKey(de);
+                best_db = db;
+                best_time = time;
+            }
+        }
+    }
+    if (best) {
+        dictDelete(best_db->io_negcache,best);
+        return REDIS_OK;
+    } else {
+        return REDIS_ERR;
+    }
+}
+
 /* ================== Disk store cache - Threaded I/O  ====================== */
 
 void freeIOJob(iojob *j) {
@@ -361,20 +393,11 @@ void vmThreadedIOCompletedJob(aeEventLoop *el, int fd, void *privdata,
                     incrRefCount(j->val);
                     if (j->expire != -1) setExpire(j->db,j->key,j->expire);
                 }
-            } else {
-                /* The key does not exist. Create a negative cache entry
-                 * for this key. */
-                cacheSetKeyDoesNotExist(j->db,j->key);
             }
             cacheScheduleIODelFlag(j->db,j->key,REDIS_IO_LOADINPROG);
             handleClientsBlockedOnSwappedKey(j->db,j->key);
             freeIOJob(j);
         } else if (j->type == REDIS_IOJOB_SAVE) {
-            if (j->val) {
-                cacheSetKeyMayExist(j->db,j->key);
-            } else {
-                cacheSetKeyDoesNotExist(j->db,j->key);
-            }
             cacheScheduleIODelFlag(j->db,j->key,REDIS_IO_SAVEINPROG);
             freeIOJob(j);
         }
@@ -740,8 +763,11 @@ void cacheCron(void) {
     while (server.ds_enabled && zmalloc_used_memory() >
             server.cache_max_memory)
     {
-        if (cacheFreeOneEntry() == REDIS_ERR) break;
+        int done = 0;
-        /* FIXME: also free negative cache entries here. */
+
+        if (cacheFreeOneEntry() == REDIS_OK) done++;
+        if (negativeCacheEvictOneEntry() == REDIS_OK) done++;
+        if (done == 0) break; /* nothing more to free */
     }
 }
 

src/redis.h

@@ -814,7 +814,7 @@ int cacheScheduleIOGetFlags(redisDb *db, robj *key);
 void cacheScheduleIO(redisDb *db, robj *key, int type);
 void cacheCron(void);
 int cacheKeyMayExist(redisDb *db, robj *key);
-void cacheSetKeyExists(redisDb *db, robj *key);
+void cacheSetKeyMayExist(redisDb *db, robj *key);
 void cacheSetKeyDoesNotExist(redisDb *db, robj *key);
 
 /* Set data type */