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diskstore more fixes

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This commit is contained in:
antirez
2011-01-03 17:18:37 +01:00
parent d158dc28f6
commit 5d46e370b7
5 changed files with 75 additions and 16 deletions
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63
src/db.c
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@ -6,6 +6,35 @@
* C-level DB API
*----------------------------------------------------------------------------*/
/* Important notes on lookup and disk store.
*
* When disk store is enabled on lookup we can have different cases.
*
* a) The key is in memory:
* - If the key is not in IO_SAVEINPROG state we can access it.
* As if it's just IO_SAVE this means we have the key in the IO queue
* but can't be accessed by the IO thread (it requires to be
* translated into an IO Job by the cache cron function.)
* - If the key is in IO_SAVEINPROG we can't touch the key and have
* to blocking wait completion of operations.
* b) The key is not in memory:
* - If it's marked as non existing on disk as well (negative cache)
* we don't need to perform the disk access.
* - if the key MAY EXIST, but is not in memory, and it is marked as IO_SAVE
* then the key can only be a deleted one. As IO_SAVE keys are never
* evicted (dirty state), so the only possibility is that key was deleted.
* - if the key MAY EXIST we need to blocking load it.
* We check that the key is not in IO_SAVEINPROG state before accessing
* the disk object. If it is in this state, we wait.
*/
void lookupWaitBusyKey(redisDb *db, robj *key) {
/* FIXME: wait just for this key, not everything */
waitEmptyIOJobsQueue();
processAllPendingIOJobs();
redisAssert((cacheScheduleIOGetFlags(db,key) & REDIS_IO_SAVEINPROG) == 0);
}
robj *lookupKey(redisDb *db, robj *key) {
dictEntry *de = dictFind(db->dict,key->ptr);
if (de) {
@ -20,11 +49,9 @@ robj *lookupKey(redisDb *db, robj *key) {
if (server.ds_enabled &&
cacheScheduleIOGetFlags(db,key) & REDIS_IO_SAVEINPROG)
{
/* There is a save in progress for this object!
* Wait for it to get out. */
waitEmptyIOJobsQueue();
processAllPendingIOJobs();
redisAssert(!(cacheScheduleIOGetFlags(db,key) & REDIS_IO_SAVEINPROG));
/* Need to wait for the key to get unbusy */
redisLog(REDIS_WARNING,"Lookup found a key in SAVEINPROG state. Waiting. (Key was in the cache)");
lookupWaitBusyKey(db,key);
}
server.stat_keyspace_hits++;
return val;
@ -36,16 +63,24 @@ robj *lookupKey(redisDb *db, robj *key) {
* enabled we may have this key on disk. If so load it in memory
* in a blocking way. */
if (server.ds_enabled && cacheKeyMayExist(db,key)) {
if (cacheScheduleIOGetFlags(db,key) & REDIS_IO_SAVEINPROG) {
/* There is a save in progress for this object!
* Wait for it to get out. */
waitEmptyIOJobsQueue();
processAllPendingIOJobs();
redisAssert((cacheScheduleIOGetFlags(db,key) & REDIS_IO_SAVEINPROG) == 0);
long flags = cacheScheduleIOGetFlags(db,key);
/* They key is not in cache, but it has a SAVE op in queue?
* The only possibility is that the key was deleted, since
* dirty keys are not evicted. */
if (flags & REDIS_IO_SAVE) {
server.stat_keyspace_misses++;
return NULL;
}
redisLog(REDIS_DEBUG,"Force loading key %s via lookup",
key->ptr);
/* At this point we need to blocking load the key in memory.
* The first thing we do is waiting here if the key is busy. */
if (flags & REDIS_IO_SAVEINPROG) {
redisLog(REDIS_WARNING,"Lookup found a key in SAVEINPROG state. Waiting (while force loading).");
lookupWaitBusyKey(db,key);
}
redisLog(REDIS_DEBUG,"Force loading key %s via lookup", key->ptr);
val = dsGet(db,key,&expire);
if (val) {
int retval = dbAdd(db,key,val);
@ -53,6 +88,8 @@ robj *lookupKey(redisDb *db, robj *key) {
if (expire != -1) setExpire(db,key,expire);
server.stat_keyspace_hits++;
return val;
} else {
cacheSetKeyDoesNotExist(db,key);
}
}
server.stat_keyspace_misses++;