* longer relevant with the new design. Here as a checklist to see if
* some old ideas still apply.
*
- * - The WATCH helper will be used to signal the cache system
- * we need to flush a given key/dbid into disk, adding this key/dbid
- * pair into a server.ds_cache_dirty linked list AND hash table (so that we
- * don't add the same thing multiple times).
- *
- * - cron() checks if there are elements on this list. When there are things
- * to flush, we create an IO Job for the I/O thread.
- * NOTE: We disalbe object sharing when server.ds_enabled == 1 so objects
- * that are referenced an IO job for flushing on disk are marked as
- * o->storage == REDIS_DS_SAVING.
- *
- * - This is what we do on key lookup:
- * 1) The key already exists in memory. object->storage == REDIS_DS_MEMORY
- * or it is object->storage == REDIS_DS_DIRTY:
- * We don't do nothing special, lookup, return value object pointer.
- * 2) The key is in memory but object->storage == REDIS_DS_SAVING.
- * When this happens we block waiting for the I/O thread to process
- * this object. Then continue.
- * 3) The key is not in memory. We block to load the key from disk.
- * Of course the key may not be present at all on the disk store as well,
- * in such case we just detect this condition and continue, returning
- * NULL from lookup.
- *
- * - Preloading of needed keys:
- * 1) As it was done with VM, also with this new system we try preloading
- * keys a client is going to use. We block the client, load keys
- * using the I/O thread, unblock the client. Same code as VM more or less.
- *
- * - Reclaiming memory.
- * In cron() we detect our memory limit was reached. What we
- * do is deleting keys that are REDIS_DS_MEMORY, using LRU.
- *
- * If this is not enough to return again under the memory limits we also
- * start to flush keys that need to be synched on disk synchronously,
- * removing it from the memory. We do this blocking as memory limit is a
- * much "harder" barrirer in the new design.
- *
- * - IO thread operations are no longer stopped for sync loading/saving of
- * things. When a key is found to be in the process of being saved
- * we simply wait for the IO thread to end its work.
- *
- * Otherwise if there is to load a key without any IO thread operation
- * just started it is blocking-loaded in the lookup function.
- *
* - What happens when an object is destroyed?
*
- * If o->storage == REDIS_DS_MEMORY then we simply destory the object.
- * If o->storage == REDIS_DS_DIRTY we can still remove the object. It had
- * changes not flushed on disk, but is being removed so
- * who cares.
- * if o->storage == REDIS_DS_SAVING then the object is being saved so
- * it is impossible that its refcount == 1, must be at
- * least two. When the object is saved the storage will
- * be set back to DS_MEMORY.
- *
- * - What happens when keys are deleted?
+ * If the object is destroyed since semantically it was deleted or
+ * replaced with something new, we don't care if there was a SAVE
+ * job pending for it. Anyway when the IO JOb will be created we'll get
+ * the pointer of the current value.
*
- * We simply schedule a key flush operation as usually, but when the
- * IO thread will be created the object pointer will be set to NULL
- * so the IO thread will know that the work to do is to delete the key
- * from the disk store.
+ * If the object is already a REDIS_IO_SAVEINPROG object, then it is
+ * impossible that we get a decrRefCount() that will reach refcount of zero
+ * since the object is both in the dataset and in the io job entry.
*
* - What happens with MULTI/EXEC?
*
- * Good question.
+ * Good question. Without some kind of versioning with a global counter
+ * it is not possible to have trasactions on disk, but they are still
+ * useful since from the point of view of memory and client bugs it is
+ * a protection anyway. Also it's useful for WATCH.
*
- * - If dsSet() fails on the write thread log the error and reschedule the
- * key for flush.
+ * Btw there is to check what happens when WATCH gets combined to keys
+ * that gets removed from the object cache. Should be save but better
+ * to check.
*
- * - Check why INCR will not update the LRU info for the object.
+ * - Check if/why INCR will not update the LRU info for the object.
*
* - Fix/Check the following race condition: a key gets a DEL so there is
* a write operation scheduled against this key. Later the same key will
* not marked as cacheKeyDoesNotExist(), otherwise, again, we can load
* data from disk that should instead be deleted.
*
- * - dsSet() use rename(2) in order to avoid corruptions.
+ * - dsSet() should use rename(2) in order to avoid corruptions.
*
* - Don't add a LOAD if there is already a LOADINPROGRESS, or is this
* impossible since anyway the io_keys stuff will work as lock?
+ *
+ * - Serialize special encoded things in a raw form.
+ *
+ * - When putting IO read operations on top of the queue, do this only if
+ * the already-on-top operation is not a save or if it is a save that
+ * is scheduled for later execution. If there is a save that is ready to
+ * fire, let's insert the load operation just before the first save that
+ * is scheduled for later exection for instance.
+ *
+ * - Support MULTI/EXEC transactions via a journal file, that is played on
+ * startup to check if there is cleanup to do. This way we can implement
+ * transactions with our simple file based KV store.
*/
/* Virtual Memory is composed mainly of two subsystems:
*/
void spawnIOThread(void);
+int cacheScheduleIOPushJobs(int flags);
+int processActiveIOJobs(int max);
/* =================== Virtual Memory - Blocking Side ====================== */
server.io_ready_clients = listCreate();
pthread_mutex_init(&server.io_mutex,NULL);
pthread_cond_init(&server.io_condvar,NULL);
+ pthread_mutex_init(&server.bgsavethread_mutex,NULL);
server.io_active_threads = 0;
if (pipe(pipefds) == -1) {
redisLog(REDIS_WARNING,"Unable to intialized DS: pipe(2): %s. Exiting."
* are swappable objects */
int maxtries = 100;
- if (dictSize(db->dict) == 0) continue;
- for (i = 0; i < 5; i++) {
+ for (i = 0; i < 5 && dictSize(db->dict); i++) {
dictEntry *de;
double swappability;
robj keyobj;
}
}
if (best == NULL) {
- /* FIXME: If there are objects that are in the write queue
- * so we can't delete them we should block here, at the cost of
- * slowness as the object cache memory limit is considered
- * n hard limit. */
+ /* Not able to free a single object? we should check if our
+ * IO queues have stuff in queue, and try to consume the queue
+ * otherwise we'll use an infinite amount of memory if changes to
+ * the dataset are faster than I/O */
+ if (listLength(server.cache_io_queue) > 0) {
+ redisLog(REDIS_DEBUG,"--- Busy waiting IO to reclaim memory");
+ cacheScheduleIOPushJobs(REDIS_IO_ASAP);
+ processActiveIOJobs(1);
+ return REDIS_OK;
+ }
+ /* Nothing to free at all... */
return REDIS_ERR;
}
key = dictGetEntryKey(best);
/* Every time a thread finished a Job, it writes a byte into the write side
* of an unix pipe in order to "awake" the main thread, and this function
- * is called. */
+ * is called.
+ *
+ * If privdata == NULL the function will try to put more jobs in the queue
+ * of IO jobs to process as more room is made. privdata is equal to NULL
+ * when the function is called from the event loop, so we want to push
+ * more IO jobs in the queue. Instead when the function is called by
+ * other functions that want to create a write-barrier to avoid race
+ * conditions we don't push new jobs in the queue. */
void vmThreadedIOCompletedJob(aeEventLoop *el, int fd, void *privdata,
int mask)
{
int retval, processed = 0, toprocess = -1;
REDIS_NOTUSED(el);
REDIS_NOTUSED(mask);
- REDIS_NOTUSED(privdata);
/* For every byte we read in the read side of the pipe, there is one
* I/O job completed to process. */
incrRefCount(j->val);
if (j->expire != -1) setExpire(j->db,j->key,j->expire);
}
+ } else {
+ /* Key not found on disk. If it is also not in memory
+ * as a cached object, nor there is a job writing it
+ * in background, we are sure the key does not exist
+ * currently.
+ *
+ * So we set a negative cache entry avoiding that the
+ * resumed client will block load what does not exist... */
+ if (dictFind(j->db->dict,j->key->ptr) == NULL &&
+ (cacheScheduleIOGetFlags(j->db,j->key) &
+ (REDIS_IO_SAVE|REDIS_IO_SAVEINPROG)) == 0)
+ {
+ cacheSetKeyDoesNotExist(j->db,j->key);
+ }
}
cacheScheduleIODelFlag(j->db,j->key,REDIS_IO_LOADINPROG);
handleClientsBlockedOnSwappedKey(j->db,j->key);
freeIOJob(j);
}
processed++;
+ if (privdata == NULL) cacheScheduleIOPushJobs(0);
if (processed == toprocess) return;
}
if (retval < 0 && errno != EAGAIN) {
iojob *j;
listNode *ln;
REDIS_NOTUSED(arg);
+ long long start;
pthread_detach(pthread_self());
lockThreadedIO();
/* Get a new job to process */
if (listLength(server.io_newjobs) == 0) {
/* Wait for more work to do */
+ redisLog(REDIS_DEBUG,"[T] wait for signal");
pthread_cond_wait(&server.io_condvar,&server.io_mutex);
+ redisLog(REDIS_DEBUG,"[T] signal received");
continue;
}
- redisLog(REDIS_DEBUG,"%ld IO jobs to process",
+ start = ustime();
+ redisLog(REDIS_DEBUG,"[T] %ld IO jobs to process",
listLength(server.io_newjobs));
ln = listFirst(server.io_newjobs);
j = ln->value;
ln = listLast(server.io_processing); /* We use ln later to remove it */
unlockThreadedIO();
- redisLog(REDIS_DEBUG,"Thread %ld: new job type %s: %p about key '%s'",
+ redisLog(REDIS_DEBUG,"[T] %ld: new job type %s: %p about key '%s'",
(long) pthread_self(),
(j->type == REDIS_IOJOB_LOAD) ? "load" : "save",
(void*)j, (char*)j->key->ptr);
if (j->val) j->expire = expire;
} else if (j->type == REDIS_IOJOB_SAVE) {
if (j->val) {
- dsSet(j->db,j->key,j->val);
+ dsSet(j->db,j->key,j->val,j->expire);
} else {
dsDel(j->db,j->key);
}
}
/* Done: insert the job into the processed queue */
- redisLog(REDIS_DEBUG,"Thread %ld completed the job: %p (key %s)",
+ redisLog(REDIS_DEBUG,"[T] %ld completed the job: %p (key %s)",
(long) pthread_self(), (void*)j, (char*)j->key->ptr);
+ redisLog(REDIS_DEBUG,"[T] lock IO");
lockThreadedIO();
+ redisLog(REDIS_DEBUG,"[T] IO locked");
listDelNode(server.io_processing,ln);
listAddNodeTail(server.io_processed,j);
/* Signal the main thread there is new stuff to process */
redisAssert(write(server.io_ready_pipe_write,"x",1) == 1);
+ redisLog(REDIS_DEBUG,"TIME (%c): %lld\n", j->type == REDIS_IOJOB_LOAD ? 'L' : 'S', ustime()-start);
}
/* never reached, but that's the full pattern... */
unlockThreadedIO();
server.io_active_threads++;
}
-/* Wait that all the pending IO Jobs are processed */
-void waitEmptyIOJobsQueue(void) {
- while(1) {
+/* Wait that up to 'max' pending IO Jobs are processed by the I/O thread.
+ * From our point of view an IO job processed means that the count of
+ * server.io_processed must increase by one.
+ *
+ * If max is -1, all the pending IO jobs will be processed.
+ *
+ * Returns the number of IO jobs processed.
+ *
+ * NOTE: while this may appear like a busy loop, we are actually blocked
+ * by IO since we continuously acquire/release the IO lock. */
+int processActiveIOJobs(int max) {
+ int processed = 0;
+
+ while(max == -1 || max > 0) {
int io_processed_len;
+ redisLog(REDIS_DEBUG,"[P] lock IO");
lockThreadedIO();
+ redisLog(REDIS_DEBUG,"Waiting IO jobs processing: new:%d proessing:%d processed:%d",listLength(server.io_newjobs),listLength(server.io_processing),listLength(server.io_processed));
+
if (listLength(server.io_newjobs) == 0 &&
listLength(server.io_processing) == 0)
{
+ /* There is nothing more to process */
+ redisLog(REDIS_DEBUG,"[P] Nothing to process, unlock IO, return");
unlockThreadedIO();
- return;
+ break;
}
+
+#if 1
/* If there are new jobs we need to signal the thread to
- * process the next one. */
- redisLog(REDIS_DEBUG,"waitEmptyIOJobsQueue: new %d, processing %d",
+ * process the next one. FIXME: drop this if useless. */
+ redisLog(REDIS_DEBUG,"[P] waitEmptyIOJobsQueue: new %d, processing %d, processed %d",
listLength(server.io_newjobs),
- listLength(server.io_processing));
- /*
+ listLength(server.io_processing),
+ listLength(server.io_processed));
+
if (listLength(server.io_newjobs)) {
+ redisLog(REDIS_DEBUG,"[P] There are new jobs, signal");
pthread_cond_signal(&server.io_condvar);
}
- */
- /* While waiting for empty jobs queue condition we post-process some
- * finshed job, as I/O threads may be hanging trying to write against
- * the io_ready_pipe_write FD but there are so much pending jobs that
- * it's blocking. */
+#endif
+
+ /* Check if we can process some finished job */
io_processed_len = listLength(server.io_processed);
+ redisLog(REDIS_DEBUG,"[P] Unblock IO");
unlockThreadedIO();
+ redisLog(REDIS_DEBUG,"[P] Wait");
+ usleep(10000);
if (io_processed_len) {
vmThreadedIOCompletedJob(NULL,server.io_ready_pipe_read,
(void*)0xdeadbeef,0);
- usleep(1000); /* 1 millisecond */
- } else {
- usleep(10000); /* 10 milliseconds */
+ processed++;
+ if (max != -1) max--;
}
}
+ return processed;
}
-/* Process all the IO Jobs already completed by threads but still waiting
- * processing from the main thread. */
-void processAllPendingIOJobs(void) {
- while(1) {
+void waitEmptyIOJobsQueue(void) {
+ processActiveIOJobs(-1);
+}
+
+/* Process up to 'max' IO Jobs already completed by threads but still waiting
+ * processing from the main thread.
+ *
+ * If max == -1 all the pending jobs are processed.
+ *
+ * The number of processed jobs is returned. */
+int processPendingIOJobs(int max) {
+ int processed = 0;
+
+ while(max == -1 || max > 0) {
int io_processed_len;
lockThreadedIO();
io_processed_len = listLength(server.io_processed);
unlockThreadedIO();
- if (io_processed_len == 0) return;
+ if (io_processed_len == 0) break;
vmThreadedIOCompletedJob(NULL,server.io_ready_pipe_read,
(void*)0xdeadbeef,0);
+ if (max != -1) max--;
+ processed++;
}
+ return processed;
+}
+
+void processAllPendingIOJobs(void) {
+ processPendingIOJobs(-1);
}
/* This function must be called while with threaded IO locked */
spawnIOThread();
}
-void dsCreateIOJob(int type, redisDb *db, robj *key, robj *val) {
+/* Consume all the IO scheduled operations, and all the thread IO jobs
+ * so that eventually the state of diskstore is a point-in-time snapshot.
+ *
+ * This is useful when we need to BGSAVE with diskstore enabled. */
+void cacheForcePointInTime(void) {
+ redisLog(REDIS_NOTICE,"Diskstore: synching on disk to reach point-in-time state.");
+ while (listLength(server.cache_io_queue) != 0) {
+ cacheScheduleIOPushJobs(REDIS_IO_ASAP);
+ processActiveIOJobs(1);
+ }
+ waitEmptyIOJobsQueue();
+ processAllPendingIOJobs();
+}
+
+void cacheCreateIOJob(int type, redisDb *db, robj *key, robj *val, time_t expire) {
iojob *j;
j = zmalloc(sizeof(*j));
incrRefCount(key);
j->val = val;
if (val) incrRefCount(val);
+ j->expire = expire;
lockThreadedIO();
queueIOJob(j);
* in queue for the same key. */
if (type == REDIS_IO_LOAD && !(flags & REDIS_IO_SAVE)) {
listAddNodeHead(server.cache_io_queue, op);
+ cacheScheduleIOPushJobs(REDIS_IO_ONLYLOADS);
} else {
/* FIXME: probably when this happens we want to at least move
* the write job about this queue on top, and set the creation time
}
}
-void cacheCron(void) {
+/* Push scheduled IO operations into IO Jobs that the IO thread can process.
+ *
+ * If flags include REDIS_IO_ONLYLOADS only load jobs are processed:this is
+ * useful since it's safe to push LOAD IO jobs from any place of the code, while
+ * SAVE io jobs should never be pushed while we are processing a command
+ * (not protected by lookupKey() that will block on keys in IO_SAVEINPROG
+ * state.
+ *
+ * The REDIS_IO_ASAP flag tells the function to don't wait for the IO job
+ * scheduled completion time, but just do the operation ASAP. This is useful
+ * when we need to reclaim memory from the IO queue.
+ */
+#define MAX_IO_JOBS_QUEUE 10
+int cacheScheduleIOPushJobs(int flags) {
time_t now = time(NULL);
listNode *ln;
- int jobs, topush = 0;
+ int jobs, topush = 0, pushed = 0;
- /* Sync stuff on disk, but only if we have less than 100 IO jobs */
+ /* Don't push new jobs if there is a threaded BGSAVE in progress. */
+ if (server.bgsavethread != (pthread_t) -1) return 0;
+
+ /* Sync stuff on disk, but only if we have less
+ * than MAX_IO_JOBS_QUEUE IO jobs. */
lockThreadedIO();
jobs = listLength(server.io_newjobs);
unlockThreadedIO();
- topush = 100-jobs;
+ topush = MAX_IO_JOBS_QUEUE-jobs;
if (topush < 0) topush = 0;
if (topush > (signed)listLength(server.cache_io_queue))
topush = listLength(server.cache_io_queue);
while((ln = listFirst(server.cache_io_queue)) != NULL) {
ioop *op = ln->value;
+ struct dictEntry *de;
+ robj *val;
if (!topush) break;
topush--;
- if (op->type == REDIS_IO_LOAD ||
- (now - op->ctime) >= server.cache_flush_delay)
+ if (op->type != REDIS_IO_LOAD && flags & REDIS_IO_ONLYLOADS) break;
+
+ /* Don't execute SAVE before the scheduled time for completion */
+ if (op->type == REDIS_IO_SAVE && !(flags & REDIS_IO_ASAP) &&
+ (now - op->ctime) < server.cache_flush_delay) break;
+
+ /* Don't add a SAVE job in the IO thread queue if there is already
+ * a save in progress for the same key. */
+ if (op->type == REDIS_IO_SAVE &&
+ cacheScheduleIOGetFlags(op->db,op->key) & REDIS_IO_SAVEINPROG)
{
- struct dictEntry *de;
- robj *val;
-
- /* Don't add a SAVE job in queue if there is already
- * a save in progress for the same key. */
- if (op->type == REDIS_IO_SAVE &&
- cacheScheduleIOGetFlags(op->db,op->key) & REDIS_IO_SAVEINPROG)
- {
- /* Move the operation at the end of the list of there
- * are other operations. Otherwise break, nothing to do
- * here. */
- if (listLength(server.cache_io_queue) > 1) {
- listDelNode(server.cache_io_queue,ln);
- listAddNodeTail(server.cache_io_queue,op);
- continue;
- } else {
- break;
- }
+ /* Move the operation at the end of the list if there
+ * are other operations, so we can try to process the next one.
+ * Otherwise break, nothing to do here. */
+ if (listLength(server.cache_io_queue) > 1) {
+ listDelNode(server.cache_io_queue,ln);
+ listAddNodeTail(server.cache_io_queue,op);
+ continue;
+ } else {
+ break;
}
+ }
- redisLog(REDIS_DEBUG,"Creating IO %s Job for key %s",
- op->type == REDIS_IO_LOAD ? "load" : "save", op->key->ptr);
+ redisLog(REDIS_DEBUG,"Creating IO %s Job for key %s",
+ op->type == REDIS_IO_LOAD ? "load" : "save", op->key->ptr);
- if (op->type == REDIS_IO_LOAD) {
- dsCreateIOJob(REDIS_IOJOB_LOAD,op->db,op->key,NULL);
+ if (op->type == REDIS_IO_LOAD) {
+ cacheCreateIOJob(REDIS_IOJOB_LOAD,op->db,op->key,NULL,0);
+ } else {
+ time_t expire = -1;
+
+ /* Lookup the key, in order to put the current value in the IO
+ * Job. Otherwise if the key does not exists we schedule a disk
+ * store delete operation, setting the value to NULL. */
+ de = dictFind(op->db->dict,op->key->ptr);
+ if (de) {
+ val = dictGetEntryVal(de);
+ expire = getExpire(op->db,op->key);
} else {
- /* Lookup the key, in order to put the current value in the IO
- * Job. Otherwise if the key does not exists we schedule a disk
- * store delete operation, setting the value to NULL. */
- de = dictFind(op->db->dict,op->key->ptr);
- if (de) {
- val = dictGetEntryVal(de);
- } else {
- /* Setting the value to NULL tells the IO thread to delete
- * the key on disk. */
- val = NULL;
- }
- dsCreateIOJob(REDIS_IOJOB_SAVE,op->db,op->key,val);
+ /* Setting the value to NULL tells the IO thread to delete
+ * the key on disk. */
+ val = NULL;
}
- /* Mark the operation as in progress. */
- cacheScheduleIODelFlag(op->db,op->key,op->type);
- cacheScheduleIOAddFlag(op->db,op->key,
- (op->type == REDIS_IO_LOAD) ? REDIS_IO_LOADINPROG :
- REDIS_IO_SAVEINPROG);
- /* Finally remove the operation from the queue.
- * But we'll have trace of it in the hash table. */
- listDelNode(server.cache_io_queue,ln);
- decrRefCount(op->key);
- zfree(op);
- } else {
- break; /* too early */
+ cacheCreateIOJob(REDIS_IOJOB_SAVE,op->db,op->key,val,expire);
}
+ /* Mark the operation as in progress. */
+ cacheScheduleIODelFlag(op->db,op->key,op->type);
+ cacheScheduleIOAddFlag(op->db,op->key,
+ (op->type == REDIS_IO_LOAD) ? REDIS_IO_LOADINPROG :
+ REDIS_IO_SAVEINPROG);
+ /* Finally remove the operation from the queue.
+ * But we'll have trace of it in the hash table. */
+ listDelNode(server.cache_io_queue,ln);
+ decrRefCount(op->key);
+ zfree(op);
+ pushed++;
}
+ return pushed;
+}
+
+void cacheCron(void) {
+ /* Push jobs */
+ cacheScheduleIOPushJobs(0);
/* Reclaim memory from the object cache */
while (server.ds_enabled && zmalloc_used_memory() >
projects / redis.git / blobdiff