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Streams: initial work to use blocking lists logic for streams XREAD.

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This commit is contained in:
antirez 2017-09-06 15:43:28 +02:00
parent 439120c620
commit 4a377cecd8
6 changed files with 234 additions and 215 deletions
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208
src/blocked.c
View File

@ -65,6 +65,8 @@
#include "server.h"
int serveClientBlockedOnList(client *receiver, robj *key, robj *dstkey, redisDb *db, robj *value, int where);
/* Get a timeout value from an object and store it into 'timeout'.
* The final timeout is always stored as milliseconds as a time where the
* timeout will expire, however the parsing is performed according to
@ -193,3 +195,209 @@ void disconnectAllBlockedClients(void) {
}
}
}
/* This function should be called by Redis every time a single command,
* a MULTI/EXEC block, or a Lua script, terminated its execution after
* being called by a client.
*
* All the keys with at least one client blocked that received at least
* one new element via some PUSH/XADD operation are accumulated into
* the server.ready_keys list. This function will run the list and will
* serve clients accordingly. Note that the function will iterate again and
* again as a result of serving BRPOPLPUSH we can have new blocking clients
* to serve because of the PUSH side of BRPOPLPUSH. */
void handleClientsBlockedOnKeys(void) {
while(listLength(server.ready_keys) != 0) {
list *l;
/* Point server.ready_keys to a fresh list and save the current one
* locally. This way as we run the old list we are free to call
* signalKeyAsReady() that may push new elements in server.ready_keys
* when handling clients blocked into BRPOPLPUSH. */
l = server.ready_keys;
server.ready_keys = listCreate();
while(listLength(l) != 0) {
listNode *ln = listFirst(l);
readyList *rl = ln->value;
/* First of all remove this key from db->ready_keys so that
* we can safely call signalKeyAsReady() against this key. */
dictDelete(rl->db->ready_keys,rl->key);
/* If the key exists and it's a list, serve blocked clients
* with data. */
robj *o = lookupKeyWrite(rl->db,rl->key);
if (o != NULL && o->type == OBJ_LIST) {
dictEntry *de;
/* We serve clients in the same order they blocked for
* this key, from the first blocked to the last. */
de = dictFind(rl->db->blocking_keys,rl->key);
if (de) {
list *clients = dictGetVal(de);
int numclients = listLength(clients);
while(numclients--) {
listNode *clientnode = listFirst(clients);
client *receiver = clientnode->value;
robj *dstkey = receiver->bpop.target;
int where = (receiver->lastcmd &&
receiver->lastcmd->proc == blpopCommand) ?
LIST_HEAD : LIST_TAIL;
robj *value = listTypePop(o,where);
if (value) {
/* Protect receiver->bpop.target, that will be
* freed by the next unblockClient()
* call. */
if (dstkey) incrRefCount(dstkey);
unblockClient(receiver);
if (serveClientBlockedOnList(receiver,
rl->key,dstkey,rl->db,value,
where) == C_ERR)
{
/* If we failed serving the client we need
* to also undo the POP operation. */
listTypePush(o,value,where);
}
if (dstkey) decrRefCount(dstkey);
decrRefCount(value);
} else {
break;
}
}
}
if (listTypeLength(o) == 0) {
dbDelete(rl->db,rl->key);
}
/* We don't call signalModifiedKey() as it was already called
* when an element was pushed on the list. */
}
/* Free this item. */
decrRefCount(rl->key);
zfree(rl);
listDelNode(l,ln);
}
listRelease(l); /* We have the new list on place at this point. */
}
}
/* This is how the current blocking POP works, we use BLPOP as example:
* - If the user calls BLPOP and the key exists and contains a non empty list
* then LPOP is called instead. So BLPOP is semantically the same as LPOP
* if blocking is not required.
* - If instead BLPOP is called and the key does not exists or the list is
* empty we need to block. In order to do so we remove the notification for
* new data to read in the client socket (so that we'll not serve new
* requests if the blocking request is not served). Also we put the client
* in a dictionary (db->blocking_keys) mapping keys to a list of clients
* blocking for this keys.
* - If a PUSH operation against a key with blocked clients waiting is
* performed, we mark this key as "ready", and after the current command,
* MULTI/EXEC block, or script, is executed, we serve all the clients waiting
* for this list, from the one that blocked first, to the last, accordingly
* to the number of elements we have in the ready list.
*/
/* Set a client in blocking mode for the specified key, with the specified
* timeout */
void blockForKeys(client *c, robj **keys, int numkeys, mstime_t timeout, robj *target) {
dictEntry *de;
list *l;
int j;
c->bpop.timeout = timeout;
c->bpop.target = target;
if (target != NULL) incrRefCount(target);
for (j = 0; j < numkeys; j++) {
/* If the key already exists in the dict ignore it. */
if (dictAdd(c->bpop.keys,keys[j],NULL) != DICT_OK) continue;
incrRefCount(keys[j]);
/* And in the other "side", to map keys -> clients */
de = dictFind(c->db->blocking_keys,keys[j]);
if (de == NULL) {
int retval;
/* For every key we take a list of clients blocked for it */
l = listCreate();
retval = dictAdd(c->db->blocking_keys,keys[j],l);
incrRefCount(keys[j]);
serverAssertWithInfo(c,keys[j],retval == DICT_OK);
} else {
l = dictGetVal(de);
}
listAddNodeTail(l,c);
}
blockClient(c,BLOCKED_LIST);
}
/* Unblock a client that's waiting in a blocking operation such as BLPOP.
* You should never call this function directly, but unblockClient() instead. */
void unblockClientWaitingData(client *c) {
dictEntry *de;
dictIterator *di;
list *l;
serverAssertWithInfo(c,NULL,dictSize(c->bpop.keys) != 0);
di = dictGetIterator(c->bpop.keys);
/* The client may wait for multiple keys, so unblock it for every key. */
while((de = dictNext(di)) != NULL) {
robj *key = dictGetKey(de);
/* Remove this client from the list of clients waiting for this key. */
l = dictFetchValue(c->db->blocking_keys,key);
serverAssertWithInfo(c,key,l != NULL);
listDelNode(l,listSearchKey(l,c));
/* If the list is empty we need to remove it to avoid wasting memory */
if (listLength(l) == 0)
dictDelete(c->db->blocking_keys,key);
}
dictReleaseIterator(di);
/* Cleanup the client structure */
dictEmpty(c->bpop.keys,NULL);
if (c->bpop.target) {
decrRefCount(c->bpop.target);
c->bpop.target = NULL;
}
}
/* If the specified key has clients blocked waiting for list pushes, this
* function will put the key reference into the server.ready_keys list.
* Note that db->ready_keys is a hash table that allows us to avoid putting
* the same key again and again in the list in case of multiple pushes
* made by a script or in the context of MULTI/EXEC.
*
* The list will be finally processed by handleClientsBlockedOnLists() */
void signalKeyAsReady(redisDb *db, robj *key) {
readyList *rl;
/* No clients blocking for this key? No need to queue it. */
if (dictFind(db->blocking_keys,key) == NULL) return;
/* Key was already signaled? No need to queue it again. */
if (dictFind(db->ready_keys,key) != NULL) return;
/* Ok, we need to queue this key into server.ready_keys. */
rl = zmalloc(sizeof(*rl));
rl->key = key;
rl->db = db;
incrRefCount(key);
listAddNodeTail(server.ready_keys,rl);
/* We also add the key in the db->ready_keys dictionary in order
* to avoid adding it multiple times into a list with a simple O(1)
* check. */
incrRefCount(key);
serverAssert(dictAdd(db->ready_keys,key,NULL) == DICT_OK);
}

9
src/db.c
View File

@ -169,9 +169,10 @@ void dbAdd(redisDb *db, robj *key, robj *val) {
int retval = dictAdd(db->dict, copy, val);
serverAssertWithInfo(NULL,key,retval == DICT_OK);
if (val->type == OBJ_LIST) signalListAsReady(db, key);
if (val->type == OBJ_LIST || val->type == OBJ_STREAM)
signalKeyAsReady(db, key);
if (server.cluster_enabled) slotToKeyAdd(key);
}
}
/* Overwrite an existing key with a new value. Incrementing the reference
* count of the new value is up to the caller.
@ -951,8 +952,8 @@ void scanDatabaseForReadyLists(redisDb *db) {
while((de = dictNext(di)) != NULL) {
robj *key = dictGetKey(de);
robj *value = lookupKey(db,key,LOOKUP_NOTOUCH);
if (value && value->type == OBJ_LIST)
signalListAsReady(db, key);
if (value && (value->type == OBJ_LIST || value->type == OBJ_STREAM))
signalKeyAsReady(db, key);
}
dictReleaseIterator(di);
}

2
src/networking.c
View File

@ -124,7 +124,7 @@ client *createClient(int fd) {
listSetDupMethod(c->reply,dupClientReplyValue);
c->btype = BLOCKED_NONE;
c->bpop.timeout = 0;
c->bpop.keys = dictCreate(&objectKeyPointerValueDictType,NULL);
c->bpop.keys = dictCreate(&objectKeyHeapPointerValueDictType,NULL);
c->bpop.target = NULL;
c->bpop.numreplicas = 0;
c->bpop.reploffset = 0;

15
src/server.c
View File

@ -550,10 +550,21 @@ dictType objectKeyPointerValueDictType = {
NULL, /* key dup */
NULL, /* val dup */
dictEncObjKeyCompare, /* key compare */
dictObjectDestructor, /* key destructor */
dictObjectDestructor, /* key destructor */
NULL /* val destructor */
};
/* Like objectKeyPointerValueDictType(), but values can be destroyed, if
* not NULL, calling zfree(). */
dictType objectKeyHeapPointerValueDictType = {
dictEncObjHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictEncObjKeyCompare, /* key compare */
dictObjectDestructor, /* key destructor */
dictVanillaFree /* val destructor */
};
/* Set dictionary type. Keys are SDS strings, values are ot used. */
dictType setDictType = {
dictSdsHash, /* hash function */
@ -2508,7 +2519,7 @@ int processCommand(client *c) {
call(c,CMD_CALL_FULL);
c->woff = server.master_repl_offset;
if (listLength(server.ready_keys))
handleClientsBlockedOnLists();
handleClientsBlockedOnKeys();
}
return C_OK;
}

11
src/server.h
View File

@ -256,6 +256,7 @@ typedef long long mstime_t; /* millisecond time type. */
#define BLOCKED_LIST 1 /* BLPOP & co. */
#define BLOCKED_WAIT 2 /* WAIT for synchronous replication. */
#define BLOCKED_MODULE 3 /* Blocked by a loadable module. */
#define BLOCKED_STREAM 4 /* XREAD. */
/* Client request types */
#define PROTO_REQ_INLINE 1
@ -641,9 +642,9 @@ typedef struct blockingState {
mstime_t timeout; /* Blocking operation timeout. If UNIX current time
* is > timeout then the operation timed out. */
/* BLOCKED_LIST */
/* BLOCKED_LIST and BLOCKED_STREAM */
dict *keys; /* The keys we are waiting to terminate a blocking
* operation such as BLPOP. Otherwise NULL. */
* operation such as BLPOP or XREAD. Or NULL. */
robj *target; /* The key that should receive the element,
* for BRPOPLPUSH. */
@ -1291,6 +1292,7 @@ typedef struct {
extern struct redisServer server;
extern struct sharedObjectsStruct shared;
extern dictType objectKeyPointerValueDictType;
extern dictType objectKeyHeapPointerValueDictType;
extern dictType setDictType;
extern dictType zsetDictType;
extern dictType clusterNodesDictType;
@ -1413,9 +1415,7 @@ int listTypeEqual(listTypeEntry *entry, robj *o);
void listTypeDelete(listTypeIterator *iter, listTypeEntry *entry);
void listTypeConvert(robj *subject, int enc);
void unblockClientWaitingData(client *c);
void handleClientsBlockedOnLists(void);
void popGenericCommand(client *c, int where);
void signalListAsReady(redisDb *db, robj *key);
/* Stream data type. */
stream *streamNew(void);
@ -1798,6 +1798,9 @@ void unblockClient(client *c);
void replyToBlockedClientTimedOut(client *c);
int getTimeoutFromObjectOrReply(client *c, robj *object, mstime_t *timeout, int unit);
void disconnectAllBlockedClients(void);
void handleClientsBlockedOnKeys(void);
void signalKeyAsReady(redisDb *db, robj *key);
void blockForKeys(client *c, robj **keys, int numkeys, mstime_t timeout, robj *target);
/* expire.c -- Handling of expired keys */
void activeExpireCycle(int type);

204
src/t_list.c
View File

@ -603,119 +603,6 @@ void rpoplpushCommand(client *c) {
* Blocking POP operations
*----------------------------------------------------------------------------*/
/* This is how the current blocking POP works, we use BLPOP as example:
* - If the user calls BLPOP and the key exists and contains a non empty list
* then LPOP is called instead. So BLPOP is semantically the same as LPOP
* if blocking is not required.
* - If instead BLPOP is called and the key does not exists or the list is
* empty we need to block. In order to do so we remove the notification for
* new data to read in the client socket (so that we'll not serve new
* requests if the blocking request is not served). Also we put the client
* in a dictionary (db->blocking_keys) mapping keys to a list of clients
* blocking for this keys.
* - If a PUSH operation against a key with blocked clients waiting is
* performed, we mark this key as "ready", and after the current command,
* MULTI/EXEC block, or script, is executed, we serve all the clients waiting
* for this list, from the one that blocked first, to the last, accordingly
* to the number of elements we have in the ready list.
*/
/* Set a client in blocking mode for the specified key, with the specified
* timeout */
void blockForKeys(client *c, robj **keys, int numkeys, mstime_t timeout, robj *target) {
dictEntry *de;
list *l;
int j;
c->bpop.timeout = timeout;
c->bpop.target = target;
if (target != NULL) incrRefCount(target);
for (j = 0; j < numkeys; j++) {
/* If the key already exists in the dict ignore it. */
if (dictAdd(c->bpop.keys,keys[j],NULL) != DICT_OK) continue;
incrRefCount(keys[j]);
/* And in the other "side", to map keys -> clients */
de = dictFind(c->db->blocking_keys,keys[j]);
if (de == NULL) {
int retval;
/* For every key we take a list of clients blocked for it */
l = listCreate();
retval = dictAdd(c->db->blocking_keys,keys[j],l);
incrRefCount(keys[j]);
serverAssertWithInfo(c,keys[j],retval == DICT_OK);
} else {
l = dictGetVal(de);
}
listAddNodeTail(l,c);
}
blockClient(c,BLOCKED_LIST);
}
/* Unblock a client that's waiting in a blocking operation such as BLPOP.
* You should never call this function directly, but unblockClient() instead. */
void unblockClientWaitingData(client *c) {
dictEntry *de;
dictIterator *di;
list *l;
serverAssertWithInfo(c,NULL,dictSize(c->bpop.keys) != 0);
di = dictGetIterator(c->bpop.keys);
/* The client may wait for multiple keys, so unblock it for every key. */
while((de = dictNext(di)) != NULL) {
robj *key = dictGetKey(de);
/* Remove this client from the list of clients waiting for this key. */
l = dictFetchValue(c->db->blocking_keys,key);
serverAssertWithInfo(c,key,l != NULL);
listDelNode(l,listSearchKey(l,c));
/* If the list is empty we need to remove it to avoid wasting memory */
if (listLength(l) == 0)
dictDelete(c->db->blocking_keys,key);
}
dictReleaseIterator(di);
/* Cleanup the client structure */
dictEmpty(c->bpop.keys,NULL);
if (c->bpop.target) {
decrRefCount(c->bpop.target);
c->bpop.target = NULL;
}
}
/* If the specified key has clients blocked waiting for list pushes, this
* function will put the key reference into the server.ready_keys list.
* Note that db->ready_keys is a hash table that allows us to avoid putting
* the same key again and again in the list in case of multiple pushes
* made by a script or in the context of MULTI/EXEC.
*
* The list will be finally processed by handleClientsBlockedOnLists() */
void signalListAsReady(redisDb *db, robj *key) {
readyList *rl;
/* No clients blocking for this key? No need to queue it. */
if (dictFind(db->blocking_keys,key) == NULL) return;
/* Key was already signaled? No need to queue it again. */
if (dictFind(db->ready_keys,key) != NULL) return;
/* Ok, we need to queue this key into server.ready_keys. */
rl = zmalloc(sizeof(*rl));
rl->key = key;
rl->db = db;
incrRefCount(key);
listAddNodeTail(server.ready_keys,rl);
/* We also add the key in the db->ready_keys dictionary in order
* to avoid adding it multiple times into a list with a simple O(1)
* check. */
incrRefCount(key);
serverAssert(dictAdd(db->ready_keys,key,NULL) == DICT_OK);
}
/* This is a helper function for handleClientsBlockedOnLists(). It's work
* is to serve a specific client (receiver) that is blocked on 'key'
* in the context of the specified 'db', doing the following:
@ -785,97 +672,6 @@ int serveClientBlockedOnList(client *receiver, robj *key, robj *dstkey, redisDb
return C_OK;
}
/* This function should be called by Redis every time a single command,
* a MULTI/EXEC block, or a Lua script, terminated its execution after
* being called by a client.
*
* All the keys with at least one client blocked that received at least
* one new element via some PUSH operation are accumulated into
* the server.ready_keys list. This function will run the list and will
* serve clients accordingly. Note that the function will iterate again and
* again as a result of serving BRPOPLPUSH we can have new blocking clients
* to serve because of the PUSH side of BRPOPLPUSH. */
void handleClientsBlockedOnLists(void) {
while(listLength(server.ready_keys) != 0) {
list *l;
/* Point server.ready_keys to a fresh list and save the current one
* locally. This way as we run the old list we are free to call
* signalListAsReady() that may push new elements in server.ready_keys
* when handling clients blocked into BRPOPLPUSH. */
l = server.ready_keys;
server.ready_keys = listCreate();
while(listLength(l) != 0) {
listNode *ln = listFirst(l);
readyList *rl = ln->value;
/* First of all remove this key from db->ready_keys so that
* we can safely call signalListAsReady() against this key. */
dictDelete(rl->db->ready_keys,rl->key);
/* If the key exists and it's a list, serve blocked clients
* with data. */
robj *o = lookupKeyWrite(rl->db,rl->key);
if (o != NULL && o->type == OBJ_LIST) {
dictEntry *de;
/* We serve clients in the same order they blocked for
* this key, from the first blocked to the last. */
de = dictFind(rl->db->blocking_keys,rl->key);
if (de) {
list *clients = dictGetVal(de);
int numclients = listLength(clients);
while(numclients--) {
listNode *clientnode = listFirst(clients);
client *receiver = clientnode->value;
robj *dstkey = receiver->bpop.target;
int where = (receiver->lastcmd &&
receiver->lastcmd->proc == blpopCommand) ?
LIST_HEAD : LIST_TAIL;
robj *value = listTypePop(o,where);
if (value) {
/* Protect receiver->bpop.target, that will be
* freed by the next unblockClient()
* call. */
if (dstkey) incrRefCount(dstkey);
unblockClient(receiver);
if (serveClientBlockedOnList(receiver,
rl->key,dstkey,rl->db,value,
where) == C_ERR)
{
/* If we failed serving the client we need
* to also undo the POP operation. */
listTypePush(o,value,where);
}
if (dstkey) decrRefCount(dstkey);
decrRefCount(value);
} else {
break;
}
}
}
if (listTypeLength(o) == 0) {
dbDelete(rl->db,rl->key);
}
/* We don't call signalModifiedKey() as it was already called
* when an element was pushed on the list. */
}
/* Free this item. */
decrRefCount(rl->key);
zfree(rl);
listDelNode(l,ln);
}
listRelease(l); /* We have the new list on place at this point. */
}
}
/* Blocking RPOP/LPOP */
void blockingPopGenericCommand(client *c, int where) {
robj *o;