Merge pull request #4479 from dvirsky/notify

Keyspace notifications API for modules

5 files changed, 302 insertions, 36 deletions

diff --git a/src/module.c b/src/module.c
index 545f1a74a..96e65f0be 100644
--- a/src/module.c
+++ b/src/module.c
@@ -216,6 +216,28 @@ static list *moduleUnblockedClients;
  * allow thread safe contexts to execute commands at a safe moment. */
 static pthread_mutex_t moduleGIL = PTHREAD_MUTEX_INITIALIZER;
 
+
+/* Function pointer type for keyspace event notification subscriptions from modules. */
+typedef int (*RedisModuleNotificationFunc) (RedisModuleCtx *ctx, int type, const char *event, RedisModuleString *key);
+
+/* Keyspace notification subscriber information. See RM_SubscribeToKeyspaceEvents */
+typedef struct RedisModuleKeyspaceSubscriber {
+    /* The module subscribed to the event */
+    RedisModule *module;    
+    /* Notification callback in the module*/
+    RedisModuleNotificationFunc notify_callback; 
+    /* A bit mask of the events the module is interested in */
+    int event_mask; 
+    /* Active flag set on entry, to avoid reentrant subscribers calling themselves */
+    int active; 
+} RedisModuleKeyspaceSubscriber;
+
+/* The module keyspace notification subscribers list */
+static list *moduleKeyspaceSubscribers;
+
+/* Static client recycled for all notification clients, to avoid allocating per round. */
+static client *moduleKeyspaceSubscribersClient;
+
 /* --------------------------------------------------------------------------
  * Prototypes
  * -------------------------------------------------------------------------- */
@@ -3669,6 +3691,126 @@ void moduleReleaseGIL(void) {
     pthread_mutex_unlock(&moduleGIL);
 }
 
+
+/* --------------------------------------------------------------------------
+ * Module Keyspace Notifications API
+ * -------------------------------------------------------------------------- */
+
+/* Subscribe to keyspace notifications. This is a low-level version of the 
+ * keyspace-notifications API. A module cand register callbacks to be notified
+ * when keyspce events occur. 
+ * 
+ * Notification events are filtered by their type (string events, set events,
+ * etc), and the subsriber callback receives only events that match a specific
+ * mask of event types. 
+ * 
+ * When subscribing to notifications with RedisModule_SubscribeToKeyspaceEvents 
+ * the module must provide an event type-mask, denoting the events the subscriber
+ * is interested in. This can be an ORed mask of any of the following flags:
+ * 
+ *  - REDISMODULE_NOTIFY_GENERIC: Generic commands like DEL, EXPIRE, RENAME
+ *  - REDISMODULE_NOTIFY_STRING: String events
+ *  - REDISMODULE_NOTIFY_LIST: List events
+ *  - REDISMODULE_NOTIFY_SET: Set events
+ *  - REDISMODULE_NOTIFY_HASH: Hash events
+ *  - REDISMODULE_NOTIFY_ZSET: Sorted Set events
+ *  - REDISMODULE_NOTIFY_EXPIRED: Expiration events
+ *  - REDISMODULE_NOTIFY_EVICTED: Eviction events
+ *  - REDISMODULE_NOTIFY_STREAM: Stream events
+ *  - REDISMODULE_NOTIFY_ALL: All events
+ * 
+ * We do not distinguish between key events and keyspace events, and it is up
+ * to the module to filter the actions taken based on the key. 
+ * 
+ * The subscriber signature is:
+ * 
+ *   int (*RedisModuleNotificationFunc) (RedisModuleCtx *ctx, int type, 
+ *                                       const char *event, 
+ *                                       RedisModuleString *key);
+ * 
+ * `type` is the event type bit, that must match the mask given at registration
+ * time. The event string is the actual command being executed, and key is the
+ * relevant Redis key. 
+ * 
+ * Notification callback gets executed with a redis context that can not be
+ * used to send anything to the client, and has the db number where the event
+ * occured as its selected db number.
+ * 
+ * Notice that it is not necessary to enable norifications in redis.conf for 
+ * module notifications to work. 
+ * 
+ * Warning: the notification callbacks are performed in a synchronous manner,
+ * so notification callbacks must to be fast, or they would slow Redis down. 
+ * If you need to take long actions, use threads to offload them.
+ * 
+ * See https://redis.io/topics/notifications for more information. 
+ */
+int RM_SubscribeToKeyspaceEvents(RedisModuleCtx *ctx, int types, RedisModuleNotificationFunc callback) {
+    RedisModuleKeyspaceSubscriber *sub = zmalloc(sizeof(*sub));
+    sub->module = ctx->module;
+    sub->event_mask = types;
+    sub->notify_callback = callback;
+    sub->active = 0;
+
+    listAddNodeTail(moduleKeyspaceSubscribers, sub);
+    return REDISMODULE_OK;
+
+}
+
+/* Dispatcher for keyspace notifications to module subscriber functions. 
+ * This gets called  only if at least one module requested to be notified on
+ * keyspace notifications */
+void moduleNotifyKeyspaceEvent(int type, const char *event, robj *key, int dbid) {
+    
+    /* Don't do anything if there aren't any subscribers */
+    if (listLength(moduleKeyspaceSubscribers) == 0) return;
+    
+    listIter li;
+    listNode *ln;
+
+    listRewind(moduleKeyspaceSubscribers,&li);
+
+    /* Remove irrelevant flags from the type mask */
+    type &= ~(NOTIFY_KEYEVENT | NOTIFY_KEYSPACE);
+
+    
+    while((ln = listNext(&li))) {
+        RedisModuleKeyspaceSubscriber *sub = ln->value;
+        /* Only notify subscribers on events matching they registration,
+         * and avoid subscribers triggering themselves */
+        if ((sub->event_mask & type) && sub->active == 0) {
+            RedisModuleCtx ctx = REDISMODULE_CTX_INIT;
+            ctx.module = sub->module;
+            ctx.client = moduleKeyspaceSubscribersClient;
+            selectDb(ctx.client, dbid);
+
+            /* mark the handler as activer to avoid reentrant loops. 
+             * If the subscriber performs an action triggering itself,
+             * it will not be notified about it. */
+            sub->active = 1;
+            sub->notify_callback(&ctx, type, event, key);
+            sub->active = 0;
+            moduleFreeContext(&ctx);
+        }
+    }
+    
+}
+
+/* Unsubscribe any notification subscirbers this module has upon unloading */
+void moduleUnsubscribeNotifications(RedisModule *module) {
+    listIter li;
+    listNode *ln;
+    listRewind(moduleKeyspaceSubscribers,&li);
+    while((ln = listNext(&li))) {
+        RedisModuleKeyspaceSubscriber *sub = ln->value;
+        if (sub->module == module) {
+            listDelNode(moduleKeyspaceSubscribers, ln);
+            zfree(sub);
+        }
+    }
+}
+
+
 /* --------------------------------------------------------------------------
  * Modules API internals
  * -------------------------------------------------------------------------- */
@@ -3706,9 +3848,15 @@ void moduleRegisterCoreAPI(void);
 
 void moduleInitModulesSystem(void) {
     moduleUnblockedClients = listCreate();
-
+    
     server.loadmodule_queue = listCreate();
     modules = dictCreate(&modulesDictType,NULL);
+    
+    /* Set up the keyspace notification susbscriber list and static client */
+    moduleKeyspaceSubscribers = listCreate();
+    moduleKeyspaceSubscribersClient = createClient(-1);
+    moduleKeyspaceSubscribersClient->flags |= CLIENT_MODULE;
+
     moduleRegisterCoreAPI();
     if (pipe(server.module_blocked_pipe) == -1) {
         serverLog(LL_WARNING,
@@ -3759,6 +3907,7 @@ void moduleFreeModuleStructure(struct RedisModule *module) {
     zfree(module);
 }
 
+
 void moduleUnregisterCommands(struct RedisModule *module) {
     /* Unregister all the commands registered by this module. */
     dictIterator *di = dictGetSafeIterator(server.commands);
@@ -3819,6 +3968,7 @@ int moduleLoad(const char *path, void **module_argv, int module_argc) {
     return C_OK;
 }
 
+
 /* Unload the module registered with the specified name. On success
  * C_OK is returned, otherwise C_ERR is returned and errno is set
  * to the following values depending on the type of error:
@@ -3840,6 +3990,9 @@ int moduleUnload(sds name) {
 
     moduleUnregisterCommands(module);
 
+    /* Remvoe any noification subscribers this module might have */
+    moduleUnsubscribeNotifications(module);
+
     /* Unregister all the hooks. TODO: Yet no hooks support here. */
 
     /* Unload the dynamic library. */
@@ -4037,4 +4190,5 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(DigestAddStringBuffer);
     REGISTER_API(DigestAddLongLong);
     REGISTER_API(DigestEndSequence);
+    REGISTER_API(SubscribeToKeyspaceEvents);
 }
diff --git a/src/modules/testmodule.c b/src/modules/testmodule.c
index 956b24179..67a861704 100644
--- a/src/modules/testmodule.c
+++ b/src/modules/testmodule.c
@@ -30,6 +30,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define REDISMODULE_EXPERIMENTAL_API
 #include "../redismodule.h"
 #include <string.h>
 
@@ -124,6 +125,7 @@ int failTest(RedisModuleCtx *ctx, const char *msg) {
     RedisModule_ReplyWithError(ctx, msg);
     return REDISMODULE_ERR;
 }
+
 int TestUnlink(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     RedisModule_AutoMemory(ctx);
     REDISMODULE_NOT_USED(argv);
@@ -153,80 +155,153 @@ int TestUnlink(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     
 }
 
+int NotifyCallback(RedisModuleCtx *ctx, int type, const char *event,
+                   RedisModuleString *key) {
+  /* Increment a counter on the notifications: for each key notified we
+   * increment a counter */
+  RedisModule_Log(ctx, "notice", "Got event type %d, event %s, key %s", type,
+                  event, RedisModule_StringPtrLen(key, NULL));
+
+  RedisModule_Call(ctx, "HINCRBY", "csc", "notifications", key, "1");
+  return REDISMODULE_OK;
+}
+
+/* TEST.NOTIFICATIONS -- Test Keyspace Notifications. */
+int TestNotifications(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    REDISMODULE_NOT_USED(argv);
+    REDISMODULE_NOT_USED(argc);
+
+#define FAIL(msg, ...)                                                                       \
+    {                                                                                        \
+        RedisModule_Log(ctx, "warning", "Failed NOTIFY Test. Reason: " #msg, ##__VA_ARGS__); \
+        goto err;                                                                            \
+    }
+    RedisModule_Call(ctx, "FLUSHDB", "");
+
+    RedisModule_Call(ctx, "SET", "cc", "foo", "bar");
+    RedisModule_Call(ctx, "SET", "cc", "foo", "baz");
+    RedisModule_Call(ctx, "SADD", "cc", "bar", "x");
+    RedisModule_Call(ctx, "SADD", "cc", "bar", "y");
+
+    RedisModule_Call(ctx, "HSET", "ccc", "baz", "x", "y");
+    /* LPUSH should be ignored and not increment any counters */
+    RedisModule_Call(ctx, "LPUSH", "cc", "l", "y");
+    RedisModule_Call(ctx, "LPUSH", "cc", "l", "y");
+
+    size_t sz;
+    const char *rep;
+    RedisModuleCallReply *r = RedisModule_Call(ctx, "HGET", "cc", "notifications", "foo");
+    if (r == NULL || RedisModule_CallReplyType(r) != REDISMODULE_REPLY_STRING) {
+        FAIL("Wrong or no reply for foo");
+    } else {
+        rep = RedisModule_CallReplyStringPtr(r, &sz);
+        if (sz != 1 || *rep != '2') {
+            FAIL("Got reply '%s'. expected '2'", RedisModule_CallReplyStringPtr(r, NULL));
+        }
+    }
+
+    r = RedisModule_Call(ctx, "HGET", "cc", "notifications", "bar");
+    if (r == NULL || RedisModule_CallReplyType(r) != REDISMODULE_REPLY_STRING) {
+        FAIL("Wrong or no reply for bar");
+    } else {
+        rep = RedisModule_CallReplyStringPtr(r, &sz);
+        if (sz != 1 || *rep != '2') {
+            FAIL("Got reply '%s'. expected '2'", rep);
+        }
+    }
+
+    r = RedisModule_Call(ctx, "HGET", "cc", "notifications", "baz");
+    if (r == NULL || RedisModule_CallReplyType(r) != REDISMODULE_REPLY_STRING) {
+        FAIL("Wrong or no reply for baz");
+    } else {
+        rep = RedisModule_CallReplyStringPtr(r, &sz);
+        if (sz != 1 || *rep != '1') {
+            FAIL("Got reply '%.*s'. expected '1'", sz, rep);
+        }
+    }
+    /* For l we expect nothing since we didn't subscribe to list events */
+    r = RedisModule_Call(ctx, "HGET", "cc", "notifications", "l");
+    if (r == NULL || RedisModule_CallReplyType(r) != REDISMODULE_REPLY_NULL) {
+        FAIL("Wrong reply for l");
+    }
+
+    RedisModule_Call(ctx, "FLUSHDB", "");
+
+    return RedisModule_ReplyWithSimpleString(ctx, "OK");
+err:
+    RedisModule_Call(ctx, "FLUSHDB", "");
+
+    return RedisModule_ReplyWithSimpleString(ctx, "ERR");
+}
+
 /* TEST.CTXFLAGS -- Test GetContextFlags. */
 int TestCtxFlags(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     REDISMODULE_NOT_USED(argc);
     REDISMODULE_NOT_USED(argv);
-  
+
     RedisModule_AutoMemory(ctx);
-  
+
     int ok = 1;
     const char *errString = NULL;
-  
-  #define FAIL(msg)    \
-    {                  \
-      ok = 0;          \
-      errString = msg; \
-      goto end;        \
+#undef FAIL
+#define FAIL(msg)        \
+    {                    \
+        ok = 0;          \
+        errString = msg; \
+        goto end;        \
     }
-  
+
     int flags = RedisModule_GetContextFlags(ctx);
     if (flags == 0) {
-      FAIL("Got no flags");
+        FAIL("Got no flags");
     }
-  
+
     if (flags & REDISMODULE_CTX_FLAGS_LUA) FAIL("Lua flag was set");
     if (flags & REDISMODULE_CTX_FLAGS_MULTI) FAIL("Multi flag was set");
-  
+
     if (flags & REDISMODULE_CTX_FLAGS_AOF) FAIL("AOF Flag was set")
     /* Enable AOF to test AOF flags */
     RedisModule_Call(ctx, "config", "ccc", "set", "appendonly", "yes");
     flags = RedisModule_GetContextFlags(ctx);
-    if (!(flags & REDISMODULE_CTX_FLAGS_AOF))
-      FAIL("AOF Flag not set after config set");
-  
+    if (!(flags & REDISMODULE_CTX_FLAGS_AOF)) FAIL("AOF Flag not set after config set");
+
     if (flags & REDISMODULE_CTX_FLAGS_RDB) FAIL("RDB Flag was set");
     /* Enable RDB to test RDB flags */
     RedisModule_Call(ctx, "config", "ccc", "set", "save", "900 1");
     flags = RedisModule_GetContextFlags(ctx);
-    if (!(flags & REDISMODULE_CTX_FLAGS_RDB))
-      FAIL("RDB Flag was not set after config set");
-  
+    if (!(flags & REDISMODULE_CTX_FLAGS_RDB)) FAIL("RDB Flag was not set after config set");
+
     if (!(flags & REDISMODULE_CTX_FLAGS_MASTER)) FAIL("Master flag was not set");
     if (flags & REDISMODULE_CTX_FLAGS_SLAVE) FAIL("Slave flag was set");
     if (flags & REDISMODULE_CTX_FLAGS_READONLY) FAIL("Read-only flag was set");
     if (flags & REDISMODULE_CTX_FLAGS_CLUSTER) FAIL("Cluster flag was set");
-  
+
     if (flags & REDISMODULE_CTX_FLAGS_MAXMEMORY) FAIL("Maxmemory flag was set");
-    ;
+
     RedisModule_Call(ctx, "config", "ccc", "set", "maxmemory", "100000000");
     flags = RedisModule_GetContextFlags(ctx);
     if (!(flags & REDISMODULE_CTX_FLAGS_MAXMEMORY))
-      FAIL("Maxmemory flag was not set after config set");
-  
+        FAIL("Maxmemory flag was not set after config set");
+
     if (flags & REDISMODULE_CTX_FLAGS_EVICT) FAIL("Eviction flag was set");
-    RedisModule_Call(ctx, "config", "ccc", "set", "maxmemory-policy",
-                     "allkeys-lru");
+    RedisModule_Call(ctx, "config", "ccc", "set", "maxmemory-policy", "allkeys-lru");
     flags = RedisModule_GetContextFlags(ctx);
-    if (!(flags & REDISMODULE_CTX_FLAGS_EVICT))
-      FAIL("Eviction flag was not set after config set");
-  
-  end:
+    if (!(flags & REDISMODULE_CTX_FLAGS_EVICT)) FAIL("Eviction flag was not set after config set");
+
+end:
     /* Revert config changes */
     RedisModule_Call(ctx, "config", "ccc", "set", "appendonly", "no");
     RedisModule_Call(ctx, "config", "ccc", "set", "save", "");
     RedisModule_Call(ctx, "config", "ccc", "set", "maxmemory", "0");
     RedisModule_Call(ctx, "config", "ccc", "set", "maxmemory-policy", "noeviction");
-  
+
     if (!ok) {
-      RedisModule_Log(ctx, "warning", "Failed CTXFLAGS Test. Reason: %s",
-                      errString);
-      return RedisModule_ReplyWithSimpleString(ctx, "ERR");
+        RedisModule_Log(ctx, "warning", "Failed CTXFLAGS Test. Reason: %s", errString);
+        return RedisModule_ReplyWithSimpleString(ctx, "ERR");
     }
-  
-    return RedisModule_ReplyWithSimpleString(ctx, "OK");
-  }
 
+    return RedisModule_ReplyWithSimpleString(ctx, "OK");
+}
 
 /* ----------------------------- Test framework ----------------------------- */
 
@@ -310,6 +385,9 @@ int TestIt(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     T("test.string.printf", "cc", "foo", "bar");
     if (!TestAssertStringReply(ctx,reply,"Got 3 args. argv[1]: foo, argv[2]: bar",38)) goto fail;
 
+    T("test.notify", "");
+    if (!TestAssertStringReply(ctx,reply,"OK",2)) goto fail;
+
     RedisModule_ReplyWithSimpleString(ctx,"ALL TESTS PASSED");
     return REDISMODULE_OK;
 
@@ -354,5 +432,14 @@ int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
         TestIt,"readonly",1,1,1) == REDISMODULE_ERR)
         return REDISMODULE_ERR;
 
+    RedisModule_SubscribeToKeyspaceEvents(ctx,
+                                            REDISMODULE_NOTIFY_HASH |
+                                            REDISMODULE_NOTIFY_SET |
+                                            REDISMODULE_NOTIFY_STRING,
+                                        NotifyCallback);
+    if (RedisModule_CreateCommand(ctx,"test.notify",
+        TestNotifications,"write deny-oom",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
     return REDISMODULE_OK;
 }
diff --git a/src/notify.c b/src/notify.c
index f98cb9204..6dd72f0a6 100644
--- a/src/notify.c
+++ b/src/notify.c
@@ -100,6 +100,12 @@ void notifyKeyspaceEvent(int type, char *event, robj *key, int dbid) {
     int len = -1;
     char buf[24];
 
+    /* If any modules are interested in events, notify the module system now. 
+     * This bypasses the notifications configuration, but the module engine
+     * will only call event subscribers if the event type matches the types
+     * they are interested in. */
+     moduleNotifyKeyspaceEvent(type, event, key, dbid);
+    
     /* If notifications for this class of events are off, return ASAP. */
     if (!(server.notify_keyspace_events & type)) return;
 
diff --git a/src/redismodule.h b/src/redismodule.h
index 09d681c27..8c14fd0d1 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -82,6 +82,18 @@
 #define REDISMODULE_CTX_FLAGS_EVICT 0x0200 
 
 
+#define REDISMODULE_NOTIFY_GENERIC (1<<2)     /* g */
+#define REDISMODULE_NOTIFY_STRING (1<<3)      /* $ */
+#define REDISMODULE_NOTIFY_LIST (1<<4)        /* l */
+#define REDISMODULE_NOTIFY_SET (1<<5)         /* s */
+#define REDISMODULE_NOTIFY_HASH (1<<6)        /* h */
+#define REDISMODULE_NOTIFY_ZSET (1<<7)        /* z */
+#define REDISMODULE_NOTIFY_EXPIRED (1<<8)     /* x */
+#define REDISMODULE_NOTIFY_EVICTED (1<<9)     /* e */
+#define REDISMODULE_NOTIFY_STREAM (1<<10)     /* t */ 
+#define REDISMODULE_NOTIFY_ALL (REDISMODULE_NOTIFY_GENERIC | REDISMODULE_NOTIFY_STRING | REDISMODULE_NOTIFY_LIST | REDISMODULE_NOTIFY_SET | REDISMODULE_NOTIFY_HASH | REDISMODULE_NOTIFY_ZSET | REDISMODULE_NOTIFY_EXPIRED | REDISMODULE_NOTIFY_EVICTED | REDISMODULE_NOTIFY_STREAM)      /* A */
+
+
 /* A special pointer that we can use between the core and the module to signal
  * field deletion, and that is impossible to be a valid pointer. */
 #define REDISMODULE_HASH_DELETE ((RedisModuleString*)(long)1)
@@ -112,6 +124,7 @@ typedef struct RedisModuleBlockedClient RedisModuleBlockedClient;
 
 typedef int (*RedisModuleCmdFunc) (RedisModuleCtx *ctx, RedisModuleString **argv, int argc);
 
+typedef int (*RedisModuleNotificationFunc) (RedisModuleCtx *ctx, int type, const char *event, RedisModuleString *key);
 typedef void *(*RedisModuleTypeLoadFunc)(RedisModuleIO *rdb, int encver);
 typedef void (*RedisModuleTypeSaveFunc)(RedisModuleIO *rdb, void *value);
 typedef void (*RedisModuleTypeRewriteFunc)(RedisModuleIO *aof, RedisModuleString *key, void *value);
@@ -251,6 +264,8 @@ RedisModuleCtx *REDISMODULE_API_FUNC(RedisModule_GetThreadSafeContext)(RedisModu
 void REDISMODULE_API_FUNC(RedisModule_FreeThreadSafeContext)(RedisModuleCtx *ctx);
 void REDISMODULE_API_FUNC(RedisModule_ThreadSafeContextLock)(RedisModuleCtx *ctx);
 void REDISMODULE_API_FUNC(RedisModule_ThreadSafeContextUnlock)(RedisModuleCtx *ctx);
+int REDISMODULE_API_FUNC(RedisModule_SubscribeToKeyspaceEvents)(RedisModuleCtx *ctx, int types, RedisModuleNotificationFunc cb);
+
 #endif
 
 /* This is included inline inside each Redis module. */
@@ -372,6 +387,8 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(IsBlockedTimeoutRequest);
     REDISMODULE_GET_API(GetBlockedClientPrivateData);
     REDISMODULE_GET_API(AbortBlock);
+    REDISMODULE_GET_API(SubscribeToKeyspaceEvents);
+
 #endif
 
     if (RedisModule_IsModuleNameBusy && RedisModule_IsModuleNameBusy(name)) return REDISMODULE_ERR;
diff --git a/src/server.h b/src/server.h
index 271f217fb..5b6074a8c 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1335,6 +1335,8 @@ void moduleBlockedClientPipeReadable(aeEventLoop *el, int fd, void *privdata, in
 size_t moduleCount(void);
 void moduleAcquireGIL(void);
 void moduleReleaseGIL(void);
+void moduleNotifyKeyspaceEvent(int type, const char *event, robj *key, int dbid);
+
 
 /* Utils */
 long long ustime(void);