first attempt to non blocking implementation of slave replication and SYNC...

first attempt to non blocking implementation of slave replication and SYNC bulk data download. Never compiled so far...

src/networking.c

@@ -467,6 +467,7 @@ void freeClient(redisClient *c) {
     /* Case 2: we lost the connection with the master. */
     if (c->flags & REDIS_MASTER) {
         server.master = NULL;
+        /* FIXME */
         server.replstate = REDIS_REPL_CONNECT;
         /* Since we lost the connection with the master, we should also
          * close the connection with all our slaves if we have any, so

src/redis.c

@@ -633,14 +633,10 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
         }
     }
 
-    /* Check if we should connect to a MASTER */
-    if (server.replstate == REDIS_REPL_CONNECT && !(loops % 10)) {
-        redisLog(REDIS_NOTICE,"Connecting to MASTER...");
-        if (syncWithMaster() == REDIS_OK) {
-            redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync succeeded");
-            if (server.appendonly) rewriteAppendOnlyFileBackground();
-        }
-    }
+    /* Replication cron function -- used to reconnect to master and
+     * to detect transfer failures. */
+    if (!(loops % 10)) replicationCron(void);
+
     return 100;
 }
 

src/redis.h

@@ -152,7 +152,8 @@
 /* Slave replication state - slave side */
 #define REDIS_REPL_NONE 0   /* No active replication */
 #define REDIS_REPL_CONNECT 1    /* Must connect to master */
-#define REDIS_REPL_CONNECTED 2  /* Connected to master */
+#define REDIS_REPL_TRANFER 2    /* Receiving .rdb from master */
+#define REDIS_REPL_CONNECTED 3  /* Connected to master */
 
 /* Slave replication state - from the point of view of master
  * Note that in SEND_BULK and ONLINE state the slave receives new updates
@@ -401,15 +402,23 @@ struct redisServer {
     int activerehashing;
     /* Replication related */
     int isslave;
+    /* Slave specific fields */
     char *masterauth;
     char *masterhost;
     int masterport;
     redisClient *master;    /* client that is master for this slave */
-    int replstate;
+    int replstate;          /* replication status if the instance is a slave */
+    off_t repl_transfer_left;  /* bytes left reading .rdb if this is a slave */
+    int repl_transfer_s;    /* slave -> master SYNC socket */
+    int repl_transfer_fd;   /* slave -> master SYNC temp file descriptor */
+    char *repl_transfer_tmpfile; /* slave-> master SYNC temp file name */
+    time_t repl_transfer_lastio; /* unix time of the latest read, for timeout */
+    /* Limits */
     unsigned int maxclients;
     unsigned long long maxmemory;
     int maxmemory_policy;
     int maxmemory_samples;
+    /* Blocked clients */
     unsigned int blpop_blocked_clients;
     unsigned int vm_blocked_clients;
     /* Sort parameters - qsort_r() is only available under BSD so we
@@ -713,6 +722,7 @@ void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc);
 void replicationFeedMonitors(list *monitors, int dictid, robj **argv, int argc);
 int syncWithMaster(void);
 void updateSlavesWaitingBgsave(int bgsaveerr);
+void replicationCron(void);
 
 /* RDB persistence */
 int rdbLoad(char *filename);

src/replication.c

@@ -5,6 +5,8 @@
 #include <fcntl.h>
 #include <sys/stat.h>
 
+/* ---------------------------------- MASTER -------------------------------- */
+
 void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
     listNode *ln;
     listIter li;
@@ -288,9 +290,68 @@ void updateSlavesWaitingBgsave(int bgsaveerr) {
     }
 }
 
+/* ----------------------------------- SLAVE -------------------------------- */
+
+/* Abort the async download of the bulk dataset while SYNC-ing with master */
+void replicationAbortSyncTransfer(void) {
+    redisAssert(server.replstate == REDIS_REPL_TRANSFER);
+
+    aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
+    close(server.repl_transfer_s);
+    close(server.repl_transfer_fd);
+    unlink(server.repl_transfer_tmpfile);
+    zfree(server.repl_transfer_tmpfile);
+    server.replstate = REDIS_REPL_CONNECT;
+}
+
+/* Asynchronously read the SYNC payload we receive from a master */
+void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
+    unsigned char buf[4096]
+    size_t nread, readlen;
+
+    readlen = (server.repl_transfer_left < sizeof(buf)) ?
+        server.repl_transfer_left : sizeof(buf);
+    nread = read(fd,buf,readlen);
+    if (nread <= 0) {
+        redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
+            (nread == -1) ? strerror(errno) : "connection lost");
+        replicationAbortSyncTransfer();
+        return;
+    }
+    server.repl_transfer_lastio = time(NULL);
+    if (write(server.repl_transfer_fd,buf,nread) != nread) {
+        redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchrnonization: %s", strerror(errno));
+        replicationAbortSyncTransfer();
+        return;
+    }
+    server.repl_transfer_left -= nread;
+    /* Check if the transfer is now complete */
+    if (server.repl_transfer_left == 0) {
+        if (rename(server.repl_transfer_tmpfile,server.dbfilename) == -1) {
+            redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
+            replicationAbortSyncTransfer();
+            return;
+        }
+        emptyDb();
+        if (rdbLoad(server.dbfilename) != REDIS_OK) {
+            redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
+            replicationAbortSyncTransfer();
+            return;
+        }
+        /* Final setup of the connected slave <- master link */
+        aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
+        zfree(server.repl_transfer_tmpfile);
+        close(server.repl_transfer_fd);
+        server.master = createClient(server.repl_transfer_s);
+        server.master->flags |= REDIS_MASTER;
+        server.master->authenticated = 1;
+        server.replstate = REDIS_REPL_CONNECTED;
+    }
+}
+
 int syncWithMaster(void) {
     char buf[1024], tmpfile[256], authcmd[1024];
-    long dumpsize;
+    off_t dumpsize;
     int fd = anetTcpConnect(NULL,server.masterhost,server.masterport);
     int dfd, maxtries = 5;
 
@@ -362,43 +423,21 @@ int syncWithMaster(void) {
         redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno));
         return REDIS_ERR;
     }
-    while(dumpsize) {
-        int nread, nwritten;
 
-        nread = read(fd,buf,(dumpsize < 1024)?dumpsize:1024);
-        if (nread <= 0) {
-            redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
-                (nread == -1) ? strerror(errno) : "connection lost");
-            close(fd);
-            close(dfd);
-            return REDIS_ERR;
-        }
-        nwritten = write(dfd,buf,nread);
-        if (nwritten == -1) {
-            redisLog(REDIS_WARNING,"Write error writing to the DB dump file needed for MASTER <-> SLAVE synchrnonization: %s", strerror(errno));
-            close(fd);
-            close(dfd);
-            return REDIS_ERR;
-        }
-        dumpsize -= nread;
-    }
-    close(dfd);
-    if (rename(tmpfile,server.dbfilename) == -1) {
-        redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
-        unlink(tmpfile);
-        close(fd);
-        return REDIS_ERR;
-    }
-    emptyDb();
-    if (rdbLoad(server.dbfilename) != REDIS_OK) {
-        redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
+    /* Setup the non blocking download of the bulk file. */
+    if (aeCreateFileEvent(server.el, fd, AE_READABLE,readSyncBulkPayload) ==
+        AE_ERR)
+    {
         close(fd);
+        redisLog(REDIS_WARNING,"Can't create readable event for SYNC");
         return REDIS_ERR;
     }
-    server.master = createClient(fd);
-    server.master->flags |= REDIS_MASTER;
-    server.master->authenticated = 1;
-    server.replstate = REDIS_REPL_CONNECTED;
+    server.replstate = REDIS_REPL_TRANSFER;
+    server.repl_transfer_left = dumpsize;
+    server.repl_transfer_s = fd;
+    server.repl_transfer_fd = dfd;
+    server.repl_transfer_lastio = time(NULL);
+    server.repl_transfer_tmpfile = zstrdup(tmpfile);
     return REDIS_OK;
 }
 
@@ -409,6 +448,8 @@ void slaveofCommand(redisClient *c) {
             sdsfree(server.masterhost);
             server.masterhost = NULL;
             if (server.master) freeClient(server.master);
+            if (server.replstate == REDIS_REPL_TRANSFER)
+                replicationAbortSyncTransfer();
             server.replstate = REDIS_REPL_NONE;
             redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)");
         }
@@ -417,9 +458,34 @@ void slaveofCommand(redisClient *c) {
         server.masterhost = sdsdup(c->argv[1]->ptr);
         server.masterport = atoi(c->argv[2]->ptr);
         if (server.master) freeClient(server.master);
+        if (server.replstate == REDIS_REPL_TRANSFER)
+            replicationAbortSyncTransfer();
         server.replstate = REDIS_REPL_CONNECT;
         redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
             server.masterhost, server.masterport);
     }
     addReply(c,shared.ok);
 }
+
+/* --------------------------- REPLICATION CRON  ---------------------------- */
+
+#define REDIS_REPL_TRANSFER_TIMEOUT 60
+
+void replicationCron(void) {
+    /* Bulk transfer I/O timeout? */
+    if (server.masterhost && server.replstate == REDIS_REPL_TRANSFER &&
+        (time(NULL)-server.repl_transfer_lastio) > REDIS_REPL_TRANSFER_TIMEOUT)
+    {
+        redisLog(REDIS_WARNING,"Timeout receiving bulk data from MASTER...");
+        replicationAbortSyncTransfer();
+    }
+
+    /* Check if we should connect to a MASTER */
+    if (server.replstate == REDIS_REPL_CONNECT && !(loops % 10)) {
+        redisLog(REDIS_NOTICE,"Connecting to MASTER...");
+        if (syncWithMaster() == REDIS_OK) {
+            redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync succeeded");
+            if (server.appendonly) rewriteAppendOnlyFileBackground();
+        }
+    }
+}