Chunked loading of RDB to prevent redis from stalling reading very large keys.

src/rdb.c

@@ -1057,21 +1057,32 @@ void stopLoading(void) {
     server.loading = 0;
 }
 
+/* Track loading progress in order to serve client's from time to time
+   and if needed calculate rdb checksum  */
+void rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
+    if (server.rdb_checksum)
+        rioGenericUpdateChecksum(r, buf, len);
+    if (server.loading_process_events_interval_bytes &&
+        (r->processed_bytes + len)/server.loading_process_events_interval_bytes > r->processed_bytes/server.loading_process_events_interval_bytes) {
+        loadingProgress(r->processed_bytes);
+        aeProcessEvents(server.el, AE_FILE_EVENTS|AE_DONT_WAIT);
+    }
+}
+
 int rdbLoad(char *filename) {
     uint32_t dbid;
     int type, rdbver;
     redisDb *db = server.db+0;
     char buf[1024];
     long long expiretime, now = mstime();
-    long loops = 0;
     FILE *fp;
     rio rdb;
 
     if ((fp = fopen(filename,"r")) == NULL) return REDIS_ERR;
 
     rioInitWithFile(&rdb,fp);
-    if (server.rdb_checksum)
-        rdb.update_cksum = rioGenericUpdateChecksum;
+    rdb.update_cksum = rdbLoadProgressCallback;
+    rdb.max_processing_chunk = server.loading_process_events_interval_bytes;
     if (rioRead(&rdb,buf,9) == 0) goto eoferr;
     buf[9] = '\0';
     if (memcmp(buf,"REDIS",5) != 0) {
@@ -1093,12 +1104,6 @@ int rdbLoad(char *filename) {
         robj *key, *val;
         expiretime = -1;
 
-        /* Serve the clients from time to time */
-        if (!(loops++ % 1000)) {
-            loadingProgress(rioTell(&rdb));
-            aeProcessEvents(server.el, AE_FILE_EVENTS|AE_DONT_WAIT);
-        }
-
         /* Read type. */
         if ((type = rdbLoadType(&rdb)) == -1) goto eoferr;
         if (type == REDIS_RDB_OPCODE_EXPIRETIME) {

src/redis.c

@@ -1250,6 +1250,7 @@ void initServerConfig() {
     server.lua_time_limit = REDIS_LUA_TIME_LIMIT;
     server.lua_client = NULL;
     server.lua_timedout = 0;
+    server.loading_process_events_interval_bytes = (1024*1024*2);
 
     updateLRUClock();
     resetServerSaveParams();

src/redis.h

@@ -596,6 +596,7 @@ struct redisServer {
     off_t loading_total_bytes;
     off_t loading_loaded_bytes;
     time_t loading_start_time;
+    off_t loading_process_events_interval_bytes;
     /* Fast pointers to often looked up command */
     struct redisCommand *delCommand, *multiCommand, *lpushCommand, *lpopCommand,
                         *rpopCommand;

src/rio.c

@@ -108,6 +108,8 @@ static const rio rioBufferIO = {
     rioBufferTell,
     NULL,           /* update_checksum */
     0,              /* current checksum */
+    0,              /* bytes read or written */
+    0,              /* read/write chunk size */
     { { NULL, 0 } } /* union for io-specific vars */
 };
 
@@ -117,6 +119,8 @@ static const rio rioFileIO = {
     rioFileTell,
     NULL,           /* update_checksum */
     0,              /* current checksum */
+    0,              /* bytes read or written */
+    0,              /* read/write chunk size */
     { { NULL, 0 } } /* union for io-specific vars */
 };
 

src/rio.h

@@ -53,6 +53,12 @@ struct _rio {
     /* The current checksum */
     uint64_t cksum;
 
+    /* number of bytes read or written */
+    size_t processed_bytes;
+
+    /* maximum simgle read or write chunk size */
+    size_t max_processing_chunk;
+
     /* Backend-specific vars. */
     union {
         struct {
@@ -74,16 +80,29 @@ typedef struct _rio rio;
  * if needed. */
 
 static inline size_t rioWrite(rio *r, const void *buf, size_t len) {
-    if (r->update_cksum) r->update_cksum(r,buf,len);
-    return r->write(r,buf,len);
+    while (len) {
+        size_t bytes_to_write = (r->max_processing_chunk && r->max_processing_chunk < len) ? r->max_processing_chunk : len;
+        if (r->update_cksum) r->update_cksum(r,buf,bytes_to_write);
+        if (r->write(r,buf,bytes_to_write) == 0)
+            return 0;
+        buf = (char*)buf + bytes_to_write;
+        len -= bytes_to_write;
+        r->processed_bytes += bytes_to_write;
+    }
+    return 1;
 }
 
 static inline size_t rioRead(rio *r, void *buf, size_t len) {
-    if (r->read(r,buf,len) == 1) {
-        if (r->update_cksum) r->update_cksum(r,buf,len);
-        return 1;
+    while (len) {
+        size_t bytes_to_read = (r->max_processing_chunk && r->max_processing_chunk < len) ? r->max_processing_chunk : len;
+        if (r->read(r,buf,bytes_to_read) == 0)
+            return 0;
+        if (r->update_cksum) r->update_cksum(r,buf,bytes_to_read);
+        buf = (char*)buf + bytes_to_read;
+        len -= bytes_to_read;
+        r->processed_bytes += bytes_to_read;
     }
-    return 0;
+    return 1;
 }
 
 static inline off_t rioTell(rio *r) {