RDB AOF preamble: WIP 4 (Mixed RDB/AOF loading).

src/aof.c

@@ -616,19 +616,23 @@ int loadAppendOnlyFile(char *filename) {
     struct redis_stat sb;
     int old_aof_state = server.aof_state;
     long loops = 0;
-    off_t valid_up_to = 0; /* Offset of the latest well-formed command loaded. */
+    off_t valid_up_to = 0; /* Offset of latest well-formed command loaded. */
-
-    if (fp && redis_fstat(fileno(fp),&sb) != -1 && sb.st_size == 0) {
-        server.aof_current_size = 0;
-        fclose(fp);
-        return C_ERR;
-    }
 
     if (fp == NULL) {
         serverLog(LL_WARNING,"Fatal error: can't open the append log file for reading: %s",strerror(errno));
         exit(1);
     }
 
+    /* Handle a zero-length AOF file as a special case. An emtpy AOF file
+     * is a valid AOF because an empty server with AOF enabled will create
+     * a zero length file at startup, that will remain like that if no write
+     * operation is received. */
+    if (fp && redis_fstat(fileno(fp),&sb) != -1 && sb.st_size == 0) {
+        server.aof_current_size = 0;
+        fclose(fp);
+        return C_ERR;
+    }
+
     /* Temporarily disable AOF, to prevent EXEC from feeding a MULTI
      * to the same file we're about to read. */
     server.aof_state = AOF_OFF;
@@ -636,6 +640,28 @@ int loadAppendOnlyFile(char *filename) {
     fakeClient = createFakeClient();
     startLoading(fp);
 
+    /* Check if this AOF file has an RDB preamble. In that case we need to
+     * load the RDB file and later continue loading the AOF tail. */
+    char sig[5]; /* "REDIS" */
+    if (fread(sig,1,5,fp) != 5 || memcmp(sig,"REDIS",5) != 0) {
+        /* No RDB preamble, seek back at 0 offset. */
+        if (fseek(fp,0,SEEK_SET) == -1) goto readerr;
+    } else {
+        /* RDB preamble. Pass loading the RDB functions. */
+        rio rdb;
+
+        serverLog(LL_NOTICE,"Reading RDB preamble from AOF file...");
+        if (fseek(fp,0,SEEK_SET) == -1) goto readerr;
+        rioInitWithFile(&rdb,fp);
+        if (rdbLoadRio(&rdb) != C_OK) {
+            serverLog(LL_WARNING,"Error reading the RDB preamble of the AOF file, AOF loading aborted");
+            goto readerr;
+        } else {
+            serverLog(LL_NOTICE,"Reading the remaining AOF tail...");
+        }
+    }
+
+    /* Read the actual AOF file, in REPL format, command by command. */
     while(1) {
         int argc, j;
         unsigned long len;

src/rdb.h

@@ -134,5 +134,6 @@ ssize_t rdbSaveRawString(rio *rdb, unsigned char *s, size_t len);
 void *rdbGenericLoadStringObject(rio *rdb, int flags, size_t *lenptr);
 int rdbSaveBinaryDoubleValue(rio *rdb, double val);
 int rdbLoadBinaryDoubleValue(rio *rdb, double *val);
+int rdbLoadRio(rio *rdb);
 
 #endif