Add Online AOF and RDB Loading to Redis 3.0.7 Without Restart

Introduction

When loading data into Redis, the traditional approach requires restarting the Redis service, which is inconvenient especially in a master‑slave replication setup. This article presents a modification to Redis 3.0.7 that adds two new commands, LOADAOF and LOADRDB, enabling online loading of AOF and RDB files without a restart.

Design and Implementation

The implementation adds two commands to the Redis command table and corresponding functions in the source code.

LOADAOF Command

void loadaofCommand(RedisClient *c) {
    if (server.rdb_child_pid != -1) {
        addReplyError(c,"Background save already in progress");
    } else if (server.aof_child_pid != -1) {
        addReplyError(c,"Can't BGSAVE while AOF log rewriting is in progress");
    } else if (c->argc != 2){
        addReply(c,shared.syntaxerr);
        return;
    } else if (loadAppendOnlyFile(c->argv[1]->ptr) == REDIS_OK) {
        addReplyStatus(c,"online loadaof started,Do not repeat!!!");
    } else {
        addReply(c,shared.err);
    }
}

LOADRDB Command

void loadrdbCommand(RedisClient *c) {
    if (server.rdb_child_pid != -1) {
        addReplyError(c,"Background save already in progress");
    } else if (server.aof_child_pid != -1) {
        addReplyError(c,"Can't BGSAVE while AOF log rewriting is in progress");
    } else if (c->argc != 2){
        addReply(c,shared.syntaxerr);
        return;
    } else if (rdbLoad(c->argv[1]->ptr) == REDIS_OK) {
        addReplyStatus(c,"online loadrdb started,Do not repeat !!!");
    } else {
        addReply(c,shared.err);
    }
}

The new commands are registered in src/Redis.c by adding entries to RedisCommandTable:

{"loadaof",loadaofCommand,2,"ar",0,NULL,0,0,0,0,0},
{"loadrdb",loadrdbCommand,2,"ar",0,NULL,0,0,0,0,0},

Function prototypes are added to src/Redis.h:

void loadrdbCommand(RedisClient *c);
void loadaofCommand(RedisClient *c);

Help entries are added in src/help.h to document the new commands.

Compilation

cd Redis-3.0.7
make && make PREFIX=/usr/local/Redis30 install

Test Results

The test demonstrates that data can be loaded into a running Redis instance without restarting the server.

Use Cases

Importing data into a test Redis instance for analysis.

Recovering data after accidental deletion, especially in Sentinel‑plus‑master‑slave architectures.

Precautions

When the master loads an AOF or RDB file online, the replica must have the same file; otherwise the replica will exit with an error.

Do not execute the same load command repeatedly on the same file, as it may cause the master or replica to crash.

The current implementation is a proof of concept and may require further robustness improvements.