Question: Is Redis Multithreaded?

Answer

No, Redis is not multithreaded for its core operations. It is a single-threaded, event-driven server that processes commands sequentially. The main event loop handles all client requests and data manipulation. This design choice enables Redis to provide predictable performance and avoid potential pitfalls associated with multithreading, like race conditions or thread synchronization issues.

However, some parts of Redis, such as background tasks (e.g., RDB snapshotting, AOF rewriting), I/O threads for certain operations, and modules can utilize multiple threads. Since Redis 6.0, it supports multithreaded I/O for reading and writing protocol buffers on the network, which can improve performance on multi-core systems when dealing with high throughput scenarios or high-latency networks.

To enable multithreaded I/O in Redis, you can update the redis.conf configuration file or set the option using the command line:

# In redis.conf, add or update this line:
io-threads 4

# OR use command-line options when starting Redis:
redis-server --io-threads 4

In the example above, we set the number of I/O threads to 4. Remember, this only affects I/O threads and does not change the single-threaded nature of Redis's core operations.