API Compatibility

Garnet is a cache-store with a new thread-scalable system architecture. The network, processing, and storage (memory and disk/cloud) layers of Garnet are all designed from the ground up. We chose the RESP API as a matter of convenience given its broad adoption in the community. Garnet is not intended to be a 100% perfect drop-in replacement for Redis, rather it should be regarded as a close-enough starting point for you to ensure compatibility for features that matter to you. Garnet does work unmodified with many Redis clients (we have in particular tested Garnet with StackExchange.Redis very well), so getting started is very easy.

A list of API calls supported today by Garnet is maintained here. Below we highlight specific non-API-related choices that may not be compatible. This list is not exhaustive, rather it is meant as a broad guideline on what differences you can expect when using Garnet.

1. Garnet being multi-threaded, MSET is not atomic. For an atomic version of MSET, you would need to express it as a transaction (stored procedure). This is easily fixable, similar to MSETNX here, let us know in issues if you prefer the atomic semantics of MSET by default.
2. Garnet does not support Redis modules. Instead, it has its own C# based extensibility mechanisms that are optimized for very high performance, thread scalability, safety, and ease of use.
3. Garnet now has full-fledged and efficient support for Lua scripting. You can enable Lua with the --lua switch.
4. Garnet respects the FIFO ordering of request-responses. However, when used with larger-than-memory data, and if you opt in to using the scatter-gather version of IO (using the EnableScatterGatherGet [--sg-get] option) for increased disk performance, then even though results are still returned in FIFO order, the read operations may be executed out-of-order to earlier write operations in the same input operation sequence.
5. When Garnet is used with the append-only-file (AOF) turned on, by default the server does not wait for commit before returning success to the user. This can be adjusted using the WaitForCommit [--aof-commit-wait] option, while the frequency of commit can be tuned using the CommitFrequencyMs [--aof-commit-freq] option.
6. You can disable the object store if your workload only consists of raw string operations, using the option DisableObjects [--no-obj]. The storage tier is disabled by default, and you can enable it using EnableStorageTier [--storage-tier]. You can disable the pub-sub feature using the option DisablePubSub [--no-pubsub].