dynamic-config-redis

Read dynamic-config configuration from a Redis key.

[dependencies]
dynamic-config = "0.2.0"
dynamic-config-redis = "0.2.0"

use dynamic_config_redis::Redis;

DbConfig::set_remote(Redis::new("redis://redis.internal:6379", "myapp/db.json")?);

DbConfig::refresh_remote()?;
DbConfig::builder("db").init()?;

Redis speaks a plain request/response protocol, so this implements the blocking RemoteSource trait: nothing here needs an async runtime, and neither does using it.

What it reads

One key, whose value is a whole configuration document — the same bytes that would be in a config file. The format comes from the key's extension, or from with_format.

A Redis hash would be the other obvious mapping — one field per setting — and is deliberately not what this does. A hash cannot hold a nested table without inventing a flattening convention, and a document already has one.

Credentials

In the URL, which is where Redis puts them and where every deployment already has them:

redis://user:password@host:6379/0
rediss://user:password@host:6380/0     # TLS — needs the `tls` feature

rediss:// needs the crate's tls feature (dynamic-config-redis = { version = "...", features = ["tls"] }), which turns on the client's rustls stack. Without it the connection fails at connect time with the client's own "TLS support is not enabled" error.

A password never reaches an error message: the URL is redacted before it is used in one. from_client takes a client the program already built, for anything a URL cannot say.

Watching

Keyspace notifications, which are genuinely change-driven — no polling, no timer. Redis publishes to __keyspace@{db}__:{key} when a key is written, and this subscribes to exactly that channel.

let watch = RemoteWatch::new();
let watching = watch.watching();

std::thread::spawn(move || redis.watch(&watching, DbConfig::apply_remote));

Notifications are off by default in Redis. A server that has not enabled them publishes nothing, and a watch waiting for them would hang — the worst way for a feature to be unavailable. So this checks at start-up and reports:

CONFIG SET notify-keyspace-events KEA

• The current value is not delivered at startup: a watch reports changes, and announcing the value the caller already has would make every restart look like an edit.
• del and expired are not changes. No configuration is not a configuration, so the running snapshot stays.
• Stopping is noticed within a quarter second, whether or not anything arrives.

Builders

Testing

The test suite drives a real Redis in a container — no mocks, with keyspace notifications enabled the way a deployment would. The image is pinned to a current release rather than the module's default of Redis 5, which is long out of support.

cargo test -p dynamic-config-redis    # needs a working Docker daemon

MSRV

1.88 — higher than dynamic-config's own 1.71, because a Redis client stack moves faster than that crate wants to. A companion pays for what it pulls in; the core stays where it is.

License

MIT