Redis source

The Redis source resolves mappings from a Redis database. It suits deployments where mappings change frequently or are shared between several proxy instances, since every proxy reads from the same central store and a change made anywhere is visible everywhere once cache entries expire. Lookups are still served from each proxy’s in-memory cache, so Redis is consulted only on cache misses.

[mapping]
source = "redis"
normalize = "lowercase"

[mapping.redis]
url = "redis://10.0.3.1:6379"
key_prefix = "route:"
pool_size = 16

The keys under [mapping.redis] are:

Key	Default	Description
`url`	required	Connection URL for the Redis server.
`key_prefix`	`route:`	Prefix prepended to each identifier to form the Redis key.
`pool_size`	`16`	Number of connections held open to the server.

The url follows the standard Redis URL syntax, including the rediss:// scheme for TLS and an optional password and database number.

Key layout

Each mapping is stored as a single string value under a key formed by concatenating key_prefix with the normalized identifier. With the default prefix, the destination for [email protected] is read from the key route:[email protected]. A lookup is a plain GET; a missing key, or a key whose value is empty, is treated as the absence of a mapping and routes the connection to the default destination.

GET route:[email protected]   ->  "legacy"
GET route:[email protected]   ->  "stalwart"

Mappings are populated using ordinary Redis commands, so an external tool can manage the table directly:

redis-cli SET route:[email protected] stalwart
redis-cli DEL route:[email protected]

Runtime updates

The Redis source is writable, so the management API can create, replace and delete mappings, which the proxy performs with SET and DEL against the prefixed keys. Because the cache sits in front of Redis, a change made directly in Redis by an external tool becomes visible to a proxy once the relevant cache entry expires, or immediately if the entry is invalidated through the management API. The proxy maintains a small pool of pool_size connections and distributes requests across them.