(untested) sanitize code

* remove peer argument from scrape swarm storage call

* replace Peer field with netip.Addr in ScrapeRequest

* add man for keydb storage

* update readme

docs/middleware/torrent_approval.md

@@ -21,9 +21,9 @@ If mode is **black list** (`invert` set to `true`), tracker will allow all hashe
 
 There are two sources of hashes: `list` and `directory`.
 
-`list` is the static set of hashes, specified in configuration file.
+* `list` is the static set of hashes, specified in configuration file.
 
-`directory` will watch for `*.torrent` files in specified path and
+* `directory` will watch for `*.torrent` files in specified path and
 append/delete records from storage. This source will parse all existing
 files at start and then watch for new files to add, or for delete events
 to remove hash from storage.

docs/storage/keydb.md

@@ -0,0 +1,46 @@
+# KeyDB Storage
+
+This storage mainly the same as Redis and uses some of [redis](redis.md) store logic
+with next exceptions:
+
+* peers stored in [sets](https://redis.io/docs/manual/data-types/#sets) 
+instead of [hashes](https://redis.io/docs/manual/data-types/#hashes);
+
+* keys such as `CHI_I`, `CHI_S_C` and `CHI_L_C` not used (at all);
+
+* peer TTL relies on KeyDB's [EXPIREMEMBER](https://docs.keydb.dev/docs/commands/#expiremember) 
+command, so MoChi does not need to periodically check peer expiration;
+
+* storage does not execute periodical statistics collection (peer/lecher/info hash count)
+because:
+  * manual calculation (INC/DEC peers count) is not usable 
+  * manual scan of all keys is quite expensive operation.
+
+## Use Case
+
+KeyDB is fork of Redis, which allows to create active-active cluster and set `set` member expiration,
+so this type of backend can be used to create fully symmetric cluster of tracker nodes with minimum
+overkill to garbage collection.
+
+## Configuration
+
+Configuration options are the same as [redis's](redis.md#Configuration), **BUT**:
+
+* `name` should be set to `keydb` instead of `redis`;
+
+* `gc_interval` and `prometheus_reporting_interval` don't have any sense.
+
+```yaml
+mochi:
+  storage:
+    name: keydb
+    config:
+	...
+```
+
+## Implementation
+
+KeyDB storage uses same key names as `redis` (`CHI_S4_<HASH>`, `CHI_L6_<HASH>`...) to store peers,
+but it is **impossible** to switch between storage providers without deleting these keys.
+You **can** use `redis` storage type with KeyDB instance (KeyDB supports all Redis commands),
+but **not** `keydb` storage type with Redis instance.