mochi/docs/storage/keydb.md

KeyDB Storage

This storage mainly the same as Redis and uses some of redis store logic with next exceptions:

• peers stored in sets instead of hashes;

• keys such as CHI_I, CHI_S_C and CHI_L_C not used (at all);

• peer TTL relies on KeyDB's 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, BUT:

• name should be set to keydb instead of redis;

• gc_interval and prometheus_reporting_interval don't have any sense.

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.