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fastcached

fastcached is a cache daemon that speaks four wire protocols off a single storage engine: memcached ASCII text, memcached binary, memcached meta (1.6+), and Redis RESP2. The protocols are detected automatically from the first bytes a client sends, so any one listening port serves clients of every supported flavor without configuration.

The project is a re-implementation. The protocols and their semantics are defined by the memcached and Redis projects, and fastcached aims to be compatible with well-behaved clients written against those references.

What's in the box

  • The full memcached ASCII command set, including the TTL-refresh family (touch, gat, gats).
  • The full memcached binary opcode set, including the Touch, GAT, GATQ, GATK, GATKQ family and arithmetic with auto-vivify.
  • The memcached meta protocol (mg, ms, md, ma, me, mn) with the spec's flag matrix.
  • A subset of Redis RESP2 covering the key-value commands used by sccache and similar clients.
  • An LRU storage engine with optional persistent backing via a copy-on-write B-tree.
  • Stats counters compatible with memcached-tool and similar monitoring scripts.

What's not in the box (yet)

  • Real SASL authentication. The opcodes are recognised so probing clients fail fast rather than hang.
  • Redis lists, hashes and sorted sets. Sets and streams are supported in part; the set-algebra verbs (SINTER, SUNION, ...) are not.
  • Key enumeration on any protocol: no KEYS, SCAN, DBSIZE or stats cachedump.
  • The watch command's streaming event subscription.
  • Multiple Redis databases. There is a single flat keyspace; SELECT is accepted as a no-op (any index replies +OK) for client compatibility but does not switch databases.

See Known limitations for the full list.

Where to start

  • Want to understand what this actually does before configuring it? Read How it works — the pieces, one compile followed end to end, and what decides whether two machines can share anything.
  • New to the project? Read Quickstart.
  • Wondering whether your client will work? Check the Coverage matrix.
  • Looking up a command? Browse the commands index.
  • Comparing to upstream? See Compatibility with upstream.
  • Wondering how fast it is, and what the number means? Read Performance.