Glossary

Terms used throughout this manual. Where a term has a chapter of its own, the definition links to it.

Active anti-entropy (AAE). A background process that compares replicas -- using Merkle trees so the comparison is cheap -- and repairs any divergence it finds. See Anti-Entropy and Repair.

Backend. The single-node storage engine a Dynomite node fronts: Valkey, Memcached, or the embedded Noxu store. The backend knows nothing about the ring.

Consistency level. The per-request quorum policy: DC_ONE, DC_QUORUM, DC_SAFE_QUORUM, DC_EACH_SAFE_QUORUM. It decides how many replicas must respond before a request succeeds and how reads pick a replica. See Replication and Consistency.

Coordinator. For a given request, the node that received it from the client and is responsible for routing it to replicas and coalescing the responses. Any node can coordinate any request.

CRDT (Convergent Replicated Data Type). A data type -- counter, set, map, register -- whose replicas merge deterministically without conflict. Dyniak feature. See Convergent Data Types.

Datacenter (DC). The top level of the topology. Replication and the consistency levels are defined across and within datacenters.

DNODE. The peer plane: the wire protocol Dynomite nodes use to talk to each other, distinct from the client-facing protocol. See DNODE.

Dyniak. The Riak-compatible layer built on the engine and backed by Noxu. See Introduction to Dyniak.

Gossip. The decentralized protocol nodes use to discover each other, share topology, and detect failures. See Membership and Gossip.

Hinted handoff. When a write's target peer is temporarily unavailable, a coordinator stores a durable "hint" and replays it when the peer returns, so the write is not lost. See Failure Handling.

Node. One dynomited process (or one embedded Server), owning one or more tokens and fronting one backend.

Noxu. The transactional Rust storage engine that backs Dyniak; a re-implementation of Berkeley DB Java Edition. Provides the XA support Dyniak's transactions use.

phi-accrual. The adaptive failure detector Dynomite uses: it outputs a continuous suspicion value rather than a binary alive/dead, adapting to observed network variance. See Failure Handling.

Quorum. A majority of the relevant replicas. For a local-DC quorum of n replicas the count is n/2 + 1.

Rack. A subdivision of a datacenter. In Dynomite's replication model a rack holds a full copy of the ring, so the number of racks in a DC is the replication factor within that DC.

Read repair. When a read observes divergent replicas, the coordinator writes the reconciled value back to the stale ones. See Failure Handling.

Replica. A node (in Dynomite's model, a rack) that holds a copy of a given key.

Ring / token ring. The circular token space over which keys are partitioned by consistent hashing. See The Ring and the Token Space.

Token. A point on the ring. A key hashes to a token; the node owning the next token clockwise owns the key.

Vnode (virtual node). A token owned by a physical node; a physical node may own several, spreading its ownership around the ring.

XA / 2PC. Two-phase commit, the protocol Dyniak uses for cross-node multi-key atomic transactions. See Distributed Transactions.