Native KRaft consensus quorum
krabka implements the Apache Kafka KRaft consensus protocol directly in memory-safe Rust (krabka-raft and krabka-kraft-core), with leader elections, metadata compaction, and no ZooKeeper dependency. The election and quorum decisions are Creusot-proved kernels, and the consensus engine has a Stateright model.
KIP-595 wire RPC interoperability
krabka implements the KIP-595 Raft RPC wire format. Controller voters exchange metadata records (PartitionRecord, TopicRecord, UserScramCredentialRecord) serialized to match Kafka's JVM implementation byte for byte.
Nodes run as dedicated controllers, dedicated brokers, or combined broker+controller nodes, grouped into node pools.
Add or decommission controller voters on live clusters through krabka-voters without restarting the metadata quorum.
Randomized election timers and asynchronous heartbeats trigger a new election after a network partition. Quorum size and vote admission are Creusot-proved kernels, and the consensus engine has a Stateright model.
Quorum configuration
# broker.toml - KRaft quorum configuration for node 1
# Start with: krabka-broker --config-file broker.toml
broker_id = 1
log_dir = "/var/lib/krabka/data"
# <node_id>@<host>:<port> of each voter's controller listener
controller_quorum_voters = [
"[email protected]:9093",
"[email protected]:9093",
"[email protected]:9093",
]
heartbeat_interval = "2s"
controller_election_timeout = "1s"
controller_heartbeat_interval = "500ms"
[process]
roles = ["controller", "broker"]
[[listeners]]
name = "PLAINTEXT"
bind_addr = "0.0.0.0:9092"
advertised = "broker-1.prod.internal:9092"
protocol = "Plaintext"In-memory metadata image and snapshots
krabka-metadata maintains an in-memory metadata image. A node can catch up from a metadata snapshot when it joins or reconnects after a network partition.
Formally verified kernels and deterministic seeding
Creusot proves contracts on selected consensus and quota decision kernels in krabka-verified, which host crates such as krabka-throttle call. Log directories are seeded with krabka-format.
Seed a log directory
krabka-format --log-dir /var/lib/krabka/data --cluster-id 3d70a78c-bb3a-4af5-a767-51e31f403c62 --node-id 1 --initial-controllers [email protected]:9093:<dir-id-1>,[email protected]:9093:<dir-id-2>,[email protected]:9093:<dir-id-3>