package danube.edge

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Edge ↔ Cluster coordination and replication service. Hosted on cluster brokers, behind the standard auth interceptor. The edge is a constrained gateway for MQTT ingestion into the cloud. Topics are defined by edge config (edge.yaml) and registered with the cluster at startup. The cluster maintains per-edge state in Raft.

• rpc EdgeHeartbeat (EdgeHeartbeatRequest, EdgeHeartbeatResponse)

  EdgeReplicator.proto:24

  Periodic heartbeat + change detection. Edge sends its config_version; cluster compares against Raft state. Fast path: versions match → no changes. Slow path: returns changelog.

  message EdgeHeartbeatRequest

  EdgeReplicator.proto:74

  • string edge_name = 1

  • uint64 config_version = 2

    Edge's current config version

  message EdgeHeartbeatResponse

  EdgeReplicator.proto:79

  • bool changed = 1

    false = fast path, nothing to do

  • uint64 config_version = 2

    Current version (same if changed=false)

  • repeated EdgeChange changes = 3

    Only populated if changed=true

• rpc RegisterEdge (RegisterEdgeRequest, RegisterEdgeResponse)

  EdgeReplicator.proto:19

  Register (or re-register) an edge broker with the cluster. Called once at startup. Creates topics on the cluster, resolves schemas from the cluster registry, and stores per-edge state in Raft. Idempotent: re-registration diffs against previous state.

  message RegisterEdgeRequest

  EdgeReplicator.proto:33

  • string edge_name = 1

    e.g. "edge1"

  • repeated EdgeTopicDeclaration topics = 2

    Full list of topics from config

  message RegisterEdgeResponse

  EdgeReplicator.proto:44

  • bool success = 1

  • string message = 2

  • uint64 config_version = 3

    Initial config version from Raft

  • repeated TopicRegistrationResult topics = 4

    Per-topic resolution results

• rpc ReplicateData (stream ReplicateBatch, stream ReplicateAck)

  EdgeReplicator.proto:28

  Bidirectional stream: edge sends message batches, cluster acks offsets. Uses batch_last_offset as idempotency key to prevent duplicate writes.

  message ReplicateBatch

  EdgeReplicator.proto:101

  • string topic_name = 1

  • repeated StreamMessage messages = 2

    Full messages from edge WAL

  • uint64 batch_last_offset = 3

    Idempotency key (highest edge offset)

  message ReplicateAck

  EdgeReplicator.proto:107

  • string topic_name = 1

  • uint64 acked_offset = 2

    Echoes batch_last_offset on success

A single change detected during heartbeat.

Used in: EdgeHeartbeatResponse

• string topic_name = 1

• EdgeChangeType change_type = 2

• optional ResolvedSchema schema = 3

  Set for SCHEMA_UPDATED

• string detail = 4

  Human-readable context

Used in: EdgeChange

• SCHEMA_UPDATED = 0

  Schema subject has a new version on the cluster

• SCHEMA_REMOVED = 1

  Schema subject was deleted from cluster registry

• TOPIC_REMOVED = 2

  Topic was deleted from cluster (admin action)

A topic declared in the edge's config (edge.yaml).

Used in: RegisterEdgeRequest

• string topic_name = 1

  e.g. "/edge1/telemetry"

• optional string schema_subject = 2

  e.g. "telemetry-events" (absent = raw bytes)

Schema definition resolved by the cluster from its registry. Sent to the edge so it can cache and validate MQTT payloads locally.

Used in: EdgeChange, TopicRegistrationResult

• string subject = 1

• uint64 schema_id = 2

• uint32 schema_version = 3

• string schema_type = 4

  "json_schema", "avro", "protobuf", etc.

• bytes schema_definition = 5

  Full definition for edge to cache

• string fingerprint = 6

  SHA-256 for change detection

• string compatibility_mode = 7

  "none", "backward", "forward", "full"

Result of registering a single topic during RegisterEdge.

Used in: RegisterEdgeResponse

• string topic_name = 1

• bool topic_created = 2

  true if newly created on cluster

• bool schema_resolved = 3

  true if schema_subject found in registry

• optional ResolvedSchema schema = 4

  Full schema info (only if resolved)

• string error = 5

  Non-empty if topic/schema setup failed