Inter-node RPC services

CockroachDB nodes talk to each other over gRPC and DRPC. The proto definitions live next to the consuming subsystems; the connection plane lives in pkg/rpc/.

Major services

Service	Proto	Used for
Internal	pkg/kv/kvpb/api.proto	Batch (KV) — the main KV RPC
RaftMessageBatch	pkg/kv/kvserver/storage_services.proto	Raft messages between peers
MultiRaft	pkg/kv/kvserver/storage_services.proto	Streaming raft transport
Heartbeat	pkg/rpc/heartbeat.proto	Connection liveness + clock offset
Admin, Status	pkg/server/serverpb/admin.proto, status.proto	REST/RPC admin/status surface
KeyVisualizerService	pkg/keyvisualizer/	Key visualizer time-series
Migration	pkg/upgrade/migrationpb/	Cluster-version migration coordination
BlobService	pkg/blobs/	nodelocal file transfers
Streaming	pkg/repstream/streampb/	Cross-cluster replication producer
LogicalReplication	pkg/crosscluster/logical/	LDR ingestion
Consensus	pkg/kv/kvserver/storeliveness/	Store-liveness fabric

Each .proto carries its DRPC counterpart via pkg/cmd/protoc-gen-go-drpc/.

Connection management

Every outbound call goes through pkg/rpc/nodedialer/Dialer.Dial(...), which:

1. Resolves the target node's address from gossip.
2. Returns a per-class connection from the peer.Peer pool.
3. Returns an error if the target is unreachable, unhealthy, or wrong cluster.

Multiple "RPC classes" (pkg/rpc/rpcbase/) keep latency-sensitive and bulk traffic on separate streams so head-of-line blocking on bulk transfers can't slow down user-visible RPCs.

Authentication

Both gRPC and DRPC use mutual TLS by default. Server-side, pkg/rpc/auth.go validates the client cert; for multi-tenant deployments, auth_tenant.go enforces that the certificate's tenant ID matches the request payload.

Related pages

• systems/rpc — connection-management details.
• systems/security — TLS material.
• systems/kv — BatchRequest is the main RPC.
• systems/raft — Raft transport sits on top of MultiRaft.