Skip to main content

Module wire_version

nodedb_types

Module wire_version 

Source
Expand description

Single source of truth for the WIRE_FORMAT_VERSION constant shared between every crate that needs to stamp or interpret it.

This is the cluster-wide wire format version, distinct from:

  • nodedb_cluster::wire::WIRE_VERSION (the binary frame layout version of the VShardEnvelope),
  • the RPC frame header version in nodedb_cluster::rpc_codec::header (a private constant of that module).

§DO NOT BUMP THIS BEFORE 1.0

It stays at 1 until the first stable release. Read this before changing it — the reflex to bump on any wire-shape change is wrong here:

  • There is nothing to be compatible with. Pre-1.0 there are no deployed clusters, so there is no older peer a new build must talk to.
  • A bump cannot buy a rolling upgrade. MIN_WIRE_FORMAT_VERSION == WIRE_FORMAT_VERSION (floor == ceiling), so a node rejects any peer whose version differs. Mixed-version clusters cannot form at all, which makes every wire_version >= V feature gate dead code: inside a cluster that exists, all nodes are provably on this exact version. Adding such a gate is unreachable-branch hardening, not safety.
  • This value is NOT persisted. It is stamped on NodeInfo for the handshake and drives ClusterVersionView, nothing more. The version written into stored raft-log and metadata entries is nodedb_cluster::wire_version::WireVersion::CURRENT, which is separate and independent. Changing the constant here therefore cannot orphan or corrupt anything already on disk.

So: adding a new enum variant, RPC, or payload field needs NO bump. Every node in a working cluster runs the same build by construction. Ratcheting this pre-1.0 only invents a stop-the-world upgrade requirement that does not otherwise exist, and would leave 1.0 shipping as “wire version 20” for no reason.

After 1.0, when real deployments exist and a genuine compatibility window is introduced, this becomes meaningful — bump it then, deliberately, and only alongside an actual MIN_WIRE_FORMAT_VERSION < WIRE_FORMAT_VERSION support window.

Constants§

MIN_WIRE_FORMAT_VERSION
Minimum wire format version this build can read. Equal to WIRE_FORMAT_VERSION: floor == ceiling, no backward compat window.
WIRE_FORMAT_VERSION
Cluster-wide wire format version. Stamped on every NodeInfo and returned by nodedb::version::WIRE_FORMAT_VERSION (a re-export).