Manage protocol version for meta server and client

tip

Expected deployment time: 5 minutes ⏱

Meta server has a build version(METASRV_COMMIT_VERSION) and the minimal compatible version of meta client(MIN_METACLI_SEMVER), which are defined in src/meta/service/src/version.rs.

Meta client has a build version(METACLI_COMMIT_SEMVER) and the minimal compatible version of meta server(MIN_METASRV_SEMVER), which are defined in src/meta/grpc/src/lib.rs.

These four versions defines compatibility between meta server and meta client. [Compatibility][Compatibility] explains how it works.

For developers, if incompatible or compatible changes are introduced, either MIN_METACLI_SEMVER or MIN_METASRV_SEMVER should be increased, in order to report a compatibility issue before actual data exchange between meta server and meta client.

According to the algorithm [Compatibility][Compatibility] defines:

• If no protocol related types change is introduced, do NOT change MIN_METACLI_SEMVER or MIN_METASRV_SEMVER;
• If new API is added to meta server, but very other API are still valid, do NOT change MIN_METACLI_SEMVER or MIN_METASRV_SEMVER;
• If meta client starts using a new API provided by meta server, upgrade MIN_METASRV_SEMVER to the build version in which this new API was introduced.
• If meta server removes an API, upgrade MIN_METACLI_SEMVER to a client build version since which this API is never used.

Protocol related crates are(this list may not be exhausted if new types are introduced in future):

• src/meta/protos: defines the protobuf messages a meta client talks to a meta server.
• src/meta/proto-conv: defines how to convert metadata types in rust from and to protobuf messages.
• src/meta/types: defines the rust types for metadata.

Compatibility