Semantic conventions for RPC

Existing RPC instrumentations that are using v1.37.0 of this document (or prior):

• SHOULD NOT change the version of the RPC conventions that they emit by default in their existing major version. Conventions include (but are not limited to) attributes, metric and span names, and unit of measure.
• SHOULD introduce an environment variable OTEL_SEMCONV_STABILITY_OPT_IN in their existing major version as a comma-separated list of category-specific values (e.g., http, databases, rpc). The list of values includes:
  • rpc - emit the stable RPC conventions, and stop emitting the experimental RPC conventions that the instrumentation emitted previously.
  • rpc/dup - emit both the experimental and stable RPC conventions, allowing for a phased rollout of the stable semantic conventions.
  • The default behavior (in the absence of one of these values) is to continue emitting whatever version of the old experimental RPC conventions the instrumentation was emitting previously.
  • Note: rpc/dup has higher precedence than rpc in case both values are present
• SHOULD maintain (security patching at a minimum) their existing major version for at least six months after it starts emitting both sets of conventions.
• MAY drop the environment variable in their next major version and emit only the stable RPC conventions.