Counter
Increment a streamz counter with the specified metric and field names. Metric names should start with a '/', generally be lowercase-only, and end in "_count". Field names should not contain an initial slash. The actual exported metric names will have "/iam/policy" prepended. Field names correspond to IAM request parameters and field values are their respective values. Supported field names: - "authority", which is "token" if IAMContext.token is present, otherwise the value of IAMContext.authority_selector if present, and otherwise a representation of IAMContext.principal; or - "iam_principal", a representation of IAMContext.principal even if a token or authority selector is present; or - "" (empty string), resulting in a counter with no fields. Examples: counter { metric: "/debug_access_count" field: "iam_principal" } ==> increment counter /iam/policy/debug_access_count {iam_principal=value of IAMContext.principal}