Tracking bug for client OptionsSpan

[devbww]

Instructions

Client operation functions should create local internal::OptionsSpan objects, with at least the default options for the service, so that our internal libraries can use internal::CurrentOptions() to obtain information about the call that is otherwise difficult to plumb through the various layers.

In general, the ServiceConnectionImpl and ServiceClient constructors, and the Service::Operation() function should look like:

ServiceConnectionImpl::ServiceConnectionImpl(..., Options options)
    : ...,
      options_(internal::MergeOptions(std::move(options),
                                      service_internal::ServiceDefaultOptions(ServiceConnection::options()))) {}

ServiceClient::ServiceClient(std::shared_ptr<ServiceConnection> connection, Options options)
    : connection_(std::move(connection)),
      options_(internal::MergeOptions(std::move(options), 
                                      service_internal::ServiceDefaultOptions(connection_->options()))) {}

ReturnType
ServiceClient::Operation(..., Options options) {
  internal::OptionsSpan span(internal::MergeOptions(std::move(options), options_));
    :
  return connection_->Operation(...);
}

This is already true for the generated libraries, but we need to ensure that the hand-written libraries follow the same pattern.

Some libraries may not yet have connection-, client-, or operation-specific Options, so you'll have to work with what you have, but the minimal operation function should be:

ReturnType
ServiceClient::Operation(...) {
  internal::OptionsSpan span(service_internal::ServiceDefaultOptions(Options{}));
    :
  return connection_->Operation(...);
}

Library List

• add bigtable support for per-operation options #7688
• Bigtable admin client OptionsSpan #8510
• Bigtable instance admin client OptionsSpan #8511
• add pubsub support for per-operation options #7689
• add spanner support for per-operation options #7690
• Spanner database admin client (legacy) OptionsSpan #8438
• Spanner instance admin client (legacy) OptionsSpan #8439
• add storage support for per-operation options #7691

[dbolduc]

We can close this, because the remaining tasks all have dedicated issues.