internal: remove transportMonitor, replace with callbacks
This refactors the internal http2 transport to use callbacks instead
of continuously monitoring the transport in a separate goroutine. This
has several advantages:
- Less goroutines.
- Less complexity: synchronous callbacks are much easier to reason to
reason about than asynchronous monitoring goroutines.
- Callbacks: these provide definitive locations for monitoring the
creation and closure of a transport, paving the way for GracefulStop.
This CL also consolidates all the logic about backoff and iterating
through the list of addresses into a single method.
Embues the status package with the ability to create statuses
from generic errors that implement the interface:
type StatusError interface {
Status() *Status
}
This was designed with the github.com/gogo/protobuf project in mind,
but is implemented in a fashion that makes it accessible to arbitrary
payloads.
Fixes#1885.
When an error implemented by the status package is returned from a service
handler, the server will transmit a rich status message in the
"grpc-status-details-bin" trailing metadata field if any detailed data is
attached to the error. Client-side, we will decode them if present in the
server's response and return them to the user code performing the RPC.
This is backward compatible with the existing errors supported by the grpc
package. However, the grpc.Errorf, grpc.Code and grpc.ErrorDesc functions for
managing errors are now deprecated; status.Errorf and status.Status type
asserions should be used instead.
Jean de Klerk