Existing trailers will be sent to the processing
server if the processing mode is set to enable them. If the
processing mode is set to sent trailers, but there are no trailers
present, then empty trailers will be sent to the server for
modification.
However, trailers may only be added in the end of the data callback
in Envoy, which may come in before a previous gRPC reply returns.
Filters that need to be able to consistently add trailers where none
existed should enable trailer processing in the Envoy filter
configuration instead of relying on being able to turn it on
dynamically.
Risk Level: Low. Trailers only enabled if a service called by the filter
is configured to ask for them.
Testing: New integration and unit tests added.
Docs Changes: API docs updated in .proto files.
Release Notes:
When the processing mode is changed to SEND
for request or response trailers, a corresponding message will be
sent to the server, which can respond with trailer mutations as desired.
In addition, if trailer processing is enabled in the filter
configuration, then trailer messages will be sent to the server
even if trailers are not present. This makes it possible for the server
to add trailers where none exist.
Finally, at the moment Envoy only implements trailers for the HTTP/2
protocol. Nothing will happen if trailer processing is enabled and
Envoy is using HTTP/1 until Envoy implements trailers for HTTP/1.
Signed-off-by: Gregory Brail <gregbrail@google.com>
Mirrored from https://github.com/envoyproxy/envoy @ 29eb17096e50fc9385edbf260c03da7adc4ca24c
data-plane-api(Azure Pipelines)
521b1db3ad