feat(event): WriteContext::write_ack_frame records events AckRangeSent

[jon-chuang]

Resolved issues:

resolves: #1416

Description of changes:

Specialize write_frame for ack frame: write_ack_frame.

Call-outs:

Advantage: essentially zero-cost: write_ack_frame only specializes for Frame::Ack anyway.

Alternatives considered:

1. expose get_publisher(&self) -> &mut Publisher (requires exposing generic Publisher through WriteContext)
2. Add a method on_ack_range_sent to WriteContext accepting event::builder::AckRangeSent/AckRanges (It looks slightly ad-hoc, and a lot of data-passing, may as well combine into write_ack_frame).

Testing:

Not sure how to generate appropriate tests - MockContext for WriteContext currently doesn't accept a publisher.

Results

Here is some sample output running the event-framework example with the async-client example.

As you can see, AckRangeSent is recorded after FrameSent {.. frame: Ack {..}, ..} is recorded.

event: ConnectionMeta { endpoint_type: Server, id: 0, timestamp: Timestamp(Timestamp(0:01:21.403762)) } FrameSent { packet_header: OneRtt { number: 7 }, path_id: 0, frame: Ack { ecn_counts: Some(EcnCounts { ect_0_count: 7, ect_1_count: 0, ce_count: 1 }), largest_acknowledged: 7, ack_range_count: 1 } }
event: ConnectionMeta { endpoint_type: Server, id: 0, timestamp: Timestamp(Timestamp(0:01:21.403762)) } AckRangeSent { packet_header: OneRtt { number: 7 }, path_id: 0, ack_range: 3..=7 }
event: ConnectionMeta { endpoint_type: Server, id: 0, timestamp: Timestamp(Timestamp(0:01:21.403762)) } FrameSent { packet_header: OneRtt { number: 7 }, path_id: 0, frame: Padding }
event: ConnectionMeta { endpoint_type: Server, id: 0, timestamp: Timestamp(Timestamp(0:01:21.403762)) } PacketSent { packet_header: OneRtt { number: 7 }, packet_len: 53 }
event: ConnectionMeta { endpoint_type: Server, id: 0, timestamp: Timestamp(Timestamp(0:01:21.403762)) } DatagramSent { len: 53, gso_offset: 0 }

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[camshaft]

Thanks for doing this! We appreciate the contribution 😃