b3170af changed the DstLabels api, but the bench test was not updated
accordingly.
Furthermore, since bench tests require a nightly rust version, we've
avoided running them in CI. This makes it easy for these tests to break, however.
This updates the benches/record.rs. Additionally, in CI, we pin the rust nightly'
version to a known-good version so that we can reliably run these bench test
without the fear of external changes breaking our build.
Currently, the proxy records a request's latency as the time between
when a request is opened and when its response stream completes. This is
not what we intend to record, especially when a response is long-lived.
In order to more accurate record latency, we want to track the time at
which the first response body frame is received (which is a close
approximation of time-to-first-byte).
Telemetry aggregation has been changed to use the first-frame time to
compute latencies; tests have been updated to exercise this behavior; and
the metrics documentation has been updated to reflect this change.
Addresses #818
Relates to #980
Proxy tasks emit events to the telemetry system. These events are used
aggregate counts and latencies, as well as to inform Tap requests.
Initially, these events included durations, describing the relevant time
that elapsed between this event and another.
This approach is somewhat inflexible -- it unnecessarily constrains the
set of measurements that can computed in the telemetry system.
To remedy this, the `Event` types can be changed to report discrete
`Instant`s (rather than `Duration`s). Then, when latencies are computed
in the telemetry system, these discrete instants can be compared to
produce durations.
There are no functional changes in this PR.
Before changing the telemetry implementation, we should have a means to
understand the impacts of such changes.
To run, you must use a nightly toolchain:
```
rustup run nightly cargo bench -p conduit-proxy -- record
```
Oliver Gould
Eliza Weisman