[oschaaf]

Fixes #1607

What

ProcessImpl::setupStatsSinks looked sinks up only in Nighthawk's own
NighthawkStatsSinkFactory registry. A bootstrap sink config naming a
linked Envoy stats sink (e.g. envoy.stat_sinks.statsd) therefore failed
with "Didn't find a registered implementation", even though the
--stats-sinks help text advertised exactly such configurations, so
users could not flush Nighthawk's benchmark metrics to any
Envoy-provided stats sink.

setupStatsSinks now consults Envoy's
Server::Configuration::StatsSinkFactory registry first — by typed
config type URL, the same lookup Envoy's own server performs — and falls
back to Nighthawk's registry when no Envoy factory matches. Configs
matching neither registry keep failing fast with an error naming the
sink. Errors returned by an Envoy sink factory's createStatsSink
propagate as an EnvoyException; they are never swallowed.

This change also links the envoy.stat_sinks.statsd extension via
extensions_build_config.bzl and points the documented example at the
cluster-free UDP address form.

Test evidence

New process_test cases (v4 and v6):

• EnvoyStatsSinkHonored: a --stats-sinks config naming
  envoy.stat_sinks.statsd with a UDP address on a loopback listener;
  the run flushes datagrams containing benchmark. counter names to
  that listener. Before this change the run aborted in
  getAndCheckFactory<NighthawkStatsSinkFactory> with
  Didn't find a registered implementation for 'envoy.stat_sinks.statsd' with type URL: 'envoy.config.metrics.v3.StatsdSink'.
• UnknownSinkNameFailsFast: sink name envoy.stat_sinks.nosuchsink
  fails the run with an error naming the sink.

Full process_test and service_test suites pass locally on macOS
except the pre-existing TestWithEncapsulation failures (a
setsockopt: Protocol not available platform limitation, reproducible
on main without this change).

DCO signed; CI will confirm on Linux.

Signed-off-by: Otto van der Schaaf oschaaf@we-amp.com

[oschaaf]

Closing for now - we'll re-submit from our fork when the timing is right. Thanks!