The test transferred only 64 KiB over loopback, which can complete
within a single clock tick on fast CI machines, causing
time.Since(start).Seconds() to return 0 and the
"transfer_time_seconds_total > 0" assertion to fail.
Increase the payload to 1 MiB so zero is genuinely implausible, and
retry up to 3 additional times. If the metric is still zero after 4
total attempts, fail hard — at that size it means the timing logic is
actually broken.
Fixes#20213
Change-Id: I3fab510ce8c567506fea5ad803d35acf40d65700
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Add HTTPBandwidth/HTTPBandwidthWithDialAddr probe classes that download a
fixed number of bytes and record transfer time and bytes transferred as
Prometheus counters for bandwidth measurement, plus HTTPWithDialAddr and
the shared NewProbeTransport and HTTPBandwidthMetrics helpers.
The dial-address override lets a probe target a specific backend (e.g. a
single Funnel ingress node) while SNI, the Host header, and TLS cert
validation continue to derive from the URL host. HTTPBandwidthMetrics is
exported so other bandwidth probes (e.g. a receiver-reported upload probe)
emit an identical metric set and compare under a shared direction label.
Updates tailscale/corp#41587
Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
