Should sbws test relays sooner when their self-reported bandwidths change?

[teor2345]

sbws might want to increase a relay's priority when its observed bandwidth or relay bandwidth rate change.

Recent Tor releases only change their observed bandwidth every 24 hours. So if sbws can do half the number of measurements it keeps in 24 hours, we don't need this feature.

A few relays may change their bandwidth rate twice a day, if they are on a home connection, or an ISP with off-peak rules.

But changing the rate to get re-measured is gameable, so maybe we should only increase relay priority for the first rate-change in N hours (or N measurement cycles).

[teor2345]

See also https://trac.torproject.org/projects/tor/ticket/2550