Adaptive inbox query rate limit

[sportdeath]

The inbox rate limit is currently set to a constant 1 second - in other words clients are instructed to wait 1 second before polling again.

For instant messaging a low rate limit is desirable, however if a client leaves a messaging app open in a tab and forgets about it, this leads to excessive polling - draining the client battery and wasting server resources.

One possibility:

• If a client continually polls a query and receives no results, the server should gradually increase the rate limit up until a maximum (10 seconds, 20 seconds, 1 minute?). If a poll returns a result, the limit should be reset to 1 second (or perhaps even lower?).

Questions:

• What process should be used to increase the rate limit?
• What should the maximum be?
• Are there issues with this or other possibilities to consider?

[sportdeath]

Use exponentially backoff with jitter:

retryAfter = min(MAX, BASE * FACTOR^countSince) * random (0.8, 1.2)

suggested:
MAX = 60
BASE = 1
FACTOR = 1.02

Reaches steady state in about an hour.