Andreas Schroeder andreas-schroeder

Akka Streams Backpressure Gauge

Measures if there is backpressure on an Akka Stream at the given stage.

Motivation

When an Akka Stream doesn't perform as intended, it is difficult to tell where the bottleneck is, since all stages operate at the same rate (see e.g. here ).

So when things are not fast as expected, this pressure gauge can help you to narrow down on the slow stage. Imagine

	local bucket_key = KEYS[1]
	local requested = tonumber(ARGV[1])

	local time = redis.call('TIME')
	local now = tonumber(time[1]) * 1000000 + tonumber(time[2]) -- time in microseconds
	local bucket = redis.call('HMGET', bucket_key, 'tokens', 'next_refill')

	local tokens, next_refill = bucket[1], bucket[2]

	if (not tokens) then