Event throttle transform released

A guide to using the new throttle transform

We’ve released a new throttle transform that provides a user the ability to throttle the throughput of specific event streams.

Large spikes in the volume of observability data can have undesirable impacts including increased costs for sink destinations that price based on volume or accidentally overwhelming internally deployed services like Loki.

To protect yourself from these effects, we’ve added a new throttle transform to Vector. The throttle transform enables you to rate limit specific subsets of your event stream to limit load on downstream services or enforce quotas on specific services (identified by fields on the log event). You can also exclude events based on a VRL condition to avoid dropping critical logs.

To ensure that each bucket’s throughput averages out to the threshold per window, rate limiting spreads load across the configured window (configured by window_secs). The rate limiter will allow up to threshold number of events through and drop any further events for that particular bucket when the rate limiter is at capacity.

A rate limiter is created with a maximum number of cells equal to the threshold, with cells replenishing at a rate of window divided by threshold. For example, a window of 60 with a threshold of 10 replenishes a cell every 6 seconds and allows a burst of up to 10 events.

See the following simple example.

Given these incoming log events:

  {"host":"host-1.hostname.com","message":"First message","timestamp":"2020-10-07T12:33:21.223543Z"},
  {"host":"host-1.hostname.com","message":"Second message","timestamp":"2020-10-07T12:33:21.223543Z"}

…and this configuration…

type = "throttle"
inputs = [ "my-source-or-transform-id" ]
threshold = 1
window_secs = 60

…only one event will be allowed through:

{"host":"host-1.hostname.com","message":"First message","timestamp":"2020-10-07T12:33:21.223543Z"}

Due to the threshold of 1 event per 60 seconds.

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