Pattern: use SLA to determine when to start load shedding

August 16th, 2022

Stability Pattern: Shed load

turn away load we can't complete in time


Where? Load balancers

How? Health check + SLA

a good health check on the first tier of services can inform the load balancer when response times are too high (in other words, higher than the SLA)

Model: health check

  • Own response time

services can measure their own response time to help with this.

They can also check their own operational state to see if requests will be answered in a timely fashion.

For instance, monitoring the degree of contention for a connection pool allows a service to estimate wait times.

  • Dependency response times

Likewise, a service can check response times on its own dependencies. If those dependencies are too slow and are required, then the health check should shot=w that this service is unavailable.

Stability pattern: back pressure

What? Http 503


(src: Book: release it! - Michael Nygard)

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