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)
- 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)