Interview › Istio & Service Mesh
What are timeouts in Istio, and how do they interact with retries?
Istio & Service Mesh · Basic level
Answer
A timeout defines the maximum time a request is allowed to take before Envoy stops waiting. Timeouts and retries must be designed together because each retry consumes part of the overall latency budget.
Technical explanation
If the overall timeout is 1 second and perTryTimeout is 400 ms with 2 retries, there is little room for network and application variability.
Too-long timeouts keep resources tied up and increase queueing; too-short timeouts cause false failures.
Timeouts should align with upstream SLOs, downstream behavior, and client expectations.
Hands-on example
Example budget:
Client SLA: 2s.
Gateway timeout: 1800ms.
Service A to Service B timeout: 800ms.
Retries: attempts=2, perTryTimeout=250ms.
Validation:
$ fortio load -qps 50 -t 2m http://checkout/
Watch p95, p99, retry count, and 5xx rate.
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