Interview › Istio & Service Mesh
How would you mirror production traffic to a new version for testing?
Istio & Service Mesh · Advanced level
Answer
To mirror production traffic to a new version, I deploy the new version in an isolated mode, route normal traffic to stable, mirror a small percentage to the new version, and compare logs, traces, latency, and correctness metrics without returning mirrored responses to users.
Technical explanation
The shadow version must not trigger irreversible side effects.
Use separate downstream dependencies, mocked side effects, or idempotency guards.
Compare request handling, error rate, and output differences before canarying real traffic.
Hands-on example
Execution plan:
1. Deploy search-v2 with label version=v2.
2. Configure mirrorPercentage 1 percent.
3. Send v2 writes to a shadow index.
4. Compare top query results and latency.
5. Increase mirror to 10 percent if stable.
6. Move to real canary only after correctness checks pass.
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