2.18.2.2.2. Additional latency

Since Istio injects a sidecar proxy on the data path, latency is an important consideration. Istio adds an authentication filter, a telemetry filter, and a metadata exchange filter to the proxy. Every additional filter adds to the path length inside the proxy and affects latency.

The Envoy proxy collects raw telemetry data after a response is sent to the client. The time spent collecting raw telemetry for a request does not contribute to the total time taken to complete that request. However, because the worker is busy handling the request, the worker does not start handling the next request immediately. This process adds to the queue wait time of the next request and affects average and tail latencies. The actual tail latency depends on the traffic pattern.

Inside the mesh, a request traverses the client-side proxy and then the server-side proxy. In the default configuration of Istio 1.12.3 (that is, Istio with telemetry v2), the two proxies add about 1.7 ms and 2.7 ms to the 90th and 99th percentile latency, respectively, over the baseline data plane latency.