Like all proxy software, Envoy takes flow control seriously because CPU/memory resources are limited. But flow control is never a simple matter. It involves all the players in the data flow path. This article tries to explain the principles and synergies involved.

The normal HTTP request was responded with HTTP status code 400 after migrating to Istio. The problem traffic has HTTP headers that do not comply with the HTTP 1.1 specification. So I try to develop an Envoy WASM Network Filter to fix the illegal HTTP Header.