Kubernetes Network Policies are not forgiving. They decide, with precision, who can talk to whom inside your cluster. When traffic is HTTP, debugging is straightforward. When it’s gRPC, the story changes. The protocol rides on HTTP/2, multiplexes requests, and often hides failure patterns from simple logs. Without clear network policy strategy, even a minor update can shut down critical services.
A Kubernetes Network Policy works by defining pod-level ingress and egress rules. For gRPC, this means thinking at both the IP and port layer, and understanding how gRPC’s persistent connections behave under restrictive rules. Policies need to allow the full set of source and destination combinations that gRPC streams require. You can’t rely on the defaults — those defaults often block exactly the connection that keeps your system alive.
A common trap is defining policies for HTTP services, then assuming gRPC will follow the same patterns. gRPC traffic may bypass certain proxies or use long-lived connections, so readiness checks may pass while the service is silently failing to communicate. Observability must include checks that operate at both the TCP and application layer. This requires a clear mapping between your gRPC service ports and the labels used in your Network Policy selectors.