Health Checking

Enabling gRPC health checking

TIL about gRPC Health Checking Protocol, and implemented it in our gRPC example code (see 07f0d9e).

The infrastructure is pretty evolved. The health checking interface is simply a gRPC service you configure and export. The auto-generated proto code is distributed (ie, you don’t have to generate it yourself). For Python, you can get it via pip grpcio-health-checking (see docs).

In the example code, I ended up exposing a new insecure port 9090 to enable clients to perform health checks using plain-text HTTP/2 (ie, without TLS). The gRPC ecosystem provides utility grpc-health-probe, basically a client for gRPC health checking. But since the protocol is simply implemented via a gRPC service, you can also perform health checks using grpcurl or a custom client. See examples below.

Health checking using grpc-health-probe

> grpc-health-probe \
    -addr=localhost:9090 \
    -connect-timeout 250ms \
    -rpc-timeout 100ms

status: SERVING

Health checking using grpcurl

> grpcurl \
    --plaintext \
    -d '{"service": "grpc.health.v1.Health"}' \
    localhost:9090 \
    grpc.health.v1.Health.Check

{
  "status": "SERVING"
}