grpc-ecosystem/grpc-health-probe

grpc_health_probe(1)

The grpc_health_probe utility allows you to query health of gRPC services that expose service their status through the gRPC Health Checking Protocol.

grpc_health_probe is meant to be used for health checking gRPC applications in Kubernetes, using the exec probes.

:warning: Kubernetes has now built-in gRPC health checking capability as generally available. As a result, you might no longer need to use this tool and can use the native Kubernetes feature instead.

This tool can still be useful if you are on older versions of Kubernetes, or using advanced configuration (such as custom metadata, TLS or finer timeout tuning), or not using Kubernetes at all.

This command-line utility makes a RPC to /grpc.health.v1.Health/Check. If it responds with a SERVING status, the grpc_health_probe will exit with success, otherwise it will exit with a non-zero exit code (documented below).

EXAMPLES

$ grpc_health_probe -addr=localhost:5000
healthy: SERVING

$ grpc_health_probe -addr=localhost:9999 -connect-timeout 250ms -rpc-timeout 100ms
failed to connect service at "localhost:9999": context deadline exceeded
exit status 2

Installation

It is recommended to use a version-stamped binary distribution:

• Choose a binary from the Releases page.

Installing from source (not recommended):

• Make sure you have git and go installed.
• Run: go install github.com/grpc-ecosystem/grpc-health-probe@latest
• This will compile the binary into your $GOPATH/bin (or $HOME/go/bin).

Using the gRPC Health Checking Protocol

To make use of the grpc_health_probe, your application must implement the gRPC Health Checking Protocol v1. This means you must register the Health service and implement the rpc Check that returns a SERVING status.

Since the Health Checking protocol is part of the gRPC core, it has packages/libraries available for the languages supported by gRPC:

[health.proto] [Go] [Java] [Python] [C#/NuGet] [Ruby] ...

Most of the languages listed above provide helper functions that hide implementation details. This eliminates the need for you to implement the Check rpc yourself.

Example: gRPC health checking on Kubernetes

Kubernetes now supports gRPC health checking. If your cluster is running a version that supports gRPC health checking, you can define a gRPC liveness probe in your Pod specification. For more information on how to define a gRPC liveness probe in Kubernetes, see the Kubernetes documentation.

However, if your Kubernetes version does not support gRPC health checking or if you want to use some advanced features that Kubernetes does not support, you can use grpc_health_probe to health-check your gRPC server. As a solution, grpc_health_probe can be used for Kubernetes to health-check gRPC servers running in the Pod.

You are recommended to use Kubernetes exec probes and define liveness and/or readiness checks for your gRPC server pods.

You can bundle the statically compiled grpc_health_probe in your container image. Choose a binary release and download it in your Dockerfile:

ARG TARGETOS TARGETARCH
RUN GRPC_HEALTH_PROBE_VERSION=v0.4.38 && \
    wget -qO/bin/grpc_health_probe https://github.com/grpc-ecosystem/grpc-health-probe/releases/download/${GRPC_HEALTH_PROBE_VERSION}/grpc_health_probe-${TARGETOS}-${TARGETARCH} && \
    chmod +x /bin/grpc_health_probe

or via release image:

COPY --from=ghcr.io/grpc-ecosystem/grpc-health-probe:v0.4.38 /ko-app/grpc-health-probe /bin/grpc_health_probe

In your Kubernetes Pod specification manifest, specify a livenessProbe and/or readinessProbe for the container:

spec:
  containers:
  - name: server
    image: "[YOUR-DOCKER-IMAGE]"
    ports:
    - containerPort: 5000
    readinessProbe:
      exec:
        command: ["/bin/grpc_health_probe", "-addr=:5000"]
      initialDelaySeconds: 5
    livenessProbe:
      exec:
        command: ["/bin/grpc_health_probe", "-addr=:5000"]
      initialDelaySeconds: 10

This approach provides proper readiness/liveness checking to your applications that implement the gRPC Health Checking Protocol.

Health Checking TLS Servers

If a gRPC server is serving traffic over TLS, or uses TLS client authentication to authorize clients, you can still use grpc_health_probe to check health with command-line options:

Health checking TLS Servers with SPIFFE issued credentials

If your gRPC server requires authentication, you can use the following command line options and set the SPIFFE_ENDPOINT_SOCKET environment variable.

Other Available Flags

Example:

1. Start the route_guide example server with TLS by running:

   go run server/server.go -tls
   

2. Run grpc_client_probe with the CA certificate (in the testdata/ directory) and hostname override the cert is signed for:

   $ grpc_health_probe -addr 127.0.0.1:10000 \
       -tls \
       -tls-ca-cert /path/to/testdata/ca.pem \
       -tls-server-name=example.com \
       -rpc-header=foo:bar \
       -rpc-header=foo2:bar2
   
   status: SERVING
   

Exit codes

It is not recommended to rely on specific exit statuses. Any failure will be a non-zero exit code.

This is not an official Google project.