Active health checks for gRPC endpoints with NGINX Plus

README.md

This solution is obsolete

This solution is for NGINX Plus prior to R23. Since NGINX Plus R23, gRPC health checks can be enabled with

health_check type=grpc;

https://www.nginx.com/blog/nginx-plus-r23-released/#grpc-health-checks

nginx.conf

user              nginx;
worker_processes  auto;
error_log         /var/log/nginx/error.log debug;
pid               nginx.pid;

events { worker_connections  1024; }

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log main;

    sendfile           on;
    keepalive_timeout  65;

    upstream grpc_endpoints {
        server 10.0.0.1;
        server 10.0.0.2;
        server 10.0.0.3;
    }

    server {
        listen 50051 http2; # This is unencrypted, plaintext gRPC. Use 'ssl' parameter to enable TLS.
 
        location / {
            # The 'grpc://' prefix is optional; unencrypted gRPC is the default
            # Use 'grpcs://' for TLS-encrypted gRPC services
            grpc_pass grpc://grpc_endpoints;
            error_page 502 = @grpc_unavailable; # If no healthy servers then send the appropriate gRPC response
        }

        # Simple gRPC health check
        # Sends a dummy gRPC request, expecting a grpc-status=14 response to indicate
        # service unavailable, which tells us there is a live gRPC service listening.
        location @grpc_health {
            health_check mandatory uri=/nginx.health/check match=grpc_response; # Other parameters as required
            grpc_set_header Content-Type application/grpc;
            grpc_set_header TE trailers;
            grpc_pass grpc://grpc_endpoints;
        }

        # Generates a gRPC-compliant error response
        location @grpc_unavailable {
            default_type application/grpc;
            add_header grpc-status 14;
            add_header grpc-message unavailable;
            return 204;
        }
    }

    # This is the expected response from a gRPC health check
    match grpc_response {
        header Content-Type = application/grpc;
        header grpc-status = 12; # unimplemented / unknown method
    }
}

Probably, @grpc_health location requires one more directive:
grpc_set_header content-type "application/grpc".

Thanks! Done (L42).