server/health: add health check handler

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

server/health/health.go

@@ -0,0 +1,87 @@
+package pb
+
+import (
+	"context"
+
+	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/errors"
+	"github.com/unistack-org/micro/v3/server"
+)
+
+var (
+	// guard to fail early
+	_ HealthServer = &handler{}
+)
+
+type handler struct {
+	server server.Server
+	opts   Options
+}
+
+type CheckFunc func(context.Context) error
+
+type Option func(*Options)
+
+type Options struct {
+	LiveChecks  []CheckFunc
+	ReadyChecks []CheckFunc
+	Version     string
+	Name        string
+}
+
+func LiveChecks(fns ...CheckFunc) Option {
+	return func(o *Options) {
+		o.LiveChecks = append(o.LiveChecks, fns...)
+	}
+}
+
+func ReadyChecks(fns ...CheckFunc) Option {
+	return func(o *Options) {
+		o.ReadyChecks = append(o.ReadyChecks, fns...)
+	}
+}
+
+func Name(name string) Option {
+	return func(o *Options) {
+		o.Name = name
+	}
+}
+
+func Version(version string) Option {
+	return func(o *Options) {
+		o.Version = version
+	}
+}
+
+func NewHealth(opts ...Option) *handler {
+	options := Options{}
+	for _, o := range opts {
+		o(&options)
+	}
+	return &handler{opts: options}
+}
+
+func (h *handler) Live(ctx context.Context, req *codec.Frame, rsp *codec.Frame) error {
+	var err error
+	for _, fn := range h.opts.LiveChecks {
+		if err = fn(ctx); err != nil {
+			return errors.ServiceUnavailable(h.opts.Name, "%v", err)
+		}
+	}
+	return nil
+}
+
+func (h *handler) Ready(ctx context.Context, req *codec.Frame, rsp *codec.Frame) error {
+	var err error
+	for _, fn := range h.opts.ReadyChecks {
+		if err = fn(ctx); err != nil {
+			return errors.ServiceUnavailable(h.opts.Name, "%v", err)
+		}
+	}
+	return nil
+}
+
+func (h *handler) Version(ctx context.Context, req *codec.Frame, rsp *codec.Frame) error {
+	rsp.Data = []byte(h.opts.Version)
+	return nil
+}