migrate healthcheck to go

closes #72

Dockerfile

@@ -6,5 +6,5 @@ COPY oidc-test-client /
 EXPOSE 9009
 WORKDIR /web-root
 ENV OIDC_BIND=0.0.0.0:9009
-HEALTHCHECK --interval=5s --start-period=1s CMD [ "wget", "--spider", "http://localhost:9009/health" ]
+HEALTHCHECK --interval=5s --start-period=1s CMD [ "/oidc-test-client", "healthcheck" ]
 ENTRYPOINT [ "/oidc-test-client" ]

cmd/healthcheck.go

@@ -0,0 +1,38 @@
+package cmd
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+
+	"beryju.io/oidc-test-client/pkg"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+var healthcheckCmd = &cobra.Command{
+	Use: "healthcheck",
+	Run: func(cmd *cobra.Command, args []string) {
+		os.Exit(check())
+	},
+}
+
+func check() int {
+	root := pkg.Env("OIDC_ROOT_URL", "http://localhost:9009")
+	url := fmt.Sprintf("%s/health", root)
+	res, err := http.DefaultClient.Head(url)
+	if err != nil {
+		log.WithError(err).Warning("failed to send healthcheck request")
+		return 1
+	}
+	if res.StatusCode >= 400 {
+		log.WithField("status", res.StatusCode).Warning("unhealthy status code")
+		return 1
+	}
+	log.Debug("successfully checked health")
+	return 0
+}
+
+func init() {
+	rootCmd.AddCommand(healthcheckCmd)
+}