Add healthcheck command (#2856)

Currently vikunja has a `/health` endpoint that was added in #998. Docker/compose cannot utilize this feature since vikunja's docker image doesn't have curl/wget as it is pruned which is great for the image size. This PR adds a `healthcheck` command that send an http request to `/health` and exits with 0 or non-zero depending on the result.
It also adds a `HEALTHCHECK` to the docker image which calls this automatically.

Reviewed-on: #2856
Reviewed-by: konrad <k@knt.li>
Co-authored-by: ScribblerCoder <omar2001.oh@gmail.com>
Co-committed-by: ScribblerCoder <omar2001.oh@gmail.com>

Dockerfile

@@ -53,3 +53,5 @@ ENV VIKUNJA_DATABASE_PATH=/db/vikunja.db
 
 COPY --from=apibuilder /build/vikunja-* vikunja
 COPY --from=apibuilder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+HEALTHCHECK --interval=30s --timeout=30s --start-period=10s --retries=3 \
+	CMD [ "/app/vikunja/vikunja", "healthcheck" ]

pkg/cmd/healthcheck.go

@@ -0,0 +1,64 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+
+	"code.vikunja.io/api/pkg/config"
+	"code.vikunja.io/api/pkg/initialize"
+
+	"github.com/spf13/cobra"
+)
+
+func init() {
+	rootCmd.AddCommand(healthcheckCmd)
+}
+
+var healthcheckCmd = &cobra.Command{
+	Use:   "healthcheck",
+	Short: "Preform a healthcheck on the Vikunja api server",
+	PreRun: func(_ *cobra.Command, _ []string) {
+		initialize.LightInit()
+	},
+	Run: func(_ *cobra.Command, _ []string) {
+		client := &http.Client{
+			Timeout: 5 * time.Second,
+		}
+		host := config.ServiceInterface.GetString()
+		url := "http://%s/health"
+		resp, err := client.Get(fmt.Sprintf(url, host))
+		if err != nil {
+			fmt.Printf("API server is not healthy: %v\n", err)
+			os.Exit(1)
+			return
+		}
+		defer resp.Body.Close()
+
+		// Check the response status
+		if resp.StatusCode == http.StatusOK {
+			fmt.Println("API server is healthy")
+			os.Exit(0)
+			return
+		}
+		fmt.Printf("API server is not healthy: HTTP %d\n", resp.StatusCode)
+		os.Exit(1)
+	},
+}