From 42a4e017c8d41d640aa2adb9f9c087baa0c8b3e1 Mon Sep 17 00:00:00 2001
From: Christian Richter <crichter@owncloud.com>
Date: Mon, 11 Apr 2022 16:09:09 +0200
Subject: [PATCH] Add reference implementation for health & readiness endpoint
 in IDP

Signed-off-by: Christian Richter <crichter@owncloud.com>
---
 idp/pkg/server/debug/server.go     | 37 +++++++++++++++++++-----------
 ocis-pkg/shared/healthchecklist.go | 29 +++++++++++++++++++++++
 2 files changed, 53 insertions(+), 13 deletions(-)
 create mode 100644 ocis-pkg/shared/healthchecklist.go

diff --git a/idp/pkg/server/debug/server.go b/idp/pkg/server/debug/server.go
index 9da10444f..fab17857f 100644
--- a/idp/pkg/server/debug/server.go
+++ b/idp/pkg/server/debug/server.go
@@ -3,9 +3,12 @@ package debug
 import (
 	"io"
 	"net/http"
+	"net/url"
 
 	"github.com/owncloud/ocis/idp/pkg/config"
+	"github.com/owncloud/ocis/ocis-pkg/log"
 	"github.com/owncloud/ocis/ocis-pkg/service/debug"
+	"github.com/owncloud/ocis/ocis-pkg/shared"
 	"github.com/owncloud/ocis/ocis-pkg/version"
 )
 
@@ -21,23 +24,30 @@ func Server(opts ...Option) (*http.Server, error) {
 		debug.Token(options.Config.Debug.Token),
 		debug.Pprof(options.Config.Debug.Pprof),
 		debug.Zpages(options.Config.Debug.Zpages),
-		debug.Health(health(options.Config)),
+		debug.Health(health(options.Config, options.Logger)),
 		debug.Ready(ready(options.Config)),
 	), nil
 }
 
 // health implements the health check.
-func health(cfg *config.Config) func(http.ResponseWriter, *http.Request) {
+func health(cfg *config.Config, l log.Logger) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Content-Type", "text/plain")
-		w.WriteHeader(http.StatusOK)
-
-		// TODO: check if services are up and running
-
-		_, err := io.WriteString(w, http.StatusText(http.StatusOK))
-		// io.WriteString should not fail but if it does we want to know.
+		targetHost, err := url.Parse(cfg.Ldap.URI)
 		if err != nil {
-			panic(err)
+			l.Fatal().Err(err).Str("uri", cfg.Ldap.URI).Msg("invalid LDAP URI")
+		}
+		err = shared.RunChecklist(shared.TCPConnect(targetHost.Host))
+		retVal := http.StatusOK
+		if err != nil {
+			l.Error().Err(err).Msg("Healtcheck failed")
+			retVal = http.StatusInternalServerError
+		}
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(retVal)
+
+		_, err = io.WriteString(w, http.StatusText(retVal))
+		if err != nil {
+			l.Fatal().Err(err).Msg("Could not write health check body")
 		}
 	}
 }
@@ -47,9 +57,10 @@ func ready(cfg *config.Config) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/plain")
 		w.WriteHeader(http.StatusOK)
-
-		// TODO: check if services are up and running
-
+		// if we can call this function, a http(200) is a valid response as
+		// there is nothing we can check at this point for IDP
+		// if there is a mishap when initializing, there is a minimal (talking ms or ns window)
+		// timeframe where this code is callable
 		_, err := io.WriteString(w, http.StatusText(http.StatusOK))
 		// io.WriteString should not fail but if it does we want to know.
 		if err != nil {
diff --git a/ocis-pkg/shared/healthchecklist.go b/ocis-pkg/shared/healthchecklist.go
new file mode 100644
index 000000000..ce240d7ed
--- /dev/null
+++ b/ocis-pkg/shared/healthchecklist.go
@@ -0,0 +1,29 @@
+package shared
+
+import "net"
+
+// Check is a single health-check
+type Check func() error
+
+// RunChecklist runs all the given checks
+func RunChecklist(checks ...Check) error {
+	for _, c := range checks {
+		err := c()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// TCPConnect connects to a given tcp endpoint
+func TCPConnect(host string) Check {
+	return func() error {
+		conn, err := net.Dial("tcp", host)
+		if err != nil {
+			return err
+		}
+		defer conn.Close()
+		return nil
+	}
+}