add persisting meta info

Author: stroebitzer

.gitignore

@@ -1,3 +1,4 @@
 training-application
 .DS_Store
 application.log
+/data/

helm-chart/templates/configmap.yaml

@@ -9,3 +9,4 @@ data:
     message: {{ .Values.message }}
     color: {{ .Values.color }}
     catMode: {{ .Values.catMode }}
+    persistMetaInfo: {{ .Values.persistMetaInfo }}

helm-chart/values.yaml

@@ -6,6 +6,7 @@ image:
 color: white
 message: "Hello from the app installed via helm"
 catMode: true
+persistMetaInfo: false
 
 deployment:
   replicas: 1

src/config.go

@@ -28,6 +28,7 @@ type appConfig struct {
 	applicationMessage   string
 	color                string
 	logToFileOnly        bool
+	persistMetaInfo      bool
 	catImageUrl          string
 }
 
@@ -47,6 +48,7 @@ func (appConfig *appConfig) String() string {
 	sb.WriteString(fmt.Sprintf("\tApplication message:    %s\n", appConfig.applicationMessage))
 	sb.WriteString(fmt.Sprintf("\tcolor:                  %s\n", appConfig.color))
 	sb.WriteString(fmt.Sprintf("\tlogToFileOnly:          %v\n", appConfig.logToFileOnly))
+	sb.WriteString(fmt.Sprintf("\tpersistMetaInfo:        %v\n", appConfig.persistMetaInfo))
 	sb.WriteString(fmt.Sprintf("\tcatImageUrl:            %s\n", appConfig.catImageUrl))
 	return sb.String()
 }
@@ -83,6 +85,7 @@ func (appConfig *appConfig) initAppConfig(isReady bool) {
 	appConfig.applicationMessage = getAppConfigStringValue(fileConfig, "message", "APP_MESSAGE", "not set")
 	appConfig.color = getAppConfigStringValue(fileConfig, "color", "APP_COLOR", "not set")
 	appConfig.logToFileOnly = getAppConfigBoolValue(fileConfig, "logToFileOnly", "", false)
+	appConfig.persistMetaInfo = getAppConfigBoolValue(fileConfig, "persistMetaInfo", "", false)
 	appConfig.startUpDelaySeconds = getAppConfigIntValue(fileConfig, "startUpDelaySeconds", "", 0)
 	appConfig.tearDownDelaySeconds = getAppConfigIntValue(fileConfig, "tearDownDelaySeconds", "", 0)
 	catMode := getAppConfigBoolValue(fileConfig, "catMode", "", false)

src/main.go

@@ -55,6 +55,17 @@ func main() {
 
 	server := newServer(config)
 
+	if !config.persistMetaInfo {
+		log.Info("Application does not persist meta info")
+	} else {
+		persister, err := newPersister(config)
+		if err != nil {
+			log.Errorf("error on starting persistence %v", err)
+		} else {
+			go persister.writeMetaInfo()
+		}
+	}
+
 	config.ready = true
 	log.Info("Application set to ready")
 	log.Info("For getting help, type 'help'")

src/persister.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type persister struct {
+	config *appConfig
+}
+
+var dirPath = "./data/"
+var metaInfoFilePath = dirPath + "metainfo.txt"
+
+func newPersister(appConfig *appConfig) (*persister, error) {
+	if _, err := os.Stat(dirPath); os.IsNotExist(err) {
+		return nil, err
+	}
+	return &persister{
+		config: appConfig,
+	}, nil
+}
+
+func (p *persister) writeMetaInfo() {
+
+	metaInfoFile, err := os.OpenFile(metaInfoFilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		log.Errorf("cannot open file %s: %v\n", metaInfoFilePath, err)
+	}
+	defer metaInfoFile.Close()
+
+	ticker := time.NewTicker(5 * time.Second)
+	defer ticker.Stop()
+
+	// TODO write application startup and shutdown into metainfo file
+
+	for {
+		select {
+		case <-ticker.C:
+			podName := os.Getenv("POD_NAME")
+			podIP := os.Getenv("POD_IP")
+			timeStamp := time.Now().Format("2006-01-02 15:04:05")
+			_, err = fmt.Fprintf(metaInfoFile, "%s pod name %s, pod ip %s\n", timeStamp, podName, podIP)
+			if err != nil {
+				log.Errorf("cannot append to file %s: %v\n", metaInfoFilePath, err)
+				return
+			}
+		}
+	}
+}

src/root.html

@@ -18,6 +18,7 @@ <h2>Configuration</h2>
   Seconds the application needs to start up: {{.StartUpDelaySeconds}}<br>
   Seconds the application needs to shut down gracefully: {{.TearDownDelaySeconds}}<br>
   Only log to file: {{.LogToFileOnly}}<br>
+  Persist Meta Info: {{.PersistMetaInfo}}<br>
 
   <h2>Tech Details</h2>
 

src/server.go

@@ -34,6 +34,7 @@ type TemplateData struct {
 	TearDownDelaySeconds int
 	RequestInfo          *requestInfo
 	LogToFileOnly        bool
+	PersistMetaInfo      bool
 	ProcessId            int
 	UserId               int
 	Hostname             string
@@ -110,6 +111,7 @@ func (s *server) handleRoot(w http.ResponseWriter, r *http.Request) {
 		StartUpDelaySeconds:  s.config.startUpDelaySeconds,
 		TearDownDelaySeconds: s.config.tearDownDelaySeconds,
 		LogToFileOnly:        s.config.logToFileOnly,
+		PersistMetaInfo:      s.config.persistMetaInfo,
 		ProcessId:            os.Getpid(),
 		UserId:               os.Getuid(),
 		RequestInfo:          requestInfo,
@@ -151,4 +153,4 @@ func (s *server) handleReadiness(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusServiceUnavailable)
 		log.Info("Readiness endpoint ('/readiness') responded with Status Code 503 Service Unavailable")
 	}
-}
+}

training-application.conf

@@ -4,6 +4,7 @@ version = v0
 message = Message from default training-application.conf
 color = lightGrey
 logToFileOnly = false
+persistMetaInfo = false
 catMode = false
 startUpDelaySeconds = 0
 tearDownDelaySeconds = 0