Added logging to a file. Named per-program and dated to that day.

.gitignore

@@ -3,4 +3,5 @@ bin/*
 nodes.json
 dist/
 .github_token
-codecov.yml
+codecov.yml
+cmd/*/logs/*

README.md

@@ -322,7 +322,8 @@ Completed to-do's:
 * **2021-08-06**, v0.0.5.  Added ability to remove a node's data from the Receiver.
 * **2021-08-07**, v0.0.6.  Added timestamp to the disk-persisted data; added macOS to build file.
 * **2021-08-08**, v0.0.7.  Added ability to export all data as JSON.
-* **2021-09-07**, v0.0.8.  Lots of changes based on comments from the nice people at the Gophers Slack, including: removing init(), removing globals (some: work in progress), cleaning up the readme, adding OS logos, using GoReleaser and more linters, basic tests and benchmarks (also work in progress), new lighter dashboard and hosts web pages, and tidied up the struct used to marshal/unmarshal data. 
+* **2021-09-07**, v0.0.8.  Lots of changes based on comments from the nice people at the Gophers Slack, including: removing init(), removing globals (some: work in progress), cleaning up the readme, adding OS logos, using GoReleaser and more linters, basic tests and benchmarks (also work in progress), new lighter dashboard and hosts web pages, and tidied up the struct used to marshal/unmarshal data.
+* **2021-09-09**, v0.0.9.  Added logging to a file. Creates folder in cwd, then creates a named and dated file, logs to it and stdout.
 
 ---
 

cmd/collector/main.go

@@ -13,11 +13,13 @@ import (
 	"net/http"
 	"os"
 	"os/exec"
+	"os/signal"
 	"os/user"
 	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 	vcms "vcms/internal"
 )
@@ -34,6 +36,7 @@ func main() {
 		debug       = false
 		testing     = false
 		receiverURL = "http://127.0.0.1:8080"
+		logName     = vcms.CreateLogName(vcms.LogFolder, cmdCodename)
 	)
 
 	flag.BoolVar(&debug, "d", debug, "Shows debugging info")
@@ -47,6 +50,20 @@ func main() {
 		os.Exit(0)
 	}
 
+	// Opens a logfile for writing and also outputs to stdout.
+	vcms.CheckLogFolder(vcms.LogFolder)
+	lf, err := os.OpenFile(logName, os.O_CREATE|os.O_APPEND|os.O_RDWR, 0755)
+	if err != nil {
+		log.Print(err)
+		log.Printf("Error: Couldn't open '%s' for writing, so logging to stdout only.\n", logName)
+	} else {
+		defer lf.Close()
+		log.SetOutput(io.MultiWriter(os.Stdout, lf))
+		log.Printf("Startup: Logging to stdout and '%s'.\n", logName)
+	}
+
+	shutdownHandler()
+
 	log.Println(vcms.Version(cmdName))
 	log.Printf("%s \n", cmdDesc)
 	log.Printf("%s \n", vcms.AppDesc)
@@ -365,3 +382,21 @@ func getCPUDetails() (int, string) {
 
 	return count, speed
 }
+
+// https://stackoverflow.com/a/12571099/254146
+func shutdownHandler() {
+	channel := make(chan os.Signal)
+	signal.Notify(channel, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-channel
+		log.Println("Close signal detected: shutting down.")
+
+		// TODO: e.g. notify Slack, send an email etc.
+
+		log.Println("Shutdown: bye bye.")
+		log.Println()
+		log.Println()
+		log.Println()
+		os.Exit(0)
+	}()
+}

cmd/receiver/main.go

@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"html/template"
+	"io"
 	"log"
 	"net/http"
 	"os"
@@ -26,7 +27,6 @@ var embeddedFiles embed.FS
 var (
 	debug = false
 	nodes = make(map[string]*vcms.SystemData)
-	// logFile  string = vcms.MakeLogName(appCodename)
 )
 
 const (
@@ -71,12 +71,13 @@ func main() {
 		cmdName                       = "VCMS - Receiver"
 		cmdDesc                       = "Receives data from the Collector apps, creates a web page."
 		cmdCodename                   = "vcms-receiver"
-		persistentStorageSaveInterval = 10 // TODO: make configurable.
+		persistentStorageSaveInterval = 60 // TODO: make configurable.
 	)
 
 	var (
 		version     = false
 		receiverURL = "127.0.0.1:8080" // Don't put e.g. http:// at the start. Add this to docs.
+		logName     = vcms.CreateLogName(vcms.LogFolder, cmdCodename)
 	)
 
 	flag.BoolVar(&debug, "d", debug, "Shows debugging info")
@@ -89,6 +90,18 @@ func main() {
 		os.Exit(0)
 	}
 
+	// Opens a logfile for writing and also outputs to stdout.
+	vcms.CheckLogFolder(vcms.LogFolder)
+	lf, err := os.OpenFile(logName, os.O_CREATE|os.O_APPEND|os.O_RDWR, 0755)
+	if err != nil {
+		log.Print(err)
+		log.Printf("Error: Couldn't open '%s' for writing, so logging to stdout only.\n", logName)
+	} else {
+		defer lf.Close()
+		log.SetOutput(io.MultiWriter(os.Stdout, lf))
+		log.Printf("Startup: Logging to stdout and '%s'.\n", logName)
+	}
+
 	shutdownHandler()
 
 	log.Println(vcms.Version(cmdName))
@@ -157,12 +170,16 @@ func shutdownHandler() {
 	signal.Notify(channel, os.Interrupt, syscall.SIGTERM)
 	go func() {
 		<-channel
-		log.Println("Close signal detected. Saving nodes to persistent storage.")
+		log.Println("Close signal detected: shutting down.")
 
+		log.Println("Shutdown: saving nodes to persistent storage.")
 		saveToPersistentStorage()
 		// TODO: e.g. notify Slack, send an email etc.
 
-		log.Println("Exiting.")
+		log.Println("Shutdown: bye bye.")
+		log.Println()
+		log.Println()
+		log.Println()
 		os.Exit(0)
 	}()
 }

internal/vcms.go

@@ -3,6 +3,8 @@ package vcms
 
 import (
 	"fmt"
+	"log"
+	"os"
 	"runtime"
 	"time"
 )
@@ -12,11 +14,12 @@ AppXxx stores strings common to both the Collector and Receiver.
 ProjectURL is the URL of the project on GitHub.
 */
 const (
-	AppDate    string = "2021-09-07"
-	AppVersion string = "0.0.8"
+	AppDate    string = "2021-09-09"
+	AppVersion string = "0.0.9"
 	AppTitle   string = "Vaughany's Computer Monitoring System"
 	ProjectURL string = "github.com/vaughany/vcms"
 	AppDesc    string = "Description of the whole system goes here."
+	LogFolder  string = "logs"
 )
 
 /*
@@ -89,3 +92,43 @@ func Version(appName string) string {
 	// return fmt.Sprintf("%s v%s (%s), %s.\n%s\n", appName, AppVersion, AppDate, runtime.Version(), AppDesc)
 	return fmt.Sprintf("%s v%s (%s), %s.", appName, AppVersion, AppDate, runtime.Version())
 }
+
+/*
+CheckLogFolder checks for the existence of the log folder.
+*/
+func CheckLogFolder(logFolder string) bool {
+	if stat, err := os.Stat(logFolder); err != nil || !stat.IsDir() {
+		log.Printf("Log folder '%s' doesn't exist.\n", logFolder)
+		if !CreateLogFolder(logFolder) {
+			log.Printf("Error: Log folder '%s' could not be created.\n", logFolder)
+			return false
+		}
+		log.Printf("Log folder '%s' created.\n", logFolder)
+		return true
+	}
+	log.Printf("Log folder '%s' exists.\n", logFolder)
+	return true
+}
+
+/*
+CreateLogFolder creates a log folder.
+*/
+func CreateLogFolder(logFolder string) bool {
+	err := os.Mkdir(logFolder, 0755)
+	if err != nil {
+		log.Print(err)
+		return false
+	}
+	return true
+}
+
+/*
+CreateLogName creates and returns a name for the log file, based on the application's start date.
+*/
+func CreateLogName(logFolder string, cmdName string) string {
+	// time := time.Now().Format("2006-01-02_15-04-05")
+	// time := time.Now().Format("2006-01-02_15-04")
+	time := time.Now().Format("2006-01-02")
+
+	return fmt.Sprintf("%s/%s_%s.log", logFolder, cmdName, time)
+}