Improve logging with multiwriter

Signed-off-by: Kedar Vijay Kulkarni <[email protected]>

README.md

@@ -17,9 +17,10 @@ This tool allows OpenShift users to run a watcher for Prometheus queries and def
   * [x] Add parameter for clearing/not-clearing screen
   * [x] Add Parameter for timeout
 * [x] Add a Makefile
+* [x] File logging the output
+* [x] Print output to screen even when logging enabled - simultaneously
 * [ ] Notify/Do Something when results don't match conditions
 * [ ] Spawn goroutines to keep running queries and evaluating results to handle scale - e.g. when we have very large number of queries in the yaml file, we can divide and concurrently run queries
-* [ ] File logging the output, screen will give current status, look at Prometheus alerts
 
 
 

main.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"io"
 	"log"
+	"os"
 	"time"
 
 	"github.com/alexflint/go-arg"
@@ -15,13 +17,27 @@ import (
 
 func main() {
 	var args struct {
-		NoClrscr bool          `arg:"--noclrscr" help:"Do not clear screen after each iteration." default:"false"`
-		Queries  string        `help:"queries file to use" default:"queries.yaml"`
-		Timeout  time.Duration `help:"Duration to run Continuous Performance Analysis. You can pass values like 4h or 1h10m10s" default:"4h"`
+		NoClrscr  bool          `arg:"--noclrscr" help:"Do not clear screen after each iteration. Clears screen by default." default:"false"`
+		Queries   string        `arg:"-q,--queries" help:"queries file to use" default:"queries.yaml"`
+		Timeout   time.Duration `arg:"-t,--timeout" help:"Duration to run Continuous Performance Analysis. You can pass values like 4h or 1h10m10s" default:"4h"`
+		LogOutput bool          `arg:"-l,--log-output" help:"Output will be stored in a log file instead of stdout." default:"false"`
 	}
 	arg.MustParse(&args)
 
 	o.RegisterFailHandler(g.Fail)
+	if args.LogOutput {
+		f, err := os.OpenFile("cpa.log", os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
+		multiWriter := io.MultiWriter(os.Stdout, f)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		//defer to close when you're done with it, not because you think it's idiomatic!
+		defer f.Close()
+
+		//set output of logs to f
+		log.SetOutput(multiWriter)
+	}
 
 	oc := exutil.NewCLI("prometheus-cpa", exutil.KubeConfigPath())
 	// secrets, err := oc.AdminKubeClient().CoreV1().Secrets("openshift-monitoring").List(metav1.ListOptions{})