Added default transient store the execution counter (#21)

* Provide a default transiant store for execution counter, so that subsequent runs will increment
between host restarts/container deployments.

* Update main.go spelling changes

* Code review comment changes

* Update go.mod

* Update counter.go

* Update counter.go

---------

Co-authored-by: Meysam <meysam@developer-friendly.blog>

Author: pstiby-truespeed

counter/counter.go

@@ -0,0 +1,95 @@
+// Package counter, provides a means of incrementing a named counter.
+package counter
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+// IncrementNamedCounter takes a key, an increment value, and a JSON file path, and updates the value in the file
+func IncrementNamedCounter(key string, increment int, filename string) (int, error) {
+	jsonData, err := loadJSONFile(filename)
+	if err != nil {
+		return 0, err
+	}
+
+	existingValue, ok := jsonData[key]
+	if !ok {
+		jsonData[key] = increment
+	} else {
+		switch v := existingValue.(type) {
+		case float64:
+			jsonData[key] = v + float64(increment)
+		case int64:
+			jsonData[key] = v + int64(increment)
+		case int32:
+			jsonData[key] = v + int32(increment)
+		case int:
+			jsonData[key] = v + increment
+		default:
+			return 0, fmt.Errorf("value for key '%s' is not a valid numeric type", key)
+		}
+	}
+
+	err = writeJSONFile(filename, jsonData)
+	if err != nil {
+		return 0, err
+	}
+
+	value, ok := jsonData[key]
+	if !ok {
+		return 1, nil
+	}
+
+	switch v := value.(type) {
+	case float64:
+		return int(v), nil
+	case int64:
+		return int(v), nil
+	case int:
+		return int(v), nil
+	default:
+		return 0, fmt.Errorf("value for key '%s' is not a valid int32", key)
+	}
+}
+
+// writeJSONFile writes the map into a JSON file
+func writeJSONFile(filename string, jsonData map[string]interface{}) error {
+	updatedData, err := json.MarshalIndent(jsonData, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	err = ioutil.WriteFile(filename, updatedData, 0644)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// loadJSONFile reads the contents of a JSON file and returns a map[string]interface{}
+func loadJSONFile(filename string) (map[string]interface{}, error) {
+
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		err := ioutil.WriteFile(filename, []byte("{}"), 0644)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create file: %w", err)
+		}
+	}
+
+	data, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	var jsonData map[string]interface{}
+	err = json.Unmarshal(data, &jsonData)
+	if err != nil {
+		return nil, err
+	}
+
+	return jsonData, nil
+}

counter/counter_test.go

@@ -0,0 +1,27 @@
+package counter
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestThatANoneExistentCounterWillBeCreatedAndIncrements(t *testing.T) {
+	tempDir := t.TempDir()
+	testFile := filepath.Join(tempDir, "test.json")
+
+	counter, err := IncrementNamedCounter("testCounter", 1, testFile)
+	if err != nil {
+		t.Errorf("Not expecting and err to be returned: %v", err)
+	}
+	if counter != 1 {
+		t.Errorf("Counter expected to be 1 but got %d", counter)
+	}
+
+	counter, err = IncrementNamedCounter("testCounter", 1, testFile)
+	if err != nil {
+		t.Errorf("Not expecting and err to be returned: %v", err)
+	}
+	if counter != 2 {
+		t.Errorf("Counter expected to be 2 but got %d", counter)
+	}
+}

main.go

@@ -6,20 +6,25 @@ import (
 	"net/http"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"runtime/debug"
+	"strconv"
 	"strings"
 	"syscall"
 	"time"
+
+	"github.com/meysam81/prometheus-command-timer/counter"
 )
 
 type Config struct {
-	PushgatewayURL string
-	JobName        string
-	InstanceName   string
-	Labels         string
-	Debug          bool
-	Version        bool
-	Info           bool
+	PushgatewayURL          string
+	JobName                 string
+	InstanceName            string
+	Labels                  string
+	ExecCountTransientStore string
+	Debug                   bool
+	Version                 bool
+	Info                    bool
 }
 
 func main() {
@@ -32,6 +37,7 @@ func main() {
 	flag.StringVar(&config.JobName, "job-name", "", "Job name for metrics (required)")
 	flag.StringVar(&config.InstanceName, "instance-name", config.InstanceName, "Instance name for metrics")
 	flag.StringVar(&config.Labels, "labels", "", "Additional labels in key=value format, comma-separated (e.g., env=prod,team=infra)")
+	flag.StringVar(&config.ExecCountTransientStore, "execution-count-store", filepath.Join(os.TempDir(), "prometheus-command-time.json"), "Override the default transient store filename (<tmp>/prometheus-command-time.json)")
 	flag.BoolVar(&config.Version, "version", false, "Output version")
 	showHelp := flag.Bool("help", false, "Show help message")
 	flag.BoolVar(showHelp, "h", false, "Show help message (shorthand)")
@@ -133,11 +139,27 @@ func executeCommand(config *Config, cmdArgs []string) int {
 	sendMetric(config, "job_duration_seconds", fmt.Sprintf("%.6f", duration), "gauge", "Total time taken for job execution in seconds")
 	sendMetric(config, "job_exit_status", fmt.Sprintf("%d", exitStatus), "gauge", "Exit status code of the last job execution (0=success)")
 	sendMetric(config, "job_last_execution_timestamp", fmt.Sprintf("%d", endTime), "gauge", "Timestamp of the last job execution")
-	sendMetric(config, "job_executions_total", "1", "counter", "Total number of job executions")
+	sendMetric(config, "job_executions_total", strconv.Itoa(incrementExecutionCounter(config)), "counter", "Total number of job executions")
 
 	return exitStatus
 }
 
+// incrementExecutionCounter will return the next value of a counter which
+// is named using the push gateway URL.
+func incrementExecutionCounter(config *Config) int {
+	counterVal := 1
+	counterName, err := buildPushgatewayURL(config)
+	if err != nil {
+		logStdout(config, "error building counter name: %v", err)
+	} else {
+		counterVal, err = counter.IncrementNamedCounter(counterName, 1, config.ExecCountTransientStore)
+		if err != nil {
+			logStdout(config, "error loading counter: %v", err)
+		}
+	}
+	return counterVal
+}
+
 func buildPushgatewayURL(config *Config) (string, error) {
 	url := fmt.Sprintf("%s/metrics/job/%s/instance/%s",
 		strings.TrimSuffix(config.PushgatewayURL, "/"),