Merge pull request #65 from kuskoman/moreeeee-refactor

More refactor, 100% test coverage

cmd/exporter/main.go

@@ -3,14 +3,15 @@ package main
 import (
 	"log"
 
+	"github.com/joho/godotenv"
 	"github.com/kuskoman/logstash-exporter/collectors"
 	"github.com/kuskoman/logstash-exporter/config"
 	"github.com/kuskoman/logstash-exporter/server"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
 func main() {
-	warn := config.InitializeEnv()
+	warn := godotenv.Load()
 	if warn != nil {
 		log.Println(warn)
 	}

config/env_helper.go

@@ -2,15 +2,8 @@ package config
 
 import (
 	"os"
-
-	"github.com/joho/godotenv"
 )
 
-// InitializeEnv loads the environment variables from the .env file
-func InitializeEnv() error {
-	return godotenv.Load()
-}
-
 func getEnvWithDefault(key string, defaultValue string) string {
 	value := os.Getenv(key)
 	if value == "" {

config/env_helper_test.go

@@ -24,12 +24,3 @@ func TestGetEnvWithDefault(t *testing.T) {
 		}
 	})
 }
-
-func TestInitializeEnv(t *testing.T) {
-	t.Run("should throw an error if .env file is not found", func(t *testing.T) {
-		err := InitializeEnv()
-		if err == nil {
-			t.Errorf("expected error but got nil")
-		}
-	})
-}

config/logstash_config.go

@@ -1,5 +1,8 @@
 package config
 
 var (
+	// LogstashUrl is the URL of the Logstash instance to be monitored.
+	// Defaults to http://localhost:9600
+	// Can be overridden by setting the LOGSTASH_URL environment variable
 	LogstashUrl = getEnvWithDefault("LOGSTASH_URL", "http://localhost:9600")
 )

config/prometheus_config.go

@@ -1,3 +1,4 @@
 package config
 
+// PrometheusNamespace is the namespace used for all metrics exported by this exporter.
 const PrometheusNamespace = "logstash"

config/server_config.go

@@ -1,6 +1,17 @@
 package config
 
 var (
+	// Port is the port the exporter will listen on.
+	// Defaults to 9198
+	// Can be overridden by setting the PORT environment variable
 	Port = getEnvWithDefault("PORT", "9198")
+
+	// Host is the host the exporter will listen on.
+	// Defaults to an empty string, which will listen on all interfaces
+	// Can be overridden by setting the HOST environment variable
+	// For windows, use "localhost", because an empty string will not work
+	// with the default windows firewall configuration.
+	// Alternatively you can change the firewall configuration to allow
+	// connections to the port from all interfaces.
 	Host = getEnvWithDefault("HOST", "")
 )

fetcher/logstash_client/client.go

@@ -8,18 +8,21 @@ import (
 	"github.com/kuskoman/logstash-exporter/fetcher/responses"
 )
 
+// Client is an interface for the Logstash client able to fetch data from the Logstash API
 type Client interface {
 	GetNodeInfo(ctx context.Context) (*responses.NodeInfoResponse, error)
 	GetNodeStats(ctx context.Context) (*responses.NodeStatsResponse, error)
 }
 
+// DefaultClient is the default implementation of the Client interface
 type DefaultClient struct {
 	httpClient *http.Client
 	endpoint   string
 }
 
 const defaultLogstashEndpoint = "http://localhost:9600"
 
+// NewClient returns a new instance of the DefaultClient configured with the given endpoint
 func NewClient(endpoint string) Client {
 	if endpoint == "" {
 		endpoint = defaultLogstashEndpoint

fetcher/logstash_client/queries.go

@@ -7,11 +7,13 @@ import (
 	"github.com/kuskoman/logstash-exporter/fetcher/responses"
 )
 
+// GetNodeInfo fetches the node info from the "/" endpoint of the Logstash API
 func (client *DefaultClient) GetNodeInfo(ctx context.Context) (*responses.NodeInfoResponse, error) {
 	fullPath := client.endpoint
 	return getMetrics[responses.NodeInfoResponse](ctx, client.httpClient, fullPath)
 }
 
+// GetNodeStats fetches the node stats from the "/_node/stats" endpoint of the Logstash API
 func (client *DefaultClient) GetNodeStats(ctx context.Context) (*responses.NodeStatsResponse, error) {
 	fullPath := fmt.Sprintf("%s/_node/stats", client.endpoint)
 	return getMetrics[responses.NodeStatsResponse](ctx, client.httpClient, fullPath)

fetcher/responses/nodeinfo_response.go

@@ -1,5 +1,6 @@
 package responses
 
+// NodeInfoResponse is the response from the "/" endpoint of the Logstash API
 type NodeInfoResponse struct {
 	Host        string `json:"host"`
 	Version     string `json:"version"`

fetcher/responses/nodestats_response.go

@@ -250,6 +250,7 @@ type QueueResponse struct {
 	EventsCount int `json:"events_count"`
 }
 
+// NodeStatsResponse is the response from the _node/stats API.
 type NodeStatsResponse struct {
 	Host        string           `json:"host"`
 	Version     string           `json:"version"`

prometheus_helper/prometheus_helper.go

@@ -9,17 +9,12 @@ import (
 	dto "github.com/prometheus/client_model/go"
 )
 
+// SimpleDescHelper is a helper struct that can be used to create prometheus.Desc objects
 type SimpleDescHelper struct {
 	Namespace string
 	Subsystem string
 }
 
-// NewDesc creates a new prometheus.Desc with the namespace and subsystem. The help text is set to the name.
-func (h *SimpleDescHelper) NewDesc(name string) *prometheus.Desc {
-	help := name
-	return prometheus.NewDesc(prometheus.BuildFQName(h.Namespace, h.Subsystem, name), help, nil, nil)
-}
-
 // NewDescWithHelp creates a new prometheus.Desc with the namespace and subsystem.
 func (h *SimpleDescHelper) NewDescWithHelp(name string, help string) *prometheus.Desc {
 	return prometheus.NewDesc(prometheus.BuildFQName(h.Namespace, h.Subsystem, name), help, nil, nil)
@@ -42,56 +37,21 @@ func ExtractFqName(metric string) (string, error) {
 	return matches[1], nil
 }
 
-// CustomCollector is a custom prometheus.Collector that collects only the given metric.
-type CustomCollector struct {
-	metric prometheus.Metric
-}
-
-// Describe implements the prometheus.Collector interface.
-func (c *CustomCollector) Describe(ch chan<- *prometheus.Desc) {
-	ch <- c.metric.Desc()
-}
-
-// Collect implements the prometheus.Collector interface.
-func (c *CustomCollector) Collect(ch chan<- prometheus.Metric) {
-	ch <- c.metric
-}
-
 // ExtractValueFromMetric extracts the value from a prometheus.Metric object.
 // It creates a custom collector and registry, registers the given metric, and then collects
 // the metric value using the registry.
 // Returns the extracted float64 value from the metric's Gauge.
 func ExtractValueFromMetric(metric prometheus.Metric) (float64, error) {
-	// Custom collector that collects only the given metric.
-	collector := &CustomCollector{
-		metric: metric,
-	}
-
-	// Create a custom registry and register the collector.
-	registry := prometheus.NewRegistry()
-	err := registry.Register(collector)
+	var dtoMetric dto.Metric
+	err := metric.Write(&dtoMetric)
 	if err != nil {
-		return 0, err
+		return 0, fmt.Errorf("error writing metric: %v", err)
 	}
 
-	var metricValue float64
-	metricChannel := make(chan prometheus.Metric)
-	go func() {
-		registry.Collect(metricChannel)
-		close(metricChannel)
-	}()
-
-	for collectedMetric := range metricChannel {
-		if collectedMetric.Desc().String() == metric.Desc().String() {
-			var dtoMetric dto.Metric
-			err = collectedMetric.Write(&dtoMetric)
-			if err != nil {
-				return 0, fmt.Errorf("error writing metric: %v", err)
-			}
-			metricValue = dtoMetric.GetGauge().GetValue()
-			break
-		}
+	gauge := dtoMetric.GetGauge()
+	if gauge == nil {
+		return 0, errors.New("the metric is not a Gauge")
 	}
 
-	return metricValue, nil
+	return gauge.GetValue(), nil
 }

prometheus_helper/prometheus_helper_test.go

@@ -1,10 +1,12 @@
 package prometheus_helper
 
 import (
+	"errors"
 	"fmt"
 	"testing"
 
 	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
 )
 
 func TestSimpleDescHelper(t *testing.T) {
@@ -13,17 +15,17 @@ func TestSimpleDescHelper(t *testing.T) {
 		Subsystem: "test",
 	}
 
-	t.Run("NewDesc", func(t *testing.T) {
-		desc := helper.NewDesc("metric")
-		expectedDesc := "Desc{fqName: \"logstash_exporter_test_metric\", help: \"metric\", constLabels: {}, variableLabels: []}"
+	t.Run("NewDescWithHelp", func(t *testing.T) {
+		desc := helper.NewDescWithHelp("metric", "help")
+		expectedDesc := "Desc{fqName: \"logstash_exporter_test_metric\", help: \"help\", constLabels: {}, variableLabels: []}"
 		if desc.String() != expectedDesc {
 			t.Errorf("incorrect metric description, expected %s but got %s", expectedDesc, desc.String())
 		}
 	})
 
-	t.Run("NewDescWithHelp", func(t *testing.T) {
-		desc := helper.NewDescWithHelp("metric", "help")
-		expectedDesc := "Desc{fqName: \"logstash_exporter_test_metric\", help: \"help\", constLabels: {}, variableLabels: []}"
+	t.Run("NewDescWithHelpAndLabel", func(t *testing.T) {
+		desc := helper.NewDescWithHelpAndLabel("metric", "help", "label")
+		expectedDesc := "Desc{fqName: \"logstash_exporter_test_metric\", help: \"help\", constLabels: {}, variableLabels: [label]}"
 		if desc.String() != expectedDesc {
 			t.Errorf("incorrect metric description, expected %s but got %s", expectedDesc, desc.String())
 		}
@@ -40,7 +42,6 @@ func TestExtractFqdnName(t *testing.T) {
 		metricSubname := "fqdn_metric"
 
 		descriptors := []*prometheus.Desc{
-			helper.NewDesc(metricSubname),
 			helper.NewDescWithHelp(metricSubname, "help"),
 			helper.NewDescWithHelpAndLabel(metricSubname, "help", "label"),
 		}
@@ -65,6 +66,16 @@ func TestExtractFqdnName(t *testing.T) {
 	})
 }
 
+type badMetricStub struct{}
+
+func (m *badMetricStub) Desc() *prometheus.Desc {
+	return nil
+}
+
+func (m *badMetricStub) Write(*dto.Metric) error {
+	return errors.New("writing metric failed")
+}
+
 func TestExtractValueFromMetric(t *testing.T) {
 	t.Run("should extract value from a metric", func(t *testing.T) {
 		metricDesc := prometheus.NewDesc("test_metric", "test metric help", nil, nil)
@@ -81,30 +92,31 @@ func TestExtractValueFromMetric(t *testing.T) {
 		}
 	})
 
-	t.Run("should return an error when unable to write metric", func(t *testing.T) {
-		metricDesc := prometheus.NewDesc("test_metric", "test metric help", nil, nil)
-		exampleErr := fmt.Errorf("example error")
-		invalidMetric := prometheus.NewInvalidMetric(metricDesc, exampleErr)
+	t.Run("should return error if writing metric fails", func(t *testing.T) {
+		badMetric := &badMetricStub{}
+		val, err := ExtractValueFromMetric(badMetric)
 
-		customCollector := &CustomCollector{
-			metric: invalidMetric,
+		if err == nil {
+			t.Errorf("Expected error, but got nil")
 		}
 
-		registry := prometheus.NewRegistry()
-		err := registry.Register(customCollector)
-
-		if err != nil {
-			t.Errorf("Unexpected error: %v", err)
+		if val != 0 {
+			t.Errorf("Expected value to be 0, got %f", val)
 		}
+	})
 
-		extractedValue, err := ExtractValueFromMetric(invalidMetric)
+	t.Run("should return error if the metric is not a Gauge", func(t *testing.T) {
+		metricDesc := prometheus.NewDesc("test_counter_metric", "test counter metric help", nil, nil)
+		metricValue := 42.0
+		metric := prometheus.MustNewConstMetric(metricDesc, prometheus.CounterValue, metricValue)
 
+		val, err := ExtractValueFromMetric(metric)
 		if err == nil {
-			t.Errorf("Expected error but got nil")
+			t.Errorf("Expected error, but got nil")
 		}
 
-		if extractedValue != 0 {
-			t.Errorf("Expected extracted value to be 0, got %f", extractedValue)
+		if val != 0 {
+			t.Errorf("Expected value to be 0, got %f", val)
 		}
 	})
 }