Hot reload

cmd/exporter/main.go

@@ -59,7 +59,7 @@ func main() {
 
 	exec := &executor.BashExecutor{}
 
-	metricsCollector := collector.NewCollector(&cfg, slog.Default(), exec, cache)
+	metricsCollector := collector.NewCollector(&cfg, slog.Default(), exec, cache, configPath)
 
 	registry := prometheus.NewRegistry()
 	registry.MustRegister(metricsCollector)
@@ -90,6 +90,19 @@ func main() {
 		}
 	}()
 
+	hReload := make(chan os.Signal, 1)
+	signal.Notify(hReload, syscall.SIGHUP)
+
+	go func() {
+		for {
+			<-hReload
+			slog.Info("received SIGHUP, attempting to reload config")
+			if err := metricsCollector.ReloadConfig(); err != nil {
+				slog.Error("config reload failed", "error", err)
+			}
+		}
+	}()
+
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
 

internal/collector/collector.go

@@ -15,22 +15,29 @@ type Executor interface {
 }
 
 type Collector struct {
-	config   *config.Config
-	logger   *slog.Logger
-	executor Executor
-	cache    *cache.Cache
+	config     *config.Config
+	logger     *slog.Logger
+	executor   Executor
+	cache      *cache.Cache
+	configPath string
+
+	mu sync.RWMutex
 }
 
-func NewCollector(cfg *config.Config, logger *slog.Logger, exec Executor, cache *cache.Cache) *Collector {
+func NewCollector(cfg *config.Config, logger *slog.Logger, exec Executor, cache *cache.Cache, configPath string) *Collector {
 	return &Collector{
-		config:   cfg,
-		logger:   logger,
-		executor: exec,
-		cache:    cache,
+		config:     cfg,
+		logger:     logger,
+		executor:   exec,
+		cache:      cache,
+		configPath: configPath,
 	}
 }
 
 func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
 	for _, metricConfig := range c.config.Metrics {
 		if len(metricConfig.SubMetrics) == 0 {
 			dynLblNames := getLabelNames(metricConfig.DynamicLabels)
@@ -65,7 +72,27 @@ func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
 
 }
 
+func (c *Collector) ReloadConfig() error {
+	var newCfg config.Config
+
+	if err := config.Load(c.configPath, &newCfg); err != nil {
+		c.logger.Error("failed to reload config", "error", err)
+		return err
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.config = &newCfg
+
+	c.logger.Info("config reloaded successfully")
+	return nil
+}
+
 func (c *Collector) Collect(ch chan<- prometheus.Metric) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
 	start := time.Now()
 
 	defer func() {

internal/collector/collector_test.go

@@ -6,6 +6,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus/testutil"
 	"io"
 	"log/slog"
+	"os"
 	"pg-bash-exporter/internal/cache"
 	"pg-bash-exporter/internal/config"
 	"strings"
@@ -238,7 +239,7 @@ matched_metric_mem{label_name="label2"} 200
 						Name:    "connections",
 						Help:    "number of connetions.",
 						Type:    "gauge",
-						Command: "echo -e 'tcp 150\nudp 25",
+						Command: "echo -e 'tcp 150\nudp 25'",
 						Field:   1,
 						DynamicLabels: []config.DynamicLabel{
 							{Name: "type", Field: 0},
@@ -396,7 +397,7 @@ not_blacklisted_metric 1
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			logger := slog.New(slog.NewJSONHandler(io.Discard, nil))
-			collector := NewCollector(tc.config, logger, tc.executor, cache.New())
+			collector := NewCollector(tc.config, logger, tc.executor, cache.New(), "")
 			reg := prometheus.NewRegistry()
 			reg.MustRegister(collector)
 
@@ -610,7 +611,7 @@ func TestInternalMetrics(t *testing.T) {
 		err: errors.New("error"),
 	}
 
-	collector := NewCollector(cfg, logger, executor, cache)
+	collector := NewCollector(cfg, logger, executor, cache, "")
 
 	ch := make(chan prometheus.Metric, 10)
 	go func() {
@@ -649,3 +650,71 @@ func TestInternalMetrics(t *testing.T) {
 		t.Errorf("CacheMisses: wnted 2, got %v", val)
 	}
 }
+
+func TestReloadConfig(t *testing.T) {
+	logger := slog.New(slog.NewJSONHandler(io.Discard, nil))
+
+	configV1 := `
+server:
+  listen_address: ":8080"
+  metrics_path: "/metrics"
+logging:
+  level: "info"
+metrics:
+  - name: "metric_v1"
+    help: "help v1"
+    type: "gauge"
+    command: "echo 1"
+`
+	configV2 := `
+server:
+  listen_address: ":8080"
+  metrics_path: "/metrics"
+logging:
+  level: "info"
+metrics:
+  - name: "metric_v2"
+    help: "help v2"
+    type: "counter"
+    command: "echo 2"
+`
+
+	tmpfile, err := os.CreateTemp(t.TempDir(), "test-config-*.yaml")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+	defer os.Remove(tmpfile.Name())
+
+	if _, err := tmpfile.Write([]byte(configV1)); err != nil {
+		t.Fatalf("failed to write v1 config: %v", err)
+	}
+
+	var cfg config.Config
+	if err := config.Load(tmpfile.Name(), &cfg); err != nil {
+		t.Fatalf("failed to load v1 config: %v", err)
+	}
+
+	collector := NewCollector(&cfg, logger, &mockExecutor{}, cache.New(), tmpfile.Name())
+
+	if collector.config.Metrics[0].Name != "metric_v1" {
+		t.Fatalf("expected initial metric to be metric_v1, got %s", collector.config.Metrics[0].Name)
+	}
+
+	if err := os.WriteFile(tmpfile.Name(), []byte(configV2), 0644); err != nil {
+		t.Fatalf("failed to write v2 config: %v", err)
+	}
+
+	if err := collector.ReloadConfig(); err != nil {
+		t.Fatalf("reload failed: %v", err)
+	}
+
+	if len(collector.config.Metrics) != 1 {
+		t.Fatalf("expected 1 metric after reload, got %d", len(collector.config.Metrics))
+	}
+	if collector.config.Metrics[0].Name != "metric_v2" {
+		t.Errorf("expected metric_v2 after reload, got %s", collector.config.Metrics[0].Name)
+	}
+	if collector.config.Metrics[0].Type != "counter" {
+		t.Errorf("expected counter type after reload, got %s", collector.config.Metrics[0].Type)
+	}
+}