fix(config): discover mounted yml config

README.md

@@ -8,7 +8,7 @@ Successor to the `*-keepalive` family: one binary, one image, six datastore adap
 
 ## Configuration
 
-By default, keepalive reads `keepalive.yaml` from the current working directory. One deployment can keep any number of services alive.
+By default, keepalive reads the first config file it finds: `keepalive.yaml`, `keepalive.yml`, `/keepalive.yaml`, then `/keepalive.yml`. One deployment can keep any number of services alive.
 
 ```yaml
 interval: 1m
@@ -66,6 +66,8 @@ docker run -d --name keepalive --restart unless-stopped \
   keepalive:local
 ```
 
+If your host config file is named `keepalive.yml`, mount it to `/keepalive.yml` instead.
+
 ## Quick start (local)
 
 ```bash

config.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"net/url"
@@ -18,6 +19,13 @@ const (
 	defaultCounterKey = "counter"
 )
 
+var defaultConfigFiles = []string{
+	"keepalive.yaml",
+	"keepalive.yml",
+	"/keepalive.yaml",
+	"/keepalive.yml",
+}
+
 type appConfig struct {
 	Interval   string              `json:"interval" yaml:"interval"`
 	CounterKey string              `json:"counter_key" yaml:"counter_key"`
@@ -52,6 +60,21 @@ func loadConfigFile(path string) ([]serviceConfig, error) {
 	return normalizeConfig(raw)
 }
 
+func defaultConfigFile() (string, error) {
+	return firstExistingConfigFile(defaultConfigFiles)
+}
+
+func firstExistingConfigFile(paths []string) (string, error) {
+	for _, path := range paths {
+		if _, err := os.Stat(path); err == nil {
+			return path, nil
+		} else if !errors.Is(err, os.ErrNotExist) {
+			return "", err
+		}
+	}
+	return "", fmt.Errorf("config file not found (looked for: %s)", strings.Join(paths, ", "))
+}
+
 func normalizeConfig(raw appConfig) ([]serviceConfig, error) {
 	if len(raw.Services) == 0 {
 		return nil, fmt.Errorf("services must contain at least one service")

config_test.go

@@ -1,6 +1,9 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 )
@@ -35,6 +38,39 @@ func TestKeepaliveExampleConfigParses(t *testing.T) {
 	}
 }
 
+func TestFirstExistingConfigFileFindsYMLFallback(t *testing.T) {
+	dir := t.TempDir()
+	ymlPath := filepath.Join(dir, "keepalive.yml")
+	if err := os.WriteFile(ymlPath, []byte("services: []\n"), 0o600); err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	got, err := firstExistingConfigFile([]string{
+		filepath.Join(dir, "keepalive.yaml"),
+		ymlPath,
+	})
+	if err != nil {
+		t.Fatalf("firstExistingConfigFile returned error: %v", err)
+	}
+	if got != ymlPath {
+		t.Fatalf("firstExistingConfigFile() = %q, want %q", got, ymlPath)
+	}
+}
+
+func TestFirstExistingConfigFileReportsCandidates(t *testing.T) {
+	dir := t.TempDir()
+	_, err := firstExistingConfigFile([]string{
+		filepath.Join(dir, "keepalive.yaml"),
+		filepath.Join(dir, "keepalive.yml"),
+	})
+	if err == nil {
+		t.Fatal("firstExistingConfigFile returned nil error")
+	}
+	if !strings.Contains(err.Error(), "keepalive.yaml") || !strings.Contains(err.Error(), "keepalive.yml") {
+		t.Fatalf("error %q does not list expected candidates", err)
+	}
+}
+
 func TestNormalizeConfigSuffixesDuplicateGeneratedNames(t *testing.T) {
 	services, err := normalizeConfig(appConfig{
 		Services: []serviceFileConfig{

main.go

@@ -11,10 +11,13 @@ import (
 	"github.com/tiennm99/keepalive/adapter"
 )
 
-const defaultConfigFile = "keepalive.yaml"
-
 func main() {
-	services, err := loadConfigFile(defaultConfigFile)
+	configPath, err := defaultConfigFile()
+	if err != nil {
+		log.Fatalf("load config: %v", err)
+	}
+
+	services, err := loadConfigFile(configPath)
 	if err != nil {
 		log.Fatalf("load config: %v", err)
 	}