feat: Allow reading config from env vars (#152)

cmd/client/client.go

@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"github.com/caarlos0/env/v6"
 	"github.com/rs/zerolog/log"
 	"github.com/soerenschneider/dyndns/client"
 	"github.com/soerenschneider/dyndns/client/resolvers"
@@ -26,8 +27,8 @@ var configPathPreferences = []string{
 
 func main() {
 	metrics.Version.WithLabelValues(internal.BuildVersion, internal.CommitHash).SetToCurrentTime()
-	defaultConfigPath := checkDefaultConfigFiles()
-	configPath := flag.String("config", defaultConfigPath, "Path to the config file")
+
+	configPath := flag.String("config", "", "Path to the config file")
 	once := flag.Bool("once", false, "Do not run as a daemon")
 	version := flag.Bool("version", false, "Print version and exit")
 	flag.Parse()
@@ -38,21 +39,24 @@ func main() {
 	}
 
 	util.InitLogging()
-	if nil == configPath {
-		log.Fatal().Msgf("No config path supplied")
+	if *configPath == "" {
+		*configPath = getDefaultConfigFileOrEmpty()
 	}
-
 	conf, err := conf.ReadClientConfig(*configPath)
 	if err != nil {
 		log.Fatal().Msgf("couldn't read config file: %v", err)
 	}
+	if err := env.Parse(conf); err != nil {
+		log.Fatal().Msgf("%+v\n", err)
+	}
+
 	// supply once flag value
 	conf.Once = *once
 	conf.Print()
 	RunClient(conf)
 }
 
-func checkDefaultConfigFiles() string {
+func getDefaultConfigFileOrEmpty() string {
 	for _, configPath := range configPathPreferences {
 		if strings.HasPrefix(configPath, "~/") {
 			configPath = path.Join(getUserHomeDirectory(), configPath[2:])
@@ -65,7 +69,7 @@ func checkDefaultConfigFiles() string {
 		}
 	}
 
-	return configPathPreferences[0]
+	return ""
 }
 
 func getUserHomeDirectory() string {

conf/client.go

@@ -8,13 +8,13 @@ import (
 	"fmt"
 	"github.com/rs/zerolog/log"
 	"github.com/soerenschneider/dyndns/internal/metrics"
-	"io/ioutil"
+	"os"
 )
 
 type ClientConf struct {
-	Host            string `json:"host"`
-	KeyPairPath     string `json:"keypair_path"`
-	MetricsListener string `json:"metrics_listen",omitempty`
+	Host            string `json:"host" env:"DYNDNS_HOST"`
+	KeyPairPath     string `json:"keypair_path" env:"DYNDNS_KEYPAIR_PATH"`
+	MetricsListener string `json:"metrics_listen",omitempty env:"DYNDNS_METRICS_LISTEN`
 	Once            bool   // this is not parsed via json, it's an cli flag
 	MqttConfig
 	*InterfaceConfig
@@ -59,7 +59,11 @@ func getDefaultClientConfig() *ClientConf {
 }
 
 func ReadClientConfig(path string) (*ClientConf, error) {
-	content, err := ioutil.ReadFile(path)
+	if path == "" {
+		return &ClientConf{}, nil
+	}
+
+	content, err := os.ReadFile(path)
 	if err != nil {
 		return nil, fmt.Errorf("could not read config file %s: %v", path, err)
 	}

conf/client_test.go

@@ -0,0 +1,69 @@
+package conf
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestReadClientConfig(t *testing.T) {
+	type args struct {
+		path string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    *ClientConf
+		wantErr bool
+	}{
+		{
+			name: "happy path",
+			args: args{"../contrib/client.json"},
+			want: &ClientConf{
+				Host:            "my.host.tld",
+				KeyPairPath:     "/keypair.json",
+				MetricsListener: ":9191",
+				MqttConfig: MqttConfig{
+					Brokers:  []string{"broker-1", "broker-2"},
+					ClientId: "my-client-id",
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name:    "non-existing-file",
+			args:    args{"some-file"},
+			want:    nil,
+			wantErr: true,
+		},
+		{
+			name:    "wrong format",
+			args:    args{"../contrib/textfile.txt"},
+			want:    nil,
+			wantErr: true,
+		},
+		{
+			name:    "empty json file content",
+			args:    args{"../contrib/empty.json"},
+			want:    getDefaultClientConfig(),
+			wantErr: false,
+		},
+		{
+			name:    "empty path",
+			args:    args{""},
+			want:    &ClientConf{},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ReadClientConfig(tt.args.path)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ReadClientConfig() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("ReadClientConfig() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

conf/mqtt.go

@@ -6,8 +6,8 @@ import (
 )
 
 type MqttConfig struct {
-	Brokers  []string `json:"brokers"`
-	ClientId string   `json:"client_id"`
+	Brokers  []string `json:"brokers" env:"DYNDNS_BROKERS" envSeparator:";"`
+	ClientId string   `json:"client_id" env:"DYNDNS_CLIENT_ID"`
 }
 
 func (conf *MqttConfig) Print() {

contrib/client.json

@@ -0,0 +1,6 @@
+{
+"host": "my.host.tld",
+  "keypair_path": "/keypair.json",
+  "client_id": "my-client-id",
+  "brokers": ["broker-1", "broker-2"]
+}

contrib/empty.json

@@ -0,0 +1 @@
+{}

contrib/textfile.txt

@@ -0,0 +1 @@
+no json here

go.mod

@@ -4,6 +4,7 @@ go 1.17
 
 require (
 	github.com/aws/aws-sdk-go v1.44.76
+	github.com/caarlos0/env/v6 v6.9.3
 	github.com/eclipse/paho.mqtt.golang v1.4.1
 	github.com/hashicorp/go-retryablehttp v0.7.1
 	github.com/prometheus/client_golang v1.13.0

go.sum

@@ -44,6 +44,8 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/caarlos0/env/v6 v6.9.3 h1:Tyg69hoVXDnpO5Qvpsu8EoquarbPyQb+YwExWHP8wWU=
+github.com/caarlos0/env/v6 v6.9.3/go.mod h1:hvp/ryKXKipEkcuYjs9mI4bBCg+UI0Yhgm5Zu0ddvwc=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cespare/xxhash/v2 v2.1.2 h1:YRXhKfTDauu4ajMg1TPgFO5jnlC2HCbmLXMcTG5cbYE=