Look up config file in default locations

docs/sources/configuration/_index.md

@@ -32,9 +32,15 @@ that the order of configs reads correctly top to bottom when viewed in Grafana's
 ## Configuration File Reference
 
 To specify which configuration file to load, pass the `-config.file` flag at the
-command line. The file is written in [YAML format](https://en.wikipedia.org/wiki/YAML),
-defined by the scheme below. Brackets indicate that a parameter is optional. For
-non-list parameters the value is set to the specified default.
+command line. The value can be a list of comma separated paths, then the first
+file that exists will be used.
+If no `-config.file` argument is specified, Loki will look up the `config.yaml` in the
+current working directory and the `config/` sub-directory and try to use that.
+
+The file is written in [YAML
+format](https://en.wikipedia.org/wiki/YAML), defined by the scheme below.
+Brackets indicate that a parameter is optional. For non-list parameters the
+value is set to the specified default.
 
 ### Use environment variables in the configuration
 

pkg/loki/config_wrapper.go

@@ -42,7 +42,7 @@ func (c *ConfigWrapper) RegisterFlags(f *flag.FlagSet) {
 	f.BoolVar(&c.ListTargets, "list-targets", false, "List available targets")
 	f.BoolVar(&c.LogConfig, "log-config-reverse-order", false, "Dump the entire Loki config object at Info log "+
 		"level with the order reversed, reversing the order makes viewing the entries easier in Grafana.")
-	f.StringVar(&c.ConfigFile, "config.file", "", "yaml file to load")
+	f.StringVar(&c.ConfigFile, "config.file", "config.yaml,config/config.yaml", "configuration file to load, can be a comma separated list of paths, first existing file will be used")
 	f.BoolVar(&c.ConfigExpandEnv, "config.expand-env", false, "Expands ${var} in config according to the values of the environment variables.")
 	c.Config.RegisterFlags(f)
 }

pkg/util/cfg/cfg.go

@@ -47,7 +47,7 @@ func Unmarshal(dst Cloneable, sources ...Source) error {
 func DefaultUnmarshal(dst Cloneable, args []string, fs *flag.FlagSet) error {
 	return Unmarshal(dst,
 		Defaults(fs),
-		YAMLFlag(args, "config.file"),
+		ConfigFileLoader(args, "config.file"),
 		Flags(args, fs),
 	)
 }

pkg/util/cfg/dynamic.go

@@ -20,16 +20,16 @@ func DynamicUnmarshal(dst DynamicCloneable, args []string, fs *flag.FlagSet) err
 		// First populate the config with defaults including flags from the command line
 		Defaults(fs),
 		// Next populate the config from the config file, we do this to populate the `common`
-		// section of the config file by taking advantage of the code in YAMLFlag which will load
+		// section of the config file by taking advantage of the code in ConfigFileLoader which will load
 		// and process the config file.
-		YAMLFlag(args, "config.file"),
+		ConfigFileLoader(args, "config.file"),
 		// Apply any dynamic logic to set other defaults in the config. This function is called after parsing the
 		// config files so that values from a common, or shared, section can be used in
 		// the dynamic evaluation
 		dst.ApplyDynamicConfig(),
 		// Load configs from the config file a second time, this will supersede anything set by the common
 		// config with values specified in the config file.
-		YAMLFlag(args, "config.file"),
+		ConfigFileLoader(args, "config.file"),
 		// Load the flags again, this will supersede anything set from config file with flags from the command line.
 		Flags(args, fs),
 	)

pkg/util/cfg/files.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"strconv"
+	"strings"
 
 	"github.com/drone/envsubst"
 	"github.com/pkg/errors"
@@ -65,7 +66,7 @@ func dYAML(y []byte) Source {
 	}
 }
 
-func YAMLFlag(args []string, name string) Source {
+func ConfigFileLoader(args []string, name string) Source {
 
 	return func(dst Cloneable) error {
 		freshFlags := flag.NewFlagSet("config-file-loader", flag.ContinueOnError)
@@ -92,13 +93,18 @@ func YAMLFlag(args []string, name string) Source {
 		if f == nil || f.Value.String() == "" {
 			return nil
 		}
-		expandEnv := false
-		expandEnvFlag := freshFlags.Lookup("config.expand-env")
-		if expandEnvFlag != nil {
-			expandEnv, _ = strconv.ParseBool(expandEnvFlag.Value.String()) // Can ignore error as false returned
-		}
-
-		return YAML(f.Value.String(), expandEnv)(dst)
 
+		for _, val := range strings.Split(f.Value.String(), ",") {
+			val := strings.TrimSpace(val)
+			expandEnv := false
+			expandEnvFlag := freshFlags.Lookup("config.expand-env")
+			if expandEnvFlag != nil {
+				expandEnv, _ = strconv.ParseBool(expandEnvFlag.Value.String()) // Can ignore error as false returned
+			}
+			if _, err := os.Stat(val); err == nil {
+				return YAML(val, expandEnv)(dst)
+			}
+		}
+		return fmt.Errorf("%s does not exist, set %s for custom config path", f.Value.String(), name)
 	}
 }

pkg/util/cfg/files_test.go

@@ -22,9 +22,9 @@ func (cfg *testCfg) Clone() flagext.Registerer {
 	}(*cfg)
 }
 
-func TestYAMLFlagDoesNotMutate(t *testing.T) {
+func TestConfigFileLoaderDoesNotMutate(t *testing.T) {
 	cfg := &testCfg{}
-	err := YAMLFlag(nil, "something")(cfg)
+	err := ConfigFileLoader(nil, "something")(cfg)
 	require.Nil(t, err)
 	require.Equal(t, 0, cfg.v)