Support .d directory for k3s config file (#3162)

Configuration will be loaded from config.yaml and then config.yaml.d/*.(yaml|yml) in
alphanumeric order.  The merging is done by just taking the last value of
a key found, so LIFO for keys.  Slices are not merged but replaced.

Signed-off-by: Darren Shepherd <darren@rancher.com>

pkg/configfilearg/parser.go

@@ -6,8 +6,10 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"path/filepath"
 	"strings"
 
+	"github.com/rancher/k3s/pkg/agent/util"
 	"github.com/rancher/wrangler/pkg/data/convert"
 	"gopkg.in/yaml.v2"
 )
@@ -19,7 +21,7 @@ type Parser struct {
 	DefaultConfig string
 }
 
-// Parser will parse an os.Args style slice looking for Parser.FlagNames after Parse.After.
+// Parse will parse an os.Args style slice looking for Parser.FlagNames after Parse.After.
 // It will read the parameter value of Parse.FlagNames and read the file, appending all flags directly after
 // the Parser.After value. This means a the non-config file flags will override, or if a slice append to, the config
 // file values.
@@ -110,7 +112,39 @@ func (p *Parser) findStart(args []string) ([]string, []string, bool) {
 	return args, nil, false
 }
 
+func dotDFiles(basefile string) (result []string, _ error) {
+	files, err := ioutil.ReadDir(basefile + ".d")
+	if os.IsNotExist(err) {
+		return nil, nil
+	} else if err != nil {
+		return nil, err
+	}
+	for _, file := range files {
+		if file.IsDir() || !util.HasSuffixI(file.Name(), ".yaml", ".yml") {
+			continue
+		}
+		result = append(result, filepath.Join(basefile+".d", file.Name()))
+	}
+	return
+}
+
 func readConfigFile(file string) (result []string, _ error) {
+	files, err := dotDFiles(file)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = os.Stat(file)
+	if os.IsNotExist(err) && len(files) > 0 {
+	} else if err != nil {
+		return nil, err
+	} else {
+		files = append([]string{file}, files...)
+	}
+
+	keySeen := map[string]bool{}
+	for i := len(files) - 1; i >= 0; i-- {
+		file := files[i]
 		bytes, err := readConfigFileData(file)
 		if err != nil {
 			return nil, err
@@ -123,6 +157,11 @@ func readConfigFile(file string) (result []string, _ error) {
 
 		for _, i := range data {
 			k, v := convert.ToString(i.Key), i.Value
+			if keySeen[k] {
+				continue
+			}
+			keySeen[k] = true
+
 			prefix := "--"
 			if len(k) == 1 {
 				prefix = "-"
@@ -137,6 +176,7 @@ func readConfigFile(file string) (result []string, _ error) {
 				result = append(result, prefix+k+"="+str)
 			}
 		}
+	}
 
 	return
 }

pkg/configfilearg/parser_test.go

@@ -150,8 +150,9 @@ func TestConfigFile(t *testing.T) {
 
 func TestParse(t *testing.T) {
 	testDataOutput := []string{
-		"--foo-bar=baz",
+		"--foo-bar=bar-foo",
 		"--a-slice=1",
+		"--a-slice=1.5",
 		"--a-slice=2",
 		"--a-slice=",
 		"--a-slice=three",
@@ -205,7 +206,7 @@ func TestParse(t *testing.T) {
 			input:  []string{"server", "-c=missing"},
 			output: []string{"server", "-c=missing"},
 			what:   "fail when missing config",
-			err:    "open missing: no such file or directory",
+			err:    "stat missing: no such file or directory",
 		},
 		{
 			parser: Parser{
@@ -217,6 +218,16 @@ func TestParse(t *testing.T) {
 			output: append(append([]string{"before", "server"}, testDataOutput...), "before", "-c", "./testdata/data.yaml", "after"),
 			what:   "read config file",
 		},
+		{
+			parser: Parser{
+				After:         []string{"server", "agent"},
+				FlagNames:     []string{"-c", "--config"},
+				DefaultConfig: "missing",
+			},
+			input:  []string{"before", "server", "before", "-c", "./testdata/data.yaml.d/02-data.yaml", "after"},
+			output: []string{"before", "server", "--foo-bar=bar-foo", "before", "-c", "./testdata/data.yaml.d/02-data.yaml", "after"},
+			what:   "read single config file",
+		},
 	}
 
 	for _, testCase := range testCases {

pkg/configfilearg/testdata/data.yaml.d/01-data.yml

@@ -0,0 +1,7 @@
+foo-bar: get-overriden
+a-slice:
+- 1
+- "1.5"
+- "2"
+- ""
+- three

pkg/configfilearg/testdata/data.yaml.d/02-data-ignore-this.txt

@@ -0,0 +1 @@
+foo-bar: ignored

pkg/configfilearg/testdata/data.yaml.d/02-data.yaml

@@ -0,0 +1 @@
+foo-bar: bar-foo