feat: Add k8smount provider

examples/read-k8smount/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"strings"
+
+	"github.com/knadh/koanf/providers/k8smount"
+	"github.com/knadh/koanf/v2"
+)
+
+var k = koanf.New(".")
+
+func main() {
+	p := k8smount.Provider("mock/mount", ".", k8smount.Opt{
+		TransformFunc: func(k, v string) (string, any) {
+			return strings.ToLower(strings.ReplaceAll(k, "_", ".")), strings.TrimSpace(v)
+		},
+	})
+
+	if err := k.Load(p, nil); err != nil {
+		log.Fatalf("error loading config: %v", err)
+	}
+
+	fmt.Println("database's host is = ", k.String("database.host"))
+	fmt.Println("database's port is = ", k.Int("database.port"))
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
+
+	if err := p.Watch(func(_ any, err error) {
+		if err != nil {
+			log.Printf("watch error: %v", err)
+			return
+		}
+
+		log.Println("config changed. Reloading ...")
+		k.Load(p, nil)
+		k.Print()
+	}); err != nil {
+		log.Fatalf("error watching config: %v", err)
+	}
+
+	log.Println("waiting forever. Try making a change under mock/mount/ to live reload")
+	<-ctx.Done()
+}

go.work

@@ -1,6 +1,6 @@
-go 1.24.4
+go 1.25
 
-toolchain go1.24.5
+toolchain go1.25
 
 use (
 	.
@@ -26,6 +26,7 @@ use (
 	./providers/etcd
 	./providers/file
 	./providers/fs
+	./providers/k8smount
 	./providers/nats
 	./providers/parameterstore
 	./providers/posflag

mock/mount/..2006_01_02_15_04_05.0000000000/database_host

@@ -0,0 +1 @@
+localhost

mock/mount/..2006_01_02_15_04_05.0000000000/database_port

@@ -0,0 +1 @@
+5432

mock/mount/..data

@@ -0,0 +1 @@
+..2006_01_02_15_04_05.0000000000

mock/mount/database_host

@@ -0,0 +1 @@
+..data/database_host

mock/mount/database_port

@@ -0,0 +1 @@
+..data/database_port

providers/k8smount/go.mod

@@ -0,0 +1,20 @@
+module github.com/knadh/koanf/providers/k8smount
+
+go 1.25
+
+require (
+	github.com/fsnotify/fsnotify v1.9.0
+	github.com/knadh/koanf/maps v0.1.2
+	github.com/knadh/koanf/v2 v2.3.4
+	github.com/stretchr/testify v1.11.1
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/sys v0.13.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

providers/k8smount/go.sum

@@ -0,0 +1,24 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
+github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9LvH92wZUgs=
+github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
+github.com/knadh/koanf/maps v0.1.2 h1:RBfmAW5CnZT+PJ1CVc1QSJKf4Xu9kxfQgYVQSu8hpbo=
+github.com/knadh/koanf/maps v0.1.2/go.mod h1:npD/QZY3V6ghQDdcQzl1W4ICNVTkohC8E73eI2xW4yI=
+github.com/knadh/koanf/v2 v2.3.4 h1:fnynNSDlujWE+v83hAp8wKr/cdoxHLO0629SN+U8Urc=
+github.com/knadh/koanf/v2 v2.3.4/go.mod h1:gRb40VRAbd4iJMYYD5IxZ6hfuopFcXBpc9bbQpZwo28=
+github.com/mitchellh/copystructure v1.2.0 h1:vpKXTN4ewci03Vljg/q9QvCGUDttBOGBIa15WveJJGw=
+github.com/mitchellh/copystructure v1.2.0/go.mod h1:qLl+cE2AmVv+CoeAwDPye/v+N2HKCj9FbZEVFJRxO9s=
+github.com/mitchellh/reflectwalk v1.0.2 h1:G2LzWKi524PWgd3mLHV8Y5k7s6XUvT0Gef6zxSIeXaQ=
+github.com/mitchellh/reflectwalk v1.0.2/go.mod h1:mSTlrgnPZtwu0c4WaC2kGObEpuNDbx0jmZXqmk4esnw=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

providers/k8smount/helper_test.go

@@ -0,0 +1,105 @@
+package k8smount_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+const (
+	mountTimeFmt = "..2006_01_02_15_04_05.0000000000"
+	dataDir      = "..data"
+)
+
+// writeVolumeMount creates a file structure that matches how a ConfigMap or Secret will be mounted
+// in a Kubernetes Pod.
+//
+// First, files are created for each data field. These exist within a timestamp-based directory,
+// likely when the ConfigMap or Secret was last modified.
+//
+//	..2025_06_28_09_28_32.3151791122/
+//	├── database_hostname
+//	├── database_name
+//	└── database_port
+//
+// A symlink is then created for "..data" to the directory containing the data:
+//
+//	..data -> ..2025_06_28_09_28_32.3151791122
+//
+// Finally, symlinks are created for the data files, via the "..data" symlink:
+//
+//	database_hostname -> ..data/database_hostname
+//	database_name -> ..data/database_name
+//	database_port -> ..data/database_port
+func writeVolumeMount(tb testing.TB, mount string, data map[string]string) error {
+	tb.Helper()
+
+	return writeVolumeMountAt(tb, time.Now(), mount, data)
+}
+
+// writeVolumeMountAtTime creates a file structure that matches how a ConfigMap or Secret will be
+// mounted in a Kubernetes Pod, using the given time. See writeVolumeMount for a detailed
+// description of the resulting file structure.
+//
+// This function can be called multiple times with different times, with the most recent call taking
+// precedence if any conflicts occur.
+func writeVolumeMountAt(tb testing.TB, t time.Time, mount string, data map[string]string) error {
+	tb.Helper()
+
+	dir := t.UTC().Format(mountTimeFmt)
+	dirPath := filepath.Join(mount, dir)
+
+	for key, value := range data {
+		if err := writeFile(tb, filepath.Join(dirPath, key), value); err != nil {
+			return err
+		}
+	}
+
+	tb.Chdir(mount)
+
+	if err := os.Remove(dataDir); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("failed to cleanup existing symlink %s: %w", dataDir, err)
+	}
+
+	if err := os.Symlink(dir, dataDir); err != nil {
+		return fmt.Errorf("failed to create %s symlink to %q: %w", "..data", dir, err)
+	}
+
+	tb.Log("created symlink: ..data ->", dir)
+
+	for key := range data {
+		target := filepath.Join(dataDir, key)
+
+		if err := os.Remove(key); err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("failed to cleanup existing symlink %s: %w", key, err)
+		}
+
+		if err := os.Symlink(target, key); err != nil {
+			return fmt.Errorf("failed to create %q symlink to %q: %w", key, target, err)
+		}
+
+		tb.Log("created symlink:", key, "->", target)
+	}
+
+	return nil
+}
+
+func writeFile(tb testing.TB, path, content string) error {
+	tb.Helper()
+
+	dir := filepath.Dir(path)
+
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return fmt.Errorf("failed to create directory %q: %w", dir, err)
+	}
+
+	if err := os.WriteFile(path, []byte(content), 0o600); err != nil {
+		return fmt.Errorf("failed to create file %q: %w", path, err)
+	}
+
+	tb.Log("wrote:", path)
+
+	return nil
+}