global: split Akvorado into 3 services

configure/clickhouse/templatedfs.go

@@ -0,0 +1,149 @@
+package clickhouse
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"io/ioutil"
+	"strings"
+	"text/template"
+	"time"
+)
+
+// templatedFS is a wrapper around fs.FS to automatically expand templates
+type templatedFS struct {
+	data interface{}
+	base fs.FS
+}
+
+// templatedFile is a wrapper around fs.File to automatically expand templates
+type templatedFile struct {
+	base     fs.File
+	offset   int
+	rendered []byte
+}
+
+// templatedDirEntry is a wrapper around fs.DirEntry to automatically expand templates
+type templatedDirEntry struct {
+	base fs.DirEntry
+}
+
+// templatedFileInfo is a wrapper around fs.FileInfo to automatically expand templates
+type templatedFileInfo struct {
+	base fs.FileInfo
+}
+
+func (tf *templatedFile) Stat() (fs.FileInfo, error) {
+	info, err := tf.base.Stat()
+	if err != nil {
+		return nil, err
+	}
+	return &templatedFileInfo{info}, nil
+}
+func (tf *templatedFile) Read(buf []byte) (int, error) {
+	if tf.offset >= len(tf.rendered) {
+		return 0, io.EOF
+	}
+	n := copy(buf, tf.rendered[tf.offset:])
+	tf.offset += n
+	return n, nil
+}
+func (tf *templatedFile) Close() error {
+	return tf.base.Close()
+}
+
+func (tfs *templatedFS) ReadDir(name string) ([]fs.DirEntry, error) {
+	entries, err := fs.ReadDir(tfs.base, name)
+	if err != nil {
+		return nil, err
+	}
+	results := []fs.DirEntry{}
+	for _, entry := range entries {
+		if strings.HasSuffix(entry.Name(), ".tmpl") {
+			results = append(results, &templatedDirEntry{entry})
+		} else {
+			results = append(results, entry)
+		}
+	}
+	return results, nil
+}
+
+func (tde *templatedDirEntry) Name() string {
+	return strings.TrimSuffix(tde.base.Name(), ".tmpl")
+}
+func (tde *templatedDirEntry) IsDir() bool {
+	return tde.base.IsDir()
+}
+func (tde *templatedDirEntry) Type() fs.FileMode {
+	return tde.base.Type()
+}
+func (tde *templatedDirEntry) Info() (fs.FileInfo, error) {
+	info, err := tde.base.Info()
+	if err != nil {
+		return nil, err
+	}
+	return &templatedFileInfo{info}, nil
+}
+
+func (tfi *templatedFileInfo) Name() string {
+	return strings.TrimSuffix(tfi.base.Name(), ".tmpl")
+}
+func (tfi *templatedFileInfo) Size() int64 {
+	return 0 // Can't be sure
+}
+func (tfi *templatedFileInfo) Mode() fs.FileMode {
+	return tfi.base.Mode()
+}
+func (tfi *templatedFileInfo) ModTime() time.Time {
+	return tfi.base.ModTime()
+}
+func (tfi *templatedFileInfo) IsDir() bool {
+	return tfi.base.IsDir()
+}
+func (tfi *templatedFileInfo) Sys() interface{} {
+	return nil
+}
+
+func (tfs *templatedFS) Open(name string) (fs.File, error) {
+	candidates := []string{fmt.Sprintf("%s.tmpl", name), name}
+	var f fs.File
+	var err error
+	var candidate string
+	for _, candidate = range candidates {
+		f, err = tfs.base.Open(candidate)
+		if err != nil && errors.Is(err, fs.ErrNotExist) {
+			continue
+		}
+		break
+	}
+	if err != nil {
+		return nil, err
+	}
+	info, err := f.Stat()
+	if err != nil {
+		return nil, fmt.Errorf("unable to stat file: %w", err)
+	}
+	if info.IsDir() {
+		panic("assumed that Open() won't be called for a directory")
+	}
+	if !strings.HasSuffix(candidate, ".tmpl") {
+		return f, nil
+	}
+
+	// Render template
+	tmpl, err := ioutil.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+	t, err := template.New("anything").Option("missingkey=error").Parse(string(tmpl))
+	if err != nil {
+		return nil, fmt.Errorf("cannot parse template: %w", err)
+	}
+	b := bytes.NewBuffer([]byte{})
+	if err := t.Execute(b, tfs.data); err != nil {
+		return nil, fmt.Errorf("cannot execute template: %w", err)
+	}
+	return &templatedFile{base: f, rendered: b.Bytes()}, nil
+}