Add ability to select compression algo by downloading location with file extension.

- Also update README.md with more useful examples.

internal/backer/consts.go

@@ -50,8 +50,8 @@ const (
 	// defaultFilenamePrefix is the default prefix for backup filenames.
 	defaultFilenamePrefix = "backup"
 
-	// defaultCompressionAlgorithm is the default compression algorithm.
-	defaultCompressionAlgorithm = "gzip"
+	// defaultDefaultCompression is the default compression algorithm.
+	defaultDefaultCompression = "gzip"
 )
 
 /* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */

internal/backer/loadConfig.go

@@ -135,15 +135,20 @@ func LoadConfig(path string) error {
 		log.Warnf("Config option filename_prefix is not set, fallback to %s", C.FilenamePrefix)
 	}
 
-	// CompressionAlgorithm: default and validate.
-	if C.CompressionAlgorithm == "" {
-		C.CompressionAlgorithm = defaultCompressionAlgorithm
-
-		log.Warnf("Config option compression_algorithm is not set, fallback to %s", C.CompressionAlgorithm)
+	// DefaultCompression: default and validate. If compression_algorithm is set (deprecated), use it as fallback.
+	if C.DefaultCompression == "" {
+		if C.CompressionAlgorithm != "" {
+			C.DefaultCompression = C.CompressionAlgorithm
+		} else {
+			C.DefaultCompression = defaultDefaultCompression
+		}
 	}
 
-	if C.CompressionAlgorithm != "gzip" && C.CompressionAlgorithm != "bzip2" && C.CompressionAlgorithm != "zstd" && C.CompressionAlgorithm != "lz4" && C.CompressionAlgorithm != "xz" && C.CompressionAlgorithm != "pgzip" {
-		return fmt.Errorf("Config option compression_algorithm must be gzip, bzip2, zstd, lz4, xz or pgzip, got %s", C.CompressionAlgorithm)
+	switch C.DefaultCompression {
+	case "gzip", "pgzip", "bzip2", "xz", "lz4", "zstd":
+		log.Infof("Using %s as defailt compression algorithm", C.DefaultCompression)
+	default:
+		return fmt.Errorf("Config option default_compression must be gzip, bzip2, zstd, lz4, xz or pgzip, got %s", C.DefaultCompression)
 	}
 
 	// Compile exclude patterns.

internal/backer/loadConfig_test.go

@@ -227,8 +227,8 @@ func TestLoadConfigDefaultValues(t *testing.T) {
 		t.Errorf("C.FilenamePrefix should default to backup, got %s", C.FilenamePrefix)
 	}
 
-	if C.CompressionAlgorithm != "gzip" {
-		t.Errorf("C.CompressionAlgorithm should default to gzip, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "gzip" {
+		t.Errorf("C.DefaultCompression should default to gzip, got %s", C.DefaultCompression)
 	}
 }
 
@@ -248,8 +248,8 @@ func TestLoadConfigCompressionAlgorithmBzip2(t *testing.T) {
 		t.Errorf("Expected no error, got %v", err)
 	}
 
-	if C.CompressionAlgorithm != "bzip2" {
-		t.Errorf("C.CompressionAlgorithm should be bzip2, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "bzip2" {
+		t.Errorf("C.DefaultCompression should be bzip2, got %s", C.DefaultCompression)
 	}
 }
 
@@ -269,8 +269,8 @@ func TestLoadConfigCompressionAlgorithmZstd(t *testing.T) {
 		t.Errorf("Expected no error, got %v", err)
 	}
 
-	if C.CompressionAlgorithm != "zstd" {
-		t.Errorf("C.CompressionAlgorithm should be zstd, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "zstd" {
+		t.Errorf("C.DefaultCompression should be zstd, got %s", C.DefaultCompression)
 	}
 }
 
@@ -290,8 +290,8 @@ func TestLoadConfigCompressionAlgorithmLz4(t *testing.T) {
 		t.Errorf("Expected no error, got %v", err)
 	}
 
-	if C.CompressionAlgorithm != "lz4" {
-		t.Errorf("C.CompressionAlgorithm should be lz4, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "lz4" {
+		t.Errorf("C.DefaultCompression should be lz4, got %s", C.DefaultCompression)
 	}
 }
 
@@ -311,8 +311,8 @@ func TestLoadConfigCompressionAlgorithmXz(t *testing.T) {
 		t.Errorf("Expected no error, got %v", err)
 	}
 
-	if C.CompressionAlgorithm != "xz" {
-		t.Errorf("C.CompressionAlgorithm should be xz, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "xz" {
+		t.Errorf("C.DefaultCompression should be xz, got %s", C.DefaultCompression)
 	}
 }
 
@@ -332,8 +332,8 @@ func TestLoadConfigCompressionAlgorithmPgzip(t *testing.T) {
 		t.Errorf("Expected no error, got %v", err)
 	}
 
-	if C.CompressionAlgorithm != "pgzip" {
-		t.Errorf("C.CompressionAlgorithm should be pgzip, got %s", C.CompressionAlgorithm)
+	if C.DefaultCompression != "pgzip" {
+		t.Errorf("C.DefaultCompression should be pgzip, got %s", C.DefaultCompression)
 	}
 }
 

internal/backer/newServer.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net"
 	"net/http"
+	"path"
 	"strings"
 	"time"
 
@@ -76,9 +77,14 @@ func NewServer(configPath string) (*http.Server, error) {
 		var (
 			archive   io.ReadCloser
 			extension string
+			algorithm string
 		)
 
-		switch C.CompressionAlgorithm {
+		requestedExt := strings.TrimPrefix(path.Ext(r.URL.Path), ".")
+
+		algorithm = getCompressionAlgorithm(requestedExt)
+
+		switch algorithm {
 		case "bzip2":
 			archive = CreateTarBzip2Stream(ctx, files)
 			extension = "tar.bz2"
@@ -207,4 +213,24 @@ func getClientIP(r *http.Request) string {
 	return host
 }
 
+// getCompressionAlgorithm determines which compression algorithm to use based on the requested extension.
+// If the extension is recognized, it returns the corresponding algorithm; otherwise, it returns the default.
+// For .tar.gz extension, pgzip is always used for parallel compression.
+func getCompressionAlgorithm(requestedExt string) string {
+	switch requestedExt {
+	case "tar.bz2":
+		return "bzip2"
+	case "tar.zst":
+		return "zstd"
+	case "tar.lz4":
+		return "lz4"
+	case "tar.xz":
+		return "xz"
+	case "tar.gz":
+		return "pgzip"
+	default:
+		return C.DefaultCompression
+	}
+}
+
 /* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */

internal/backer/types.go

@@ -18,7 +18,8 @@ type (
 		CompressionLevel     int      `json:"compression_level"`     // Compression level (1-9, default 9).
 		ExcludePatterns      []string `json:"exclude_patterns"`      // Regex patterns to exclude from backup.
 		FilenamePrefix       string   `json:"filename_prefix"`       // Prefix for backup filename (default: "backup").
-		CompressionAlgorithm string   `json:"compression_algorithm"` // Compression algorithm: gzip, pgzip, bzip2, zstd, lz4 or xz.
+		CompressionAlgorithm string   `json:"compression_algorithm"` // Compression algorithm alias (deprecated: use default_compression).
+		DefaultCompression   string   `json:"default_compression"`   // Default compression algorithm: gzip, pgzip, bzip2, zstd, lz4 or xz.
 	}
 )