1 files changed, 47 insertions, 2 deletions

diff --git a/modules/actions/log.go b/modules/actions/log.go
index c38082b5dc..5a1425e031 100644
--- a/modules/actions/log.go
+++ b/modules/actions/log.go
@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/models/dbfs"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/storage"
+	"code.gitea.io/gitea/modules/zstd"
 
 	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
 	"google.golang.org/protobuf/types/known/timestamppb"
@@ -28,6 +29,9 @@ const (
 	defaultBufSize = MaxLineSize
 )
 
+// WriteLogs appends logs to DBFS file for temporary storage.
+// It doesn't respect the file format in the filename like ".zst", since it's difficult to reopen a closed compressed file and append new content.
+// Why doesn't it store logs in object storage directly? Because it's not efficient to append content to object storage.
 func WriteLogs(ctx context.Context, filename string, offset int64, rows []*runnerv1.LogRow) ([]int, error) {
 	flag := os.O_WRONLY
 	if offset == 0 {
@@ -106,6 +110,17 @@ func ReadLogs(ctx context.Context, inStorage bool, filename string, offset, limi
 	return rows, nil
 }
 
+const (
+	// logZstdBlockSize is the block size for zstd compression.
+	// 128KB leads the compression ratio to be close to the regular zstd compression.
+	// And it means each read from the underlying object storage will be at least 128KB*(compression ratio).
+	// The compression ratio is about 30% for text files, so the actual read size is about 38KB, which should be acceptable.
+	logZstdBlockSize = 128 * 1024 // 128KB
+)
+
+// TransferLogs transfers logs from DBFS to object storage.
+// It happens when the file is complete and no more logs will be appended.
+// It respects the file format in the filename like ".zst", and compresses the content if needed.
 func TransferLogs(ctx context.Context, filename string) (func(), error) {
 	name := DBFSPrefix + filename
 	remove := func() {
@@ -119,7 +134,26 @@ func TransferLogs(ctx context.Context, filename string) (func(), error) {
 	}
 	defer f.Close()
 
-	if _, err := storage.Actions.Save(filename, f, -1); err != nil {
+	var reader io.Reader = f
+	if strings.HasSuffix(filename, ".zst") {
+		r, w := io.Pipe()
+		reader = r
+		zstdWriter, err := zstd.NewSeekableWriter(w, logZstdBlockSize)
+		if err != nil {
+			return nil, fmt.Errorf("zstd NewSeekableWriter: %w", err)
+		}
+		go func() {
+			defer func() {
+				_ = w.CloseWithError(zstdWriter.Close())
+			}()
+			if _, err := io.Copy(zstdWriter, f); err != nil {
+				_ = w.CloseWithError(err)
+				return
+			}
+		}()
+	}
+
+	if _, err := storage.Actions.Save(filename, reader, -1); err != nil {
 		return nil, fmt.Errorf("storage save %q: %w", filename, err)
 	}
 	return remove, nil
@@ -150,11 +184,22 @@ func OpenLogs(ctx context.Context, inStorage bool, filename string) (io.ReadSeek
 		}
 		return f, nil
 	}
+
 	f, err := storage.Actions.Open(filename)
 	if err != nil {
 		return nil, fmt.Errorf("storage open %q: %w", filename, err)
 	}
-	return f, nil
+
+	var reader io.ReadSeekCloser = f
+	if strings.HasSuffix(filename, ".zst") {
+		r, err := zstd.NewSeekableReader(f)
+		if err != nil {
+			return nil, fmt.Errorf("zstd NewSeekableReader: %w", err)
+		}
+		reader = r
+	}
+
+	return reader, nil
 }
 
 func FormatLog(timestamp time.Time, content string) string {