feature: memory buffer container io backend

daemon/containerio/mem_buffer.go

@@ -0,0 +1,38 @@
+package containerio
+
+import (
+	"bytes"
+	"io"
+)
+
+func init() {
+	Register(func() Backend {
+		return &memBuffer{}
+	})
+}
+
+type memBuffer struct {
+	buffer *bytes.Buffer
+}
+
+func (b *memBuffer) Name() string {
+	return "memBuffer"
+}
+
+func (b *memBuffer) Init(opt *Option) error {
+	b.buffer = opt.memBuffer
+	return nil
+}
+
+func (b *memBuffer) Out() io.Writer {
+	return b.buffer
+}
+
+func (b *memBuffer) In() io.Reader {
+	return b.buffer
+}
+
+func (b *memBuffer) Close() error {
+	// Don't need to close bytes.Buffer.
+	return nil
+}

daemon/containerio/options.go

@@ -1,6 +1,7 @@
 package containerio
 
 import (
+	"bytes"
 	"net/http"
 )
 
@@ -12,6 +13,7 @@ type Option struct {
 	hijack        http.Hijacker
 	hijackUpgrade bool
 	stdinBackend  string
+	memBuffer     *bytes.Buffer
 }
 
 // NewOption creates the Option instance.
@@ -77,3 +79,14 @@ func WithStdinHijack() func(*Option) {
 		opt.stdinBackend = "hijack"
 	}
 }
+
+// WithMemBuffer specified the memory buffer backend.
+func WithMemBuffer(memBuffer *bytes.Buffer) func(*Option) {
+	return func(opt *Option) {
+		if opt.backends == nil {
+			opt.backends = make(map[string]struct{})
+		}
+		opt.backends["memBuffer"] = struct{}{}
+		opt.memBuffer = memBuffer
+	}
+}

daemon/mgr/container.go

@@ -618,9 +618,15 @@ func (mgr *ContainerManager) openIO(id string, attach *AttachConfig, exec bool)
 	}
 
 	if attach != nil {
-		options = append(options, containerio.WithHijack(attach.Hijack, attach.Upgrade))
-		if attach.Stdin {
-			options = append(options, containerio.WithStdinHijack())
+		if attach.Hijack != nil {
+			// Attaching using http.
+			options = append(options, containerio.WithHijack(attach.Hijack, attach.Upgrade))
+			if attach.Stdin {
+				options = append(options, containerio.WithStdinHijack())
+			}
+		} else if attach.MemBuffer != nil {
+			// Attaching using memory buffer.
+			options = append(options, containerio.WithMemBuffer(attach.MemBuffer))
 		}
 	} else if !exec {
 		options = append(options, containerio.WithRawFile())

daemon/mgr/container_types.go

@@ -1,6 +1,7 @@
 package mgr
 
 import (
+	"bytes"
 	"net/http"
 	"sync"
 	"time"
@@ -30,11 +31,16 @@ type containerExecConfig struct {
 
 // AttachConfig wraps some infos of attaching.
 type AttachConfig struct {
+	Stdin  bool
+	Stdout bool
+	Stderr bool
+
+	// Attach using http.
 	Hijack  http.Hijacker
-	Stdin   bool
-	Stdout  bool
-	Stderr  bool
 	Upgrade bool
+
+	// Attach using memory buffer.
+	MemBuffer *bytes.Buffer
 }
 
 // ContainerRemoveOption wraps the container remove interface params.