multi: add buffer.Write and pool.WriteBuffer, make GCQueue generic

pool/write_buffer.go

@@ -0,0 +1,48 @@
+package pool
+
+import (
+	"time"
+
+	"github.com/lightningnetwork/lnd/buffer"
+)
+
+const (
+	// DefaultWriteBufferGCInterval is the default interval that a Write
+	// will perform a sweep to see which expired buffer.Writes can be
+	// released to the runtime.
+	DefaultWriteBufferGCInterval = 15 * time.Second
+
+	// DefaultWriteBufferExpiryInterval is the default, minimum interval
+	// that must elapse before a Write will release a buffer.Write.  The
+	// maximum time before the buffer can be released is equal to the expiry
+	// interval plus the gc interval.
+	DefaultWriteBufferExpiryInterval = 30 * time.Second
+)
+
+// WriteBuffer is a pool of recycled buffer.Write items, that dynamically
+// allocates and reclaims buffers in response to load.
+type WriteBuffer struct {
+	pool *Recycle
+}
+
+// NewWriteBuffer returns a freshly instantiated WriteBuffer, using the given
+// gcInterval and expiryIntervals.
+func NewWriteBuffer(gcInterval, expiryInterval time.Duration) *WriteBuffer {
+	return &WriteBuffer{
+		pool: NewRecycle(
+			func() interface{} { return new(buffer.Write) },
+			100, gcInterval, expiryInterval,
+		),
+	}
+}
+
+// Take returns a fresh buffer.Write to the caller.
+func (p *WriteBuffer) Take() *buffer.Write {
+	return p.pool.Take().(*buffer.Write)
+}
+
+// Return returns the buffer.Write to the pool, so that it can be recycled or
+// released.
+func (p *WriteBuffer) Return(buf *buffer.Write) {
+	p.pool.Return(buf)
+}