lnpeer/write_buffer_pool: adds write buffer pool

lnpeer/write_buffer_pool.go

@@ -0,0 +1,79 @@
+package lnpeer
+
+import (
+	"time"
+
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/queue"
+)
+
+const (
+	// DefaultGCInterval is the default interval that the WriteBufferPool
+	// will perform a sweep to see which expired buffers can be released to
+	// the runtime.
+	DefaultGCInterval = 15 * time.Second
+
+	// DefaultExpiryInterval is the default, minimum interval that must
+	// elapse before a WriteBuffer will be released. The maximum time before
+	// the buffer can be released is equal to the expiry interval plus the
+	// gc interval.
+	DefaultExpiryInterval = 30 * time.Second
+)
+
+// WriteBuffer is static byte array occupying to maximum-allowed
+// plaintext-message size.
+type WriteBuffer [lnwire.MaxMessagePayload]byte
+
+// Recycle zeroes the WriteBuffer, making it fresh for another use.
+// Zeroing the buffer using a logarithmic number of calls to the optimized copy
+// method. Benchmarking shows this to be ~30 times faster than a for loop that
+// sets each index to 0 for this buffer size. Inspired by:
+// https://stackoverflow.com/questions/30614165/is-there-analog-of-memset-in-go
+//
+// This is part of the queue.Recycler interface.
+func (b *WriteBuffer) Recycle() {
+	b[0] = 0
+	for i := 1; i < lnwire.MaxMessagePayload; i *= 2 {
+		copy(b[i:], b[:i])
+	}
+}
+
+// newRecyclableWriteBuffer is a constructor that returns a WriteBuffer typed as
+// a queue.Recycler.
+func newRecyclableWriteBuffer() queue.Recycler {
+	return new(WriteBuffer)
+}
+
+// A compile-time constraint to ensure that *WriteBuffer implements the
+// queue.Recycler interface.
+var _ queue.Recycler = (*WriteBuffer)(nil)
+
+// WriteBufferPool acts a global pool of WriteBuffers, that dynamically
+// allocates and reclaims buffers in response to load.
+type WriteBufferPool struct {
+	pool *queue.GCQueue
+}
+
+// NewWriteBufferPool returns a freshly instantiated WriteBufferPool, using the
+// given gcInterval and expiryIntervals.
+func NewWriteBufferPool(
+	gcInterval, expiryInterval time.Duration) *WriteBufferPool {
+
+	return &WriteBufferPool{
+		pool: queue.NewGCQueue(
+			newRecyclableWriteBuffer, 100,
+			gcInterval, expiryInterval,
+		),
+	}
+}
+
+// Take returns a fresh WriteBuffer to the caller.
+func (p *WriteBufferPool) Take() *WriteBuffer {
+	return p.pool.Take().(*WriteBuffer)
+}
+
+// Return returns the WriteBuffer to the pool, so that it can be recycled or
+// released.
+func (p *WriteBufferPool) Return(buf *WriteBuffer) {
+	p.pool.Return(buf)
+}