syncpool

README

zstdpool-syncpool

github.com/klauspost/compress/zstd is a native Go implementation of Zstandard, with an API that leaks memory and goroutines if you don't call Close() on every Encoder and Decoder that you create, and Decoders cannot be reused after they are closed.

zstdpool-syncpool is a Go wrapper for github.com/klauspost/compress/zstd and sync.Pool, which automatically frees resources if you forget to call Close() and/or when items are dropped from the sync.Pool.

Background: https://github.com/klauspost/compress/issues/264

Usage

import (
	"github.com/klauspost/compress/zstd"
	syncpool "github.com/mostynb/zstdpool-syncpool"
)

// Create a sync.Pool which returns wrapped *zstd.Decoder's.
decoderPool := syncpool.NewDecoderPool(zstd.WithDecoderConcurrency(1))

// Get a DecoderWrapper and use it.
decoder := decoderPool.Get().(*syncpool.DecoderWrapper) 
decoder.Reset(compressedDataReader)
_, err = io.Copy(uncompressedDataWriter, decoder)

// Return the decoder to the pool. If we forget this, then the zstd.Decoder
// won't leak resources.
decoderPool.Put(decoder)


// Create a sync.Pool which returns wrapped *zstd.Endoder's.
encoderPool := syncpool.NewEncoderPool(zstd.WithEncoderConcurrency(1))

// Get an EncoderWrapper and use it.
encoder := encoderPool.Get().(*syncpool.EncoderWrapper)
encoder.Reset(compressedDataWriter)
_, err = io.Copy(encoder, uncompressedDataReader)

// Return the encoder to the pool. If we forget this, then the zstd.Encoder
// won't leak resources.
encoderPool.Put(encoder)

Contributing

Bug reports, feature requests, PRs welcome.

License

Licensed under the Apache License, Version 2.0. See the LICENSE file.

Documentation

Overview

Package syncpool provides a non-leaky sync.Pool for github.com/klauspost/compress/zstd's Encoder and Decoder types, using wrappers (EncoderWrapper and DecoderWrapper).

Index

• func NewDecoderPool(options ...zstd.DOption) *sync.Pool
• func NewEncoderPool(options ...zstd.EOption) *sync.Pool
• type DecoderWrapper
  • func (w *DecoderWrapper) Close()
  • func (w *DecoderWrapper) IOReadCloser() io.ReadCloser
• type EncoderWrapper

Functions

func NewDecoderPool

func NewDecoderPool(options ...zstd.DOption) *sync.Pool

NewDecoderPool returns a sync.Pool that provides DecoderWrapper objects, which embed *zstd.Decoders. You probably want to include zstd.WithDecoderConcurrency(1) in the list of options.

func NewEncoderPool

func NewEncoderPool(options ...zstd.EOption) *sync.Pool

NewEncoderPool returns a sync.Pool that provides EncoderWrapper objects which embed a *zstd.Encoder. You probably want to include zstd.WithEncoderConcurrency(1) in the list of options.

Types

type DecoderWrapper

type DecoderWrapper struct {
	// *zstd.Decoder is not safe for use in a sync.Pool directly, since it
	// leaks data and goroutines. Finalizers on the *zstd.Decoder don't help
	// because the aforementioned goroutines reference the *zstd.Decoder and
	// prevent it from being garbage collected (so the finalizers don't run).
	//
	// We can work around this by storing this wrapper with an embedded
	// *zstd.Decoder in the sync.Pool, and using a finalizer on the wrapper
	// to Close the *zstd.Decoder.
	*zstd.Decoder
	// contains filtered or unexported fields
}

DecoderWrapper is a wrapper that embeds a *zstd.Decoder, and is safe for use in a sync.Pool.

func (*DecoderWrapper) Close

func (w *DecoderWrapper) Close()

Close does not close the embedded *zstd.Decoder (once closed, they cannot be reused), but instead resets it and places this *DecoderWrapper back in the pool.

func (*DecoderWrapper) IOReadCloser

func (w *DecoderWrapper) IOReadCloser() io.ReadCloser

IOReadCloser returns an io.ReadCloser that will return this *DecoderWrapper to the pool when it is closed.

type EncoderWrapper

type EncoderWrapper struct {
	*zstd.Encoder
}

EncoderWrapper is a wrapper that embeds a *zstd.Encoder, and is safe for use in a sync.Pool.