decompress.go

// Copyright (c) 2018 Ashley Jeffs
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package processor

import (
	"bytes"
	"compress/bzip2"
	"compress/flate"
	"compress/gzip"
	"compress/zlib"
	"fmt"
	"io"

	"github.com/Jeffail/benthos/lib/log"
	"github.com/Jeffail/benthos/lib/metrics"
	"github.com/Jeffail/benthos/lib/response"
	"github.com/Jeffail/benthos/lib/types"
)

//------------------------------------------------------------------------------

func init() {
	Constructors[TypeDecompress] = TypeSpec{
		constructor: NewDecompress,
		description: `
Decompresses message parts according to the selected algorithm. Supported
decompression types are: gzip, zlib, bzip2, flate.

Parts that fail to decompress (invalid format) will be removed from the message.
If the message results in zero parts it is skipped entirely.`,
	}
}

//------------------------------------------------------------------------------

// DecompressConfig contains configuration fields for the Decompress processor.
type DecompressConfig struct {
	Algorithm string `json:"algorithm" yaml:"algorithm"`
	Parts     []int  `json:"parts" yaml:"parts"`
}

// NewDecompressConfig returns a DecompressConfig with default values.
func NewDecompressConfig() DecompressConfig {
	return DecompressConfig{
		Algorithm: "gzip",
		Parts:     []int{},
	}
}

//------------------------------------------------------------------------------

type decompressFunc func(bytes []byte) ([]byte, error)

func gzipDecompress(b []byte) ([]byte, error) {
	buf := bytes.NewBuffer(b)
	zr, err := gzip.NewReader(buf)
	if err != nil {
		return nil, err
	}

	outBuf := bytes.Buffer{}
	if _, err = outBuf.ReadFrom(zr); err != nil && err != io.EOF {
		return nil, err
	}
	zr.Close()
	return outBuf.Bytes(), nil
}

func zlibDecompress(b []byte) ([]byte, error) {
	buf := bytes.NewBuffer(b)
	zr, err := zlib.NewReader(buf)
	if err != nil {
		return nil, err
	}

	outBuf := bytes.Buffer{}
	if _, err = outBuf.ReadFrom(zr); err != nil && err != io.EOF {
		return nil, err
	}
	zr.Close()
	return outBuf.Bytes(), nil
}

func flateDecompress(b []byte) ([]byte, error) {
	buf := bytes.NewBuffer(b)
	zr := flate.NewReader(buf)

	outBuf := bytes.Buffer{}
	if _, err := outBuf.ReadFrom(zr); err != nil && err != io.EOF {
		return nil, err
	}
	zr.Close()
	return outBuf.Bytes(), nil
}

func bzip2Decompress(b []byte) ([]byte, error) {
	buf := bytes.NewBuffer(b)
	zr := bzip2.NewReader(buf)

	outBuf := bytes.Buffer{}
	if _, err := outBuf.ReadFrom(zr); err != nil && err != io.EOF {
		return nil, err
	}
	return outBuf.Bytes(), nil
}

func strToDecompressor(str string) (decompressFunc, error) {
	switch str {
	case "gzip":
		return gzipDecompress, nil
	case "zlib":
		return zlibDecompress, nil
	case "flate":
		return flateDecompress, nil
	case "bzip2":
		return bzip2Decompress, nil
	}
	return nil, fmt.Errorf("decompression type not recognised: %v", str)
}

//------------------------------------------------------------------------------

// Decompress is a processor that can decompress parts of a message following a
// chosen compression algorithm.
type Decompress struct {
	conf   DecompressConfig
	decomp decompressFunc

	log   log.Modular
	stats metrics.Type

	mCount     metrics.StatCounter
	mSucc      metrics.StatCounter
	mErr       metrics.StatCounter
	mSkipped   metrics.StatCounter
	mSent      metrics.StatCounter
	mSentParts metrics.StatCounter
}

// NewDecompress returns a Decompress processor.
func NewDecompress(
	conf Config, mgr types.Manager, log log.Modular, stats metrics.Type,
) (Type, error) {
	dcor, err := strToDecompressor(conf.Decompress.Algorithm)
	if err != nil {
		return nil, err
	}
	return &Decompress{
		conf:   conf.Decompress,
		decomp: dcor,
		log:    log.NewModule(".processor.decompress"),
		stats:  stats,

		mCount:     stats.GetCounter("processor.decompress.count"),
		mSucc:      stats.GetCounter("processor.decompress.success"),
		mErr:       stats.GetCounter("processor.decompress.error"),
		mSkipped:   stats.GetCounter("processor.decompress.skipped"),
		mSent:      stats.GetCounter("processor.decompress.sent"),
		mSentParts: stats.GetCounter("processor.decompress.parts.sent"),
	}, nil
}

//------------------------------------------------------------------------------

// ProcessMessage applies the processor to a message, either creating >0
// resulting messages or a response to be sent back to the message source.
func (d *Decompress) ProcessMessage(msg types.Message) ([]types.Message, types.Response) {
	d.mCount.Incr(1)

	newMsg := msg.Copy()

	targetParts := d.conf.Parts
	if len(targetParts) == 0 {
		targetParts = make([]int, newMsg.Len())
		for i := range targetParts {
			targetParts[i] = i
		}
	}

	for _, index := range targetParts {
		part := msg.Get(index).Get()
		newPart, err := d.decomp(part)
		if err == nil {
			d.mSucc.Incr(1)
			newMsg.Get(index).Set(newPart)
		} else {
			d.mErr.Incr(1)
		}
	}

	if newMsg.Len() == 0 {
		d.mSkipped.Incr(1)
		return nil, response.NewAck()
	}

	d.mSent.Incr(1)
	d.mSentParts.Incr(int64(newMsg.Len()))
	msgs := [1]types.Message{newMsg}
	return msgs[:], nil
}

//------------------------------------------------------------------------------