insert_part.go

package processor

import (
	"fmt"
	"time"

	"github.com/Jeffail/benthos/v3/internal/bloblang"
	"github.com/Jeffail/benthos/v3/internal/bloblang/field"
	"github.com/Jeffail/benthos/v3/internal/docs"
	"github.com/Jeffail/benthos/v3/lib/log"
	"github.com/Jeffail/benthos/v3/lib/message"
	"github.com/Jeffail/benthos/v3/lib/metrics"
	"github.com/Jeffail/benthos/v3/lib/types"
)

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

func init() {
	Constructors[TypeInsertPart] = TypeSpec{
		constructor: NewInsertPart,
		Categories: []Category{
			CategoryComposition,
		},
		Summary: `
Insert a new message into a batch at an index. If the specified index is greater
than the length of the existing batch it will be appended to the end.`,
		Description: `
The index can be negative, and if so the message will be inserted from the end
counting backwards starting from -1. E.g. if index = -1 then the new message
will become the last of the batch, if index = -2 then the new message will be
inserted before the last message, and so on. If the negative index is greater
than the length of the existing batch it will be inserted at the beginning.

The new message will have metadata copied from the first pre-existing message of
the batch.

This processor will interpolate functions within the 'content' field, you can
find a list of functions [here](/docs/configuration/interpolation#bloblang-queries).`,
		FieldSpecs: docs.FieldSpecs{
			docs.FieldCommon("index", "The index within the batch to insert the message at."),
			docs.FieldCommon("content", "The content of the message being inserted.").IsInterpolated(),
		},
	}
}

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

// InsertPartConfig contains configuration fields for the InsertPart processor.
type InsertPartConfig struct {
	Index   int    `json:"index" yaml:"index"`
	Content string `json:"content" yaml:"content"`
}

// NewInsertPartConfig returns a InsertPartConfig with default values.
func NewInsertPartConfig() InsertPartConfig {
	return InsertPartConfig{
		Index:   -1,
		Content: "",
	}
}

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

// InsertPart is a processor that inserts a new message part at a specific
// index.
type InsertPart struct {
	part *field.Expression

	conf  Config
	log   log.Modular
	stats metrics.Type

	mCount     metrics.StatCounter
	mSent      metrics.StatCounter
	mBatchSent metrics.StatCounter
}

// NewInsertPart returns a InsertPart processor.
func NewInsertPart(
	conf Config, mgr types.Manager, log log.Modular, stats metrics.Type,
) (Type, error) {
	part, err := bloblang.NewField(conf.InsertPart.Content)
	if err != nil {
		return nil, fmt.Errorf("failed to parse content expression: %v", err)
	}
	return &InsertPart{
		part: part,

		conf:  conf,
		log:   log,
		stats: stats,

		mCount:     stats.GetCounter("count"),
		mSent:      stats.GetCounter("sent"),
		mBatchSent: stats.GetCounter("batch.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 (p *InsertPart) ProcessMessage(msg types.Message) ([]types.Message, types.Response) {
	p.mCount.Incr(1)

	newPartBytes := p.part.Bytes(0, msg)
	index := p.conf.InsertPart.Index
	msgLen := msg.Len()
	if index < 0 {
		index = msgLen + index + 1
		if index < 0 {
			index = 0
		}
	} else if index > msgLen {
		index = msgLen
	}

	newMsg := message.New(nil)
	newPart := msg.Get(0).Copy()
	newPart.Set(newPartBytes)
	msg.Iter(func(i int, p types.Part) error {
		if i == index {
			newMsg.Append(newPart)
		}
		newMsg.Append(p.Copy())
		return nil
	})
	if index == msg.Len() {
		newMsg.Append(newPart)
	}

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

// CloseAsync shuts down the processor and stops processing requests.
func (p *InsertPart) CloseAsync() {
}

// WaitForClose blocks until the processor has closed down.
func (p *InsertPart) WaitForClose(timeout time.Duration) error {
	return nil
}

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