broker.go

// Copyright (c) 2014 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 input

import (
	"encoding/json"
	"errors"
	"fmt"
	"strconv"
	"strings"

	"gopkg.in/yaml.v2"

	"github.com/Jeffail/benthos/lib/broker"
	"github.com/Jeffail/benthos/lib/pipeline"
	"github.com/Jeffail/benthos/lib/types"
	"github.com/Jeffail/benthos/lib/util/service/log"
	"github.com/Jeffail/benthos/lib/util/service/metrics"
)

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

var (
	// ErrBrokerNoInputs is returned when creating a broker with zero inputs.
	ErrBrokerNoInputs = errors.New("attempting to create broker input type with no inputs")
)

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

func init() {
	Constructors["broker"] = TypeSpec{
		brokerConstructor: NewBroker,
		description: `
The broker type allows you to combine multiple inputs, where each input will be
read in parallel. A broker type is configured with its own list of input
configurations and a field to specify how many copies of the list of inputs
should be created.

Adding more input types allows you to merge streams from multiple sources into
one. For example, reading from both RabbitMQ and Kafka:

` + "``` yaml" + `
type: broker
broker:
  copies: 1
  inputs:
  - type: amqp
    amqp:
      url: amqp://guest:guest@localhost:5672/
      consumer_tag: benthos-consumer
      exchange: benthos-exchange
      exchange_type: direct
      key: benthos-key
      queue: benthos-queue
  - type: kafka
    kafka:
      addresses:
      - localhost:9092
      client_id: benthos_kafka_input
      consumer_group: benthos_consumer_group
      partition: 0
      topic: benthos_stream

` + "```" + `

If the number of copies is greater than zero the list will be copied that number
of times. For example, if your inputs were of type foo and bar, with 'copies'
set to '2', you would end up with two 'foo' inputs and two 'bar' inputs.

Sometimes you will want several inputs of similar configuration. For this
purpose you can use the special type 'ditto', which duplicates the previous
config and applies selective changes.

For example, if combining two Kafka inputs with mostly the same set up but
reading different partitions you can use this shortcut:

` + "``` yaml" + `
inputs:
- type: kafka
  kafka:
    addresses:
      - localhost:9092
    client_id: benthos_kafka_input
    consumer_group: benthos_consumer_group
    topic: benthos_stream
    partition: 0
- type: ditto
  kafka:
    partition: 1
` + "```" + `

Which will result in two inputs targeting the same Kafka brokers, on the same
consumer group etc, but consuming their own partitions.

Ditto can also be specified with a multiplier, which is useful if you want
multiple inputs that do not differ in config, like this:

` + "``` yaml" + `
inputs:
- type: kafka_balanced
  kafka:
    addresses:
      - localhost:9092
    client_id: benthos_kafka_input
    consumer_group: benthos_consumer_group
    topic: benthos_stream
- type: ditto_3
` + "```" + `

Which results in a total of four kafka_balanced inputs. Note that ditto_0 will
result in no duplicate configs, this might be useful if the config is generated
and there's a chance you won't want any duplicates.`,
	}
}

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

// BrokerConfig is configuration for the Broker input type.
type BrokerConfig struct {
	Copies int             `json:"copies" yaml:"copies"`
	Inputs brokerInputList `json:"inputs" yaml:"inputs"`
}

// NewBrokerConfig creates a new BrokerConfig with default values.
func NewBrokerConfig() BrokerConfig {
	return BrokerConfig{
		Copies: 1,
		Inputs: brokerInputList{},
	}
}

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

type brokerInputList []Config

// UnmarshalJSON ensures that when parsing configs that are in a map or slice
// the default values are still applied.
func (b *brokerInputList) UnmarshalJSON(bytes []byte) error {
	genericInputs := []interface{}{}
	if err := json.Unmarshal(bytes, &genericInputs); err != nil {
		return err
	}

	inputConfs, err := parseInputConfsWithDefaults(genericInputs)
	if err != nil {
		return err
	}

	*b = inputConfs
	return nil
}

// UnmarshalYAML ensures that when parsing configs that are in a map or slice
// the default values are still applied.
func (b *brokerInputList) UnmarshalYAML(unmarshal func(interface{}) error) error {
	genericInputs := []interface{}{}
	if err := unmarshal(&genericInputs); err != nil {
		return err
	}

	inputConfs, err := parseInputConfsWithDefaults(genericInputs)
	if err != nil {
		return err
	}

	*b = inputConfs
	return nil
}

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

// parseInputConfsWithDefaults takes a slice of generic input configs and
// returns a slice of input configs with default values in place of omitted
// values. This is necessary because when unmarshalling config files using
// structs you can pre-populate non-reference type struct fields with default
// values, but array objects will lose those defaults.
//
// In order to ensure that omitted values are set to default we initially parse
// the array as interface{} types and then individually apply the defaults by
// marshalling and unmarshalling. The correct way to do this would be to use
// json.RawMessage, but our config files can contain a range of different
// formats that we do not know at this stage, therefore we use the more hacky
// method as performance is not an issue at this stage.
func parseInputConfsWithDefaults(rawInputs []interface{}) ([]Config, error) {
	type confAlias Config

	inputConfs := []Config{}

	// NOTE: Use yaml here as it supports more types than JSON
	// (map[interface{}]interface{}).
	for i, boxedConfig := range rawInputs {
		newConfs := []confAlias{confAlias(NewConfig())}
		if i > 0 {
			// If the type of this output is 'ditto' we want to start with a
			// duplicate of the previous config.
			newConfsFromDitto := func(label string) error {
				// Remove the vanilla config.
				newConfs = []confAlias{}

				// Check if there is a ditto multiplier.
				if len(label) > 5 && label[5] == '_' {
					if label[6:] == "0" {
						// This is a special case where we are expressing that
						// we want to end up with zero duplicates.
						return nil
					}
					n, err := strconv.Atoi(label[6:])
					if err != nil {
						return fmt.Errorf("failed to parse ditto multiplier: %v", err)
					}
					for j := 0; j < n; j++ {
						newConfs = append(newConfs, confAlias(inputConfs[i-1]))
					}
				} else {
					// Otherwise just add a single dupe of the previous config.
					newConfs = append(newConfs, confAlias(inputConfs[i-1]))
				}
				return nil
			}
			switch unboxed := boxedConfig.(type) {
			case map[string]interface{}:
				if t, ok := unboxed["type"].(string); ok && strings.Index(t, "ditto") == 0 {
					if err := newConfsFromDitto(t); err != nil {
						return nil, err
					}
					if len(newConfs) > 0 {
						unboxed["type"] = newConfs[0].Type
					}
				}
			case map[interface{}]interface{}:
				if t, ok := unboxed["type"].(string); ok && strings.Index(t, "ditto") == 0 {
					if err := newConfsFromDitto(t); err != nil {
						return nil, err
					}
					if len(newConfs) > 0 {
						unboxed["type"] = newConfs[0].Type
					}
				}
			}
		}
		for _, conf := range newConfs {
			rawBytes, err := yaml.Marshal(boxedConfig)
			if err != nil {
				return nil, err
			}
			if err = yaml.Unmarshal(rawBytes, &conf); err != nil {
				return nil, err
			}
			inputConfs = append(inputConfs, Config(conf))
		}
	}

	return inputConfs, nil
}

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

// NewBroker creates a new Broker input type.
func NewBroker(
	conf Config,
	mgr types.Manager,
	log log.Modular,
	stats metrics.Type,
	pipelines ...pipeline.ConstructorFunc,
) (Type, error) {
	lInputs := len(conf.Broker.Inputs) * conf.Broker.Copies

	if lInputs <= 0 {
		return nil, ErrBrokerNoInputs
	}
	if lInputs == 1 {
		return New(conf.Broker.Inputs[0], mgr, log, stats, pipelines...)
	}

	inputs := make([]types.Producer, lInputs)

	var err error
	for j := 0; j < conf.Broker.Copies; j++ {
		for i, iConf := range conf.Broker.Inputs {
			inputs[len(conf.Broker.Inputs)*j+i], err = New(iConf, mgr, log, stats, pipelines...)
			if err != nil {
				return nil, err
			}
		}
	}

	return broker.NewFanIn(inputs, stats)
}

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