constructor.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 metrics

import (
	"bytes"
	"errors"
	"sort"
	"strings"
)

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

// Errors for the metrics package.
var (
	ErrInvalidMetricOutputType = errors.New("invalid metrics output type")
)

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

// typeSpec is a constructor and a usage description for each metric output
// type.
type typeSpec struct {
	constructor func(conf Config) (Type, error)
	description string
}

var constructors = map[string]typeSpec{}

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

// Config is the all encompassing configuration struct for all metric output
// types.
type Config struct {
	Type    string        `json:"type" yaml:"type"`
	Prefix  string        `json:"prefix" yaml:"prefix"`
	HTTP    struct{}      `json:"http_server" yaml:"http_server"`
	Riemann RiemannConfig `json:"riemann" yaml:"riemann"`
	Statsd  StatsdConfig  `json:"statsd" yaml:"statsd"`
}

// NewConfig returns a configuration struct fully populated with default values.
func NewConfig() Config {
	return Config{
		Type:    "http_server",
		Prefix:  "service",
		HTTP:    struct{}{},
		Riemann: NewRiemannConfig(),
		Statsd:  NewStatsdConfig(),
	}
}

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

// Descriptions returns a formatted string of collated descriptions of each
// type.
func Descriptions() string {
	// Order our input types alphabetically
	names := []string{}
	for name := range constructors {
		names = append(names, name)
	}
	sort.Strings(names)

	buf := bytes.Buffer{}
	buf.WriteString("METRIC TARGETS\n")
	buf.WriteString(strings.Repeat("=", 80))
	buf.WriteString("\n\n")
	buf.WriteString("This document has been generated with `benthos --list-metrics`.")
	buf.WriteString("\n\n")

	// Append each description
	for i, name := range names {
		buf.WriteString("## ")
		buf.WriteString("`" + name + "`")
		buf.WriteString("\n")
		buf.WriteString(constructors[name].description)
		if i != (len(names) - 1) {
			buf.WriteString("\n\n")
		}
	}
	return buf.String()
}

// New creates a metric output type based on a configuration.
func New(conf Config) (Type, error) {
	if conf.Type == "none" {
		return DudType{}, nil
	}
	if c, ok := constructors[conf.Type]; ok {
		return c.constructor(conf)
	}
	return nil, ErrInvalidMetricOutputType
}

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