telegraf/internal/config/config.go

package config

import (
	"bytes"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"time"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/internal/models"
	"github.com/influxdata/telegraf/plugins/inputs"
	"github.com/influxdata/telegraf/plugins/outputs"
	"github.com/influxdata/telegraf/plugins/parsers"
	"github.com/influxdata/telegraf/plugins/serializers"

	"github.com/influxdata/config"
	"github.com/influxdata/toml"
	"github.com/influxdata/toml/ast"
)

var (
	// Default input plugins
	inputDefaults = []string{"cpu", "mem", "swap", "system", "kernel",
		"processes", "disk", "diskio"}

	// Default output plugins
	outputDefaults = []string{"influxdb"}

	// envVarRe is a regex to find environment variables in the config file
	envVarRe = regexp.MustCompile(`\$\w+`)
)

// Config specifies the URL/user/password for the database that telegraf
// will be logging to, as well as all the plugins that the user has
// specified
type Config struct {
	Tags          map[string]string
	InputFilters  []string
	OutputFilters []string

	Agent   *AgentConfig
	Inputs  []*internal_models.RunningInput
	Outputs []*internal_models.RunningOutput
}

func NewConfig() *Config {
	c := &Config{
		// Agent defaults:
		Agent: &AgentConfig{
			Interval:      internal.Duration{Duration: 10 * time.Second},
			RoundInterval: true,
			FlushInterval: internal.Duration{Duration: 10 * time.Second},
			FlushJitter:   internal.Duration{Duration: 5 * time.Second},
		},

		Tags:          make(map[string]string),
		Inputs:        make([]*internal_models.RunningInput, 0),
		Outputs:       make([]*internal_models.RunningOutput, 0),
		InputFilters:  make([]string, 0),
		OutputFilters: make([]string, 0),
	}
	return c
}

type AgentConfig struct {
	// Interval at which to gather information
	Interval internal.Duration

	// RoundInterval rounds collection interval to 'interval'.
	//     ie, if Interval=10s then always collect on :00, :10, :20, etc.
	RoundInterval bool

	// CollectionJitter is used to jitter the collection by a random amount.
	// Each plugin will sleep for a random time within jitter before collecting.
	// This can be used to avoid many plugins querying things like sysfs at the
	// same time, which can have a measurable effect on the system.
	CollectionJitter internal.Duration

	// FlushInterval is the Interval at which to flush data
	FlushInterval internal.Duration

	// FlushJitter Jitters the flush interval by a random amount.
	// This is primarily to avoid large write spikes for users running a large
	// number of telegraf instances.
	// ie, a jitter of 5s and interval 10s means flushes will happen every 10-15s
	FlushJitter internal.Duration

	// MetricBatchSize is the maximum number of metrics that is wrote to an
	// output plugin in one call.
	MetricBatchSize int

	// MetricBufferLimit is the max number of metrics that each output plugin
	// will cache. The buffer is cleared when a successful write occurs. When
	// full, the oldest metrics will be overwritten. This number should be a
	// multiple of MetricBatchSize. Due to current implementation, this could
	// not be less than 2 times MetricBatchSize.
	MetricBufferLimit int

	// FlushBufferWhenFull tells Telegraf to flush the metric buffer whenever
	// it fills up, regardless of FlushInterval. Setting this option to true
	// does _not_ deactivate FlushInterval.
	FlushBufferWhenFull bool

	// TODO(cam): Remove UTC and Precision parameters, they are no longer
	// valid for the agent config. Leaving them here for now for backwards-
	// compatability
	UTC       bool `toml:"utc"`
	Precision string

	// Debug is the option for running in debug mode
	Debug bool

	// Quiet is the option for running in quiet mode
	Quiet        bool
	Hostname     string
	OmitHostname bool

	//
	WebhookServiceAddress  string
}

// Inputs returns a list of strings of the configured inputs.
func (c *Config) InputNames() []string {
	var name []string
	for _, input := range c.Inputs {
		name = append(name, input.Name)
	}
	return name
}

// Outputs returns a list of strings of the configured inputs.
func (c *Config) OutputNames() []string {
	var name []string
	for _, output := range c.Outputs {
		name = append(name, output.Name)
	}
	return name
}

// ListTags returns a string of tags specified in the config,
// line-protocol style
func (c *Config) ListTags() string {
	var tags []string

	for k, v := range c.Tags {
		tags = append(tags, fmt.Sprintf("%s=%s", k, v))
	}

	sort.Strings(tags)

	return strings.Join(tags, " ")
}

var header = `# Telegraf Configuration
#
# Telegraf is entirely plugin driven. All metrics are gathered from the
# declared inputs, and sent to the declared outputs.
#
# Plugins must be declared in here to be active.
# To deactivate a plugin, comment out the name and any variables.
#
# Use 'telegraf -config telegraf.conf -test' to see what metrics a config
# file would generate.
#
# Environment variables can be used anywhere in this config file, simply prepend
# them with $. For strings the variable must be within quotes (ie, "$STR_VAR"),
# for numbers and booleans they should be plain (ie, $INT_VAR, $BOOL_VAR)


# Global tags can be specified here in key="value" format.
[global_tags]
  # dc = "us-east-1" # will tag all metrics with dc=us-east-1
  # rack = "1a"
  ## Environment variables can be used as tags, and throughout the config file
  # user = "$USER"


# Configuration for telegraf agent
[agent]
  ## Default data collection interval for all inputs
  interval = "10s"
  ## Rounds collection interval to 'interval'
  ## ie, if interval="10s" then always collect on :00, :10, :20, etc.
  round_interval = true

  ## Telegraf will send metrics to outputs in batches of at
  ## most metric_batch_size metrics.
  metric_batch_size = 1000
  ## For failed writes, telegraf will cache metric_buffer_limit metrics for each
  ## output, and will flush this buffer on a successful write. Oldest metrics
  ## are dropped first when this buffer fills.
  metric_buffer_limit = 10000

  ## Collection jitter is used to jitter the collection by a random amount.
  ## Each plugin will sleep for a random time within jitter before collecting.
  ## This can be used to avoid many plugins querying things like sysfs at the
  ## same time, which can have a measurable effect on the system.
  collection_jitter = "0s"

  ## Default flushing interval for all outputs. You shouldn't set this below
  ## interval. Maximum flush_interval will be flush_interval + flush_jitter
  flush_interval = "10s"
  ## Jitter the flush interval by a random amount. This is primarily to avoid
  ## large write spikes for users running a large number of telegraf instances.
  ## ie, a jitter of 5s and interval 10s means flushes will happen every 10-15s
  flush_jitter = "0s"

  ## Run telegraf in debug mode
  debug = false
  ## Run telegraf in quiet mode
  quiet = false
  ## Override default hostname, if empty use os.Hostname()
  hostname = ""
  ## If set to true, do no set the "host" tag in the telegraf agent.
  omit_hostname = false


###############################################################################
#                            OUTPUT PLUGINS                                   #
###############################################################################
`

var inputHeader = `

###############################################################################
#                            INPUT PLUGINS                                    #
###############################################################################
`

var serviceInputHeader = `

###############################################################################
#                            SERVICE INPUT PLUGINS                            #
###############################################################################
`

// PrintSampleConfig prints the sample config
func PrintSampleConfig(inputFilters []string, outputFilters []string) {
	fmt.Printf(header)

	if len(outputFilters) != 0 {
		printFilteredOutputs(outputFilters, false)
	} else {
		printFilteredOutputs(outputDefaults, false)
		// Print non-default outputs, commented
		var pnames []string
		for pname := range outputs.Outputs {
			if !sliceContains(pname, outputDefaults) {
				pnames = append(pnames, pname)
			}
		}
		sort.Strings(pnames)
		printFilteredOutputs(pnames, true)
	}

	fmt.Printf(inputHeader)
	if len(inputFilters) != 0 {
		printFilteredInputs(inputFilters, false)
	} else {
		printFilteredInputs(inputDefaults, false)
		// Print non-default inputs, commented
		var pnames []string
		for pname := range inputs.Inputs {
			if !sliceContains(pname, inputDefaults) {
				pnames = append(pnames, pname)
			}
		}
		sort.Strings(pnames)
		printFilteredInputs(pnames, true)
	}
}

func printFilteredInputs(inputFilters []string, commented bool) {
	// Filter inputs
	var pnames []string
	for pname := range inputs.Inputs {
		if sliceContains(pname, inputFilters) {
			pnames = append(pnames, pname)
		}
	}
	sort.Strings(pnames)

	// cache service inputs to print them at the end
	servInputs := make(map[string]telegraf.ServiceInput)
	// for alphabetical looping:
	servInputNames := []string{}

	// Print Inputs
	for _, pname := range pnames {
		creator := inputs.Inputs[pname]
		input := creator()

		switch p := input.(type) {
		case telegraf.ServiceInput:
			servInputs[pname] = p
			servInputNames = append(servInputNames, pname)
			continue
		}

		printConfig(pname, input, "inputs", commented)
	}

	// Print Service Inputs
	if len(servInputs) == 0 {
		return
	}
	sort.Strings(servInputNames)
	fmt.Printf(serviceInputHeader)
	for _, name := range servInputNames {
		printConfig(name, servInputs[name], "inputs", commented)
	}
}

func printFilteredOutputs(outputFilters []string, commented bool) {
	// Filter outputs
	var onames []string
	for oname := range outputs.Outputs {
		if sliceContains(oname, outputFilters) {
			onames = append(onames, oname)
		}
	}
	sort.Strings(onames)

	// Print Outputs
	for _, oname := range onames {
		creator := outputs.Outputs[oname]
		output := creator()
		printConfig(oname, output, "outputs", commented)
	}
}

type printer interface {
	Description() string
	SampleConfig() string
}

func printConfig(name string, p printer, op string, commented bool) {
	comment := ""
	if commented {
		comment = "# "
	}
	fmt.Printf("\n%s# %s\n%s[[%s.%s]]", comment, p.Description(), comment,
		op, name)

	config := p.SampleConfig()
	if config == "" {
		fmt.Printf("\n%s  # no configuration\n\n", comment)
	} else {
		lines := strings.Split(config, "\n")
		for i, line := range lines {
			if i == 0 || i == len(lines)-1 {
				fmt.Print("\n")
				continue
			}
			fmt.Print(comment + line + "\n")
		}
	}
}

func sliceContains(name string, list []string) bool {
	for _, b := range list {
		if b == name {
			return true
		}
	}
	return false
}

// PrintInputConfig prints the config usage of a single input.
func PrintInputConfig(name string) error {
	if creator, ok := inputs.Inputs[name]; ok {
		printConfig(name, creator(), "inputs", false)
	} else {
		return errors.New(fmt.Sprintf("Input %s not found", name))
	}
	return nil
}

// PrintOutputConfig prints the config usage of a single output.
func PrintOutputConfig(name string) error {
	if creator, ok := outputs.Outputs[name]; ok {
		printConfig(name, creator(), "outputs", false)
	} else {
		return errors.New(fmt.Sprintf("Output %s not found", name))
	}
	return nil
}

func (c *Config) LoadDirectory(path string) error {
	directoryEntries, err := ioutil.ReadDir(path)
	if err != nil {
		return err
	}
	for _, entry := range directoryEntries {
		if entry.IsDir() {
			continue
		}
		name := entry.Name()
		if len(name) < 6 || name[len(name)-5:] != ".conf" {
			continue
		}
		err := c.LoadConfig(filepath.Join(path, name))
		if err != nil {
			return err
		}
	}
	return nil
}

// Try to find a default config file at these locations (in order):
//   1. $TELEGRAF_CONFIG_PATH
//   2. $HOME/.telegraf/telegraf.conf
//   3. /etc/telegraf/telegraf.conf
//
func getDefaultConfigPath() (string, error) {
	envfile := os.Getenv("TELEGRAF_CONFIG_PATH")
	homefile := os.ExpandEnv("${HOME}/.telegraf/telegraf.conf")
	etcfile := "/etc/telegraf/telegraf.conf"
	for _, path := range []string{envfile, homefile, etcfile} {
		if _, err := os.Stat(path); err == nil {
			log.Printf("Using config file: %s", path)
			return path, nil
		}
	}

	// if we got here, we didn't find a file in a default location
	return "", fmt.Errorf("No config file specified, and could not find one"+
		" in $TELEGRAF_CONFIG_PATH, %s, or %s", homefile, etcfile)
}

// LoadConfig loads the given config file and applies it to c
func (c *Config) LoadConfig(path string) error {
	var err error
	if path == "" {
		if path, err = getDefaultConfigPath(); err != nil {
			return err
		}
	}
	tbl, err := parseFile(path)
	if err != nil {
		return fmt.Errorf("Error parsing %s, %s", path, err)
	}

	// Parse tags tables first:
	for _, tableName := range []string{"tags", "global_tags"} {
		if val, ok := tbl.Fields[tableName]; ok {
			subTable, ok := val.(*ast.Table)
			if !ok {
				return fmt.Errorf("%s: invalid configuration", path)
			}
			if err = config.UnmarshalTable(subTable, c.Tags); err != nil {
				log.Printf("Could not parse [global_tags] config\n")
				return fmt.Errorf("Error parsing %s, %s", path, err)
			}
		}
	}

	// Parse agent table:
	if val, ok := tbl.Fields["agent"]; ok {
		subTable, ok := val.(*ast.Table)
		if !ok {
			return fmt.Errorf("%s: invalid configuration", path)
		}
		if err = config.UnmarshalTable(subTable, c.Agent); err != nil {
			log.Printf("Could not parse [agent] config\n")
			return fmt.Errorf("Error parsing %s, %s", path, err)
		}
	}

	// Parse all the rest of the plugins:
	for name, val := range tbl.Fields {
		subTable, ok := val.(*ast.Table)
		if !ok {
			return fmt.Errorf("%s: invalid configuration", path)
		}

		switch name {
		case "agent", "global_tags", "tags":
		case "outputs":
			for pluginName, pluginVal := range subTable.Fields {
				switch pluginSubTable := pluginVal.(type) {
				case *ast.Table:
					if err = c.addOutput(pluginName, pluginSubTable); err != nil {
						return fmt.Errorf("Error parsing %s, %s", path, err)
					}
				case []*ast.Table:
					for _, t := range pluginSubTable {
						if err = c.addOutput(pluginName, t); err != nil {
							return fmt.Errorf("Error parsing %s, %s", path, err)
						}
					}
				default:
					return fmt.Errorf("Unsupported config format: %s, file %s",
						pluginName, path)
				}
			}
		case "inputs", "plugins":
			for pluginName, pluginVal := range subTable.Fields {
				switch pluginSubTable := pluginVal.(type) {
				case *ast.Table:
					if err = c.addInput(pluginName, pluginSubTable); err != nil {
						return fmt.Errorf("Error parsing %s, %s", path, err)
					}
				case []*ast.Table:
					for _, t := range pluginSubTable {
						if err = c.addInput(pluginName, t); err != nil {
							return fmt.Errorf("Error parsing %s, %s", path, err)
						}
					}
				default:
					return fmt.Errorf("Unsupported config format: %s, file %s",
						pluginName, path)
				}
			}
		// Assume it's an input input for legacy config file support if no other
		// identifiers are present
		default:
			if err = c.addInput(name, subTable); err != nil {
				return fmt.Errorf("Error parsing %s, %s", path, err)
			}
		}
	}
	return nil
}

// parseFile loads a TOML configuration from a provided path and
// returns the AST produced from the TOML parser. When loading the file, it
// will find environment variables and replace them.
func parseFile(fpath string) (*ast.Table, error) {
	contents, err := ioutil.ReadFile(fpath)
	if err != nil {
		return nil, err
	}

	env_vars := envVarRe.FindAll(contents, -1)
	for _, env_var := range env_vars {
		env_val := os.Getenv(strings.TrimPrefix(string(env_var), "$"))
		if env_val != "" {
			contents = bytes.Replace(contents, env_var, []byte(env_val), 1)
		}
	}

	return toml.Parse(contents)
}

func (c *Config) addOutput(name string, table *ast.Table) error {
	if len(c.OutputFilters) > 0 && !sliceContains(name, c.OutputFilters) {
		return nil
	}
	creator, ok := outputs.Outputs[name]
	if !ok {
		return fmt.Errorf("Undefined but requested output: %s", name)
	}
	output := creator()

	// If the output has a SetSerializer function, then this means it can write
	// arbitrary types of output, so build the serializer and set it.
	switch t := output.(type) {
	case serializers.SerializerOutput:
		serializer, err := buildSerializer(name, table)
		if err != nil {
			return err
		}
		t.SetSerializer(serializer)
	}

	outputConfig, err := buildOutput(name, table)
	if err != nil {
		return err
	}

	if err := config.UnmarshalTable(table, output); err != nil {
		return err
	}

	ro := internal_models.NewRunningOutput(name, output, outputConfig,
		c.Agent.MetricBatchSize, c.Agent.MetricBufferLimit)
	c.Outputs = append(c.Outputs, ro)
	return nil
}

func (c *Config) addInput(name string, table *ast.Table) error {
	if len(c.InputFilters) > 0 && !sliceContains(name, c.InputFilters) {
		return nil
	}
	// Legacy support renaming io input to diskio
	if name == "io" {
		name = "diskio"
	}

	creator, ok := inputs.Inputs[name]
	if !ok {
		return fmt.Errorf("Undefined but requested input: %s", name)
	}
	input := creator()

	// If the input has a SetParser function, then this means it can accept
	// arbitrary types of input, so build the parser and set it.
	switch t := input.(type) {
	case parsers.ParserInput:
		parser, err := buildParser(name, table)
		if err != nil {
			return err
		}
		t.SetParser(parser)
	}

	pluginConfig, err := buildInput(name, table)
	if err != nil {
		return err
	}

	if err := config.UnmarshalTable(table, input); err != nil {
		return err
	}

	rp := &internal_models.RunningInput{
		Name:   name,
		Input:  input,
		Config: pluginConfig,
	}
	c.Inputs = append(c.Inputs, rp)
	return nil
}

// buildFilter builds a Filter
// (tagpass/tagdrop/namepass/namedrop/fieldpass/fielddrop) to
// be inserted into the internal_models.OutputConfig/internal_models.InputConfig
// to be used for glob filtering on tags and measurements
func buildFilter(tbl *ast.Table) (internal_models.Filter, error) {
	f := internal_models.Filter{}

	if node, ok := tbl.Fields["namepass"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						f.NamePass = append(f.NamePass, str.Value)
						f.IsActive = true
					}
				}
			}
		}
	}

	if node, ok := tbl.Fields["namedrop"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						f.NameDrop = append(f.NameDrop, str.Value)
						f.IsActive = true
					}
				}
			}
		}
	}

	fields := []string{"pass", "fieldpass"}
	for _, field := range fields {
		if node, ok := tbl.Fields[field]; ok {
			if kv, ok := node.(*ast.KeyValue); ok {
				if ary, ok := kv.Value.(*ast.Array); ok {
					for _, elem := range ary.Value {
						if str, ok := elem.(*ast.String); ok {
							f.FieldPass = append(f.FieldPass, str.Value)
							f.IsActive = true
						}
					}
				}
			}
		}
	}

	fields = []string{"drop", "fielddrop"}
	for _, field := range fields {
		if node, ok := tbl.Fields[field]; ok {
			if kv, ok := node.(*ast.KeyValue); ok {
				if ary, ok := kv.Value.(*ast.Array); ok {
					for _, elem := range ary.Value {
						if str, ok := elem.(*ast.String); ok {
							f.FieldDrop = append(f.FieldDrop, str.Value)
							f.IsActive = true
						}
					}
				}
			}
		}
	}

	if node, ok := tbl.Fields["tagpass"]; ok {
		if subtbl, ok := node.(*ast.Table); ok {
			for name, val := range subtbl.Fields {
				if kv, ok := val.(*ast.KeyValue); ok {
					tagfilter := &internal_models.TagFilter{Name: name}
					if ary, ok := kv.Value.(*ast.Array); ok {
						for _, elem := range ary.Value {
							if str, ok := elem.(*ast.String); ok {
								tagfilter.Filter = append(tagfilter.Filter, str.Value)
							}
						}
					}
					f.TagPass = append(f.TagPass, *tagfilter)
					f.IsActive = true
				}
			}
		}
	}

	if node, ok := tbl.Fields["tagdrop"]; ok {
		if subtbl, ok := node.(*ast.Table); ok {
			for name, val := range subtbl.Fields {
				if kv, ok := val.(*ast.KeyValue); ok {
					tagfilter := &internal_models.TagFilter{Name: name}
					if ary, ok := kv.Value.(*ast.Array); ok {
						for _, elem := range ary.Value {
							if str, ok := elem.(*ast.String); ok {
								tagfilter.Filter = append(tagfilter.Filter, str.Value)
							}
						}
					}
					f.TagDrop = append(f.TagDrop, *tagfilter)
					f.IsActive = true
				}
			}
		}
	}

	if node, ok := tbl.Fields["tagexclude"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						f.TagExclude = append(f.TagExclude, str.Value)
					}
				}
			}
		}
	}

	if node, ok := tbl.Fields["taginclude"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						f.TagInclude = append(f.TagInclude, str.Value)
					}
				}
			}
		}
	}
	if err := f.CompileFilter(); err != nil {
		return f, err
	}

	delete(tbl.Fields, "namedrop")
	delete(tbl.Fields, "namepass")
	delete(tbl.Fields, "fielddrop")
	delete(tbl.Fields, "fieldpass")
	delete(tbl.Fields, "drop")
	delete(tbl.Fields, "pass")
	delete(tbl.Fields, "tagdrop")
	delete(tbl.Fields, "tagpass")
	delete(tbl.Fields, "tagexclude")
	delete(tbl.Fields, "taginclude")
	return f, nil
}

// buildInput parses input specific items from the ast.Table,
// builds the filter and returns a
// internal_models.InputConfig to be inserted into internal_models.RunningInput
func buildInput(name string, tbl *ast.Table) (*internal_models.InputConfig, error) {
	cp := &internal_models.InputConfig{Name: name}
	if node, ok := tbl.Fields["interval"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				dur, err := time.ParseDuration(str.Value)
				if err != nil {
					return nil, err
				}

				cp.Interval = dur
			}
		}
	}

	if node, ok := tbl.Fields["name_prefix"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				cp.MeasurementPrefix = str.Value
			}
		}
	}

	if node, ok := tbl.Fields["name_suffix"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				cp.MeasurementSuffix = str.Value
			}
		}
	}

	if node, ok := tbl.Fields["name_override"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				cp.NameOverride = str.Value
			}
		}
	}

	cp.Tags = make(map[string]string)
	if node, ok := tbl.Fields["tags"]; ok {
		if subtbl, ok := node.(*ast.Table); ok {
			if err := config.UnmarshalTable(subtbl, cp.Tags); err != nil {
				log.Printf("Could not parse tags for input %s\n", name)
			}
		}
	}

	delete(tbl.Fields, "name_prefix")
	delete(tbl.Fields, "name_suffix")
	delete(tbl.Fields, "name_override")
	delete(tbl.Fields, "interval")
	delete(tbl.Fields, "tags")
	var err error
	cp.Filter, err = buildFilter(tbl)
	if err != nil {
		return cp, err
	}
	return cp, nil
}

// buildParser grabs the necessary entries from the ast.Table for creating
// a parsers.Parser object, and creates it, which can then be added onto
// an Input object.
func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
	c := &parsers.Config{}

	if node, ok := tbl.Fields["data_format"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.DataFormat = str.Value
			}
		}
	}

	// Legacy support, exec plugin originally parsed JSON by default.
	if name == "exec" && c.DataFormat == "" {
		c.DataFormat = "json"
	} else if c.DataFormat == "" {
		c.DataFormat = "influx"
	}

	if node, ok := tbl.Fields["separator"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.Separator = str.Value
			}
		}
	}

	if node, ok := tbl.Fields["templates"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						c.Templates = append(c.Templates, str.Value)
					}
				}
			}
		}
	}

	if node, ok := tbl.Fields["tag_keys"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if ary, ok := kv.Value.(*ast.Array); ok {
				for _, elem := range ary.Value {
					if str, ok := elem.(*ast.String); ok {
						c.TagKeys = append(c.TagKeys, str.Value)
					}
				}
			}
		}
	}

	if node, ok := tbl.Fields["data_type"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.DataType = str.Value
			}
		}
	}

	c.MetricName = name

	delete(tbl.Fields, "data_format")
	delete(tbl.Fields, "separator")
	delete(tbl.Fields, "templates")
	delete(tbl.Fields, "tag_keys")
	delete(tbl.Fields, "data_type")

	return parsers.NewParser(c)
}

// buildSerializer grabs the necessary entries from the ast.Table for creating
// a serializers.Serializer object, and creates it, which can then be added onto
// an Output object.
func buildSerializer(name string, tbl *ast.Table) (serializers.Serializer, error) {
	c := &serializers.Config{}

	if node, ok := tbl.Fields["data_format"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.DataFormat = str.Value
			}
		}
	}

	if c.DataFormat == "" {
		c.DataFormat = "influx"
	}

	if node, ok := tbl.Fields["prefix"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.Prefix = str.Value
			}
		}
	}

	if node, ok := tbl.Fields["template"]; ok {
		if kv, ok := node.(*ast.KeyValue); ok {
			if str, ok := kv.Value.(*ast.String); ok {
				c.Template = str.Value
			}
		}
	}

	delete(tbl.Fields, "data_format")
	delete(tbl.Fields, "prefix")
	delete(tbl.Fields, "template")
	return serializers.NewSerializer(c)
}

// buildOutput parses output specific items from the ast.Table,
// builds the filter and returns an
// internal_models.OutputConfig to be inserted into internal_models.RunningInput
// Note: error exists in the return for future calls that might require error
func buildOutput(name string, tbl *ast.Table) (*internal_models.OutputConfig, error) {
	filter, err := buildFilter(tbl)
	if err != nil {
		return nil, err
	}
	oc := &internal_models.OutputConfig{
		Name:   name,
		Filter: filter,
	}
	// Outputs don't support FieldDrop/FieldPass, so set to NameDrop/NamePass
	if len(oc.Filter.FieldDrop) > 0 {
		oc.Filter.NameDrop = oc.Filter.FieldDrop
	}
	if len(oc.Filter.FieldPass) > 0 {
		oc.Filter.NamePass = oc.Filter.FieldPass
	}
	return oc, nil
}