cli.go

// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0

package main

import (
	"context"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"sync"
	"time"

	"github.com/coreos/go-systemd/v22/daemon"
	"github.com/hashicorp/consul-template/config"
	"github.com/hashicorp/consul-template/logging"
	"github.com/hashicorp/consul-template/manager"
	"github.com/hashicorp/consul-template/service_os"
	"github.com/hashicorp/consul-template/signals"
	"github.com/hashicorp/consul-template/version"
)

// Exit codes are int values that represent an exit code for a particular error.
// Sub-systems may check this unique error to determine the cause of an error
// without parsing the output or help text.
//
// Errors start at 10
const (
	ExitCodeOK int = 0

	ExitCodeError = 10 + iota
	ExitCodeInterrupt
	ExitCodeParseFlagsError
	ExitCodeRunnerError
	ExitCodeConfigError
)

// CLI is the main entry point.
type CLI struct {
	sync.Mutex

	// outSteam and errStream are the standard out and standard error streams to
	// write messages from the CLI.
	outStream, errStream io.Writer

	// signalCh is the channel where the cli receives signals.
	signalCh chan os.Signal

	// stopCh is an internal channel used to trigger a shutdown of the CLI.
	stopCh  chan struct{}
	stopped bool
}

// NewCLI creates a new CLI object with the given stdout and stderr streams.
func NewCLI(out, err io.Writer) *CLI {
	return &CLI{
		outStream: out,
		errStream: err,
		signalCh:  make(chan os.Signal, 10),
		stopCh:    make(chan struct{}),
	}
}

// Run accepts a slice of arguments and returns an int representing the exit
// status from the command.
func (cli *CLI) Run(args []string) int {
	// Parse the flags
	config, paths, dry, isVersion, err := cli.ParseFlags(args[1:])
	if err != nil {
		if err == flag.ErrHelp {
			fmt.Fprintf(cli.outStream, usage, version.Name)
			return 0
		}
		fmt.Fprintln(cli.errStream, err.Error())
		return ExitCodeParseFlagsError
	}

	// Save original config (defaults + parsed flags) for handling reloads
	cliConfig := config.Copy()

	// Load configuration paths, with CLI taking precedence
	config, err = loadConfigs(paths, cliConfig)
	if err != nil {
		return logError(err, ExitCodeConfigError)
	}

	config.Finalize()

	// Setup the config and logging
	config, err = cli.setup(config)
	if err != nil {
		return logError(err, ExitCodeConfigError)
	}

	// Print version information for debugging
	log.Printf("[INFO] %s", version.HumanVersion)

	// If the version was requested, return an "error" containing the version
	// information. This might sound weird, but most *nix applications actually
	// print their version on stderr anyway.
	if isVersion {
		log.Printf("[DEBUG] (cli) version flag was given, exiting now")
		fmt.Fprintf(cli.outStream, "%s\n", version.HumanVersion)
		return ExitCodeOK
	}

	// Create a context with cancellation
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Create a channel for signaling readiness to the systemd init system.
	readyCh := make(chan struct{})

	// Start a goroutine that listens for signals on the readyCh channel.
	// When a signal (an empty struct) is received, it notifies systemd that
	// the application is ready by calling daemon.SdNotify with SdNotifyReady.
	// If an error occurs during the notification, it logs a warning message.
	go func() {
		for {
			select {
			case <-readyCh:
				_, err := daemon.SdNotify(false, daemon.SdNotifyReady)
				if err != nil {
					log.Printf("[WARN] failed to signal readiness to systemd: %v", err)
				}
			case <-ctx.Done():
				return
			}
		}
	}()

	// Initial runner
	runner, err := manager.NewRunner(config, dry)
	if err != nil {
		return logError(err, ExitCodeRunnerError)
	}

	runner.SetReadyChannel(readyCh)
	go runner.Start()

	// Listen for monitored signals
	signal.Notify(cli.signalCh, signals.MonitoredSignals...)

	for {
		select {
		case err := <-runner.ErrCh:
			// Check if the runner's error returned a specific exit status, and
			// return that value.
			// If no value was given, return a generic exit status.
			code := ExitCodeRunnerError
			if typed, ok := err.(manager.ErrExitable); ok {
				code = typed.ExitStatus()
			}
			switch code {
			case 0:
				log.Printf("[INFO] (cli) %s", err)
				return ExitCodeOK
			default:
				return logError(err, code)
			}
		case <-runner.DoneCh:
			return ExitCodeOK
		case <-service_os.Shutdown_Channel():
			fmt.Fprintf(cli.errStream, "Cleaning up...\n")
			runner.StopImmediately()
			cancel() // Cancel the context to stop the readyCh goroutine
			return ExitCodeInterrupt
		case s := <-cli.signalCh:
			log.Printf("[DEBUG] (cli) receiving signal %q", s)

			switch s {
			case *config.ReloadSignal:
				fmt.Fprintf(cli.errStream, "Reloading configuration...\n")
				runner.Stop()

				// Re-parse any configuration files or paths
				config, err = loadConfigs(paths, cliConfig)
				if err != nil {
					return logError(err, ExitCodeConfigError)
				}
				config.Finalize()

				// Load the new configuration from disk
				config, err = cli.setup(config)
				if err != nil {
					return logError(err, ExitCodeConfigError)
				}

				runner, err = manager.NewRunner(config, dry)
				if err != nil {
					return logError(err, ExitCodeRunnerError)
				}
				runner.SetReadyChannel(readyCh)
				go runner.Start()
			case *config.KillSignal:
				fmt.Fprintf(cli.errStream, "Cleaning up...\n")
				runner.StopImmediately()
				return ExitCodeInterrupt
			default:
				// Propagate the signal to the child process
				runner.Signal(s)
			}
		case <-cli.stopCh:
			return ExitCodeOK
		}
	}
}

// stop is used internally to shutdown a running CLI
func (cli *CLI) stop() {
	cli.Lock()
	defer cli.Unlock()

	if cli.stopped {
		return
	}

	close(cli.stopCh)
	cli.stopped = true
}

// ParseFlags is a helper function for parsing command line flags using Go's
// Flag library. This is extracted into a helper to keep the main function
// small, but it also makes writing tests for parsing command line arguments
// much easier and cleaner.
func (cli *CLI) ParseFlags(args []string) (
	*config.Config, []string, bool, bool, error,
) {
	var dry, isVersion bool

	c := config.DefaultConfig()

	if s := os.Getenv("CT_LOCAL_CONFIG"); s != "" {
		envConfig, err := config.Parse(s)
		if err != nil {
			return nil, nil, false, false, err
		}
		c = c.Merge(envConfig)
	}

	// configPaths stores the list of configuration paths on disk
	configPaths := make([]string, 0, 6)

	// Parse the flags and options
	flags := flag.NewFlagSet(version.Name, flag.ContinueOnError)
	flags.SetOutput(io.Discard)
	flags.Usage = func() {}

	flags.Var((funcVar)(func(s string) error {
		configPaths = append(configPaths, s)
		return nil
	}), "config", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.Address = config.String(s)
		return nil
	}), "consul-addr", "")

	flags.Var((funcVar)(func(s string) error {
		a, err := config.ParseAuthConfig(s)
		if err != nil {
			return err
		}
		c.Consul.Auth = a
		return nil
	}), "consul-auth", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Consul.Retry.Enabled = config.Bool(b)
		return nil
	}), "consul-retry", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.Consul.Retry.Attempts = config.Int(i)
		return nil
	}), "consul-retry-attempts", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Retry.Backoff = config.TimeDuration(d)
		return nil
	}), "consul-retry-backoff", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Retry.MaxBackoff = config.TimeDuration(d)
		return nil
	}), "consul-retry-max-backoff", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Consul.SSL.Enabled = config.Bool(b)
		return nil
	}), "consul-ssl", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.SSL.CaCert = config.String(s)
		return nil
	}), "consul-ssl-ca-cert", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.SSL.CaPath = config.String(s)
		return nil
	}), "consul-ssl-ca-path", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.SSL.Cert = config.String(s)
		return nil
	}), "consul-ssl-cert", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.SSL.Key = config.String(s)
		return nil
	}), "consul-ssl-key", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.SSL.ServerName = config.String(s)
		return nil
	}), "consul-ssl-server-name", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Consul.SSL.Verify = config.Bool(b)
		return nil
	}), "consul-ssl-verify", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.Token = config.String(s)
		return nil
	}), "consul-token", "")

	flags.Var((funcVar)(func(s string) error {
		c.Consul.TokenFile = config.String(s)
		return nil
	}), "consul-token-file", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Transport.DialKeepAlive = config.TimeDuration(d)
		return nil
	}), "consul-transport-dial-keep-alive", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Transport.DialTimeout = config.TimeDuration(d)
		return nil
	}), "consul-transport-dial-timeout", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Consul.Transport.DisableKeepAlives = config.Bool(b)
		return nil
	}), "consul-transport-disable-keep-alives", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.Consul.Transport.MaxIdleConnsPerHost = config.Int(i)
		return nil
	}), "consul-transport-max-idle-conns-per-host", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Transport.TLSHandshakeTimeout = config.TimeDuration(d)
		return nil
	}), "consul-transport-tls-handshake-timeout", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Dedup.Enabled = config.Bool(b)
		return nil
	}), "dedup", "")

	flags.Var((funcVar)(func(s string) error {
		c.DefaultDelims.Left = config.String(s)
		return nil
	}), "default-left-delimiter", "")

	flags.Var((funcVar)(func(s string) error {
		c.DefaultDelims.Right = config.String(s)
		return nil
	}), "default-right-delimiter", "")

	flags.BoolVar(&dry, "dry", false, "")

	flags.Var((funcVar)(func(s string) error {
		c.Exec.Enabled = config.Bool(true)
		c.Exec.Command = []string{s}
		return nil
	}), "exec", "")

	flags.Var((funcVar)(func(s string) error {
		sig, err := signals.Parse(s)
		if err != nil {
			return err
		}
		c.Exec.KillSignal = config.Signal(sig)
		return nil
	}), "exec-kill-signal", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Exec.KillTimeout = config.TimeDuration(d)
		return nil
	}), "exec-kill-timeout", "")

	flags.Var((funcVar)(func(s string) error {
		sig, err := signals.Parse(s)
		if err != nil {
			return err
		}
		c.Exec.ReloadSignal = config.Signal(sig)
		return nil
	}), "exec-reload-signal", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Exec.Splay = config.TimeDuration(d)
		return nil
	}), "exec-splay", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Exec.Env.Pristine = config.Bool(b)
		return nil
	}), "exec-env-pristine", "")

	flags.Var((funcVar)(func(s string) error {
		c.Exec.Env.Custom = append(c.Exec.Env.Custom, s)
		return nil
	}), "exec-env-custom", "")

	flags.Var((funcVar)(func(s string) error {
		c.Exec.Env.Allowlist = append(c.Exec.Env.Allowlist, s)
		return nil
	}), "exec-env-allowlist", "")

	flags.Var((funcVar)(func(s string) error {
		c.Exec.Env.Denylist = append(c.Exec.Env.Denylist, s)
		return nil
	}), "exec-env-denylist", "")

	flags.Var((funcVar)(func(s string) error {
		sig, err := signals.Parse(s)
		if err != nil {
			return err
		}
		c.KillSignal = config.Signal(sig)
		return nil
	}), "kill-signal", "")

	flags.Var((funcVar)(func(s string) error {
		c.LogLevel = config.String(s)
		return nil
	}), "log-level", "")

	flags.Var((funcVar)(func(s string) error {
		c.FileLog.LogFilePath = config.String(s)
		return nil
	}), "log-file", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.FileLog.LogRotateBytes = config.Int(i)
		return nil
	}), "log-rotate-bytes", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.FileLog.LogRotateDuration = config.TimeDuration(d)
		return nil
	}), "log-rotate-duration", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.FileLog.LogRotateMaxFiles = config.Int(i)
		return nil
	}), "log-rotate-max-files", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.MaxStale = config.TimeDuration(d)
		return nil
	}), "max-stale", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Once = *(config.Bool(b))
		return nil
	}), "once", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.ParseOnly = *(config.Bool(b))
		return nil
	}), "parse-only", "")

	flags.Var((funcVar)(func(s string) error {
		c.PidFile = config.String(s)
		return nil
	}), "pid-file", "")

	flags.Var((funcVar)(func(s string) error {
		sig, err := signals.Parse(s)
		if err != nil {
			return err
		}
		c.ReloadSignal = config.Signal(sig)
		return nil
	}), "reload-signal", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Consul.Retry.Backoff = config.TimeDuration(d)
		return nil
	}), "retry", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Syslog.Enabled = config.Bool(b)
		return nil
	}), "syslog", "")

	flags.Var((funcVar)(func(s string) error {
		c.Syslog.Facility = config.String(s)
		return nil
	}), "syslog-facility", "")

	flags.Var((funcVar)(func(s string) error {
		c.Syslog.Name = config.String(s)
		return nil
	}), "syslog-name", "")

	flags.Var((funcVar)(func(s string) error {
		t, err := config.ParseTemplateConfig(s)
		if err != nil {
			return err
		}
		*c.Templates = append(*c.Templates, t)
		return nil
	}), "template", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.TemplateErrFatal = config.Bool(b)
		return nil
	}), "template-error-fatal", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.Address = config.String(s)
		return nil
	}), "vault-addr", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.RenewToken = config.Bool(b)
		return nil
	}), "vault-renew-token", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.Retry.Enabled = config.Bool(b)
		return nil
	}), "vault-retry", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.Vault.Retry.Attempts = config.Int(i)
		return nil
	}), "vault-retry-attempts", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.Retry.Backoff = config.TimeDuration(d)
		return nil
	}), "vault-retry-backoff", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.Retry.MaxBackoff = config.TimeDuration(d)
		return nil
	}), "vault-retry-max-backoff", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.ClientUserAgent = config.String(s)
		return nil
	}), "vault-client-user-agent", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.SSL.Enabled = config.Bool(b)
		return nil
	}), "vault-ssl", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.SSL.CaCert = config.String(s)
		return nil
	}), "vault-ssl-ca-cert", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.SSL.CaPath = config.String(s)
		return nil
	}), "vault-ssl-ca-path", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.SSL.Cert = config.String(s)
		return nil
	}), "vault-ssl-cert", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.SSL.Key = config.String(s)
		return nil
	}), "vault-ssl-key", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.SSL.ServerName = config.String(s)
		return nil
	}), "vault-ssl-server-name", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.SSL.Verify = config.Bool(b)
		return nil
	}), "vault-ssl-verify", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.Transport.DialKeepAlive = config.TimeDuration(d)
		return nil
	}), "vault-transport-dial-keep-alive", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.Transport.DialTimeout = config.TimeDuration(d)
		return nil
	}), "vault-transport-dial-timeout", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.Transport.DisableKeepAlives = config.Bool(b)
		return nil
	}), "vault-transport-disable-keep-alives", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.Vault.Transport.MaxIdleConnsPerHost = config.Int(i)
		return nil
	}), "vault-transport-max-idle-conns-per-host", "")

	flags.Var((funcIntVar)(func(i int) error {
		c.Vault.Transport.MaxConnsPerHost = config.Int(i)
		return nil
	}), "vault-transport-max-conns-per-host", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.Transport.TLSHandshakeTimeout = config.TimeDuration(d)
		return nil
	}), "vault-transport-tls-handshake-timeout", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.Token = config.String(s)
		return nil
	}), "vault-token", "")

	flags.Var((funcVar)(func(s string) error {
		c.Vault.VaultAgentTokenFile = config.String(s)
		return nil
	}), "vault-agent-token-file", "")

	flags.Var((funcBoolVar)(func(b bool) error {
		c.Vault.UnwrapToken = config.Bool(b)
		return nil
	}), "vault-unwrap-token", "")

	flags.Var((funcDurationVar)(func(d time.Duration) error {
		c.Vault.DefaultLeaseDuration = config.TimeDuration(d)
		return nil
	}), "vault-default-lease-duration", "")

	flags.Var((funcVar)(func(s string) error {
		w, err := config.ParseWaitConfig(s)
		if err != nil {
			return err
		}
		c.Wait = w
		return nil
	}), "wait", "")

	flags.BoolVar(&isVersion, "v", false, "")
	flags.BoolVar(&isVersion, "version", false, "")

	// If there was a parser error, stop
	if err := flags.Parse(args); err != nil {
		return nil, nil, false, false, err
	}

	// Error if extra arguments are present
	args = flags.Args()
	if len(args) > 0 {
		return nil, nil, false, false, fmt.Errorf("cli: extra args: %q", args)
	}

	return c, configPaths, dry, isVersion, nil
}

// loadConfigs loads the configuration from the list of paths. The optional
// configuration is the list of overrides to apply at the very end, taking
// precedence over any configurations that were loaded from the paths. If any
// errors occur when reading or parsing those sub-configs, it is returned.
func loadConfigs(paths []string, o *config.Config) (*config.Config, error) {
	finalC := config.DefaultConfig()

	for _, path := range paths {
		c, err := config.FromPath(path)
		if err != nil {
			return nil, err
		}

		finalC = finalC.Merge(c)
	}

	finalC = finalC.Merge(o)
	if o.TemplateErrFatal != nil {
		for _, tmpl := range *finalC.Templates {
			tmpl.ErrFatal = o.TemplateErrFatal
		}
	}
	finalC.Finalize()
	return finalC, nil
}

// logError logs an error message and then returns the given status.
func logError(err error, status int) int {
	log.Printf("[ERR] (cli) %s", err)
	return status
}

func (cli *CLI) setup(conf *config.Config) (*config.Config, error) {
	if err := logging.Setup(&logging.Config{
		Level:             config.StringVal(conf.LogLevel),
		LogFilePath:       config.StringVal(conf.FileLog.LogFilePath),
		LogRotateBytes:    config.IntVal(conf.FileLog.LogRotateBytes),
		LogRotateDuration: config.TimeDurationVal(conf.FileLog.LogRotateDuration),
		LogRotateMaxFiles: config.IntVal(conf.FileLog.LogRotateMaxFiles),
		Syslog:            config.BoolVal(conf.Syslog.Enabled),
		SyslogFacility:    config.StringVal(conf.Syslog.Facility),
		SyslogName:        config.StringVal(conf.Syslog.Name),
		Writer:            cli.errStream,
	}); err != nil {
		return nil, err
	}

	return conf, nil
}

const usage = `Usage: %s [options]

  Watches a series of templates on the file system, writing new changes when
  Consul is updated. It runs until an interrupt is received unless the -once
  flag is specified.

Options:

  -config=<path>
      Sets the path to a configuration file or folder on disk. This can be
      specified multiple times to load multiple files or folders. If multiple
      values are given, they are merged left-to-right, and CLI arguments take
      the top-most precedence.

  -consul-addr=<address>
      Sets the address of the Consul instance

  -consul-auth=<username[:password]>
      Set the basic authentication username and password for communicating
      with Consul.

  -consul-retry
      Use retry logic when communication with Consul fails

  -consul-retry-attempts=<int>
      The number of attempts to use when retrying failed communications

  -consul-retry-backoff=<duration>
      The base amount to use for the backoff duration. This number will be
      increased exponentially for each retry attempt.

  -consul-retry-max-backoff=<duration>
      The maximum limit of the retry backoff duration. Default is one minute.
      0 means infinite. The backoff will increase exponentially until given value.

  -consul-ssl
      Use SSL when connecting to Consul

  -consul-ssl-ca-cert=<string>
      Validate server certificate against this CA certificate file list

  -consul-ssl-ca-path=<string>
      Sets the path to the CA to use for TLS verification

  -consul-ssl-cert=<string>
      SSL client certificate to send to server

  -consul-ssl-key=<string>
      SSL/TLS private key for use in client authentication key exchange

  -consul-ssl-server-name=<string>
      Sets the name of the server to use when validating TLS.

  -consul-ssl-verify
      Verify certificates when connecting via SSL

  -consul-token=<token>
      Sets the Consul API token

  -consul-token-file=<path>
      Sets the path to a file containing the Consul API token

  -consul-transport-dial-keep-alive=<duration>
      Sets the amount of time to use for keep-alives

  -consul-transport-dial-timeout=<duration>
      Sets the amount of time to wait to establish a connection

  -consul-transport-disable-keep-alives
      Disables keep-alives (this will impact performance)

  -consul-transport-max-idle-conns-per-host=<int>
      Sets the maximum number of idle connections to permit per host

  -consul-transport-tls-handshake-timeout=<duration>
      Sets the handshake timeout

  -dedup
      Enable de-duplication mode - reduces load on Consul when many instances of
      Consul Template are rendering a common template

  -default-left-delimiter
      The default left delimiter for templating

  -default-right-delimiter
      The default right delimiter for templating

  -dry
      Print generated templates to stdout instead of rendering

  -exec=<command>
      Enable exec mode to run as a supervisor-like process - the given command
      will receive all signals provided to the parent process and will receive a
      signal when templates change

  -exec-kill-signal=<signal>
      Signal to send when gracefully killing the process

  -exec-kill-timeout=<duration>
      Amount of time to wait before force-killing the child

  -exec-reload-signal=<signal>
      Signal to send when a reload takes place

  -exec-splay=<duration>
      Amount of time to wait before sending signals

  -exec-env-pristine
      Child process should not inherit the parent process's environment.

  -exec-env-custom
      Additional custom environment variables to inject into the child's
      runtime. Even if pristine, allowlist, or denylist is specified, all
      values in this option are given to the child process. Can be specified
      multiple times.

  -exec-env-allowlist
      List of environment variables to exclusively include in the list of
      environment variables exposed to the child process. Only those environment
      variables matching the given patterns are exposed to the child process.
      Wildcards are permitted. Can be specified multiple times.

  -exec-env-denylist
      List of environment variables to exclusively prohibit in the list of
      environment variables exposed to the child process. The values in this
      option take precedence over the values in the allowlist.
      Wildcards are permitted. Can be specified multiple times.

  -kill-signal=<signal>
      Signal to listen to gracefully terminate the process

  -log-level=<level>
      Set the logging level - values are "debug", "info", "warn", and "err"

  -max-stale=<duration>
      Set the maximum staleness and allow stale queries to Consul which will
      distribute work among all servers instead of just the leader

  -once
      Do not run the process as a daemon. This disables wait/quiescence timers.

  -parse-only
      Do not process templates. Parse them for structure.

  -pid-file=<path>
      Path on disk to write the PID of the process

  -reload-signal=<signal>
      Signal to listen to reload configuration

  -retry=<duration>
      The amount of time to wait if Consul returns an error when communicating
      with the API

  -syslog
      Send the output to syslog instead of standard error and standard out. The
      syslog facility defaults to LOCAL0 and can be changed using a
      configuration file

  -syslog-facility=<facility>
      Set the facility where syslog should log - if this attribute is supplied,
      the -syslog flag must also be supplied

  -syslog-name=<name>
      Set the name of the application which will appear in syslog, if this
      attribute is supplied, the -syslog flag must also be supplied

  -template=<template>
      Adds a new template to watch on disk in the format 'in:out(:command)'

  -template-error-fatal=<bool>
      Control whether template errors cause consul-template to immediately exit.
      This overrides the per-template setting.

  -vault-addr=<address>
      Sets the address of the Vault server

  -vault-renew-token
      Periodically renew the provided Vault API token - this defaults to "true"
      and will renew the token at half of the lease duration

  -vault-retry
      Use retry logic when communication with Vault fails

  -vault-retry-attempts=<int>
      The number of attempts to use when retrying failed communications

  -vault-retry-backoff=<duration>
      The base amount to use for the backoff duration. This number will be
      increased exponentially for each retry attempt.

  -vault-retry-max-backoff=<duration>
      The maximum limit of the retry backoff duration. Default is one minute.
      0 means infinite. The backoff will increase exponentially until given value.

  -vault-ssl
      Specifies whether communications with Vault should be done via SSL

  -vault-ssl-ca-cert=<string>
      Sets the path to the CA certificate to use for TLS verification

  -vault-ssl-ca-path=<string>
      Sets the path to the CA to use for TLS verification

  -vault-ssl-cert=<string>
      Sets the path to the certificate to use for TLS verification

  -vault-ssl-key=<string>
      Sets the path to the key to use for TLS verification

  -vault-ssl-server-name=<string>
      Sets the name of the server to use when validating TLS.

  -vault-ssl-verify
      Enable SSL verification for communications with Vault.

  -vault-token=<token>
      Sets the Vault API token

  -vault-agent-token-file=<token-file>
      File to read Vault API token from.

  -vault-transport-dial-keep-alive=<duration>
      Sets the amount of time to use for keep-alives

  -vault-transport-dial-timeout=<duration>
      Sets the amount of time to wait to establish a connection

  -vault-transport-disable-keep-alives
      Disables keep-alives (this will impact performance)

  -vault-transport-max-idle-conns-per-host=<int>
      Sets the maximum number of idle connections to permit per host

  -vault-transport-max-conns-per-host=<int>
      Sets the maximum number of total connections to permit per host

  -vault-transport-tls-handshake-timeout=<duration>
      Sets the handshake timeout

  -vault-unwrap-token
      Unwrap the provided Vault API token (see Vault documentation for more
      information on this feature)

  -vault-default-lease-duration=<duration>
	  configures the default lease duration when not explicitly
	  set by vault

  -wait=<duration>
      Sets the 'min(:max)' amount of time to wait before writing a template (and
      triggering a command)

  -v, -version
      Print the version of this daemon
`