cmd

var RootCmd = &cobra.Command{
	Use:   buildtime.PROGNAME,
	Short: buildtime.PROGNAME + `pre-faults PostgreSQL heap pages based on WAL files`,
	Long: `
PostgreSQL's WAL-receiver applies WAL files in serial.  This design implicitly
assumes that the heap page required to apply the WAL entry is within the
operating system's filesystem cache.  If the filesystem cache does not contain
the necessary heap page, the PostgreSQL WAL apply process will be block while
the OS faults in the page from its storage.  For large working sets of data or
when the filesystem cache is cold, this is problematic for streaming replicas
because they will lag and fall behind.

` + buildtime.PROGNAME + `(1) mitigates this serially scheduled IO problem by
reading WAL entries via pg_xlogdump(1) and performing parallel pread(2) calls in
order to "pre-fault" the page into the OS's filesystem cache so that when the
PostgreSQL WAL receiver goes to apply a WAL entry to its heap, the page is
already loaded into the OS'es filesystem cache.

`,

	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {

		switch logLevel := strings.ToUpper(viper.GetString(config.KeyLogLevel)); logLevel {
		case "DEBUG":
			zerolog.SetGlobalLevel(zerolog.DebugLevel)
		case "INFO":
			zerolog.SetGlobalLevel(zerolog.InfoLevel)
		case "WARN":
			zerolog.SetGlobalLevel(zerolog.WarnLevel)
		case "ERROR":
			zerolog.SetGlobalLevel(zerolog.ErrorLevel)
		case "FATAL":
			zerolog.SetGlobalLevel(zerolog.FatalLevel)
		default:

			return fmt.Errorf("unsupported error level: %q (supported levels: %s)", logLevel,
				strings.Join([]string{"DEBUG", "INFO", "WARN", "ERROR", "FATAL"}, " "))
		}

		go func() {
			if !viper.GetBool(config.KeyGoogleAgentEnable) {
				log.Debug().Msg("gops(1) agent disabled by request")
				return
			}

			log.Debug().Msg("starting gops(1) agent")
			if err := agent.Listen(nil); err != nil {
				log.Fatal().Err(err).Msg("unable to start the gops(1) agent thread")
			}
		}()

		return nil
	},
}