code: func collectGlobalMetrics(c context.Context) {
  	version, err := module.DefaultVersion(c, "")
  	if err != nil {
  		logging.Errorf(c, "Error getting default appengine version: %s", err)
  		defaultVersion.Set(c, "(unknown)")
  	} else {
  		defaultVersion.Set(c, version)
  	}
  }
docs: // collectGlobalMetrics populates service-global metrics.
  //
  // Called by tsmon from inside /housekeeping cron handler. Metrics reported must
  // not depend on the state of the particular process that happens to report
  // them.