Code Standard

The code standard for development.

This doc describes the code standards and suggestion for crane project, mainly for new contributor of the project

import need to be organized

import should be categorized with blank line as system imports, community imports and crane apis and crane imports, like the following example

import (

	vpa ""

logs standard

  • logs are required for troubleshooting purpose
  • log message should always start with capital letter
  • log message should be a complete sentence that contains enough context, for example: object key, action, parameters, status, error message
  • by default, you don’t need to set log level
  • set 4 for debug level.
  • set 6 for more detail debug level.
  • set 10 for massive data log level.
  • can use klog.KObj() to contain object key to let we know which object the message is printed for
klog.Infof("Failed to setup webhook %s", "value")
klog.V(4).Infof("Debug info %s", "value")
klog.Errorf("Failed to get scale, ehpa %s error %v", klog.KObj(ehpa), err)
klog.ErrorDepth(5, fmt.Errorf("failed to get ehpa %s: %v", klog.KObj(ehpa), err))

event is needed for critical reconcile loop

  • event is to let user know what happens on serverside, only print info we want user to know
  • consider failure paths and success paths
  • event do not need the object key
c.Recorder.Event(ehpa, v1.EventTypeWarning, "FailedGetSubstitute", err.Error())


  • every interface should have comments to clarify
  • comment should be a complete sentence
// Interface is a source of monitoring metric that provides metrics that can be used for
// prediction, such as 'cpu usage', 'memory footprint', 'request per second (qps)', etc.
type Interface interface {
	// GetTimeSeries returns the metric time series that meet the given
	// conditions from the specified time range.
	GetTimeSeries(metricName string, Conditions []common.QueryCondition,
		startTime time.Time, endTime time.Time, step time.Duration) ([]*common.TimeSeries, error)

	// GetLatestTimeSeries returns the latest metric values that meet the given conditions.
	GetLatestTimeSeries(metricName string, Conditions []common.QueryCondition) ([]*common.TimeSeries, error)

	// QueryTimeSeries returns the time series based on a promql like query string.
	QueryTimeSeries(queryExpr string, startTime time.Time, endTime time.Time, step time.Duration) ([]*common.TimeSeries, error)

	// QueryLatestTimeSeries returns the latest metric values that meet the given query.
	QueryLatestTimeSeries(queryExpr string) ([]*common.TimeSeries, error)


  • function name should clarify what do this function do, for example: verb + noun
  • similar functions should be refactored, merge or divide them
  • common functions should move to common folder like utils


  • variable name should clarify what do this variable does, better not use too short name and too simple name
  • better to use more meaningful variable name for tmp variable, for example: foo loop

folder and file

  • folder name should be letter with lower case and number
  • file name should be letter and number and _

unit test

  • Test-driven developing
  • Complex function that include condition decide should add unit test for it

don’t forget to run make fmt before you submit code