submit-queue.go

/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package mungers

import (
	"bytes"
	"encoding/json"
	"fmt"
	"math"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"k8s.io/kubernetes/pkg/util"

	"k8s.io/contrib/mungegithub/admin"
	"k8s.io/contrib/mungegithub/features"
	"k8s.io/contrib/mungegithub/github"
	"k8s.io/contrib/mungegithub/mungers/e2e"
	fake_e2e "k8s.io/contrib/mungegithub/mungers/e2e/fake"
	"k8s.io/contrib/mungegithub/mungers/mungerutil"
	"k8s.io/contrib/mungegithub/mungers/shield"
	"k8s.io/contrib/test-utils/utils"

	"github.com/NYTimes/gziphandler"
	"github.com/golang/glog"
	githubapi "github.com/google/go-github/github"
	"github.com/spf13/cobra"
)

const (
	lgtmLabel                      = "lgtm"
	retestNotRequiredLabel         = "retest-not-required"
	retestNotRequiredDocsOnlyLabel = "retest-not-required-docs-only"
	doNotMergeLabel                = "do-not-merge"
	claYesLabel                    = "cla: yes"
	claNoLabel                     = "cla: no"
	cncfClaYesLabel                = "cncf-cla: yes"
	cncfClaNoLabel                 = "cncf-cla: no"
	claHumanLabel                  = "cla: human-approved"
	sqContext                      = "Submit Queue"

	retestNotRequiredMergePriority = -1 // used for retestNotRequiredLabel
	defaultMergePriority           = 3  // when an issue is unlabeled

	githubE2EPollTime = 30 * time.Second
)

var (
	_ = fmt.Print
	// This MUST cause a RETEST of everything in the sq.RequiredRetestContexts
	retestBody = fmt.Sprintf("@%s test this [submit-queue is verifying that this PR is safe to merge]", jenkinsBotName)
)

type submitStatus struct {
	Time time.Time
	statusPullRequest
	Reason string
}

type statusPullRequest struct {
	Number    int
	URL       string
	Title     string
	Login     string
	AvatarURL string
	Additions int
	Deletions int
	ExtraInfo []string
}

type e2eQueueStatus struct {
	E2ERunning *statusPullRequest
	E2EQueue   []*statusPullRequest
}

type submitQueueStatus struct {
	PRStatus map[string]submitStatus
}

// Information about the e2e test health. Call updateHealth on the SubmitQueue
// at roughly constant intervals to keep this up to date. The mergeable fraction
// of time for the queue as a whole and the individual jobs will then be
// NumStable[PerJob] / TotalLoops.
type submitQueueHealth struct {
	TotalLoops       int
	NumStable        int
	NumStablePerJob  map[string]int
	MergePossibleNow bool
}

// Generate health information using a queue of healthRecords. The bools are
// true for stable and false otherwise.
type healthRecord struct {
	Time    time.Time
	Overall bool
	Jobs    map[string]bool
}

// information about the sq itself including how fast things are merging and
// how long since the last merge
type submitQueueStats struct {
	Added              int // Number of items added to the queue since restart
	FlakesIgnored      int
	Initialized        bool // true if we've made at least one complete pass
	InstantMerges      int  // Number of commits without retests required
	LastMergeTime      time.Time
	MergeRate          float64
	MergesSinceRestart int
	Removed            int // Number of items dequeued since restart
	RetestsAvoided     int
	StartTime          time.Time
	Tested             int // Number of e2e tests completed
}

// pull-request that has been tested as successful, but interrupted because head flaked
type submitQueueInterruptedObject struct {
	obj *github.MungeObject
	// If these two items match when we're about to kick off a retest, it's safe to skip the retest.
	interruptedMergeHeadSHA string
	interruptedMergeBaseSHA string
}

// Contains metadata about this instance of the submit queue such as URLs.
// Consumed by the template system.
type submitQueueMetadata struct {
	ProjectName string

	ChartUrl    string
	HistoryUrl  string
	RepoPullUrl string
}

// SubmitQueue will merge PR which meet a set of requirements.
//  PR must have LGTM after the last commit
//  PR must have passed all github CI checks
//  The google internal jenkins instance must be passing the BlockingJobNames e2e tests
type SubmitQueue struct {
	githubConfig        *github.Config
	BlockingJobNames    []string
	NonBlockingJobNames []string
	PresubmitJobNames   []string
	WeakStableJobNames  []string

	// If FakeE2E is true, don't try to connect to JenkinsHost, all jobs are passing.
	FakeE2E bool

	Committers             string
	RequiredStatusContexts []string
	DoNotMergeMilestones   []string

	RequiredRetestContexts []string
	RetestBody             string
	Metadata               submitQueueMetadata
	AdminPort              int

	sync.Mutex
	lastPRStatus  map[string]submitStatus
	prStatus      map[string]submitStatus // protected by sync.Mutex
	statusHistory []submitStatus          // protected by sync.Mutex

	clock         util.Clock
	startTime     time.Time // when the queue started (duh)
	lastMergeTime time.Time
	totalMerges   int32
	mergeRate     float64 // per 24 hours
	loopStarts    int32   // if > 1, then we must have made a complete pass.

	githubE2ERunning  *github.MungeObject         // protect by sync.Mutex!
	githubE2EQueue    map[int]*github.MungeObject // protected by sync.Mutex!
	githubE2EPollTime time.Duration
	lgtmTimeCache     *mungerutil.LabelTimeCache

	lastE2EStable bool // was e2e stable last time they were checked, protect by sync.Mutex
	e2e           e2e.E2ETester

	interruptedObj *submitQueueInterruptedObject
	flakesIgnored  int32 // Increments for each merge while 1+ job is flaky
	instantMerges  int32 // Increments whenever we commit without retesting
	prsAdded       int32 // Increments whenever an items queues
	prsRemoved     int32 // Increments whenever an item dequeues
	prsTested      int32 // Number of prs that completed second testing
	retestsAvoided int32 // Increments whenever we skip due to head not changing.

	health        submitQueueHealth
	healthHistory []healthRecord

	emergencyMergeStopFlag int32

	features *features.Features
}

func init() {
	clock := util.RealClock{}
	sq := &SubmitQueue{
		clock:          clock,
		startTime:      clock.Now(),
		lastMergeTime:  clock.Now(),
		lastE2EStable:  true,
		prStatus:       map[string]submitStatus{},
		lastPRStatus:   map[string]submitStatus{},
		githubE2EQueue: map[int]*github.MungeObject{},
	}
	RegisterMungerOrDie(sq)
	RegisterStaleComments(sq)
}

// Name is the name usable in --pr-mungers
func (sq *SubmitQueue) Name() string { return "submit-queue" }

// RequiredFeatures is a slice of 'features' that must be provided
func (sq *SubmitQueue) RequiredFeatures() []string {
	return []string{features.GCSFeature, features.TestOptionsFeature}
}

func (sq *SubmitQueue) emergencyMergeStop() bool {
	return atomic.LoadInt32(&sq.emergencyMergeStopFlag) != 0
}

func (sq *SubmitQueue) setEmergencyMergeStop(stopMerges bool) {
	if stopMerges {
		atomic.StoreInt32(&sq.emergencyMergeStopFlag, 1)
	} else {
		atomic.StoreInt32(&sq.emergencyMergeStopFlag, 0)
	}
}

// EmergencyStopHTTP sets the emergency stop flag. It expects the path of
// req.URL to contain either "emergency/stop", "emergency/resume", or "emergency/status".
func (sq *SubmitQueue) EmergencyStopHTTP(res http.ResponseWriter, req *http.Request) {
	switch {
	case strings.Contains(req.URL.Path, "emergency/stop"):
		sq.setEmergencyMergeStop(true)
	case strings.Contains(req.URL.Path, "emergency/resume"):
		sq.setEmergencyMergeStop(false)
	case strings.Contains(req.URL.Path, "emergency/status"):
	default:
		http.NotFound(res, req)
		return
	}
	sq.serve(sq.marshal(struct{ EmergencyInProgress bool }{sq.emergencyMergeStop()}), res, req)
}

func round(num float64) int {
	return int(num + math.Copysign(0.5, num))
}

func toFixed(num float64) float64 {
	output := math.Pow(10, float64(3))
	return float64(round(num*output)) / output
}

// This is the calculation of the exponential smoothing factor. It tries to
// make sure that if we get lots of fast merges we don't race the 'daily'
// avg really high really fast. But more importantly it means that if merges
// start going slowly the 'daily' average will get pulled down a lot by one
// slow merge instead of requiring numerous merges to get pulled down
func getSmoothFactor(dur time.Duration) float64 {
	hours := dur.Hours()
	smooth := .155*math.Log(hours) + .422
	if smooth < .1 {
		return .1
	}
	if smooth > .999 {
		return .999
	}
	return smooth
}

// This calculates an exponentially smoothed merge Rate based on the formula
//   newRate = (1-smooth)oldRate + smooth*newRate
// Which is really great and simple for constant time series data. But of course
// ours isn't time series data so I vary the smoothing factor based on how long
// its been since the last entry. See the comments on the `getSmoothFactor` for
// a discussion of why.
//    This whole thing was dreamed up by eparis one weekend via a combination
//    of guess-and-test and intuition. Someone who knows about this stuff
//    is likely to laugh at the naivete. Point him to where someone intelligent
//    has thought about this stuff and he will gladly do something smart.
// Merges that took less than 5 minutes are ignored completely for the rate
// calculation.
func calcMergeRate(oldRate float64, last, now time.Time) float64 {
	since := now.Sub(last)
	if since <= 5*time.Minute {
		// retest-not-required PR merges shouldn't affect our best
		// guess about the rate.
		return oldRate
	}
	var rate float64
	if since == 0 {
		rate = 96
	} else {
		rate = 24.0 * time.Hour.Hours() / since.Hours()
	}
	smoothingFactor := getSmoothFactor(since)
	mergeRate := ((1.0 - smoothingFactor) * oldRate) + (smoothingFactor * rate)
	return toFixed(mergeRate)
}

// Updates a smoothed rate at which PRs are merging per day.
// Updates merge stats. Should be called once for every merge.
func (sq *SubmitQueue) updateMergeRate() {
	now := sq.clock.Now()
	sq.mergeRate = calcMergeRate(sq.mergeRate, sq.lastMergeTime, now)

	// Update stats
	atomic.AddInt32(&sq.totalMerges, 1)
	sq.lastMergeTime = now
}

// This calculated the smoothed merge rate BUT it looks at the time since
// the last merge vs 'Now'. If we have not passed the next 'expected' time
// for a merge this just returns previous calculations. If 'Now' is later
// than we would expect given the existing mergeRate then pretend a merge
// happened right now and return the new merge rate. This way the merge rate
// is lower even if no merge has happened in a long time.
func (sq *SubmitQueue) calcMergeRateWithTail() float64 {
	now := sq.clock.Now()

	if sq.mergeRate == 0 {
		return 0
	}
	// Figure out when we think the next merge would happen given the history
	next := time.Duration(24/sq.mergeRate*time.Hour.Hours()) * time.Hour
	expectedMergeTime := sq.lastMergeTime.Add(next)

	// If we aren't there yet, just return the history
	if !now.After(expectedMergeTime) {
		return sq.mergeRate
	}

	// Pretend as though a merge happened right now to pull down the rate
	return calcMergeRate(sq.mergeRate, sq.lastMergeTime, now)
}

// Given a string slice with a single empty value this function will return a empty slice.
// This is extremely useful for StringSlice flags, so the user can do --flag="" and instead
// of getting []string{""} they will get []string{}
func cleanStringSlice(in []string) []string {
	if len(in) == 1 && len(in[0]) == 0 {
		return []string{}
	}
	return in
}

// Initialize will initialize the munger
func (sq *SubmitQueue) Initialize(config *github.Config, features *features.Features) error {
	sq.features = features
	sq.RequiredRetestContexts = features.TestOptions.RequiredRetestContexts
	return sq.internalInitialize(config, features, "")
}

// internalInitialize will initialize the munger.
// if overrideUrl is specified, will create testUtils
func (sq *SubmitQueue) internalInitialize(config *github.Config, features *features.Features, overrideUrl string) error {
	sq.Lock()
	defer sq.Unlock()

	// Clean up all of our flags which we wish --flag="" to mean []string{}
	sq.BlockingJobNames = cleanStringSlice(sq.BlockingJobNames)
	sq.NonBlockingJobNames = cleanStringSlice(sq.NonBlockingJobNames)
	sq.PresubmitJobNames = cleanStringSlice(sq.PresubmitJobNames)
	sq.WeakStableJobNames = cleanStringSlice(sq.WeakStableJobNames)
	sq.RequiredStatusContexts = cleanStringSlice(sq.RequiredStatusContexts)
	sq.RequiredRetestContexts = cleanStringSlice(sq.RequiredRetestContexts)
	sq.DoNotMergeMilestones = cleanStringSlice(sq.DoNotMergeMilestones)
	sq.Metadata.RepoPullUrl = fmt.Sprintf("https://github.com/%s/%s/pulls/", config.Org, config.Project)
	sq.Metadata.ProjectName = strings.Title(config.Project)
	sq.githubConfig = config

	// TODO: This is not how injection for tests should work.
	if sq.FakeE2E {
		sq.e2e = &fake_e2e.FakeE2ETester{
			JobNames:           sq.BlockingJobNames,
			WeakStableJobNames: sq.WeakStableJobNames,
		}
	} else {
		var gcs *utils.Utils
		if overrideUrl != "" {
			gcs = utils.NewTestUtils("bucket", "logs", overrideUrl)
		} else {
			gcs = utils.NewWithPresubmitDetection(
				sq.features.GCSInfo.BucketName, sq.features.GCSInfo.LogDir,
				sq.features.GCSInfo.PullKey, sq.features.GCSInfo.PullLogDir,
			)
		}

		sq.e2e = (&e2e.RealE2ETester{
			BlockingJobNames:     sq.BlockingJobNames,
			NonBlockingJobNames:  sq.NonBlockingJobNames,
			WeakStableJobNames:   sq.WeakStableJobNames,
			BuildStatus:          map[string]e2e.BuildInfo{},
			GoogleGCSBucketUtils: gcs,
		}).Init(admin.Mux)
	}

	sq.lgtmTimeCache = mungerutil.NewLabelTimeCache(lgtmLabel)

	if len(config.Address) > 0 {
		if len(config.WWWRoot) > 0 {
			http.Handle("/", gziphandler.GzipHandler(http.FileServer(http.Dir(config.WWWRoot))))
		}
		http.Handle("/prs", gziphandler.GzipHandler(http.HandlerFunc(sq.servePRs)))
		http.Handle("/history", gziphandler.GzipHandler(http.HandlerFunc(sq.serveHistory)))
		http.Handle("/github-e2e-queue", gziphandler.GzipHandler(http.HandlerFunc(sq.serveGithubE2EStatus)))
		http.Handle("/google-internal-ci", gziphandler.GzipHandler(http.HandlerFunc(sq.serveGoogleInternalStatus)))
		http.Handle("/merge-info", gziphandler.GzipHandler(http.HandlerFunc(sq.serveMergeInfo)))
		http.Handle("/priority-info", gziphandler.GzipHandler(http.HandlerFunc(sq.servePriorityInfo)))
		http.Handle("/health", gziphandler.GzipHandler(http.HandlerFunc(sq.serveHealth)))
		http.Handle("/health.svg", gziphandler.GzipHandler(http.HandlerFunc(sq.serveHealthSVG)))
		http.Handle("/sq-stats", gziphandler.GzipHandler(http.HandlerFunc(sq.serveSQStats)))
		http.Handle("/flakes", gziphandler.GzipHandler(http.HandlerFunc(sq.serveFlakes)))
		http.Handle("/metadata", gziphandler.GzipHandler(http.HandlerFunc(sq.serveMetadata)))
		config.ServeDebugStats("/stats")
		go http.ListenAndServe(config.Address, nil)
	}

	admin.Mux.HandleFunc("/api/emergency/stop", sq.EmergencyStopHTTP)
	admin.Mux.HandleFunc("/api/emergency/resume", sq.EmergencyStopHTTP)
	admin.Mux.HandleFunc("/api/emergency/status", sq.EmergencyStopHTTP)

	if sq.githubE2EPollTime == 0 {
		sq.githubE2EPollTime = githubE2EPollTime
	}

	sq.healthHistory = make([]healthRecord, 0)

	go sq.handleGithubE2EAndMerge()
	go sq.updateGoogleE2ELoop()

	if sq.AdminPort != 0 {
		go http.ListenAndServe(fmt.Sprintf("0.0.0.0:%v", sq.AdminPort), admin.Mux)
	}
	return nil
}

// EachLoop is called at the start of every munge loop
func (sq *SubmitQueue) EachLoop() error {
	sq.Lock()
	sq.updateHealth()
	sq.lastPRStatus = sq.prStatus
	sq.prStatus = map[string]submitStatus{}

	objs := []*github.MungeObject{}
	for _, obj := range sq.githubE2EQueue {
		objs = append(objs, obj)
	}
	sq.Unlock()

	for _, obj := range objs {
		obj.Refresh()
		// This should recheck it and clean up the queue, we don't care about the result
		_ = sq.validForMerge(obj)
	}
	atomic.AddInt32(&sq.loopStarts, 1)
	return nil
}

// AddFlags will add any request flags to the cobra `cmd`
func (sq *SubmitQueue) AddFlags(cmd *cobra.Command, config *github.Config) {
	cmd.Flags().StringSliceVar(&sq.NonBlockingJobNames, "nonblocking-jenkins-jobs", []string{}, "Comma separated list of jobs that don't block merges, but will have status reported and issues filed.")
	cmd.Flags().StringSliceVar(&sq.BlockingJobNames, "jenkins-jobs", []string{}, "Comma separated list of jobs in Jenkins that should block merges if failing.")
	cmd.Flags().StringSliceVar(&sq.PresubmitJobNames, "presubmit-jobs", []string{""}, "Comma separated list of jobs in Jenkins that run presubmit and should have issues filed for flakes.")
	cmd.Flags().StringSliceVar(&sq.WeakStableJobNames, "weak-stable-jobs",
		[]string{},
		"Comma separated list of jobs in Jenkins to use for stability testing that needs only weak success")
	cmd.Flags().StringSliceVar(&sq.RequiredStatusContexts, "required-contexts", []string{}, "Comma separate list of status contexts required for a PR to be considered ok to merge")
	cmd.Flags().StringVar(&sq.RetestBody, "retest-body", retestBody, "message which, when posted to the PR, will cause ALL `required-retest-contexts` to be re-tested")
	cmd.Flags().BoolVar(&sq.FakeE2E, "fake-e2e", false, "Whether to use a fake for testing E2E stability.")
	cmd.Flags().StringSliceVar(&sq.DoNotMergeMilestones, "do-not-merge-milestones", []string{}, "List of milestones which, when applied, will cause the PR to not be merged")
	cmd.Flags().IntVar(&sq.AdminPort, "admin-port", 9999, "If non-zero, will serve administrative actions on this port.")
	// If you create a StringSliceVar you may wish to check out 'cleanStringSliceVar()'
	cmd.Flags().StringVar(&sq.Metadata.HistoryUrl, "history-url", "", "URL to access the submit-queue instance's health history.")
	cmd.Flags().StringVar(&sq.Metadata.ChartUrl, "chart-url", "", "URL to access the submit-queue instance's health charts.")
}

// Hold the lock
func (sq *SubmitQueue) updateHealth() {
	// Remove old entries from the front.
	for len(sq.healthHistory) > 0 && time.Since(sq.healthHistory[0].Time).Hours() > 24.0 {
		sq.healthHistory = sq.healthHistory[1:]
	}
	// Make the current record
	stable, _ := sq.e2e.GCSBasedStable()
	emergencyStop := sq.emergencyMergeStop()
	newEntry := healthRecord{
		Time:    time.Now(),
		Overall: stable && !emergencyStop,
		Jobs:    map[string]bool{},
	}
	for job, status := range sq.e2e.GetBuildStatus() {
		// Ignore flakes.
		newEntry.Jobs[job] = status.Status != "Not Stable"
	}
	if emergencyStop {
		// invent an "emergency stop" job that's failing.
		newEntry.Jobs["Emergency Stop"] = false
	}
	sq.healthHistory = append(sq.healthHistory, newEntry)
	// Now compute the health structure so we don't have to do it on page load
	sq.health.TotalLoops = len(sq.healthHistory)
	sq.health.NumStable = 0
	sq.health.NumStablePerJob = map[string]int{}
	sq.health.MergePossibleNow = stable && !emergencyStop
	for _, record := range sq.healthHistory {
		if record.Overall {
			sq.health.NumStable += 1
		}
		for job, stable := range record.Jobs {
			if _, ok := sq.health.NumStablePerJob[job]; !ok {
				sq.health.NumStablePerJob[job] = 0
			}
			if stable {
				sq.health.NumStablePerJob[job]++
			}
		}
	}
}

func (sq *SubmitQueue) e2eStable(aboutToMerge bool) bool {
	wentStable := false
	wentUnstable := false

	stable, ignorableFlakes := sq.e2e.GCSBasedStable()
	if stable && sq.emergencyMergeStop() {
		stable = false
	}

	weakStable := sq.e2e.GCSWeakStable()
	if !weakStable {
		stable = weakStable
		glog.Errorf("E2E is not stable because weak stable check failed.")
	}

	if aboutToMerge && stable && ignorableFlakes {
		atomic.AddInt32(&sq.flakesIgnored, 1)
	}

	sq.Lock()
	last := sq.lastE2EStable
	if last && !stable {
		wentUnstable = true
	} else if !last && stable {
		wentStable = true

	}
	sq.lastE2EStable = stable
	sq.Unlock()

	reason := ""
	avatar := ""
	if wentStable {
		reason = e2eRecover
		avatar = "success.png"
	} else if wentUnstable {
		reason = e2eFailure
		avatar = "error.png"
	}
	if reason != "" {
		submitStatus := submitStatus{
			Time: sq.clock.Now(),
			statusPullRequest: statusPullRequest{
				Title:     reason,
				AvatarURL: avatar,
			},
			Reason: reason,
		}
		sq.Lock()
		sq.statusHistory = append(sq.statusHistory, submitStatus)
		sq.Unlock()
	}
	return stable
}

// This serves little purpose other than to show updates every minute in the
// web UI. Stable() will get called as needed against individual PRs as well.
func (sq *SubmitQueue) updateGoogleE2ELoop() {
	for {
		_ = sq.e2eStable(false)
		time.Sleep(1 * time.Minute)
	}

}

func objToStatusPullRequest(obj *github.MungeObject) *statusPullRequest {
	if obj == nil {
		return &statusPullRequest{}
	}
	res := statusPullRequest{
		Number:    *obj.Issue.Number,
		URL:       *obj.Issue.HTMLURL,
		Title:     *obj.Issue.Title,
		Login:     *obj.Issue.User.Login,
		AvatarURL: *obj.Issue.User.AvatarURL,
	}
	pr, err := obj.GetPR()
	if err != nil {
		return &res
	}
	if pr.Additions != nil {
		res.Additions = *pr.Additions
	}
	if pr.Deletions != nil {
		res.Deletions = *pr.Deletions
	}

	prio, ok := obj.Annotations["priority"]
	if !ok {
		var prio string
		p := priority(obj)
		if p == retestNotRequiredMergePriority {
			prio = retestNotRequiredLabel
		} else {
			prio = fmt.Sprintf("P%d", p) // store it a P1, P2, P3.  Not just 1,2,3
		}
		obj.Annotations["priority"] = prio
	}
	if prio != "" {
		res.ExtraInfo = append(res.ExtraInfo, prio)
	}

	milestone, ok := obj.Annotations["milestone"]
	if !ok {
		milestone = obj.ReleaseMilestone()
		obj.Annotations["milestone"] = milestone
	}
	if milestone != "" {
		res.ExtraInfo = append(res.ExtraInfo, milestone)
	}
	return &res
}

func reasonToState(reason string) string {
	switch reason {
	case merged:
		return "success"
	case mergedByHand:
		return "success"
	case e2eFailure:
		return "success"
	case ghE2EQueued:
		return "success"
	case ghE2EWaitingStart:
		return "success"
	case ghE2ERunning:
		return "success"
	case unknown:
		return "failure"
	default:
		return "pending"
	}
}

// SetMergeStatus will set the status given a particular PR. This function should
// be used instead of manipulating the prStatus directly as sq.Lock() must be
// called when manipulating that structure
// `obj` is the active github object
// `reason` is the new 'status' for this object
func (sq *SubmitQueue) SetMergeStatus(obj *github.MungeObject, reason string) {
	glog.V(4).Infof("SubmitQueue not merging %d because %q", *obj.Issue.Number, reason)
	submitStatus := submitStatus{
		Time:              sq.clock.Now(),
		statusPullRequest: *objToStatusPullRequest(obj),
		Reason:            reason,
	}

	status := obj.GetStatus(sqContext)
	if status == nil || *status.Description != reason {
		state := reasonToState(reason)
		url := fmt.Sprintf("http://submit-queue.k8s.io/#/prs/?prDisplay=%d&historyDisplay=%d", *obj.Issue.Number, *obj.Issue.Number)
		_ = obj.SetStatus(state, url, reason, sqContext)
	}

	sq.Lock()
	defer sq.Unlock()

	// If we are currently retesting E2E the normal munge loop might find
	// that the ci tests are not green. That's normal and expected and we
	// should just ignore that status update entirely.
	if sq.githubE2ERunning != nil && *sq.githubE2ERunning.Issue.Number == *obj.Issue.Number && reason == ciFailure {
		return
	}

	if sq.onQueue(obj) {
		sq.statusHistory = append(sq.statusHistory, submitStatus)
		if len(sq.statusHistory) > 128 {
			sq.statusHistory = sq.statusHistory[1:]
		}
	}
	sq.prStatus[strconv.Itoa(*obj.Issue.Number)] = submitStatus
	sq.cleanupOldE2E(obj, reason)
}

// sq.Lock() MUST be held!
func (sq *SubmitQueue) getE2EQueueStatus() []*statusPullRequest {
	queue := []*statusPullRequest{}
	keys := sq.orderedE2EQueue()
	for _, k := range keys {
		obj := sq.githubE2EQueue[k]
		request := objToStatusPullRequest(obj)
		queue = append(queue, request)
	}
	return queue
}

func (sq *SubmitQueue) marshal(data interface{}) []byte {
	b, err := json.Marshal(data)
	if err != nil {
		glog.Errorf("Unable to Marshal data: %#v: %v", data, err)
		return nil
	}
	return b
}

func (sq *SubmitQueue) getQueueHistory() []byte {
	sq.Lock()
	defer sq.Unlock()
	return sq.marshal(sq.statusHistory)
}

// GetQueueStatus returns a json representation of the state of the submit
// queue. This can be used to generate web pages about the submit queue.
func (sq *SubmitQueue) getQueueStatus() []byte {
	status := submitQueueStatus{}
	sq.Lock()
	defer sq.Unlock()
	outputStatus := sq.lastPRStatus
	for key, value := range sq.prStatus {
		outputStatus[key] = value
	}
	status.PRStatus = outputStatus

	return sq.marshal(status)
}

func (sq *SubmitQueue) getGithubE2EStatus() []byte {
	sq.Lock()
	defer sq.Unlock()
	status := e2eQueueStatus{
		E2EQueue:   sq.getE2EQueueStatus(),
		E2ERunning: objToStatusPullRequest(sq.githubE2ERunning),
	}
	return sq.marshal(status)
}

func (sq *SubmitQueue) getGoogleInternalStatus() []byte {
	sq.Lock()
	defer sq.Unlock()
	return sq.marshal(sq.e2e.GetBuildStatus())
}

func (sq *SubmitQueue) getHealth() []byte {
	sq.Lock()
	defer sq.Unlock()
	return sq.marshal(sq.health)
}

func (sq *SubmitQueue) getMetaData() []byte {
	sq.Lock()
	defer sq.Unlock()
	return sq.marshal(sq.Metadata)
}

const (
	unknown                 = "unknown failure"
	noCLA                   = "PR does not have " + claYesLabel + " or " + claHumanLabel
	noLGTM                  = "PR does not have LGTM."
	lgtmEarly               = "The PR was changed after the LGTM label was added."
	unmergeable             = "PR is unable to be automatically merged. Needs rebase."
	undeterminedMergability = "Unable to determine is PR is mergeable. Will try again later."
	noMerge                 = "Will not auto merge because " + doNotMergeLabel + " is present"
	ciFailure               = "Github CI tests are not green."
	e2eFailure              = "The e2e tests are failing. The entire submit queue is blocked."
	e2eRecover              = "The e2e tests started passing. The submit queue is unblocked."
	merged                  = "MERGED!"
	mergedByHand            = "MERGED! (by hand outside of submit queue)"
	ghE2EQueued             = "Queued to run github e2e tests a second time."
	ghE2EWaitingStart       = "Requested and waiting for github e2e test to start running a second time."
	ghE2ERunning            = "Running github e2e tests a second time."
	ghE2EFailed             = "Second github e2e run failed."
	unmergeableMilestone    = "Milestone is for a future release and cannot be merged"
)

// validForMerge is the base logic about what PR can be automatically merged.
// PRs must pass this logic to be placed on the queue and they must pass this
// logic a second time to be retested/merged after they get to the top of
// the queue.
//
// If you update the logic PLEASE PLEASE PLEASE update serveMergeInfo() as well.
func (sq *SubmitQueue) validForMerge(obj *github.MungeObject) bool {
	// Can't merge an issue!
	if !obj.IsPR() {
		return false
	}

	// Can't merge something already merged.
	if m, err := obj.IsMerged(); err != nil {
		glog.Errorf("%d: unknown err: %v", *obj.Issue.Number, err)
		sq.SetMergeStatus(obj, unknown)
		return false
	} else if m {
		sq.SetMergeStatus(obj, mergedByHand)
		return false
	}

	if milestone := obj.Issue.Milestone; true {
		title := ""
		// Net set means the empty milestone, ""
		if milestone != nil && milestone.Title != nil {
			title = *milestone.Title
		}
		for _, blocked := range sq.DoNotMergeMilestones {
			if title == blocked {
				sq.SetMergeStatus(obj, unmergeableMilestone)
				return false
			}
		}
	}

	// Must pass CLA checks
	if !obj.HasLabel(claYesLabel) && !obj.HasLabel(claHumanLabel) {
		sq.SetMergeStatus(obj, noCLA)
		return false
	}

	// Obviously must be mergeable
	if mergeable, err := obj.IsMergeable(); err != nil {
		sq.SetMergeStatus(obj, undeterminedMergability)
		return false
	} else if !mergeable {
		sq.SetMergeStatus(obj, unmergeable)
		return false
	}

	// Validate the status information for this PR
	if len(sq.RequiredStatusContexts) > 0 {
		if ok := obj.IsStatusSuccess(sq.RequiredStatusContexts); !ok {
			sq.SetMergeStatus(obj, ciFailure)
			return false
		}
	}
	if len(sq.RequiredRetestContexts) > 0 {
		if ok := obj.IsStatusSuccess(sq.RequiredRetestContexts); !ok {
			sq.SetMergeStatus(obj, ciFailure)
			return false
		}
	}

	// Clearly
	if !obj.HasLabel(lgtmLabel) {
		sq.SetMergeStatus(obj, noLGTM)
		return false
	}

	// PR cannot change since LGTM was added
	lastModifiedTime := obj.LastModifiedTime()
	lgtmTime := obj.LabelTime(lgtmLabel)

	if lastModifiedTime == nil || lgtmTime == nil {
		glog.Errorf("PR %d was unable to determine when LGTM was added or when last modified", *obj.Issue.Number)
		sq.SetMergeStatus(obj, unknown)
		return false
	}

	if lastModifiedTime.After(*lgtmTime) {
		sq.SetMergeStatus(obj, lgtmEarly)
		return false
	}

	// PR cannot have the label which prevents merging.
	if obj.HasLabel(doNotMergeLabel) {
		sq.SetMergeStatus(obj, noMerge)
		return false
	}

	return true
}

// Munge is the workhorse the will actually make updates to the PR
func (sq *SubmitQueue) Munge(obj *github.MungeObject) {
	if !sq.validForMerge(obj) {
		return
	}

	added := false
	sq.Lock()
	if _, ok := sq.githubE2EQueue[*obj.Issue.Number]; !ok {
		atomic.AddInt32(&sq.prsAdded, 1)
		added = true
	}
	// Add this most-recent object in place of the existing object. It will
	// have more up2date information. Even though we explicitly refresh the
	// PR information before do anything with it, this allow things like the
	// queue order to change dynamically as labels are added/removed.
	sq.githubE2EQueue[*obj.Issue.Number] = obj
	sq.Unlock()
	if added {
		sq.SetMergeStatus(obj, ghE2EQueued)
	}

	return
}

func (sq *SubmitQueue) deleteQueueItem(obj *github.MungeObject) {
	if sq.onQueue(obj) {
		atomic.AddInt32(&sq.prsRemoved, 1)
	}
	delete(sq.githubE2EQueue, *obj.Issue.Number)
}

// If the PR was put in the github e2e queue previously, but now we don't
// think it should be in the e2e queue, remove it. MUST be called with sq.Lock()
// held.
func (sq *SubmitQueue) cleanupOldE2E(obj *github.MungeObject, reason string) {
	switch reason {
	case e2eFailure:
	case ghE2EQueued:
	case ghE2EWaitingStart:
	case ghE2ERunning:
		// Do nothing
	case ciFailure:
		// ciFailure is intersting. If the PR is being actively retested and then the
		// time based loop finds the same PR it will try to set ciFailure. We should in fact
		// not ever call this function in this case, but if we do call here, log it.
		if sq.githubE2ERunning != nil && *sq.githubE2ERunning.Issue.Number == *obj.Issue.Number {
			glog.Errorf("Trying to clean up %d due to ciFailure while it is being tested")
			return
		}
		fallthrough
	default:
		if sq.githubE2ERunning != nil && *sq.githubE2ERunning.Issue.Number == *obj.Issue.Number {
			sq.githubE2ERunning = nil
		}
		sq.deleteQueueItem(obj)
	}

}

func priority(obj *github.MungeObject) int {
	// jump to the front of the queue if you don't need retested
	if obj.HasLabel(retestNotRequiredLabel) || obj.HasLabel(retestNotRequiredDocsOnlyLabel) {
		return retestNotRequiredMergePriority
	}

	prio := obj.Priority()
	// eparis randomly decided that unlabel issues count at p3
	if prio == math.MaxInt32 {
		return defaultMergePriority
	}
	return prio
}

type queueSorter struct {
	queue          []*github.MungeObject
	labelTimeCache *mungerutil.LabelTimeCache
}

func (s queueSorter) Len() int      { return len(s.queue) }
func (s queueSorter) Swap(i, j int) { s.queue[i], s.queue[j] = s.queue[j], s.queue[i] }

// If you update the function PLEASE PLEASE PLEASE also update servePriorityInfo()
func (s queueSorter) Less(i, j int) bool {
	a := s.queue[i]
	b := s.queue[j]

	aPrio := priority(a)
	bPrio := priority(b)

	if aPrio < bPrio {
		return true
	} else if aPrio > bPrio {
		return false
	}

	aDue := a.ReleaseMilestoneDue()
	bDue := b.ReleaseMilestoneDue()

	if aDue.Before(bDue) {
		return true
	} else if aDue.After(bDue) {
		return false
	}

	aTime, aOK := s.labelTimeCache.FirstLabelTime(a)
	bTime, bOK := s.labelTimeCache.FirstLabelTime(b)

	// Shouldn't really happen since these have been LGTMed to be
	// in the queue at all. But just in case, .
	if !aOK && bOK {
		return false
	} else if aOK && !bOK {
		return true
	} else if !aOK && !bOK {
		return false
	}

	return aTime.Before(bTime)
}

// onQueue just tells if a PR is already on the queue.
// sq.Lock() must be held
func (sq *SubmitQueue) onQueue(obj *github.MungeObject) bool {
	for _, queueObj := range sq.githubE2EQueue {
		if *queueObj.Issue.Number == *obj.Issue.Number {
			return true
		}

	}
	return false
}

// sq.Lock() better held!!!
func (sq *SubmitQueue) orderedE2EQueue() []int {
	prs := []*github.MungeObject{}
	for _, obj := range sq.githubE2EQueue {
		prs = append(prs, obj)
	}
	sort.Sort(queueSorter{prs, sq.lgtmTimeCache})

	var ordered []int
	for _, obj := range prs {
		ordered = append(ordered, *obj.Issue.Number)
	}
	return ordered
}

// handleGithubE2EAndMerge waits for PRs that are ready to re-run the github
// e2e tests, runs the test, and then merges if everything was successful.
func (sq *SubmitQueue) handleGithubE2EAndMerge() {
	for {
		sq.Lock()
		l := len(sq.githubE2EQueue)
		sq.Unlock()
		// Wait until something is ready to be processed
		if l == 0 || !sq.e2eStable(false) {
			time.Sleep(sq.githubE2EPollTime)
			continue
		}

		obj := sq.selectPullRequest()
		if obj == nil {
			continue
		}

		// re-test and maybe merge
		if sq.doGithubE2EAndMerge(obj) {
			// remove it from the map after we finish testing
			sq.Lock()
			sq.githubE2ERunning = nil
			sq.deleteQueueItem(obj)
			sq.Unlock()
		}
	}
}

func (sq *SubmitQueue) mergePullRequest(obj *github.MungeObject) {
	obj.MergePR("submit-queue")
	sq.SetMergeStatus(obj, merged)
	sq.updateMergeRate()
}

func (sq *SubmitQueue) selectPullRequest() *github.MungeObject {
	if sq.interruptedObj != nil {
		return sq.interruptedObj.obj
	}
	sq.Lock()
	defer sq.Unlock()
	if len(sq.githubE2EQueue) == 0 {
		return nil
	}
	keys := sq.orderedE2EQueue()
	obj := sq.githubE2EQueue[keys[0]]
	sq.githubE2ERunning = obj

	return obj
}

func (interruptedObj *submitQueueInterruptedObject) hasSHAChanged() bool {
	headSHA, baseRef, gotHeadSHA := interruptedObj.obj.GetHeadAndBase()
	if !gotHeadSHA {
		return true
	}

	baseSHA, gotBaseSHA := interruptedObj.obj.GetSHAFromRef(baseRef)
	if !gotBaseSHA {
		return true
	}

	return interruptedObj.interruptedMergeBaseSHA != baseSHA ||
		interruptedObj.interruptedMergeHeadSHA != headSHA
}

func newInterruptedObject(obj *github.MungeObject) *submitQueueInterruptedObject {
	if headSHA, baseRef, gotHeadSHA := obj.GetHeadAndBase(); !gotHeadSHA {
		return nil
	} else if baseSHA, gotBaseSHA := obj.GetSHAFromRef(baseRef); !gotBaseSHA {
		return nil
	} else {
		return &submitQueueInterruptedObject{obj, headSHA, baseSHA}
	}
}

// Returns true if we can discard the PR from the queue, false if we must keep it for later.
func (sq *SubmitQueue) doGithubE2EAndMerge(obj *github.MungeObject) bool {
	interruptedObj := sq.interruptedObj
	sq.interruptedObj = nil

	err := obj.Refresh()
	if err != nil {
		glog.Errorf("%d: unknown err: %v", *obj.Issue.Number, err)
		sq.SetMergeStatus(obj, unknown)
		return true
	}

	if !sq.validForMerge(obj) {
		return true
	}

	if obj.HasLabel(retestNotRequiredLabel) || obj.HasLabel(retestNotRequiredDocsOnlyLabel) {
		atomic.AddInt32(&sq.instantMerges, 1)
		sq.mergePullRequest(obj)
		return true
	}

	if interruptedObj != nil {
		if interruptedObj.hasSHAChanged() {
			// This PR will have to be rested.
			// Make sure we don't have higher priority first.
			return false
		}
		glog.Infof("Skipping retest since head and base sha match previous attempt!")
		atomic.AddInt32(&sq.retestsAvoided, 1)
	} else if sq.retestPR(obj) {
		return true
	}

	if !sq.e2eStable(true) {
		if sq.validForMerge(obj) {
			sq.interruptedObj = newInterruptedObject(obj)
		}
		sq.SetMergeStatus(obj, e2eFailure)
		return true
	}

	sq.mergePullRequest(obj)
	return true
}

// Returns true if merge status changes, and false otherwise.
func (sq *SubmitQueue) retestPR(obj *github.MungeObject) bool {
	if len(sq.RequiredRetestContexts) == 0 {
		return false
	}

	if err := obj.WriteComment(retestBody); err != nil {
		glog.Errorf("%d: unknown err: %v", *obj.Issue.Number, err)
		sq.SetMergeStatus(obj, unknown)
		return true
	}

	// Wait for the retest to start
	sq.SetMergeStatus(obj, ghE2EWaitingStart)
	atomic.AddInt32(&sq.prsTested, 1)
	err := obj.WaitForPending(sq.RequiredRetestContexts)
	if err != nil {
		sq.SetMergeStatus(obj, fmt.Sprintf("Failed waiting for PR to start testing: %v", err))
		return true
	}

	// Wait for the status to go back to something other than pending
	sq.SetMergeStatus(obj, ghE2ERunning)
	err = obj.WaitForNotPending(sq.RequiredRetestContexts)
	if err != nil {
		sq.SetMergeStatus(obj, fmt.Sprintf("Failed waiting for PR to finish testing: %v", err))
		return true
	}

	// Check if the thing we care about is success
	if ok := obj.IsStatusSuccess(sq.RequiredRetestContexts); !ok {
		sq.SetMergeStatus(obj, ghE2EFailed)
		return true
	}

	// no action taken.
	return false
}

func (sq *SubmitQueue) serve(data []byte, res http.ResponseWriter, req *http.Request) {
	if data == nil {
		res.Header().Set("Content-type", "text/plain")
		res.WriteHeader(http.StatusInternalServerError)
	} else {
		res.Header().Set("Content-type", "application/json")
		res.WriteHeader(http.StatusOK)
		res.Write(data)
	}
}

func (sq *SubmitQueue) serveHistory(res http.ResponseWriter, req *http.Request) {
	data := sq.getQueueHistory()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) servePRs(res http.ResponseWriter, req *http.Request) {
	data := sq.getQueueStatus()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) serveGithubE2EStatus(res http.ResponseWriter, req *http.Request) {
	data := sq.getGithubE2EStatus()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) serveGoogleInternalStatus(res http.ResponseWriter, req *http.Request) {
	data := sq.getGoogleInternalStatus()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) serveHealth(res http.ResponseWriter, req *http.Request) {
	data := sq.getHealth()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) serveSQStats(res http.ResponseWriter, req *http.Request) {
	data := submitQueueStats{
		Added:              int(atomic.LoadInt32(&sq.prsAdded)),
		FlakesIgnored:      int(atomic.LoadInt32(&sq.flakesIgnored)),
		Initialized:        atomic.LoadInt32(&sq.loopStarts) > 1,
		InstantMerges:      int(atomic.LoadInt32(&sq.instantMerges)),
		LastMergeTime:      sq.lastMergeTime,
		MergeRate:          sq.calcMergeRateWithTail(),
		MergesSinceRestart: int(atomic.LoadInt32(&sq.totalMerges)),
		Removed:            int(atomic.LoadInt32(&sq.prsRemoved)),
		RetestsAvoided:     int(atomic.LoadInt32(&sq.retestsAvoided)),
		StartTime:          sq.startTime,
		Tested:             int(atomic.LoadInt32(&sq.prsTested)),
	}
	sq.serve(sq.marshal(data), res, req)
}

func (sq *SubmitQueue) serveFlakes(res http.ResponseWriter, req *http.Request) {
	data := sq.e2e.Flakes()
	sq.serve(mungerutil.PrettyMarshal(data), res, req)
}

func (sq *SubmitQueue) serveMetadata(res http.ResponseWriter, req *http.Request) {
	data := sq.getMetaData()
	sq.serve(data, res, req)
}

func (sq *SubmitQueue) serveMergeInfo(res http.ResponseWriter, req *http.Request) {
	res.Header().Set("Content-type", "text/plain")
	res.WriteHeader(http.StatusOK)
	var out bytes.Buffer
	out.WriteString("PRs must meet the following set of conditions to be considered for automatic merging by the submit queue.")
	out.WriteString("<ol>")
	out.WriteString(fmt.Sprintf("<li>The PR must have the label %q or %q</li>", claYesLabel, claHumanLabel))
	out.WriteString("<li>The PR must be mergeable. aka cannot need a rebase</li>")
	if len(sq.RequiredStatusContexts) > 0 || len(sq.RequiredRetestContexts) > 0 {
		out.WriteString("<li>All of the following github statuses must be green")
		out.WriteString("<ul>")
		for _, context := range sq.RequiredStatusContexts {
			out.WriteString(fmt.Sprintf("<li>%s</li>", context))
		}
		for _, context := range sq.RequiredRetestContexts {
			out.WriteString(fmt.Sprintf("<li>%s</li>", context))
		}
		out.WriteString("</ul>")
	}
	out.WriteString(fmt.Sprintf("<li>The PR cannot have any of the following milestones: %q</li>", sq.DoNotMergeMilestones))
	out.WriteString(fmt.Sprintf(`<li>The PR must have the %q label</li>`, lgtmLabel))
	out.WriteString(fmt.Sprintf("<li>The PR must not have been updated since the %q label was applied</li>", lgtmLabel))
	out.WriteString(fmt.Sprintf("<li>The PR must not have the %q label</li>", doNotMergeLabel))
	out.WriteString(`</ol><br>`)
	out.WriteString("The PR can then be queued to re-test before merge. Once it reaches the top of the queue all of the above conditions must be true but so must the following:")
	out.WriteString("<ol>")
	out.WriteString(fmt.Sprintf("<li>All of the <a href=http://submit-queue.k8s.io/#/e2e>continuously running e2e tests</a> must be passing</li>"))
	if len(sq.RequiredRetestContexts) > 0 {
		out.WriteString("<li>All of the following tests must pass a second time")
		out.WriteString("<ul>")
		for _, context := range sq.RequiredRetestContexts {
			out.WriteString(fmt.Sprintf("<li>%s</li>", context))
		}
		out.WriteString("</ul>")
		out.WriteString(fmt.Sprintf("Unless the %q or %q label is present</li>", retestNotRequiredLabel, retestNotRequiredDocsOnlyLabel))
	}
	out.WriteString("</ol>")
	out.WriteString("And then the PR will be merged!!")
	res.Write(out.Bytes())
}

func (sq *SubmitQueue) servePriorityInfo(res http.ResponseWriter, req *http.Request) {
	res.Header().Set("Content-type", "text/plain")
	res.WriteHeader(http.StatusOK)
	res.Write([]byte(`The merge queue is sorted by the following. If there is a tie in any test the next test will be used. A P0 will always come before a P1, no matter how the other tests compare.
<ol>
  <li>Priority
    <ul>
      <li>Determined by a label of the form 'priority/pX'
      <li>P0 -&gt; P1 -&gt; P2</li>
      <li>A PR with no priority label is considered equal to a P3</li>
      <li>A PR with the '` + retestNotRequiredLabel + `' or '` + retestNotRequiredDocsOnlyLabel + `' label will come first, before even P0</li>
    </ul>
  </li>
  <li>Release milestone due date
    <ul>
      <li>Release milestones are of the form vX.Y where X and Y are integers</li>
      <li>Other milestones are ignored.
      <li>PR with no release milestone will be considered after any PR with a milestone</li>
    </ul>
  </li>
  <li>First time at which the LGTM label was applied.
    <ul>
      <li>This means all PRs start at the bottom of the queue (within their priority and milestone bands, of course) and progress towards the top.</li>
    </ul>
  </li>
</ol> `))
}

func (sq *SubmitQueue) getHealthSVG() []byte {
	sq.Lock()
	defer sq.Unlock()
	blocked := false
	blockingJobs := make([]string, 0)
	blocked = !sq.health.MergePossibleNow
	status := "running"
	color := "brightgreen"
	if blocked {
		status = "blocked"
		color = "red"
		for job, status := range sq.e2e.GetBuildStatus() {
			if status.Status == "Not Stable" {
				job = strings.Replace(job, "kubernetes-", "", -1)
				blockingJobs = append(blockingJobs, job)
			}
		}
		sort.Strings(blockingJobs)
		if len(blockingJobs) > 3 {
			blockingJobs = append(blockingJobs[:3], "...")
		}
		if len(blockingJobs) > 0 {
			status += " by " + strings.Join(blockingJobs, ", ")
		}
	}
	return shield.Make("queue", status, color)
}

func (sq *SubmitQueue) serveHealthSVG(res http.ResponseWriter, req *http.Request) {
	res.Header().Set("Content-type", "image/svg+xml")
	res.Header().Set("Cache-Control", "max-age=60")
	res.WriteHeader(http.StatusOK)
	res.Write(sq.getHealthSVG())
}

func (sq *SubmitQueue) isStaleComment(obj *github.MungeObject, comment *githubapi.IssueComment) bool {
	if !mergeBotComment(comment) {
		return false
	}
	if *comment.Body != retestBody {
		return false
	}
	stale := commentBeforeLastCI(obj, comment, sq.RequiredRetestContexts)
	if stale {
		glog.V(6).Infof("Found stale SubmitQueue safe to merge comment")
	}
	return stale
}

// StaleComments returns a slice of stale comments
func (sq *SubmitQueue) StaleComments(obj *github.MungeObject, comments []*githubapi.IssueComment) []*githubapi.IssueComment {
	return forEachCommentTest(obj, comments, sq.isStaleComment)
}