re-implement data usage crawler to be more efficient (minio#9075)

Implementation overview: 

https://gist.github.com/klauspost/1801c858d5e0df391114436fdad6987b

Makefile

@@ -22,7 +22,7 @@ getdeps:
 ifeq ($(GOARCH),s390x)
 	@which staticcheck 1>/dev/null || (echo "Installing staticcheck" && GO111MODULE=off go get honnef.co/go/tools/cmd/staticcheck)
 else
-	@which staticcheck 1>/dev/null || (echo "Installing staticcheck" && wget --quiet https://github.com/dominikh/go-tools/releases/download/2019.2.3/staticcheck_${GOOS}_${GOARCH}.tar.gz && tar xf staticcheck_${GOOS}_${GOARCH}.tar.gz && mv staticcheck/staticcheck ${GOPATH}/bin/staticcheck && chmod +x ${GOPATH}/bin/staticcheck && rm -f staticcheck_${GOOS}_${GOARCH}.tar.gz && rm -rf staticcheck)
+	@which staticcheck 1>/dev/null || (echo "Installing staticcheck" && wget --quiet https://github.com/dominikh/go-tools/releases/download/2020.1.3/staticcheck_${GOOS}_${GOARCH}.tar.gz && tar xf staticcheck_${GOOS}_${GOARCH}.tar.gz && mv staticcheck/staticcheck ${GOPATH}/bin/staticcheck && chmod +x ${GOPATH}/bin/staticcheck && rm -f staticcheck_${GOOS}_${GOARCH}.tar.gz && rm -rf staticcheck)
 endif
 	@which misspell 1>/dev/null || (echo "Installing misspell" && GO111MODULE=off go get -u github.com/client9/misspell/cmd/misspell)
 

browser/staticcheck.conf

@@ -0,0 +1 @@
+checks = ["all", "-ST1005", "-ST1000", "-SA4000", "-SA9004", "-SA1019", "-SA1008", "-U1000", "-ST1003", "-ST1018"]

cmd/admin-heal-ops.go

@@ -106,12 +106,12 @@ func initHealState() *allHealState {
 		healSeqMap: make(map[string]*healSequence),
 	}
 
-	go healState.periodicHealSeqsClean()
+	go healState.periodicHealSeqsClean(GlobalContext)
 
 	return healState
 }
 
-func (ahs *allHealState) periodicHealSeqsClean() {
+func (ahs *allHealState) periodicHealSeqsClean(ctx context.Context) {
 	// Launch clean-up routine to remove this heal sequence (after
 	// it ends) from the global state after timeout has elapsed.
 	ticker := time.NewTicker(time.Minute * 5)
@@ -127,7 +127,7 @@ func (ahs *allHealState) periodicHealSeqsClean() {
 				}
 			}
 			ahs.Unlock()
-		case <-GlobalServiceDoneCh:
+		case <-ctx.Done():
 			// server could be restarting - need
 			// to exit immediately
 			return
@@ -369,7 +369,7 @@ func newHealSequence(bucket, objPrefix, clientAddr string,
 
 	reqInfo := &logger.ReqInfo{RemoteHost: clientAddr, API: "Heal", BucketName: bucket}
 	reqInfo.AppendTags("prefix", objPrefix)
-	ctx := logger.SetReqInfo(context.Background(), reqInfo)
+	ctx := logger.SetReqInfo(GlobalContext, reqInfo)
 
 	return &healSequence{
 		bucket:         bucket,
@@ -603,7 +603,7 @@ func (h *healSequence) healItemsFromSourceCh() error {
 			h.lastHealActivity = UTCNow()
 		case <-h.traverseAndHealDoneCh:
 			return nil
-		case <-GlobalServiceDoneCh:
+		case <-h.ctx.Done():
 			return nil
 		}
 	}
@@ -630,11 +630,6 @@ func (h *healSequence) healItems(bucketsOnly bool) error {
 		return err
 	}
 
-	// Start healing the background ops prefix.
-	if err := h.healMinioSysMeta(backgroundOpsMetaPrefix)(); err != nil {
-		logger.LogIf(h.ctx, err)
-	}
-
 	// Heal buckets and objects
 	return h.healBuckets(bucketsOnly)
 }

cmd/config-current.go

@@ -26,7 +26,6 @@ import (
 	"github.com/minio/minio/cmd/config/cache"
 	"github.com/minio/minio/cmd/config/compress"
 	"github.com/minio/minio/cmd/config/etcd"
-	xetcd "github.com/minio/minio/cmd/config/etcd"
 	"github.com/minio/minio/cmd/config/etcd/dns"
 	xldap "github.com/minio/minio/cmd/config/identity/ldap"
 	"github.com/minio/minio/cmd/config/identity/openid"
@@ -304,13 +303,13 @@ func lookupConfigs(s config.Config) {
 		}
 	}
 
-	etcdCfg, err := xetcd.LookupConfig(s[config.EtcdSubSys][config.Default], globalRootCAs)
+	etcdCfg, err := etcd.LookupConfig(s[config.EtcdSubSys][config.Default], globalRootCAs)
 	if err != nil {
 		logger.LogIf(ctx, fmt.Errorf("Unable to initialize etcd config: %w", err))
 	}
 
 	if etcdCfg.Enabled {
-		globalEtcdClient, err = xetcd.New(etcdCfg)
+		globalEtcdClient, err = etcd.New(etcdCfg)
 		if err != nil {
 			logger.LogIf(ctx, fmt.Errorf("Unable to initialize etcd config: %w", err))
 		}

cmd/config/errors-utils.go

@@ -46,7 +46,7 @@ func (u Err) Clone() Err {
 	}
 }
 
-// Return the error message
+// Error returns the error message
 func (u Err) Error() string {
 	if u.detail == "" {
 		if u.msg != "" {

cmd/config/etcd/dns/etcd_dns.go

@@ -60,11 +60,7 @@ func (c *CoreDNS) List() (map[string][]SrvRecord, error) {
 			if record.Key == "" {
 				continue
 			}
-			if _, ok := srvRecords[record.Key]; ok {
-				srvRecords[record.Key] = append(srvRecords[record.Key], record)
-			} else {
-				srvRecords[record.Key] = []SrvRecord{record}
-			}
+			srvRecords[record.Key] = append(srvRecords[record.Key], record)
 		}
 	}
 	return srvRecords, nil