vendor/google.golang.org/grpc/internal/channelz/funcs.go - voltha-go - Gitiles

 /*
  *
  * Copyright 2018 gRPC 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 channelz defines APIs for enabling channelz service, entry
 // registration/deletion, and accessing channelz data. It also defines channelz
 // metric struct formats.
 //
 // All APIs in this package are experimental.
 package channelz

 import (
 	"sort"
 	"sync"
 	"sync/atomic"
 	"time"

 	"google.golang.org/grpc/grpclog"
 )

 const (
 	defaultMaxTraceEntry int32 = 30
 )

 var (
 	db    dbWrapper
 	idGen idGenerator
 	// EntryPerPage defines the number of channelz entries to be shown on a web page.
 	EntryPerPage  = 50
 	curState      int32
 	maxTraceEntry = defaultMaxTraceEntry
 )

 // TurnOn turns on channelz data collection.
 func TurnOn() {
 	if !IsOn() {
 		NewChannelzStorage()
 		atomic.StoreInt32(&curState, 1)
 	}
 }

 // IsOn returns whether channelz data collection is on.
 func IsOn() bool {
 	return atomic.CompareAndSwapInt32(&curState, 1, 1)
 }

 // SetMaxTraceEntry sets maximum number of trace entry per entity (i.e. channel/subchannel).
 // Setting it to 0 will disable channel tracing.
 func SetMaxTraceEntry(i int32) {
 	atomic.StoreInt32(&maxTraceEntry, i)
 }

 // ResetMaxTraceEntryToDefault resets the maximum number of trace entry per entity to default.
 func ResetMaxTraceEntryToDefault() {
 	atomic.StoreInt32(&maxTraceEntry, defaultMaxTraceEntry)
 }

 func getMaxTraceEntry() int {
 	i := atomic.LoadInt32(&maxTraceEntry)
 	return int(i)
 }

 // dbWarpper wraps around a reference to internal channelz data storage, and
 // provide synchronized functionality to set and get the reference.
 type dbWrapper struct {
 	mu sync.RWMutex
 	DB *channelMap
 }

 func (d *dbWrapper) set(db *channelMap) {
 	d.mu.Lock()
 	d.DB = db
 	d.mu.Unlock()
 }

 func (d *dbWrapper) get() *channelMap {
 	d.mu.RLock()
 	defer d.mu.RUnlock()
 	return d.DB
 }

 // NewChannelzStorage initializes channelz data storage and id generator.
 //
 // Note: This function is exported for testing purpose only. User should not call
 // it in most cases.
 func NewChannelzStorage() {
 	db.set(&channelMap{
 		topLevelChannels: make(map[int64]struct{}),
 		channels:         make(map[int64]*channel),
 		listenSockets:    make(map[int64]*listenSocket),
 		normalSockets:    make(map[int64]*normalSocket),
 		servers:          make(map[int64]*server),
 		subChannels:      make(map[int64]*subChannel),
 	})
 	idGen.reset()
 }

 // GetTopChannels returns a slice of top channel's ChannelMetric, along with a
 // boolean indicating whether there's more top channels to be queried for.
 //
 // The arg id specifies that only top channel with id at or above it will be included
 // in the result. The returned slice is up to a length of EntryPerPage, and is
 // sorted in ascending id order.
 func GetTopChannels(id int64) ([]*ChannelMetric, bool) {
 	return db.get().GetTopChannels(id)
 }

 // GetServers returns a slice of server's ServerMetric, along with a
 // boolean indicating whether there's more servers to be queried for.
 //
 // The arg id specifies that only server with id at or above it will be included
 // in the result. The returned slice is up to a length of EntryPerPage, and is
 // sorted in ascending id order.
 func GetServers(id int64) ([]*ServerMetric, bool) {
 	return db.get().GetServers(id)
 }

 // GetServerSockets returns a slice of server's (identified by id) normal socket's
 // SocketMetric, along with a boolean indicating whether there's more sockets to
 // be queried for.
 //
 // The arg startID specifies that only sockets with id at or above it will be
 // included in the result. The returned slice is up to a length of EntryPerPage,
 // and is sorted in ascending id order.
 func GetServerSockets(id int64, startID int64) ([]*SocketMetric, bool) {
 	return db.get().GetServerSockets(id, startID)
 }

 // GetChannel returns the ChannelMetric for the channel (identified by id).
 func GetChannel(id int64) *ChannelMetric {
 	return db.get().GetChannel(id)
 }

 // GetSubChannel returns the SubChannelMetric for the subchannel (identified by id).
 func GetSubChannel(id int64) *SubChannelMetric {
 	return db.get().GetSubChannel(id)
 }

 // GetSocket returns the SocketInternalMetric for the socket (identified by id).
 func GetSocket(id int64) *SocketMetric {
 	return db.get().GetSocket(id)
 }

 // RegisterChannel registers the given channel c in channelz database with ref
 // as its reference name, and add it to the child list of its parent (identified
 // by pid). pid = 0 means no parent. It returns the unique channelz tracking id
 // assigned to this channel.
 func RegisterChannel(c Channel, pid int64, ref string) int64 {
 	id := idGen.genID()
 	cn := &channel{
 		refName:     ref,
 		c:           c,
 		subChans:    make(map[int64]string),
 		nestedChans: make(map[int64]string),
 		id:          id,
 		pid:         pid,
 		trace:       &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
 	}
 	if pid == 0 {
 		db.get().addChannel(id, cn, true, pid, ref)
 	} else {
 		db.get().addChannel(id, cn, false, pid, ref)
 	}
 	return id
 }

 // RegisterSubChannel registers the given channel c in channelz database with ref
 // as its reference name, and add it to the child list of its parent (identified
 // by pid). It returns the unique channelz tracking id assigned to this subchannel.
 func RegisterSubChannel(c Channel, pid int64, ref string) int64 {
 	if pid == 0 {
 		grpclog.Error("a SubChannel's parent id cannot be 0")
 		return 0
 	}
 	id := idGen.genID()
 	sc := &subChannel{
 		refName: ref,
 		c:       c,
 		sockets: make(map[int64]string),
 		id:      id,
 		pid:     pid,
 		trace:   &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
 	}
 	db.get().addSubChannel(id, sc, pid, ref)
 	return id
 }

 // RegisterServer registers the given server s in channelz database. It returns
 // the unique channelz tracking id assigned to this server.
 func RegisterServer(s Server, ref string) int64 {
 	id := idGen.genID()
 	svr := &server{
 		refName:       ref,
 		s:             s,
 		sockets:       make(map[int64]string),
 		listenSockets: make(map[int64]string),
 		id:            id,
 	}
 	db.get().addServer(id, svr)
 	return id
 }

 // RegisterListenSocket registers the given listen socket s in channelz database
 // with ref as its reference name, and add it to the child list of its parent
 // (identified by pid). It returns the unique channelz tracking id assigned to
 // this listen socket.
 func RegisterListenSocket(s Socket, pid int64, ref string) int64 {
 	if pid == 0 {
 		grpclog.Error("a ListenSocket's parent id cannot be 0")
 		return 0
 	}
 	id := idGen.genID()
 	ls := &listenSocket{refName: ref, s: s, id: id, pid: pid}
 	db.get().addListenSocket(id, ls, pid, ref)
 	return id
 }

 // RegisterNormalSocket registers the given normal socket s in channelz database
 // with ref as its reference name, and add it to the child list of its parent
 // (identified by pid). It returns the unique channelz tracking id assigned to
 // this normal socket.
 func RegisterNormalSocket(s Socket, pid int64, ref string) int64 {
 	if pid == 0 {
 		grpclog.Error("a NormalSocket's parent id cannot be 0")
 		return 0
 	}
 	id := idGen.genID()
 	ns := &normalSocket{refName: ref, s: s, id: id, pid: pid}
 	db.get().addNormalSocket(id, ns, pid, ref)
 	return id
 }

 // RemoveEntry removes an entry with unique channelz trakcing id to be id from
 // channelz database.
 func RemoveEntry(id int64) {
 	db.get().removeEntry(id)
 }

 // TraceEventDesc is what the caller of AddTraceEvent should provide to describe the event to be added
 // to the channel trace.
 // The Parent field is optional. It is used for event that will be recorded in the entity's parent
 // trace also.
 type TraceEventDesc struct {
 	Desc     string
 	Severity Severity
 	Parent   *TraceEventDesc
 }

 // AddTraceEvent adds trace related to the entity with specified id, using the provided TraceEventDesc.
 func AddTraceEvent(id int64, desc *TraceEventDesc) {
 	if getMaxTraceEntry() == 0 {
 		return
 	}
 	db.get().traceEvent(id, desc)
 }

 // channelMap is the storage data structure for channelz.
 // Methods of channelMap can be divided in two two categories with respect to locking.
 // 1. Methods acquire the global lock.
 // 2. Methods that can only be called when global lock is held.
 // A second type of method need always to be called inside a first type of method.
 type channelMap struct {
 	mu               sync.RWMutex
 	topLevelChannels map[int64]struct{}
 	servers          map[int64]*server
 	channels         map[int64]*channel
 	subChannels      map[int64]*subChannel
 	listenSockets    map[int64]*listenSocket
 	normalSockets    map[int64]*normalSocket
 }

 func (c *channelMap) addServer(id int64, s *server) {
 	c.mu.Lock()
 	s.cm = c
 	c.servers[id] = s
 	c.mu.Unlock()
 }

 func (c *channelMap) addChannel(id int64, cn *channel, isTopChannel bool, pid int64, ref string) {
 	c.mu.Lock()
 	cn.cm = c
 	cn.trace.cm = c
 	c.channels[id] = cn
 	if isTopChannel {
 		c.topLevelChannels[id] = struct{}{}
 	} else {
 		c.findEntry(pid).addChild(id, cn)
 	}
 	c.mu.Unlock()
 }

 func (c *channelMap) addSubChannel(id int64, sc *subChannel, pid int64, ref string) {
 	c.mu.Lock()
 	sc.cm = c
 	sc.trace.cm = c
 	c.subChannels[id] = sc
 	c.findEntry(pid).addChild(id, sc)
 	c.mu.Unlock()
 }

 func (c *channelMap) addListenSocket(id int64, ls *listenSocket, pid int64, ref string) {
 	c.mu.Lock()
 	ls.cm = c
 	c.listenSockets[id] = ls
 	c.findEntry(pid).addChild(id, ls)
 	c.mu.Unlock()
 }

 func (c *channelMap) addNormalSocket(id int64, ns *normalSocket, pid int64, ref string) {
 	c.mu.Lock()
 	ns.cm = c
 	c.normalSockets[id] = ns
 	c.findEntry(pid).addChild(id, ns)
 	c.mu.Unlock()
 }

 // removeEntry triggers the removal of an entry, which may not indeed delete the entry, if it has to
 // wait on the deletion of its children and until no other entity's channel trace references it.
 // It may lead to a chain of entry deletion. For example, deleting the last socket of a gracefully
 // shutting down server will lead to the server being also deleted.
 func (c *channelMap) removeEntry(id int64) {
 	c.mu.Lock()
 	c.findEntry(id).triggerDelete()
 	c.mu.Unlock()
 }

 // c.mu must be held by the caller
 func (c *channelMap) decrTraceRefCount(id int64) {
 	e := c.findEntry(id)
 	if v, ok := e.(tracedChannel); ok {
 		v.decrTraceRefCount()
 		e.deleteSelfIfReady()
 	}
 }

 // c.mu must be held by the caller.
 func (c *channelMap) findEntry(id int64) entry {
 	var v entry
 	var ok bool
 	if v, ok = c.channels[id]; ok {
 		return v
 	}
 	if v, ok = c.subChannels[id]; ok {
 		return v
 	}
 	if v, ok = c.servers[id]; ok {
 		return v
 	}
 	if v, ok = c.listenSockets[id]; ok {
 		return v
 	}
 	if v, ok = c.normalSockets[id]; ok {
 		return v
 	}
 	return &dummyEntry{idNotFound: id}
 }

 // c.mu must be held by the caller
 // deleteEntry simply deletes an entry from the channelMap. Before calling this
 // method, caller must check this entry is ready to be deleted, i.e removeEntry()
 // has been called on it, and no children still exist.
 // Conditionals are ordered by the expected frequency of deletion of each entity
 // type, in order to optimize performance.
 func (c *channelMap) deleteEntry(id int64) {
 	var ok bool
 	if _, ok = c.normalSockets[id]; ok {
 		delete(c.normalSockets, id)
 		return
 	}
 	if _, ok = c.subChannels[id]; ok {
 		delete(c.subChannels, id)
 		return
 	}
 	if _, ok = c.channels[id]; ok {
 		delete(c.channels, id)
 		delete(c.topLevelChannels, id)
 		return
 	}
 	if _, ok = c.listenSockets[id]; ok {
 		delete(c.listenSockets, id)
 		return
 	}
 	if _, ok = c.servers[id]; ok {
 		delete(c.servers, id)
 		return
 	}
 }

 func (c *channelMap) traceEvent(id int64, desc *TraceEventDesc) {
 	c.mu.Lock()
 	child := c.findEntry(id)
 	childTC, ok := child.(tracedChannel)
 	if !ok {
 		c.mu.Unlock()
 		return
 	}
 	childTC.getChannelTrace().append(&TraceEvent{Desc: desc.Desc, Severity: desc.Severity, Timestamp: time.Now()})
 	if desc.Parent != nil {
 		parent := c.findEntry(child.getParentID())
 		var chanType RefChannelType
 		switch child.(type) {
 		case *channel:
 			chanType = RefChannel
 		case *subChannel:
 			chanType = RefSubChannel
 		}
 		if parentTC, ok := parent.(tracedChannel); ok {
 			parentTC.getChannelTrace().append(&TraceEvent{
 				Desc:      desc.Parent.Desc,
 				Severity:  desc.Parent.Severity,
 				Timestamp: time.Now(),
 				RefID:     id,
 				RefName:   childTC.getRefName(),
 				RefType:   chanType,
 			})
 			childTC.incrTraceRefCount()
 		}
 	}
 	c.mu.Unlock()
 }

 type int64Slice []int64

 func (s int64Slice) Len() int           { return len(s) }
 func (s int64Slice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 func (s int64Slice) Less(i, j int) bool { return s[i] < s[j] }

 func copyMap(m map[int64]string) map[int64]string {
 	n := make(map[int64]string)
 	for k, v := range m {
 		n[k] = v
 	}
 	return n
 }

 func min(a, b int) int {
 	if a < b {
 		return a
 	}
 	return b
 }

 func (c *channelMap) GetTopChannels(id int64) ([]*ChannelMetric, bool) {
 	c.mu.RLock()
 	l := len(c.topLevelChannels)
 	ids := make([]int64, 0, l)
 	cns := make([]*channel, 0, min(l, EntryPerPage))

 	for k := range c.topLevelChannels {
 		ids = append(ids, k)
 	}
 	sort.Sort(int64Slice(ids))
 	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
 	count := 0
 	var end bool
 	var t []*ChannelMetric
 	for i, v := range ids[idx:] {
 		if count == EntryPerPage {
 			break
 		}
 		if cn, ok := c.channels[v]; ok {
 			cns = append(cns, cn)
 			t = append(t, &ChannelMetric{
 				NestedChans: copyMap(cn.nestedChans),
 				SubChans:    copyMap(cn.subChans),
 			})
 			count++
 		}
 		if i == len(ids[idx:])-1 {
 			end = true
 			break
 		}
 	}
 	c.mu.RUnlock()
 	if count == 0 {
 		end = true
 	}

 	for i, cn := range cns {
 		t[i].ChannelData = cn.c.ChannelzMetric()
 		t[i].ID = cn.id
 		t[i].RefName = cn.refName
 		t[i].Trace = cn.trace.dumpData()
 	}
 	return t, end
 }

 func (c *channelMap) GetServers(id int64) ([]*ServerMetric, bool) {
 	c.mu.RLock()
 	l := len(c.servers)
 	ids := make([]int64, 0, l)
 	ss := make([]*server, 0, min(l, EntryPerPage))
 	for k := range c.servers {
 		ids = append(ids, k)
 	}
 	sort.Sort(int64Slice(ids))
 	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
 	count := 0
 	var end bool
 	var s []*ServerMetric
 	for i, v := range ids[idx:] {
 		if count == EntryPerPage {
 			break
 		}
 		if svr, ok := c.servers[v]; ok {
 			ss = append(ss, svr)
 			s = append(s, &ServerMetric{
 				ListenSockets: copyMap(svr.listenSockets),
 			})
 			count++
 		}
 		if i == len(ids[idx:])-1 {
 			end = true
 			break
 		}
 	}
 	c.mu.RUnlock()
 	if count == 0 {
 		end = true
 	}

 	for i, svr := range ss {
 		s[i].ServerData = svr.s.ChannelzMetric()
 		s[i].ID = svr.id
 		s[i].RefName = svr.refName
 	}
 	return s, end
 }

 func (c *channelMap) GetServerSockets(id int64, startID int64) ([]*SocketMetric, bool) {
 	var svr *server
 	var ok bool
 	c.mu.RLock()
 	if svr, ok = c.servers[id]; !ok {
 		// server with id doesn't exist.
 		c.mu.RUnlock()
 		return nil, true
 	}
 	svrskts := svr.sockets
 	l := len(svrskts)
 	ids := make([]int64, 0, l)
 	sks := make([]*normalSocket, 0, min(l, EntryPerPage))
 	for k := range svrskts {
 		ids = append(ids, k)
 	}
 	sort.Sort(int64Slice(ids))
 	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= startID })
 	count := 0
 	var end bool
 	for i, v := range ids[idx:] {
 		if count == EntryPerPage {
 			break
 		}
 		if ns, ok := c.normalSockets[v]; ok {
 			sks = append(sks, ns)
 			count++
 		}
 		if i == len(ids[idx:])-1 {
 			end = true
 			break
 		}
 	}
 	c.mu.RUnlock()
 	if count == 0 {
 		end = true
 	}
 	var s []*SocketMetric
 	for _, ns := range sks {
 		sm := &SocketMetric{}
 		sm.SocketData = ns.s.ChannelzMetric()
 		sm.ID = ns.id
 		sm.RefName = ns.refName
 		s = append(s, sm)
 	}
 	return s, end
 }

 func (c *channelMap) GetChannel(id int64) *ChannelMetric {
 	cm := &ChannelMetric{}
 	var cn *channel
 	var ok bool
 	c.mu.RLock()
 	if cn, ok = c.channels[id]; !ok {
 		// channel with id doesn't exist.
 		c.mu.RUnlock()
 		return nil
 	}
 	cm.NestedChans = copyMap(cn.nestedChans)
 	cm.SubChans = copyMap(cn.subChans)
 	// cn.c can be set to &dummyChannel{} when deleteSelfFromMap is called. Save a copy of cn.c when
 	// holding the lock to prevent potential data race.
 	chanCopy := cn.c
 	c.mu.RUnlock()
 	cm.ChannelData = chanCopy.ChannelzMetric()
 	cm.ID = cn.id
 	cm.RefName = cn.refName
 	cm.Trace = cn.trace.dumpData()
 	return cm
 }

 func (c *channelMap) GetSubChannel(id int64) *SubChannelMetric {
 	cm := &SubChannelMetric{}
 	var sc *subChannel
 	var ok bool
 	c.mu.RLock()
 	if sc, ok = c.subChannels[id]; !ok {
 		// subchannel with id doesn't exist.
 		c.mu.RUnlock()
 		return nil
 	}
 	cm.Sockets = copyMap(sc.sockets)
 	// sc.c can be set to &dummyChannel{} when deleteSelfFromMap is called. Save a copy of sc.c when
 	// holding the lock to prevent potential data race.
 	chanCopy := sc.c
 	c.mu.RUnlock()
 	cm.ChannelData = chanCopy.ChannelzMetric()
 	cm.ID = sc.id
 	cm.RefName = sc.refName
 	cm.Trace = sc.trace.dumpData()
 	return cm
 }

 func (c *channelMap) GetSocket(id int64) *SocketMetric {
 	sm := &SocketMetric{}
 	c.mu.RLock()
 	if ls, ok := c.listenSockets[id]; ok {
 		c.mu.RUnlock()
 		sm.SocketData = ls.s.ChannelzMetric()
 		sm.ID = ls.id
 		sm.RefName = ls.refName
 		return sm
 	}
 	if ns, ok := c.normalSockets[id]; ok {
 		c.mu.RUnlock()
 		sm.SocketData = ns.s.ChannelzMetric()
 		sm.ID = ns.id
 		sm.RefName = ns.refName
 		return sm
 	}
 	c.mu.RUnlock()
 	return nil
 }

 type idGenerator struct {
 	id int64
 }

 func (i *idGenerator) reset() {
 	atomic.StoreInt64(&i.id, 0)
 }

 func (i *idGenerator) genID() int64 {
 	return atomic.AddInt64(&i.id, 1)
 }
	/*
	*
	* Copyright 2018 gRPC 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 channelz defines APIs for enabling channelz service, entry
	// registration/deletion, and accessing channelz data. It also defines channelz
	// metric struct formats.
	//
	// All APIs in this package are experimental.
	package channelz

	import (
	"sort"
	"sync"
	"sync/atomic"
	"time"

	"google.golang.org/grpc/grpclog"
	)

	const (
	defaultMaxTraceEntry int32 = 30
	)

	var (
	db dbWrapper
	idGen idGenerator
	// EntryPerPage defines the number of channelz entries to be shown on a web page.
	EntryPerPage = 50
	curState int32
	maxTraceEntry = defaultMaxTraceEntry
	)

	// TurnOn turns on channelz data collection.
	func TurnOn() {
	if !IsOn() {
	NewChannelzStorage()
	atomic.StoreInt32(&curState, 1)
	}
	}

	// IsOn returns whether channelz data collection is on.
	func IsOn() bool {
	return atomic.CompareAndSwapInt32(&curState, 1, 1)
	}

	// SetMaxTraceEntry sets maximum number of trace entry per entity (i.e. channel/subchannel).
	// Setting it to 0 will disable channel tracing.
	func SetMaxTraceEntry(i int32) {
	atomic.StoreInt32(&maxTraceEntry, i)
	}

	// ResetMaxTraceEntryToDefault resets the maximum number of trace entry per entity to default.
	func ResetMaxTraceEntryToDefault() {
	atomic.StoreInt32(&maxTraceEntry, defaultMaxTraceEntry)
	}

	func getMaxTraceEntry() int {
	i := atomic.LoadInt32(&maxTraceEntry)
	return int(i)
	}

	// dbWarpper wraps around a reference to internal channelz data storage, and
	// provide synchronized functionality to set and get the reference.
	type dbWrapper struct {
	mu sync.RWMutex
	DB *channelMap
	}

	func (d dbWrapper) set(db channelMap) {
	d.mu.Lock()
	d.DB = db
	d.mu.Unlock()
	}

	func (d dbWrapper) get() channelMap {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.DB
	}

	// NewChannelzStorage initializes channelz data storage and id generator.
	//
	// Note: This function is exported for testing purpose only. User should not call
	// it in most cases.
	func NewChannelzStorage() {
	db.set(&channelMap{
	topLevelChannels: make(map[int64]struct{}),
	channels: make(map[int64]*channel),
	listenSockets: make(map[int64]*listenSocket),
	normalSockets: make(map[int64]*normalSocket),
	servers: make(map[int64]*server),
	subChannels: make(map[int64]*subChannel),
	})
	idGen.reset()
	}

	// GetTopChannels returns a slice of top channel's ChannelMetric, along with a
	// boolean indicating whether there's more top channels to be queried for.
	//
	// The arg id specifies that only top channel with id at or above it will be included
	// in the result. The returned slice is up to a length of EntryPerPage, and is
	// sorted in ascending id order.
	func GetTopChannels(id int64) ([]*ChannelMetric, bool) {
	return db.get().GetTopChannels(id)
	}

	// GetServers returns a slice of server's ServerMetric, along with a
	// boolean indicating whether there's more servers to be queried for.
	//
	// The arg id specifies that only server with id at or above it will be included
	// in the result. The returned slice is up to a length of EntryPerPage, and is
	// sorted in ascending id order.
	func GetServers(id int64) ([]*ServerMetric, bool) {
	return db.get().GetServers(id)
	}

	// GetServerSockets returns a slice of server's (identified by id) normal socket's
	// SocketMetric, along with a boolean indicating whether there's more sockets to
	// be queried for.
	//
	// The arg startID specifies that only sockets with id at or above it will be
	// included in the result. The returned slice is up to a length of EntryPerPage,
	// and is sorted in ascending id order.
	func GetServerSockets(id int64, startID int64) ([]*SocketMetric, bool) {
	return db.get().GetServerSockets(id, startID)
	}

	// GetChannel returns the ChannelMetric for the channel (identified by id).
	func GetChannel(id int64) *ChannelMetric {
	return db.get().GetChannel(id)
	}

	// GetSubChannel returns the SubChannelMetric for the subchannel (identified by id).
	func GetSubChannel(id int64) *SubChannelMetric {
	return db.get().GetSubChannel(id)
	}

	// GetSocket returns the SocketInternalMetric for the socket (identified by id).
	func GetSocket(id int64) *SocketMetric {
	return db.get().GetSocket(id)
	}

	// RegisterChannel registers the given channel c in channelz database with ref
	// as its reference name, and add it to the child list of its parent (identified
	// by pid). pid = 0 means no parent. It returns the unique channelz tracking id
	// assigned to this channel.
	func RegisterChannel(c Channel, pid int64, ref string) int64 {
	id := idGen.genID()
	cn := &channel{
	refName: ref,
	c: c,
	subChans: make(map[int64]string),
	nestedChans: make(map[int64]string),
	id: id,
	pid: pid,
	trace: &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
	}
	if pid == 0 {
	db.get().addChannel(id, cn, true, pid, ref)
	} else {
	db.get().addChannel(id, cn, false, pid, ref)
	}
	return id
	}

	// RegisterSubChannel registers the given channel c in channelz database with ref
	// as its reference name, and add it to the child list of its parent (identified
	// by pid). It returns the unique channelz tracking id assigned to this subchannel.
	func RegisterSubChannel(c Channel, pid int64, ref string) int64 {
	if pid == 0 {
	grpclog.Error("a SubChannel's parent id cannot be 0")
	return 0
	}
	id := idGen.genID()
	sc := &subChannel{
	refName: ref,
	c: c,
	sockets: make(map[int64]string),
	id: id,
	pid: pid,
	trace: &channelTrace{createdTime: time.Now(), events: make([]*TraceEvent, 0, getMaxTraceEntry())},
	}
	db.get().addSubChannel(id, sc, pid, ref)
	return id
	}

	// RegisterServer registers the given server s in channelz database. It returns
	// the unique channelz tracking id assigned to this server.
	func RegisterServer(s Server, ref string) int64 {
	id := idGen.genID()
	svr := &server{
	refName: ref,
	s: s,
	sockets: make(map[int64]string),
	listenSockets: make(map[int64]string),
	id: id,
	}
	db.get().addServer(id, svr)
	return id
	}

	// RegisterListenSocket registers the given listen socket s in channelz database
	// with ref as its reference name, and add it to the child list of its parent
	// (identified by pid). It returns the unique channelz tracking id assigned to
	// this listen socket.
	func RegisterListenSocket(s Socket, pid int64, ref string) int64 {
	if pid == 0 {
	grpclog.Error("a ListenSocket's parent id cannot be 0")
	return 0
	}
	id := idGen.genID()
	ls := &listenSocket{refName: ref, s: s, id: id, pid: pid}
	db.get().addListenSocket(id, ls, pid, ref)
	return id
	}

	// RegisterNormalSocket registers the given normal socket s in channelz database
	// with ref as its reference name, and add it to the child list of its parent
	// (identified by pid). It returns the unique channelz tracking id assigned to
	// this normal socket.
	func RegisterNormalSocket(s Socket, pid int64, ref string) int64 {
	if pid == 0 {
	grpclog.Error("a NormalSocket's parent id cannot be 0")
	return 0
	}
	id := idGen.genID()
	ns := &normalSocket{refName: ref, s: s, id: id, pid: pid}
	db.get().addNormalSocket(id, ns, pid, ref)
	return id
	}

	// RemoveEntry removes an entry with unique channelz trakcing id to be id from
	// channelz database.
	func RemoveEntry(id int64) {
	db.get().removeEntry(id)
	}

	// TraceEventDesc is what the caller of AddTraceEvent should provide to describe the event to be added
	// to the channel trace.
	// The Parent field is optional. It is used for event that will be recorded in the entity's parent
	// trace also.
	type TraceEventDesc struct {
	Desc string
	Severity Severity
	Parent *TraceEventDesc
	}

	// AddTraceEvent adds trace related to the entity with specified id, using the provided TraceEventDesc.
	func AddTraceEvent(id int64, desc *TraceEventDesc) {
	if getMaxTraceEntry() == 0 {
	return
	}
	db.get().traceEvent(id, desc)
	}

	// channelMap is the storage data structure for channelz.
	// Methods of channelMap can be divided in two two categories with respect to locking.
	// 1. Methods acquire the global lock.
	// 2. Methods that can only be called when global lock is held.
	// A second type of method need always to be called inside a first type of method.
	type channelMap struct {
	mu sync.RWMutex
	topLevelChannels map[int64]struct{}
	servers map[int64]*server
	channels map[int64]*channel
	subChannels map[int64]*subChannel
	listenSockets map[int64]*listenSocket
	normalSockets map[int64]*normalSocket
	}

	func (c channelMap) addServer(id int64, s server) {
	c.mu.Lock()
	s.cm = c
	c.servers[id] = s
	c.mu.Unlock()
	}

	func (c channelMap) addChannel(id int64, cn channel, isTopChannel bool, pid int64, ref string) {
	c.mu.Lock()
	cn.cm = c
	cn.trace.cm = c
	c.channels[id] = cn
	if isTopChannel {
	c.topLevelChannels[id] = struct{}{}
	} else {
	c.findEntry(pid).addChild(id, cn)
	}
	c.mu.Unlock()
	}

	func (c channelMap) addSubChannel(id int64, sc subChannel, pid int64, ref string) {
	c.mu.Lock()
	sc.cm = c
	sc.trace.cm = c
	c.subChannels[id] = sc
	c.findEntry(pid).addChild(id, sc)
	c.mu.Unlock()
	}

	func (c channelMap) addListenSocket(id int64, ls listenSocket, pid int64, ref string) {
	c.mu.Lock()
	ls.cm = c
	c.listenSockets[id] = ls
	c.findEntry(pid).addChild(id, ls)
	c.mu.Unlock()
	}

	func (c channelMap) addNormalSocket(id int64, ns normalSocket, pid int64, ref string) {
	c.mu.Lock()
	ns.cm = c
	c.normalSockets[id] = ns
	c.findEntry(pid).addChild(id, ns)
	c.mu.Unlock()
	}

	// removeEntry triggers the removal of an entry, which may not indeed delete the entry, if it has to
	// wait on the deletion of its children and until no other entity's channel trace references it.
	// It may lead to a chain of entry deletion. For example, deleting the last socket of a gracefully
	// shutting down server will lead to the server being also deleted.
	func (c *channelMap) removeEntry(id int64) {
	c.mu.Lock()
	c.findEntry(id).triggerDelete()
	c.mu.Unlock()
	}

	// c.mu must be held by the caller
	func (c *channelMap) decrTraceRefCount(id int64) {
	e := c.findEntry(id)
	if v, ok := e.(tracedChannel); ok {
	v.decrTraceRefCount()
	e.deleteSelfIfReady()
	}
	}

	// c.mu must be held by the caller.
	func (c *channelMap) findEntry(id int64) entry {
	var v entry
	var ok bool
	if v, ok = c.channels[id]; ok {
	return v
	}
	if v, ok = c.subChannels[id]; ok {
	return v
	}
	if v, ok = c.servers[id]; ok {
	return v
	}
	if v, ok = c.listenSockets[id]; ok {
	return v
	}
	if v, ok = c.normalSockets[id]; ok {
	return v
	}
	return &dummyEntry{idNotFound: id}
	}

	// c.mu must be held by the caller
	// deleteEntry simply deletes an entry from the channelMap. Before calling this
	// method, caller must check this entry is ready to be deleted, i.e removeEntry()
	// has been called on it, and no children still exist.
	// Conditionals are ordered by the expected frequency of deletion of each entity
	// type, in order to optimize performance.
	func (c *channelMap) deleteEntry(id int64) {
	var ok bool
	if _, ok = c.normalSockets[id]; ok {
	delete(c.normalSockets, id)
	return
	}
	if _, ok = c.subChannels[id]; ok {
	delete(c.subChannels, id)
	return
	}
	if _, ok = c.channels[id]; ok {
	delete(c.channels, id)
	delete(c.topLevelChannels, id)
	return
	}
	if _, ok = c.listenSockets[id]; ok {
	delete(c.listenSockets, id)
	return
	}
	if _, ok = c.servers[id]; ok {
	delete(c.servers, id)
	return
	}
	}

	func (c channelMap) traceEvent(id int64, desc TraceEventDesc) {
	c.mu.Lock()
	child := c.findEntry(id)
	childTC, ok := child.(tracedChannel)
	if !ok {
	c.mu.Unlock()
	return
	}
	childTC.getChannelTrace().append(&TraceEvent{Desc: desc.Desc, Severity: desc.Severity, Timestamp: time.Now()})
	if desc.Parent != nil {
	parent := c.findEntry(child.getParentID())
	var chanType RefChannelType
	switch child.(type) {
	case *channel:
	chanType = RefChannel
	case *subChannel:
	chanType = RefSubChannel
	}
	if parentTC, ok := parent.(tracedChannel); ok {
	parentTC.getChannelTrace().append(&TraceEvent{
	Desc: desc.Parent.Desc,
	Severity: desc.Parent.Severity,
	Timestamp: time.Now(),
	RefID: id,
	RefName: childTC.getRefName(),
	RefType: chanType,
	})
	childTC.incrTraceRefCount()
	}
	}
	c.mu.Unlock()
	}

	type int64Slice []int64

	func (s int64Slice) Len() int { return len(s) }
	func (s int64Slice) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
	func (s int64Slice) Less(i, j int) bool { return s[i] < s[j] }

	func copyMap(m map[int64]string) map[int64]string {
	n := make(map[int64]string)
	for k, v := range m {
	n[k] = v
	}
	return n
	}

	func min(a, b int) int {
	if a < b {
	return a
	}
	return b
	}

	func (c channelMap) GetTopChannels(id int64) ([]ChannelMetric, bool) {
	c.mu.RLock()
	l := len(c.topLevelChannels)
	ids := make([]int64, 0, l)
	cns := make([]*channel, 0, min(l, EntryPerPage))

	for k := range c.topLevelChannels {
	ids = append(ids, k)
	}
	sort.Sort(int64Slice(ids))
	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
	count := 0
	var end bool
	var t []*ChannelMetric
	for i, v := range ids[idx:] {
	if count == EntryPerPage {
	break
	}
	if cn, ok := c.channels[v]; ok {
	cns = append(cns, cn)
	t = append(t, &ChannelMetric{
	NestedChans: copyMap(cn.nestedChans),
	SubChans: copyMap(cn.subChans),
	})
	count++
	}
	if i == len(ids[idx:])-1 {
	end = true
	break
	}
	}
	c.mu.RUnlock()
	if count == 0 {
	end = true
	}

	for i, cn := range cns {
	t[i].ChannelData = cn.c.ChannelzMetric()
	t[i].ID = cn.id
	t[i].RefName = cn.refName
	t[i].Trace = cn.trace.dumpData()
	}
	return t, end
	}

	func (c channelMap) GetServers(id int64) ([]ServerMetric, bool) {
	c.mu.RLock()
	l := len(c.servers)
	ids := make([]int64, 0, l)
	ss := make([]*server, 0, min(l, EntryPerPage))
	for k := range c.servers {
	ids = append(ids, k)
	}
	sort.Sort(int64Slice(ids))
	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= id })
	count := 0
	var end bool
	var s []*ServerMetric
	for i, v := range ids[idx:] {
	if count == EntryPerPage {
	break
	}
	if svr, ok := c.servers[v]; ok {
	ss = append(ss, svr)
	s = append(s, &ServerMetric{
	ListenSockets: copyMap(svr.listenSockets),
	})
	count++
	}
	if i == len(ids[idx:])-1 {
	end = true
	break
	}
	}
	c.mu.RUnlock()
	if count == 0 {
	end = true
	}

	for i, svr := range ss {
	s[i].ServerData = svr.s.ChannelzMetric()
	s[i].ID = svr.id
	s[i].RefName = svr.refName
	}
	return s, end
	}

	func (c channelMap) GetServerSockets(id int64, startID int64) ([]SocketMetric, bool) {
	var svr *server
	var ok bool
	c.mu.RLock()
	if svr, ok = c.servers[id]; !ok {
	// server with id doesn't exist.
	c.mu.RUnlock()
	return nil, true
	}
	svrskts := svr.sockets
	l := len(svrskts)
	ids := make([]int64, 0, l)
	sks := make([]*normalSocket, 0, min(l, EntryPerPage))
	for k := range svrskts {
	ids = append(ids, k)
	}
	sort.Sort(int64Slice(ids))
	idx := sort.Search(len(ids), func(i int) bool { return ids[i] >= startID })
	count := 0
	var end bool
	for i, v := range ids[idx:] {
	if count == EntryPerPage {
	break
	}
	if ns, ok := c.normalSockets[v]; ok {
	sks = append(sks, ns)
	count++
	}
	if i == len(ids[idx:])-1 {
	end = true
	break
	}
	}
	c.mu.RUnlock()
	if count == 0 {
	end = true
	}
	var s []*SocketMetric
	for _, ns := range sks {
	sm := &SocketMetric{}
	sm.SocketData = ns.s.ChannelzMetric()
	sm.ID = ns.id
	sm.RefName = ns.refName
	s = append(s, sm)
	}
	return s, end
	}

	func (c channelMap) GetChannel(id int64) ChannelMetric {
	cm := &ChannelMetric{}
	var cn *channel
	var ok bool
	c.mu.RLock()
	if cn, ok = c.channels[id]; !ok {
	// channel with id doesn't exist.
	c.mu.RUnlock()
	return nil
	}
	cm.NestedChans = copyMap(cn.nestedChans)
	cm.SubChans = copyMap(cn.subChans)
	// cn.c can be set to &dummyChannel{} when deleteSelfFromMap is called. Save a copy of cn.c when
	// holding the lock to prevent potential data race.
	chanCopy := cn.c
	c.mu.RUnlock()
	cm.ChannelData = chanCopy.ChannelzMetric()
	cm.ID = cn.id
	cm.RefName = cn.refName
	cm.Trace = cn.trace.dumpData()
	return cm
	}

	func (c channelMap) GetSubChannel(id int64) SubChannelMetric {
	cm := &SubChannelMetric{}
	var sc *subChannel
	var ok bool
	c.mu.RLock()
	if sc, ok = c.subChannels[id]; !ok {
	// subchannel with id doesn't exist.
	c.mu.RUnlock()
	return nil
	}
	cm.Sockets = copyMap(sc.sockets)
	// sc.c can be set to &dummyChannel{} when deleteSelfFromMap is called. Save a copy of sc.c when
	// holding the lock to prevent potential data race.
	chanCopy := sc.c
	c.mu.RUnlock()
	cm.ChannelData = chanCopy.ChannelzMetric()
	cm.ID = sc.id
	cm.RefName = sc.refName
	cm.Trace = sc.trace.dumpData()
	return cm
	}

	func (c channelMap) GetSocket(id int64) SocketMetric {
	sm := &SocketMetric{}
	c.mu.RLock()
	if ls, ok := c.listenSockets[id]; ok {
	c.mu.RUnlock()
	sm.SocketData = ls.s.ChannelzMetric()
	sm.ID = ls.id
	sm.RefName = ls.refName
	return sm
	}
	if ns, ok := c.normalSockets[id]; ok {
	c.mu.RUnlock()
	sm.SocketData = ns.s.ChannelzMetric()
	sm.ID = ns.id
	sm.RefName = ns.refName
	return sm
	}
	c.mu.RUnlock()
	return nil
	}

	type idGenerator struct {
	id int64
	}

	func (i *idGenerator) reset() {
	atomic.StoreInt64(&i.id, 0)
	}

	func (i *idGenerator) genID() int64 {
	return atomic.AddInt64(&i.id, 1)
	}