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// Package zk is a native Go client library for the ZooKeeper orchestration service.
package zk
/*
TODO:
* make sure a ping response comes back in a reasonable time
Possible watcher events:
* Event{Type: EventNotWatching, State: StateDisconnected, Path: path, Err: err}
*/
import (
"context"
"crypto/rand"
"encoding/binary"
"errors"
"fmt"
"io"
"net"
"strings"
"sync"
"sync/atomic"
"time"
)
// ErrNoServer indicates that an operation cannot be completed
// because attempts to connect to all servers in the list failed.
var ErrNoServer = errors.New("zk: could not connect to a server")
// ErrInvalidPath indicates that an operation was being attempted on
// an invalid path. (e.g. empty path).
var ErrInvalidPath = errors.New("zk: invalid path")
// DefaultLogger uses the stdlib log package for logging.
var DefaultLogger Logger = defaultLogger{}
const (
bufferSize = 1536 * 1024
eventChanSize = 6
sendChanSize = 16
protectedPrefix = "_c_"
)
type watchType int
const (
watchTypeData watchType = iota
watchTypeExist
watchTypeChild
)
type watchPathType struct {
path string
wType watchType
}
// Dialer is a function to be used to establish a connection to a single host.
type Dialer func(network, address string, timeout time.Duration) (net.Conn, error)
// Logger is an interface that can be implemented to provide custom log output.
type Logger interface {
Printf(string, ...interface{})
}
type authCreds struct {
scheme string
auth []byte
}
// Conn is the client connection and tracks all details for communication with the server.
type Conn struct {
lastZxid int64
sessionID int64
state State // must be 32-bit aligned
xid uint32
sessionTimeoutMs int32 // session timeout in milliseconds
passwd []byte
dialer Dialer
hostProvider HostProvider
serverMu sync.Mutex // protects server
server string // remember the address/port of the current server
conn net.Conn
eventChan chan Event
eventCallback EventCallback // may be nil
shouldQuit chan struct{}
shouldQuitOnce sync.Once
pingInterval time.Duration
recvTimeout time.Duration
connectTimeout time.Duration
maxBufferSize int
creds []authCreds
credsMu sync.Mutex // protects server
sendChan chan *request
requests map[int32]*request // Xid -> pending request
requestsLock sync.Mutex
watchers map[watchPathType][]chan Event
watchersLock sync.Mutex
closeChan chan struct{} // channel to tell send loop stop
// Debug (used by unit tests)
reconnectLatch chan struct{}
setWatchLimit int
setWatchCallback func([]*setWatchesRequest)
// Debug (for recurring re-auth hang)
debugCloseRecvLoop bool
resendZkAuthFn func(context.Context, *Conn) error
logger Logger
logInfo bool // true if information messages are logged; false if only errors are logged
buf []byte
}
// connOption represents a connection option.
type connOption func(c *Conn)
type request struct {
xid int32
opcode int32
pkt interface{}
recvStruct interface{}
recvChan chan response
// Because sending and receiving happen in separate go routines, there's
// a possible race condition when creating watches from outside the read
// loop. We must ensure that a watcher gets added to the list synchronously
// with the response from the server on any request that creates a watch.
// In order to not hard code the watch logic for each opcode in the recv
// loop the caller can use recvFunc to insert some synchronously code
// after a response.
recvFunc func(*request, *responseHeader, error)
}
type response struct {
zxid int64
err error
}
// Event is an Znode event sent by the server.
// Refer to EventType for more details.
type Event struct {
Type EventType
State State
Path string // For non-session events, the path of the watched node.
Err error
Server string // For connection events
}
// HostProvider is used to represent a set of hosts a ZooKeeper client should connect to.
// It is an analog of the Java equivalent:
// http://svn.apache.org/viewvc/zookeeper/trunk/src/java/main/org/apache/zookeeper/client/HostProvider.java?view=markup
type HostProvider interface {
// Init is called first, with the servers specified in the connection string.
Init(servers []string) error
// Len returns the number of servers.
Len() int
// Next returns the next server to connect to. retryStart will be true if we've looped through
// all known servers without Connected() being called.
Next() (server string, retryStart bool)
// Notify the HostProvider of a successful connection.
Connected()
}
// ConnectWithDialer establishes a new connection to a pool of zookeeper servers
// using a custom Dialer. See Connect for further information about session timeout.
// This method is deprecated and provided for compatibility: use the WithDialer option instead.
func ConnectWithDialer(servers []string, sessionTimeout time.Duration, dialer Dialer) (*Conn, <-chan Event, error) {
return Connect(servers, sessionTimeout, WithDialer(dialer))
}
// Connect establishes a new connection to a pool of zookeeper
// servers. The provided session timeout sets the amount of time for which
// a session is considered valid after losing connection to a server. Within
// the session timeout it's possible to reestablish a connection to a different
// server and keep the same session. This is means any ephemeral nodes and
// watches are maintained.
func Connect(servers []string, sessionTimeout time.Duration, options ...connOption) (*Conn, <-chan Event, error) {
if len(servers) == 0 {
return nil, nil, errors.New("zk: server list must not be empty")
}
srvs := FormatServers(servers)
// Randomize the order of the servers to avoid creating hotspots
stringShuffle(srvs)
ec := make(chan Event, eventChanSize)
conn := &Conn{
dialer: net.DialTimeout,
hostProvider: NewDNSHostProvider(),
conn: nil,
state: StateDisconnected,
eventChan: ec,
shouldQuit: make(chan struct{}),
connectTimeout: 1 * time.Second,
sendChan: make(chan *request, sendChanSize),
requests: make(map[int32]*request),
watchers: make(map[watchPathType][]chan Event),
passwd: emptyPassword,
logger: DefaultLogger,
logInfo: true, // default is true for backwards compatability
buf: make([]byte, bufferSize),
resendZkAuthFn: resendZkAuth,
}
// Set provided options.
for _, option := range options {
option(conn)
}
if err := conn.hostProvider.Init(srvs); err != nil {
return nil, nil, err
}
conn.setTimeouts(int32(sessionTimeout / time.Millisecond))
// TODO: This context should be passed in by the caller to be the connection lifecycle context.
ctx := context.Background()
go func() {
conn.loop(ctx)
conn.flushRequests(ErrClosing)
conn.invalidateWatches(ErrClosing)
close(conn.eventChan)
}()
return conn, ec, nil
}
// WithDialer returns a connection option specifying a non-default Dialer.
func WithDialer(dialer Dialer) connOption {
return func(c *Conn) {
c.dialer = dialer
}
}
// WithHostProvider returns a connection option specifying a non-default HostProvider.
func WithHostProvider(hostProvider HostProvider) connOption {
return func(c *Conn) {
c.hostProvider = hostProvider
}
}
// WithLogger returns a connection option specifying a non-default Logger.
func WithLogger(logger Logger) connOption {
return func(c *Conn) {
c.logger = logger
}
}
// WithLogInfo returns a connection option specifying whether or not information messages
// should be logged.
func WithLogInfo(logInfo bool) connOption {
return func(c *Conn) {
c.logInfo = logInfo
}
}
// EventCallback is a function that is called when an Event occurs.
type EventCallback func(Event)
// WithEventCallback returns a connection option that specifies an event
// callback.
// The callback must not block - doing so would delay the ZK go routines.
func WithEventCallback(cb EventCallback) connOption {
return func(c *Conn) {
c.eventCallback = cb
}
}
// WithMaxBufferSize sets the maximum buffer size used to read and decode
// packets received from the Zookeeper server. The standard Zookeeper client for
// Java defaults to a limit of 1mb. For backwards compatibility, this Go client
// defaults to unbounded unless overridden via this option. A value that is zero
// or negative indicates that no limit is enforced.
//
// This is meant to prevent resource exhaustion in the face of potentially
// malicious data in ZK. It should generally match the server setting (which
// also defaults ot 1mb) so that clients and servers agree on the limits for
// things like the size of data in an individual znode and the total size of a
// transaction.
//
// For production systems, this should be set to a reasonable value (ideally
// that matches the server configuration). For ops tooling, it is handy to use a
// much larger limit, in order to do things like clean-up problematic state in
// the ZK tree. For example, if a single znode has a huge number of children, it
// is possible for the response to a "list children" operation to exceed this
// buffer size and cause errors in clients. The only way to subsequently clean
// up the tree (by removing superfluous children) is to use a client configured
// with a larger buffer size that can successfully query for all of the child
// names and then remove them. (Note there are other tools that can list all of
// the child names without an increased buffer size in the client, but they work
// by inspecting the servers' transaction logs to enumerate children instead of
// sending an online request to a server.
func WithMaxBufferSize(maxBufferSize int) connOption {
return func(c *Conn) {
c.maxBufferSize = maxBufferSize
}
}
// WithMaxConnBufferSize sets maximum buffer size used to send and encode
// packets to Zookeeper server. The standard Zookeeper client for java defaults
// to a limit of 1mb. This option should be used for non-standard server setup
// where znode is bigger than default 1mb.
func WithMaxConnBufferSize(maxBufferSize int) connOption {
return func(c *Conn) {
c.buf = make([]byte, maxBufferSize)
}
}
// Close will submit a close request with ZK and signal the connection to stop
// sending and receiving packets.
func (c *Conn) Close() {
c.shouldQuitOnce.Do(func() {
close(c.shouldQuit)
select {
case <-c.queueRequest(opClose, &closeRequest{}, &closeResponse{}, nil):
case <-time.After(time.Second):
}
})
}
// State returns the current state of the connection.
func (c *Conn) State() State {
return State(atomic.LoadInt32((*int32)(&c.state)))
}
// SessionID returns the current session id of the connection.
func (c *Conn) SessionID() int64 {
return atomic.LoadInt64(&c.sessionID)
}
// SetLogger sets the logger to be used for printing errors.
// Logger is an interface provided by this package.
func (c *Conn) SetLogger(l Logger) {
c.logger = l
}
func (c *Conn) setTimeouts(sessionTimeoutMs int32) {
c.sessionTimeoutMs = sessionTimeoutMs
sessionTimeout := time.Duration(sessionTimeoutMs) * time.Millisecond
c.recvTimeout = sessionTimeout * 2 / 3
c.pingInterval = c.recvTimeout / 2
}
func (c *Conn) setState(state State) {
atomic.StoreInt32((*int32)(&c.state), int32(state))
c.sendEvent(Event{Type: EventSession, State: state, Server: c.Server()})
}
func (c *Conn) sendEvent(evt Event) {
if c.eventCallback != nil {
c.eventCallback(evt)
}
select {
case c.eventChan <- evt:
default:
// panic("zk: event channel full - it must be monitored and never allowed to be full")
}
}
func (c *Conn) connect() error {
var retryStart bool
for {
c.serverMu.Lock()
c.server, retryStart = c.hostProvider.Next()
c.serverMu.Unlock()
c.setState(StateConnecting)
if retryStart {
c.flushUnsentRequests(ErrNoServer)
select {
case <-time.After(time.Second):
// pass
case <-c.shouldQuit:
c.setState(StateDisconnected)
c.flushUnsentRequests(ErrClosing)
return ErrClosing
}
}
zkConn, err := c.dialer("tcp", c.Server(), c.connectTimeout)
if err == nil {
c.conn = zkConn
c.setState(StateConnected)
if c.logInfo {
c.logger.Printf("connected to %s", c.Server())
}
return nil
}
c.logger.Printf("failed to connect to %s: %v", c.Server(), err)
}
}
func (c *Conn) sendRequest(
opcode int32,
req interface{},
res interface{},
recvFunc func(*request, *responseHeader, error),
) (
<-chan response,
error,
) {
rq := &request{
xid: c.nextXid(),
opcode: opcode,
pkt: req,
recvStruct: res,
recvChan: make(chan response, 1),
recvFunc: recvFunc,
}
if err := c.sendData(rq); err != nil {
return nil, err
}
return rq.recvChan, nil
}
func (c *Conn) loop(ctx context.Context) {
for {
if err := c.connect(); err != nil {
// c.Close() was called
return
}
err := c.authenticate()
switch {
case err == ErrSessionExpired:
c.logger.Printf("authentication failed: %s", err)
c.invalidateWatches(err)
case err != nil && c.conn != nil:
c.logger.Printf("authentication failed: %s", err)
c.conn.Close()
case err == nil:
if c.logInfo {
c.logger.Printf("authenticated: id=%d, timeout=%d", c.SessionID(), c.sessionTimeoutMs)
}
c.hostProvider.Connected() // mark success
c.closeChan = make(chan struct{}) // channel to tell send loop stop
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer c.conn.Close() // causes recv loop to EOF/exit
defer wg.Done()
if err := c.resendZkAuthFn(ctx, c); err != nil {
c.logger.Printf("error in resending auth creds: %v", err)
return
}
if err := c.sendLoop(); err != nil || c.logInfo {
c.logger.Printf("send loop terminated: %v", err)
}
}()
wg.Add(1)
go func() {
defer close(c.closeChan) // tell send loop to exit
defer wg.Done()
var err error
if c.debugCloseRecvLoop {
err = errors.New("DEBUG: close recv loop")
} else {
err = c.recvLoop(c.conn)
}
if err != io.EOF || c.logInfo {
c.logger.Printf("recv loop terminated: %v", err)
}
if err == nil {
panic("zk: recvLoop should never return nil error")
}
}()
c.sendSetWatches()
wg.Wait()
}
c.setState(StateDisconnected)
select {
case <-c.shouldQuit:
c.flushRequests(ErrClosing)
return
default:
}
if err != ErrSessionExpired {
err = ErrConnectionClosed
}
c.flushRequests(err)
if c.reconnectLatch != nil {
select {
case <-c.shouldQuit:
return
case <-c.reconnectLatch:
}
}
}
}
func (c *Conn) flushUnsentRequests(err error) {
for {
select {
default:
return
case req := <-c.sendChan:
req.recvChan <- response{-1, err}
}
}
}
// Send error to all pending requests and clear request map
func (c *Conn) flushRequests(err error) {
c.requestsLock.Lock()
for _, req := range c.requests {
req.recvChan <- response{-1, err}
}
c.requests = make(map[int32]*request)
c.requestsLock.Unlock()
}
// Send event to all interested watchers
func (c *Conn) notifyWatches(ev Event) {
var wTypes []watchType
switch ev.Type {
case EventNodeCreated:
wTypes = []watchType{watchTypeExist}
case EventNodeDataChanged:
wTypes = []watchType{watchTypeExist, watchTypeData}
case EventNodeChildrenChanged:
wTypes = []watchType{watchTypeChild}
case EventNodeDeleted:
wTypes = []watchType{watchTypeExist, watchTypeData, watchTypeChild}
}
c.watchersLock.Lock()
defer c.watchersLock.Unlock()
for _, t := range wTypes {
wpt := watchPathType{ev.Path, t}
if watchers := c.watchers[wpt]; len(watchers) > 0 {
for _, ch := range watchers {
ch <- ev
close(ch)
}
delete(c.watchers, wpt)
}
}
}
// Send error to all watchers and clear watchers map
func (c *Conn) invalidateWatches(err error) {
c.watchersLock.Lock()
defer c.watchersLock.Unlock()
if len(c.watchers) >= 0 {
for pathType, watchers := range c.watchers {
ev := Event{Type: EventNotWatching, State: StateDisconnected, Path: pathType.path, Err: err}
c.sendEvent(ev) // also publish globally
for _, ch := range watchers {
ch <- ev
close(ch)
}
}
c.watchers = make(map[watchPathType][]chan Event)
}
}
func (c *Conn) sendSetWatches() {
c.watchersLock.Lock()
defer c.watchersLock.Unlock()
if len(c.watchers) == 0 {
return
}
// NB: A ZK server, by default, rejects packets >1mb. So, if we have too
// many watches to reset, we need to break this up into multiple packets
// to avoid hitting that limit. Mirroring the Java client behavior: we are
// conservative in that we limit requests to 128kb (since server limit is
// is actually configurable and could conceivably be configured smaller
// than default of 1mb).
limit := 128 * 1024
if c.setWatchLimit > 0 {
limit = c.setWatchLimit
}
var reqs []*setWatchesRequest
var req *setWatchesRequest
var sizeSoFar int
n := 0
for pathType, watchers := range c.watchers {
if len(watchers) == 0 {
continue
}
addlLen := 4 + len(pathType.path)
if req == nil || sizeSoFar+addlLen > limit {
if req != nil {
// add to set of requests that we'll send
reqs = append(reqs, req)
}
sizeSoFar = 28 // fixed overhead of a set-watches packet
req = &setWatchesRequest{
RelativeZxid: c.lastZxid,
DataWatches: make([]string, 0),
ExistWatches: make([]string, 0),
ChildWatches: make([]string, 0),
}
}
sizeSoFar += addlLen
switch pathType.wType {
case watchTypeData:
req.DataWatches = append(req.DataWatches, pathType.path)
case watchTypeExist:
req.ExistWatches = append(req.ExistWatches, pathType.path)
case watchTypeChild:
req.ChildWatches = append(req.ChildWatches, pathType.path)
}
n++
}
if n == 0 {
return
}
if req != nil { // don't forget any trailing packet we were building
reqs = append(reqs, req)
}
if c.setWatchCallback != nil {
c.setWatchCallback(reqs)
}
go func() {
res := &setWatchesResponse{}
// TODO: Pipeline these so queue all of them up before waiting on any
// response. That will require some investigation to make sure there
// aren't failure modes where a blocking write to the channel of requests
// could hang indefinitely and cause this goroutine to leak...
for _, req := range reqs {
_, err := c.request(opSetWatches, req, res, nil)
if err != nil {
c.logger.Printf("Failed to set previous watches: %v", err)
break
}
}
}()
}
func (c *Conn) authenticate() error {
buf := make([]byte, 256)
// Encode and send a connect request.
n, err := encodePacket(buf[4:], &connectRequest{
ProtocolVersion: protocolVersion,
LastZxidSeen: c.lastZxid,
TimeOut: c.sessionTimeoutMs,
SessionID: c.SessionID(),
Passwd: c.passwd,
})
if err != nil {
return err
}
binary.BigEndian.PutUint32(buf[:4], uint32(n))
c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout * 10))
_, err = c.conn.Write(buf[:n+4])
c.conn.SetWriteDeadline(time.Time{})
if err != nil {
return err
}
// Receive and decode a connect response.
c.conn.SetReadDeadline(time.Now().Add(c.recvTimeout * 10))
_, err = io.ReadFull(c.conn, buf[:4])
c.conn.SetReadDeadline(time.Time{})
if err != nil {
return err
}
blen := int(binary.BigEndian.Uint32(buf[:4]))
if cap(buf) < blen {
buf = make([]byte, blen)
}
_, err = io.ReadFull(c.conn, buf[:blen])
if err != nil {
return err
}
r := connectResponse{}
_, err = decodePacket(buf[:blen], &r)
if err != nil {
return err
}
if r.SessionID == 0 {
atomic.StoreInt64(&c.sessionID, int64(0))
c.passwd = emptyPassword
c.lastZxid = 0
c.setState(StateExpired)
return ErrSessionExpired
}
atomic.StoreInt64(&c.sessionID, r.SessionID)
c.setTimeouts(r.TimeOut)
c.passwd = r.Passwd
c.setState(StateHasSession)
return nil
}
func (c *Conn) sendData(req *request) error {
header := &requestHeader{req.xid, req.opcode}
n, err := encodePacket(c.buf[4:], header)
if err != nil {
req.recvChan <- response{-1, err}
return nil
}
n2, err := encodePacket(c.buf[4+n:], req.pkt)
if err != nil {
req.recvChan <- response{-1, err}
return nil
}
n += n2
binary.BigEndian.PutUint32(c.buf[:4], uint32(n))
c.requestsLock.Lock()
select {
case <-c.closeChan:
req.recvChan <- response{-1, ErrConnectionClosed}
c.requestsLock.Unlock()
return ErrConnectionClosed
default:
}
c.requests[req.xid] = req
c.requestsLock.Unlock()
c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout))
_, err = c.conn.Write(c.buf[:n+4])
c.conn.SetWriteDeadline(time.Time{})
if err != nil {
req.recvChan <- response{-1, err}
c.conn.Close()
return err
}
return nil
}
func (c *Conn) sendLoop() error {
pingTicker := time.NewTicker(c.pingInterval)
defer pingTicker.Stop()
for {
select {
case req := <-c.sendChan:
if err := c.sendData(req); err != nil {
return err
}
case <-pingTicker.C:
n, err := encodePacket(c.buf[4:], &requestHeader{Xid: -2, Opcode: opPing})
if err != nil {
panic("zk: opPing should never fail to serialize")
}
binary.BigEndian.PutUint32(c.buf[:4], uint32(n))
c.conn.SetWriteDeadline(time.Now().Add(c.recvTimeout))
_, err = c.conn.Write(c.buf[:n+4])
c.conn.SetWriteDeadline(time.Time{})
if err != nil {
c.conn.Close()
return err
}
case <-c.closeChan:
return nil
}
}
}
func (c *Conn) recvLoop(conn net.Conn) error {
sz := bufferSize
if c.maxBufferSize > 0 && sz > c.maxBufferSize {
sz = c.maxBufferSize
}
buf := make([]byte, sz)
for {
// package length
if err := conn.SetReadDeadline(time.Now().Add(c.recvTimeout)); err != nil {
c.logger.Printf("failed to set connection deadline: %v", err)
}
_, err := io.ReadFull(conn, buf[:4])
if err != nil {
return fmt.Errorf("failed to read from connection: %v", err)
}
blen := int(binary.BigEndian.Uint32(buf[:4]))
if cap(buf) < blen {
if c.maxBufferSize > 0 && blen > c.maxBufferSize {
return fmt.Errorf("received packet from server with length %d, which exceeds max buffer size %d", blen, c.maxBufferSize)
}
buf = make([]byte, blen)
}
_, err = io.ReadFull(conn, buf[:blen])
conn.SetReadDeadline(time.Time{})
if err != nil {
return err
}
res := responseHeader{}
_, err = decodePacket(buf[:16], &res)
if err != nil {
return err
}
if res.Xid == -1 {
res := &watcherEvent{}
_, err = decodePacket(buf[16:blen], res)
if err != nil {
return err
}
ev := Event{
Type: res.Type,
State: res.State,
Path: res.Path,
Err: nil,
}
c.sendEvent(ev)
c.notifyWatches(ev)
} else if res.Xid == -2 {
// Ping response. Ignore.
} else if res.Xid < 0 {
c.logger.Printf("Xid < 0 (%d) but not ping or watcher event", res.Xid)
} else {
if res.Zxid > 0 {
c.lastZxid = res.Zxid
}
c.requestsLock.Lock()
req, ok := c.requests[res.Xid]
if ok {
delete(c.requests, res.Xid)
}
c.requestsLock.Unlock()
if !ok {
c.logger.Printf("Response for unknown request with xid %d", res.Xid)
} else {
if res.Err != 0 {
err = res.Err.toError()
} else {
_, err = decodePacket(buf[16:blen], req.recvStruct)
}
if req.recvFunc != nil {
req.recvFunc(req, &res, err)
}
req.recvChan <- response{res.Zxid, err}
if req.opcode == opClose {
return io.EOF
}
}
}
}
}
func (c *Conn) nextXid() int32 {
return int32(atomic.AddUint32(&c.xid, 1) & 0x7fffffff)
}
func (c *Conn) addWatcher(path string, watchType watchType) <-chan Event {
c.watchersLock.Lock()
defer c.watchersLock.Unlock()
ch := make(chan Event, 1)
wpt := watchPathType{path, watchType}
c.watchers[wpt] = append(c.watchers[wpt], ch)
return ch
}
func (c *Conn) queueRequest(opcode int32, req interface{}, res interface{}, recvFunc func(*request, *responseHeader, error)) <-chan response {
rq := &request{
xid: c.nextXid(),
opcode: opcode,
pkt: req,
recvStruct: res,
recvChan: make(chan response, 2),
recvFunc: recvFunc,
}
switch opcode {
case opClose:
// always attempt to send close ops.
select {
case c.sendChan <- rq:
case <-time.After(c.connectTimeout * 2):
c.logger.Printf("gave up trying to send opClose to server")
rq.recvChan <- response{-1, ErrConnectionClosed}
}
default:
// otherwise avoid deadlocks for dumb clients who aren't aware that
// the ZK connection is closed yet.
select {
case <-c.shouldQuit:
rq.recvChan <- response{-1, ErrConnectionClosed}
case c.sendChan <- rq:
// check for a tie
select {
case <-c.shouldQuit:
// maybe the caller gets this, maybe not- we tried.
rq.recvChan <- response{-1, ErrConnectionClosed}
default:
}
}
}
return rq.recvChan
}
func (c *Conn) request(opcode int32, req interface{}, res interface{}, recvFunc func(*request, *responseHeader, error)) (int64, error) {
recv := c.queueRequest(opcode, req, res, recvFunc)
select {
case r := <-recv:
return r.zxid, r.err
case <-c.shouldQuit:
// queueRequest() can be racy, double-check for the race here and avoid
// a potential data-race. otherwise the client of this func may try to
// access `res` fields concurrently w/ the async response processor.
// NOTE: callers of this func should check for (at least) ErrConnectionClosed
// and avoid accessing fields of the response object if such error is present.
return -1, ErrConnectionClosed
}
}
// AddAuth adds an authentication config to the connection.
func (c *Conn) AddAuth(scheme string, auth []byte) error {
_, err := c.request(opSetAuth, &setAuthRequest{Type: 0, Scheme: scheme, Auth: auth}, &setAuthResponse{}, nil)
if err != nil {
return err
}
// Remember authdata so that it can be re-submitted on reconnect
//
// FIXME(prozlach): For now we treat "userfoo:passbar" and "userfoo:passbar2"
// as two different entries, which will be re-submitted on reconnect. Some
// research is needed on how ZK treats these cases and
// then maybe switch to something like "map[username] = password" to allow
// only single password for given user with users being unique.
obj := authCreds{
scheme: scheme,
auth: auth,
}
c.credsMu.Lock()
c.creds = append(c.creds, obj)
c.credsMu.Unlock()
return nil
}
// Children returns the children of a znode.
func (c *Conn) Children(path string) ([]string, *Stat, error) {
if err := validatePath(path, false); err != nil {
return nil, nil, err
}
res := &getChildren2Response{}
_, err := c.request(opGetChildren2, &getChildren2Request{Path: path, Watch: false}, res, nil)
if err == ErrConnectionClosed {
return nil, nil, err
}
return res.Children, &res.Stat, err
}
// ChildrenW returns the children of a znode and sets a watch.
func (c *Conn) ChildrenW(path string) ([]string, *Stat, <-chan Event, error) {
if err := validatePath(path, false); err != nil {
return nil, nil, nil, err
}
var ech <-chan Event
res := &getChildren2Response{}
_, err := c.request(opGetChildren2, &getChildren2Request{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
if err == nil {
ech = c.addWatcher(path, watchTypeChild)
}
})
if err != nil {
return nil, nil, nil, err
}
return res.Children, &res.Stat, ech, err
}
// Get gets the contents of a znode.
func (c *Conn) Get(path string) ([]byte, *Stat, error) {
if err := validatePath(path, false); err != nil {
return nil, nil, err
}
res := &getDataResponse{}
_, err := c.request(opGetData, &getDataRequest{Path: path, Watch: false}, res, nil)
if err == ErrConnectionClosed {
return nil, nil, err
}
return res.Data, &res.Stat, err
}
// GetW returns the contents of a znode and sets a watch
func (c *Conn) GetW(path string) ([]byte, *Stat, <-chan Event, error) {
if err := validatePath(path, false); err != nil {
return nil, nil, nil, err
}
var ech <-chan Event
res := &getDataResponse{}
_, err := c.request(opGetData, &getDataRequest{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
if err == nil {
ech = c.addWatcher(path, watchTypeData)
}
})
if err != nil {
return nil, nil, nil, err
}
return res.Data, &res.Stat, ech, err
}
// Set updates the contents of a znode.
func (c *Conn) Set(path string, data []byte, version int32) (*Stat, error) {
if err := validatePath(path, false); err != nil {
return nil, err
}
res := &setDataResponse{}
_, err := c.request(opSetData, &SetDataRequest{path, data, version}, res, nil)
if err == ErrConnectionClosed {
return nil, err
}
return &res.Stat, err
}
// Create creates a znode.
// The returned path is the new path assigned by the server, it may not be the
// same as the input, for example when creating a sequence znode the returned path
// will be the input path with a sequence number appended.
func (c *Conn) Create(path string, data []byte, flags int32, acl []ACL) (string, error) {
createMode, err := parseCreateMode(flags)
if err != nil {
return "", err
}
if err := validatePath(path, createMode.isSequential); err != nil {
return "", err
}
if createMode.isTTL {
return "", fmt.Errorf("Create with TTL flag disallowed: %w", ErrInvalidFlags)
}
res := &createResponse{}
_, err = c.request(opCreate, &CreateRequest{path, data, acl, createMode.flag}, res, nil)
if err == ErrConnectionClosed {
return "", err
}
return res.Path, err
}
// CreateContainer creates a container znode and returns the path.
//
// Containers cannot be ephemeral or sequential, or have TTLs.
// Ensure that we reject flags for TTL, Sequence, and Ephemeral.
func (c *Conn) CreateContainer(path string, data []byte, flag int32, acl []ACL) (string, error) {
createMode, err := parseCreateMode(flag)
if err != nil {
return "", err
}
if err := validatePath(path, createMode.isSequential); err != nil {
return "", err
}
if !createMode.isContainer {
return "", fmt.Errorf("CreateContainer requires container flag: %w", ErrInvalidFlags)
}
res := &createResponse{}
_, err = c.request(opCreateContainer, &CreateRequest{path, data, acl, createMode.flag}, res, nil)
return res.Path, err
}
// CreateTTL creates a TTL znode, which will be automatically deleted by server after the TTL.
func (c *Conn) CreateTTL(path string, data []byte, flag int32, acl []ACL, ttl time.Duration) (string, error) {
createMode, err := parseCreateMode(flag)
if err != nil {
return "", err
}
if err := validatePath(path, createMode.isSequential); err != nil {
return "", err
}
if !createMode.isTTL {
return "", fmt.Errorf("CreateTTL requires TTL flag: %w", ErrInvalidFlags)
}
res := &createResponse{}
_, err = c.request(opCreateTTL, &CreateTTLRequest{path, data, acl, createMode.flag, ttl.Milliseconds()}, res, nil)
return res.Path, err
}
// CreateProtectedEphemeralSequential fixes a race condition if the server crashes
// after it creates the node. On reconnect the session may still be valid so the
// ephemeral node still exists. Therefore, on reconnect we need to check if a node
// with a GUID generated on create exists.
func (c *Conn) CreateProtectedEphemeralSequential(path string, data []byte, acl []ACL) (string, error) {
if err := validatePath(path, true); err != nil {
return "", err
}
var guid [16]byte
_, err := io.ReadFull(rand.Reader, guid[:16])
if err != nil {
return "", err
}
guidStr := fmt.Sprintf("%x", guid)
parts := strings.Split(path, "/")
parts[len(parts)-1] = fmt.Sprintf("%s%s-%s", protectedPrefix, guidStr, parts[len(parts)-1])
rootPath := strings.Join(parts[:len(parts)-1], "/")
protectedPath := strings.Join(parts, "/")
var newPath string
for i := 0; i < 3; i++ {
newPath, err = c.Create(protectedPath, data, FlagEphemeral|FlagSequence, acl)
switch err {
case ErrSessionExpired:
// No need to search for the node since it can't exist. Just try again.
case ErrConnectionClosed:
children, _, err := c.Children(rootPath)
if err != nil {
return "", err
}
for _, p := range children {
parts := strings.Split(p, "/")
if pth := parts[len(parts)-1]; strings.HasPrefix(pth, protectedPrefix) {
if g := pth[len(protectedPrefix) : len(protectedPrefix)+32]; g == guidStr {
return rootPath + "/" + p, nil
}
}
}
case nil:
return newPath, nil
default:
return "", err
}
}
return "", err
}
// Delete deletes a znode.
func (c *Conn) Delete(path string, version int32) error {
if err := validatePath(path, false); err != nil {
return err
}
_, err := c.request(opDelete, &DeleteRequest{path, version}, &deleteResponse{}, nil)
return err
}
// Exists tells the existence of a znode.
func (c *Conn) Exists(path string) (bool, *Stat, error) {
if err := validatePath(path, false); err != nil {
return false, nil, err
}
res := &existsResponse{}
_, err := c.request(opExists, &existsRequest{Path: path, Watch: false}, res, nil)
if err == ErrConnectionClosed {
return false, nil, err
}
exists := true
if err == ErrNoNode {
exists = false
err = nil
}
return exists, &res.Stat, err
}
// ExistsW tells the existence of a znode and sets a watch.
func (c *Conn) ExistsW(path string) (bool, *Stat, <-chan Event, error) {
if err := validatePath(path, false); err != nil {
return false, nil, nil, err
}
var ech <-chan Event
res := &existsResponse{}
_, err := c.request(opExists, &existsRequest{Path: path, Watch: true}, res, func(req *request, res *responseHeader, err error) {
if err == nil {
ech = c.addWatcher(path, watchTypeData)
} else if err == ErrNoNode {
ech = c.addWatcher(path, watchTypeExist)
}
})
exists := true
if err == ErrNoNode {
exists = false
err = nil
}
if err != nil {
return false, nil, nil, err
}
return exists, &res.Stat, ech, err
}
// GetACL gets the ACLs of a znode.
func (c *Conn) GetACL(path string) ([]ACL, *Stat, error) {
if err := validatePath(path, false); err != nil {
return nil, nil, err
}
res := &getAclResponse{}
_, err := c.request(opGetAcl, &getAclRequest{Path: path}, res, nil)
if err == ErrConnectionClosed {
return nil, nil, err
}
return res.Acl, &res.Stat, err
}
// SetACL updates the ACLs of a znode.
func (c *Conn) SetACL(path string, acl []ACL, version int32) (*Stat, error) {
if err := validatePath(path, false); err != nil {
return nil, err
}
res := &setAclResponse{}
_, err := c.request(opSetAcl, &setAclRequest{Path: path, Acl: acl, Version: version}, res, nil)
if err == ErrConnectionClosed {
return nil, err
}
return &res.Stat, err
}
// Sync flushes the channel between process and the leader of a given znode,
// you may need it if you want identical views of ZooKeeper data for 2 client instances.
// Please refer to the "Consistency Guarantees" section of ZK document for more details.
func (c *Conn) Sync(path string) (string, error) {
if err := validatePath(path, false); err != nil {
return "", err
}
res := &syncResponse{}
_, err := c.request(opSync, &syncRequest{Path: path}, res, nil)
if err == ErrConnectionClosed {
return "", err
}
return res.Path, err
}
// MultiResponse is the result of a Multi call.
type MultiResponse struct {
Stat *Stat
String string
Error error
}
// Multi executes multiple ZooKeeper operations or none of them. The provided
// ops must be one of *CreateRequest, *DeleteRequest, *SetDataRequest, or
// *CheckVersionRequest.
func (c *Conn) Multi(ops ...interface{}) ([]MultiResponse, error) {
req := &multiRequest{
Ops: make([]multiRequestOp, 0, len(ops)),
DoneHeader: multiHeader{Type: -1, Done: true, Err: -1},
}
for _, op := range ops {
var opCode int32
switch op.(type) {
case *CreateRequest:
opCode = opCreate
case *SetDataRequest:
opCode = opSetData
case *DeleteRequest:
opCode = opDelete
case *CheckVersionRequest:
opCode = opCheck
default:
return nil, fmt.Errorf("unknown operation type %T", op)
}
req.Ops = append(req.Ops, multiRequestOp{multiHeader{opCode, false, -1}, op})
}
res := &multiResponse{}
_, err := c.request(opMulti, req, res, nil)
if err == ErrConnectionClosed {
return nil, err
}
mr := make([]MultiResponse, len(res.Ops))
for i, op := range res.Ops {
mr[i] = MultiResponse{Stat: op.Stat, String: op.String, Error: op.Err.toError()}
}
return mr, err
}
// IncrementalReconfig is the zookeeper reconfiguration api that allows adding and removing servers
// by lists of members. For more info refer to the ZK documentation.
//
// An optional version allows for conditional reconfigurations, -1 ignores the condition.
//
// Returns the new configuration znode stat.
func (c *Conn) IncrementalReconfig(joining, leaving []string, version int64) (*Stat, error) {
// TODO: validate the shape of the member string to give early feedback.
request := &reconfigRequest{
JoiningServers: []byte(strings.Join(joining, ",")),
LeavingServers: []byte(strings.Join(leaving, ",")),
CurConfigId: version,
}
return c.internalReconfig(request)
}
// Reconfig is the non-incremental update functionality for Zookeeper where the list provided
// is the entire new member list. For more info refer to the ZK documentation.
//
// An optional version allows for conditional reconfigurations, -1 ignores the condition.
//
// Returns the new configuration znode stat.
func (c *Conn) Reconfig(members []string, version int64) (*Stat, error) {
request := &reconfigRequest{
NewMembers: []byte(strings.Join(members, ",")),
CurConfigId: version,
}
return c.internalReconfig(request)
}
func (c *Conn) internalReconfig(request *reconfigRequest) (*Stat, error) {
response := &reconfigReponse{}
_, err := c.request(opReconfig, request, response, nil)
return &response.Stat, err
}
// Server returns the current or last-connected server name.
func (c *Conn) Server() string {
c.serverMu.Lock()
defer c.serverMu.Unlock()
return c.server
}
func resendZkAuth(ctx context.Context, c *Conn) error {
shouldCancel := func() bool {
select {
case <-c.shouldQuit:
return true
case <-c.closeChan:
return true
default:
return false
}
}
c.credsMu.Lock()
defer c.credsMu.Unlock()
if c.logInfo {
c.logger.Printf("re-submitting `%d` credentials after reconnect", len(c.creds))
}
for _, cred := range c.creds {
// return early before attempting to send request.
if shouldCancel() {
return nil
}
// do not use the public API for auth since it depends on the send/recv loops
// that are waiting for this to return
resChan, err := c.sendRequest(
opSetAuth,
&setAuthRequest{Type: 0,
Scheme: cred.scheme,
Auth: cred.auth,
},
&setAuthResponse{},
nil, /* recvFunc*/
)
if err != nil {
return fmt.Errorf("failed to send auth request: %v", err)
}
var res response
select {
case res = <-resChan:
case <-c.closeChan:
c.logger.Printf("recv closed, cancel re-submitting credentials")
return nil
case <-c.shouldQuit:
c.logger.Printf("should quit, cancel re-submitting credentials")
return nil
case <-ctx.Done():
return ctx.Err()
}
if res.err != nil {
return fmt.Errorf("failed connection setAuth request: %v", res.err)
}
}
return nil
}
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