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cluster.go

File metadata and controls

1882 lines (1581 loc) · 41.4 KB
package redis
import (
"context"
"crypto/tls"
"fmt"
"math"
"net"
"net/url"
"runtime"
"sort"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/go-redis/redis/v9/internal"
"github.com/go-redis/redis/v9/internal/hashtag"
"github.com/go-redis/redis/v9/internal/pool"
"github.com/go-redis/redis/v9/internal/proto"
"github.com/go-redis/redis/v9/internal/rand"
)
var errClusterNoNodes = fmt.Errorf("redis: cluster has no nodes")
// ClusterOptions are used to configure a cluster client and should be
// passed to NewClusterClient.
type ClusterOptions struct {
// A seed list of host:port addresses of cluster nodes.
Addrs []string
// ClientName will execute the `CLIENT SETNAME ClientName` command for each conn.
ClientName string
// NewClient creates a cluster node client with provided name and options.
NewClient func(opt *Options) *Client
// The maximum number of retries before giving up. Command is retried
// on network errors and MOVED/ASK redirects.
// Default is 3 retries.
MaxRedirects int
// Enables read-only commands on slave nodes.
ReadOnly bool
// Allows routing read-only commands to the closest master or slave node.
// It automatically enables ReadOnly.
RouteByLatency bool
// Allows routing read-only commands to the random master or slave node.
// It automatically enables ReadOnly.
RouteRandomly bool
// Optional function that returns cluster slots information.
// It is useful to manually create cluster of standalone Redis servers
// and load-balance read/write operations between master and slaves.
// It can use service like ZooKeeper to maintain configuration information
// and Cluster.ReloadState to manually trigger state reloading.
ClusterSlots func(context.Context) ([]ClusterSlot, error)
// Following options are copied from Options struct.
Dialer func(ctx context.Context, network, addr string) (net.Conn, error)
OnConnect func(ctx context.Context, cn *Conn) error
Username string
Password string
MaxRetries int
MinRetryBackoff time.Duration
MaxRetryBackoff time.Duration
DialTimeout time.Duration
ReadTimeout time.Duration
WriteTimeout time.Duration
ContextTimeoutEnabled bool
PoolFIFO bool
PoolSize int // applies per cluster node and not for the whole cluster
PoolTimeout time.Duration
MinIdleConns int
MaxIdleConns int
ConnMaxIdleTime time.Duration
ConnMaxLifetime time.Duration
TLSConfig *tls.Config
}
func (opt *ClusterOptions) init() {
if opt.MaxRedirects == -1 {
opt.MaxRedirects = 0
} else if opt.MaxRedirects == 0 {
opt.MaxRedirects = 3
}
if opt.RouteByLatency || opt.RouteRandomly {
opt.ReadOnly = true
}
if opt.PoolSize == 0 {
opt.PoolSize = 5 * runtime.GOMAXPROCS(0)
}
switch opt.ReadTimeout {
case -1:
opt.ReadTimeout = 0
case 0:
opt.ReadTimeout = 3 * time.Second
}
switch opt.WriteTimeout {
case -1:
opt.WriteTimeout = 0
case 0:
opt.WriteTimeout = opt.ReadTimeout
}
if opt.MaxRetries == 0 {
opt.MaxRetries = -1
}
switch opt.MinRetryBackoff {
case -1:
opt.MinRetryBackoff = 0
case 0:
opt.MinRetryBackoff = 8 * time.Millisecond
}
switch opt.MaxRetryBackoff {
case -1:
opt.MaxRetryBackoff = 0
case 0:
opt.MaxRetryBackoff = 512 * time.Millisecond
}
if opt.NewClient == nil {
opt.NewClient = NewClient
}
}
// ParseClusterURL parses a URL into ClusterOptions that can be used to connect to Redis.
// The URL must be in the form:
// redis://<user>:<password>@<host>:<port>
// or
// rediss://<user>:<password>@<host>:<port>
// To add additional addresses, specify the query parameter, "addr" one or more times. e.g:
// redis://<user>:<password>@<host>:<port>?addr=<host2>:<port2>&addr=<host3>:<port3>
// or
// rediss://<user>:<password>@<host>:<port>?addr=<host2>:<port2>&addr=<host3>:<port3>
//
// Most Option fields can be set using query parameters, with the following restrictions:
// - field names are mapped using snake-case conversion: to set MaxRetries, use max_retries
// - only scalar type fields are supported (bool, int, time.Duration)
// - for time.Duration fields, values must be a valid input for time.ParseDuration();
// additionally a plain integer as value (i.e. without unit) is intepreted as seconds
// - to disable a duration field, use value less than or equal to 0; to use the default
// value, leave the value blank or remove the parameter
// - only the last value is interpreted if a parameter is given multiple times
// - fields "network", "addr", "username" and "password" can only be set using other
// URL attributes (scheme, host, userinfo, resp.), query paremeters using these
// names will be treated as unknown parameters
// - unknown parameter names will result in an error
// Example:
// redis://user:password@localhost:6789?dial_timeout=3&read_timeout=6s&addr=localhost:6790&addr=localhost:6791
// is equivalent to:
// &ClusterOptions{
// Addr: ["localhost:6789", "localhost:6790", "localhost:6791"]
// DialTimeout: 3 * time.Second, // no time unit = seconds
// ReadTimeout: 6 * time.Second,
// }
func ParseClusterURL(redisURL string) (*ClusterOptions, error) {
o := &ClusterOptions{}
u, err := url.Parse(redisURL)
if err != nil {
return nil, err
}
// add base URL to the array of addresses
// more addresses may be added through the URL params
h, p := getHostPortWithDefaults(u)
o.Addrs = append(o.Addrs, net.JoinHostPort(h, p))
// setup username, password, and other configurations
o, err = setupClusterConn(u, h, o)
if err != nil {
return nil, err
}
return o, nil
}
// setupClusterConn gets the username and password from the URL and the query parameters.
func setupClusterConn(u *url.URL, host string, o *ClusterOptions) (*ClusterOptions, error) {
switch u.Scheme {
case "rediss":
o.TLSConfig = &tls.Config{ServerName: host}
fallthrough
case "redis":
o.Username, o.Password = getUserPassword(u)
default:
return nil, fmt.Errorf("redis: invalid URL scheme: %s", u.Scheme)
}
// retrieve the configuration from the query parameters
o, err := setupClusterQueryParams(u, o)
if err != nil {
return nil, err
}
return o, nil
}
// setupClusterQueryParams converts query parameters in u to option value in o.
func setupClusterQueryParams(u *url.URL, o *ClusterOptions) (*ClusterOptions, error) {
q := queryOptions{q: u.Query()}
o.ClientName = q.string("client_name")
o.MaxRedirects = q.int("max_redirects")
o.ReadOnly = q.bool("read_only")
o.RouteByLatency = q.bool("route_by_latency")
o.RouteRandomly = q.bool("route_randomly")
o.MaxRetries = q.int("max_retries")
o.MinRetryBackoff = q.duration("min_retry_backoff")
o.MaxRetryBackoff = q.duration("max_retry_backoff")
o.DialTimeout = q.duration("dial_timeout")
o.ReadTimeout = q.duration("read_timeout")
o.WriteTimeout = q.duration("write_timeout")
o.PoolFIFO = q.bool("pool_fifo")
o.PoolSize = q.int("pool_size")
o.MinIdleConns = q.int("min_idle_conns")
o.PoolTimeout = q.duration("pool_timeout")
o.ConnMaxLifetime = q.duration("conn_max_lifetime")
o.ConnMaxIdleTime = q.duration("conn_max_idle_time")
if q.err != nil {
return nil, q.err
}
// addr can be specified as many times as needed
addrs := q.strings("addr")
for _, addr := range addrs {
h, p, err := net.SplitHostPort(addr)
if err != nil || h == "" || p == "" {
return nil, fmt.Errorf("redis: unable to parse addr param: %s", addr)
}
o.Addrs = append(o.Addrs, net.JoinHostPort(h, p))
}
// any parameters left?
if r := q.remaining(); len(r) > 0 {
return nil, fmt.Errorf("redis: unexpected option: %s", strings.Join(r, ", "))
}
return o, nil
}
func (opt *ClusterOptions) clientOptions() *Options {
return &Options{
ClientName: opt.ClientName,
Dialer: opt.Dialer,
OnConnect: opt.OnConnect,
Username: opt.Username,
Password: opt.Password,
MaxRetries: opt.MaxRetries,
MinRetryBackoff: opt.MinRetryBackoff,
MaxRetryBackoff: opt.MaxRetryBackoff,
DialTimeout: opt.DialTimeout,
ReadTimeout: opt.ReadTimeout,
WriteTimeout: opt.WriteTimeout,
PoolFIFO: opt.PoolFIFO,
PoolSize: opt.PoolSize,
PoolTimeout: opt.PoolTimeout,
MinIdleConns: opt.MinIdleConns,
MaxIdleConns: opt.MaxIdleConns,
ConnMaxIdleTime: opt.ConnMaxIdleTime,
ConnMaxLifetime: opt.ConnMaxLifetime,
TLSConfig: opt.TLSConfig,
// If ClusterSlots is populated, then we probably have an artificial
// cluster whose nodes are not in clustering mode (otherwise there isn't
// much use for ClusterSlots config). This means we cannot execute the
// READONLY command against that node -- setting readOnly to false in such
// situations in the options below will prevent that from happening.
readOnly: opt.ReadOnly && opt.ClusterSlots == nil,
}
}
//------------------------------------------------------------------------------
type clusterNode struct {
Client *Client
latency uint32 // atomic
generation uint32 // atomic
failing uint32 // atomic
}
func newClusterNode(clOpt *ClusterOptions, addr string) *clusterNode {
opt := clOpt.clientOptions()
opt.Addr = addr
node := clusterNode{
Client: clOpt.NewClient(opt),
}
node.latency = math.MaxUint32
if clOpt.RouteByLatency {
go node.updateLatency()
}
return &node
}
func (n *clusterNode) String() string {
return n.Client.String()
}
func (n *clusterNode) Close() error {
return n.Client.Close()
}
func (n *clusterNode) updateLatency() {
const numProbe = 10
var dur uint64
successes := 0
for i := 0; i < numProbe; i++ {
time.Sleep(time.Duration(10+rand.Intn(10)) * time.Millisecond)
start := time.Now()
err := n.Client.Ping(context.TODO()).Err()
if err == nil {
dur += uint64(time.Since(start) / time.Microsecond)
successes++
}
}
var latency float64
if successes == 0 {
// If none of the pings worked, set latency to some arbitrarily high value so this node gets
// least priority.
latency = float64((1 * time.Minute) / time.Microsecond)
} else {
latency = float64(dur) / float64(successes)
}
atomic.StoreUint32(&n.latency, uint32(latency+0.5))
}
func (n *clusterNode) Latency() time.Duration {
latency := atomic.LoadUint32(&n.latency)
return time.Duration(latency) * time.Microsecond
}
func (n *clusterNode) MarkAsFailing() {
atomic.StoreUint32(&n.failing, uint32(time.Now().Unix()))
}
func (n *clusterNode) Failing() bool {
const timeout = 15 // 15 seconds
failing := atomic.LoadUint32(&n.failing)
if failing == 0 {
return false
}
if time.Now().Unix()-int64(failing) < timeout {
return true
}
atomic.StoreUint32(&n.failing, 0)
return false
}
func (n *clusterNode) Generation() uint32 {
return atomic.LoadUint32(&n.generation)
}
func (n *clusterNode) SetGeneration(gen uint32) {
for {
v := atomic.LoadUint32(&n.generation)
if gen < v || atomic.CompareAndSwapUint32(&n.generation, v, gen) {
break
}
}
}
//------------------------------------------------------------------------------
type clusterNodes struct {
opt *ClusterOptions
mu sync.RWMutex
addrs []string
nodes map[string]*clusterNode
activeAddrs []string
closed bool
onNewNode []func(rdb *Client)
_generation uint32 // atomic
}
func newClusterNodes(opt *ClusterOptions) *clusterNodes {
return &clusterNodes{
opt: opt,
addrs: opt.Addrs,
nodes: make(map[string]*clusterNode),
}
}
func (c *clusterNodes) Close() error {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return nil
}
c.closed = true
var firstErr error
for _, node := range c.nodes {
if err := node.Client.Close(); err != nil && firstErr == nil {
firstErr = err
}
}
c.nodes = nil
c.activeAddrs = nil
return firstErr
}
func (c *clusterNodes) OnNewNode(fn func(rdb *Client)) {
c.mu.Lock()
c. fn)
c.mu.Unlock()
}
func (c *clusterNodes) Addrs() ([]string, error) {
var addrs []string
c.mu.RLock()
closed := c.closed //nolint:ifshort
if !closed {
if len(c.activeAddrs) > 0 {
addrs = c.activeAddrs
} else {
addrs = c.addrs
}
}
c.mu.RUnlock()
if closed {
return nil, pool.ErrClosed
}
if len(addrs) == 0 {
return nil, errClusterNoNodes
}
return addrs, nil
}
func (c *clusterNodes) NextGeneration() uint32 {
return atomic.AddUint32(&c._generation, 1)
}
// GC removes unused nodes.
func (c *clusterNodes) GC(generation uint32) {
//nolint:prealloc
var collected []*clusterNode
c.mu.Lock()
c.activeAddrs = c.activeAddrs[:0]
for addr, node := range c.nodes {
if node.Generation() >= generation {
c.activeAddrs = append(c.activeAddrs, addr)
if c.opt.RouteByLatency {
go node.updateLatency()
}
continue
}
delete(c.nodes, addr)
collected = append(collected, node)
}
c.mu.Unlock()
for _, node := range collected {
_ = node.Client.Close()
}
}
func (c *clusterNodes) GetOrCreate(addr string) (*clusterNode, error) {
node, err := c.get(addr)
if err != nil {
return nil, err
}
if node != nil {
return node, nil
}
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return nil, pool.ErrClosed
}
node, ok := c.nodes[addr]
if ok {
return node, nil
}
node = newClusterNode(c.opt, addr)
for _, fn := range c.onNewNode {
fn(node.Client)
}
c.addrs = appendIfNotExists(c.addrs, addr)
c.nodes[addr] = node
return node, nil
}
func (c *clusterNodes) get(addr string) (*clusterNode, error) {
var node *clusterNode
var err error
c.mu.RLock()
if c.closed {
err = pool.ErrClosed
} else {
node = c.nodes[addr]
}
c.mu.RUnlock()
return node, err
}
func (c *clusterNodes) All() ([]*clusterNode, error) {
c.mu.RLock()
defer c.mu.RUnlock()
if c.closed {
return nil, pool.ErrClosed
}
cp := make([]*clusterNode, 0, len(c.nodes))
for _, node := range c.nodes {
cp = append(cp, node)
}
return cp, nil
}
func (c *clusterNodes) Random() (*clusterNode, error) {
addrs, err := c.Addrs()
if err != nil {
return nil, err
}
n := rand.Intn(len(addrs))
return c.GetOrCreate(addrs[n])
}
//------------------------------------------------------------------------------
type clusterSlot struct {
start, end int
nodes []*clusterNode
}
type clusterSlotSlice []*clusterSlot
func (p clusterSlotSlice) Len() int {
return len(p)
}
func (p clusterSlotSlice) Less(i, j int) bool {
return p[i].start < p[j].start
}
func (p clusterSlotSlice) Swap(i, j int) {
p[i], p[j] = p[j], p[i]
}
type clusterState struct {
nodes *clusterNodes
Masters []*clusterNode
Slaves []*clusterNode
slots []*clusterSlot
generation uint32
createdAt time.Time
}
func newClusterState(
nodes *clusterNodes, slots []ClusterSlot, origin string,
) (*clusterState, error) {
c := clusterState{
nodes: nodes,
slots: make([]*clusterSlot, 0, len(slots)),
generation: nodes.NextGeneration(),
createdAt: time.Now(),
}
originHost, _, _ := net.SplitHostPort(origin)
isLoopbackOrigin := isLoopback(originHost)
for _, slot := range slots {
var nodes []*clusterNode
for i, slotNode := range slot.Nodes {
addr := slotNode.Addr
if !isLoopbackOrigin {
addr = replaceLoopbackHost(addr, originHost)
}
node, err := c.nodes.GetOrCreate(addr)
if err != nil {
return nil, err
}
node.SetGeneration(c.generation)
nodes = append(nodes, node)
if i == 0 {
c.Masters = appendUniqueNode(c.Masters, node)
} else {
c.Slaves = appendUniqueNode(c.Slaves, node)
}
}
c.slots = append(c.slots, &clusterSlot{
start: slot.Start,
end: slot.End,
nodes: nodes,
})
}
sort.Sort(clusterSlotSlice(c.slots))
time.AfterFunc(time.Minute, func() {
nodes.GC(c.generation)
})
return &c, nil
}
func replaceLoopbackHost(nodeAddr, originHost string) string {
nodeHost, nodePort, err := net.SplitHostPort(nodeAddr)
if err != nil {
return nodeAddr
}
nodeIP := net.ParseIP(nodeHost)
if nodeIP == nil {
return nodeAddr
}
if !nodeIP.IsLoopback() {
return nodeAddr
}
// Use origin host which is not loopback and node port.
return net.JoinHostPort(originHost, nodePort)
}
func isLoopback(host string) bool {
ip := net.ParseIP(host)
if ip == nil {
return true
}
return ip.IsLoopback()
}
func (c *clusterState) slotMasterNode(slot int) (*clusterNode, error) {
nodes := c.slotNodes(slot)
if len(nodes) > 0 {
return nodes[0], nil
}
return c.nodes.Random()
}
func (c *clusterState) slotSlaveNode(slot int) (*clusterNode, error) {
nodes := c.slotNodes(slot)
switch len(nodes) {
case 0:
return c.nodes.Random()
case 1:
return nodes[0], nil
case 2:
if slave := nodes[1]; !slave.Failing() {
return slave, nil
}
return nodes[0], nil
default:
var slave *clusterNode
for i := 0; i < 10; i++ {
n := rand.Intn(len(nodes)-1) + 1
slave = nodes[n]
if !slave.Failing() {
return slave, nil
}
}
// All slaves are loading - use master.
return nodes[0], nil
}
}
func (c *clusterState) slotClosestNode(slot int) (*clusterNode, error) {
nodes := c.slotNodes(slot)
if len(nodes) == 0 {
return c.nodes.Random()
}
var node *clusterNode
for _, n := range nodes {
if n.Failing() {
continue
}
if node == nil || n.Latency() < node.Latency() {
node = n
}
}
if node != nil {
return node, nil
}
// If all nodes are failing - return random node
return c.nodes.Random()
}
func (c *clusterState) slotRandomNode(slot int) (*clusterNode, error) {
nodes := c.slotNodes(slot)
if len(nodes) == 0 {
return c.nodes.Random()
}
if len(nodes) == 1 {
return nodes[0], nil
}
randomNodes := rand.Perm(len(nodes))
for _, idx := range randomNodes {
if node := nodes[idx]; !node.Failing() {
return node, nil
}
}
return nodes[randomNodes[0]], nil
}
func (c *clusterState) slotNodes(slot int) []*clusterNode {
i := sort.Search(len(c.slots), func(i int) bool {
return c.slots[i].end >= slot
})
if i >= len(c.slots) {
return nil
}
x := c.slots[i]
if slot >= x.start && slot <= x.end {
return x.nodes
}
return nil
}
//------------------------------------------------------------------------------
type clusterStateHolder struct {
load func(ctx context.Context) (*clusterState, error)
state atomic.Value
reloading uint32 // atomic
}
func newClusterStateHolder(fn func(ctx context.Context) (*clusterState, error)) *clusterStateHolder {
return &clusterStateHolder{
load: fn,
}
}
func (c *clusterStateHolder) Reload(ctx context.Context) (*clusterState, error) {
state, err := c.load(ctx)
if err != nil {
return nil, err
}
c.state.Store(state)
return state, nil
}
func (c *clusterStateHolder) LazyReload() {
if !atomic.CompareAndSwapUint32(&c.reloading, 0, 1) {
return
}
go func() {
defer atomic.StoreUint32(&c.reloading, 0)
_, err := c.Reload(context.Background())
if err != nil {
return
}
time.Sleep(200 * time.Millisecond)
}()
}
func (c *clusterStateHolder) Get(ctx context.Context) (*clusterState, error) {
v := c.state.Load()
if v == nil {
return c.Reload(ctx)
}
state := v.(*clusterState)
if time.Since(state.createdAt) > 10*time.Second {
c.LazyReload()
}
return state, nil
}
func (c *clusterStateHolder) ReloadOrGet(ctx context.Context) (*clusterState, error) {
state, err := c.Reload(ctx)
if err == nil {
return state, nil
}
return c.Get(ctx)
}
//------------------------------------------------------------------------------
// ClusterClient is a Redis Cluster client representing a pool of zero
// or more underlying connections. It's safe for concurrent use by
// multiple goroutines.
type ClusterClient struct {
opt *ClusterOptions
nodes *clusterNodes
state *clusterStateHolder
cmdsInfoCache *cmdsInfoCache
cmdable
hooks
}
// NewClusterClient returns a Redis Cluster client as described in
// http://redis.io/topics/cluster-spec.
func NewClusterClient(opt *ClusterOptions) *ClusterClient {
opt.init()
c := &ClusterClient{
opt: opt,
nodes: newClusterNodes(opt),
}
c.state = newClusterStateHolder(c.loadState)
c.cmdsInfoCache = newCmdsInfoCache(c.cmdsInfo)
c.cmdable = c.Process
c.hooks.setProcess(c.process)
c.hooks.setProcessPipeline(c.processPipeline)
c.hooks.setProcessTxPipeline(c.processTxPipeline)
return c
}
// Options returns read-only Options that were used to create the client.
func (c *ClusterClient) Options() *ClusterOptions {
return c.opt
}
// ReloadState reloads cluster state. If available it calls ClusterSlots func
// to get cluster slots information.
func (c *ClusterClient) ReloadState(ctx context.Context) {
c.state.LazyReload()
}
// Close closes the cluster client, releasing any open resources.
//
// It is rare to Close a ClusterClient, as the ClusterClient is meant
// to be long-lived and shared between many goroutines.
func (c *ClusterClient) Close() error {
return c.nodes.Close()
}
// Do create a Cmd from the args and processes the cmd.
func (c *ClusterClient) Do(ctx context.Context, args ...interface{}) *Cmd {
cmd := NewCmd(ctx, args...)
_ = c.Process(ctx, cmd)
return cmd
}
func (c *ClusterClient) Process(ctx context.Context, cmd Cmder) error {
err := c.hooks.process(ctx, cmd)
cmd.SetErr(err)
return err
}
func (c *ClusterClient) process(ctx context.Context, cmd Cmder) error {
cmdInfo := c.cmdInfo(ctx, cmd.Name())
slot := c.cmdSlot(ctx, cmd)
var node *clusterNode
var ask bool
var lastErr error
for attempt := 0; attempt <= c.opt.MaxRedirects; attempt++ {
if attempt > 0 {
if err := internal.Sleep(ctx, c.retryBackoff(attempt)); err != nil {
return err
}
}
if node == nil {
var err error
node, err = c.cmdNode(ctx, cmdInfo, slot)
if err != nil {
return err
}
}
if ask {
ask = false
pipe := node.Client.Pipeline()
_ = pipe.Process(ctx, NewCmd(ctx, "asking"))
_ = pipe.Process(ctx, cmd)
_, lastErr = pipe.Exec(ctx)
} else {
lastErr = node.Client.Process(ctx, cmd)
}
// If there is no error - we are done.
if lastErr == nil {
return nil
}
if isReadOnly := isReadOnlyError(lastErr); isReadOnly || lastErr == pool.ErrClosed {
if isReadOnly {
c.state.LazyReload()
}
node = nil
continue
}
// If slave is loading - pick another node.
if c.opt.ReadOnly && isLoadingError(lastErr) {
node.MarkAsFailing()
node = nil
continue
}
var moved bool
var addr string
moved, ask, addr = isMovedError(lastErr)
if moved || ask {
c.state.LazyReload()
var err error
node, err = c.nodes.GetOrCreate(addr)
if err != nil {
return err
}
continue
}
if shouldRetry(lastErr, cmd.readTimeout() == nil) {
// First retry the same node.
if attempt == 0 {
continue
}
// Second try another node.
node.MarkAsFailing()
node = nil
continue
}
return lastErr
}
return lastErr
}
func (c *ClusterClient) OnNewNode(fn func(rdb *Client)) {
c.nodes.OnNewNode(fn)
}
// ForEachMaster concurrently calls the fn on each master node in the cluster.
// It returns the first error if any.
func (c *ClusterClient) ForEachMaster(
ctx context.Context,
fn func(ctx context.Context, client *Client) error,
) error {
state, err := c.state.ReloadOrGet(ctx)
if err != nil {
return err
}
var wg sync.WaitGroup
errCh := make(chan error, 1)
for _, master := range state.Masters {
wg.Add(1)
go func(node *clusterNode) {
defer wg.Done()
err := fn(ctx, node.Client)
if err != nil {
select {
case errCh <- err:
default:
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