go微服務框架kratos學習筆記六(kratos 服務發現 discovery)
目錄node
go微服務框架kratos學習筆記六(kratos 服務發現 discovery)
除了上次的warden直連方式外，kratos有另外一個服務發現sdk : discoverygit
discovery 能夠先簡單理解爲一個http服務、github
它最簡單的發現過程多是這樣的:golang
一、service 向discovery 服務註冊 appid
二、client 經過 appid 從discovery 查詢 service 的addrredis
固然 遠不止這麼簡單，還包含了不少功能在裏面的，例如服務自發現、負載均衡等算法
本節僅先看個最簡單的服務發現的demosql
首先走一遍discovery的http的apijson
http api
// innerRouter init local router api path.
func innerRouter(e *bm.Engine) {
group := e.Group("/discovery")
{
group.POST("/register", register)
group.POST("/renew", renew)
group.POST("/cancel", cancel)
group.GET("/fetch/all", initProtect, fetchAll)
group.GET("/fetch", initProtect, fetch)
group.GET("/fetchs", initProtect, fetchs)
group.GET("/poll", initProtect, poll)
group.GET("/polls", initProtect, polls)
//manager
group.POST("/set", set)
group.GET("/nodes", initProtect, nodes)
}
}
discovery裏面的bm引擎註冊了這些接口, 接着我用postman 測了測。api
register 服務註冊
fetch 獲取實例
fetchs 批量獲取實例
polls 批量獲取實例
nodes 批量獲取節點
renew 心跳
POST http://HOST/discovery/renewapp
curl 'http://127.0.0.1:7171/discovery/renew' -d "zone=sh1&env=test&appid=provider&hostname=myhostname"
*****成功*****
{
"code":0,
"message":""
}
****失敗****
{
"code":-400,
"message":"-400"
}
cancel 下線
POST http://HOST/discovery/cancel
curl 'http://127.0.0.1:7171/discovery/cancel' -d "zone=sh1&env=test&appid=provider&hostname=myhostname"
*****成功*****
{
"code":0,
"message":""
}
****失敗****
{
"code":-400,
"message":"-400"
}
應用發現邏輯
官方應用發現實現邏輯
選擇可用的節點，將應用appid加入poll的appid列表
若是polls請求返回err，則切換node節點，切換邏輯與自發現錯誤時切換邏輯一致
若是polls返回-304 ，說明appid無變動，從新發起poll監聽變動
polls接口返回appid的instances列表，完成服務發現，根據須要選擇不一樣的負載均衡算法進行節點的調度
服務註冊
服務註冊demo
直接new一個demo服務而後將demo服務註冊到discovery
主函數裏面服務註冊部分添加相似下面註冊代碼。
ip := "127.0.0.1"
port := "9000"
hn, _ := os.Hostname()
dis := discovery.New(nil)
ins := &naming.Instance{
Zone: env.Zone,
Env: env.DeployEnv,
AppID: "demo.service",
Hostname: hn,
Addrs: []string{
"grpc://" + ip + ":" + port,
},
}
cancel, err := dis.Register(context.Background(), ins)
if err != nil {
panic(err)
}
defer cancel()
panic 找不到節點,這個是咱們discovery的節點地址 能夠在環境變量裏面添加。
I:\VSProject\kratos-note\kratos-note\warden\discovery\server>kratos run INFO 01/04-19:32:28.198 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/net/rpc/warden/server.go:329 warden: start grpc listen addr: [::]:9000 panic: invalid discovery config nodes:[] region:region01 zone:zone01 deployEnv:dev host:DESKTOP-NUEKD5O
配置discovery節點後成功註冊
I:\VSProject\kratos-note\kratos-note\warden\discovery\server>set DISCOVERY_NODES=127.0.0.1:7171
I:\VSProject\kratos-note\kratos-note\warden\discovery\server>kratos run
INFO 01/04-19:40:25.426 I:/VSProject/kratos-note/kratos-note/warden/discovery/server/cmd/main.go:23 abc start
2020/01/04 19:40:25 start watch filepath: I:\VSProject\kratos-note\kratos-note\warden\discovery\server\configs
INFO 01/04-19:40:25.497 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/net/http/blademaster/server.go:98 blademaster: start http listen addr: 0.0.0.0:8000
[warden] config is Deprecated, argument will be ignored. please use -grpc flag or GRPC env to configure warden server.
INFO 01/04-19:40:25.500 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/net/rpc/warden/server.go:329 warden: start grpc listen addr: [::]:9000
INFO 01/04-19:40:25.501 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/naming/discovery/discovery.go:248 disocvery: AddWatch(infra.discovery) already watch(false)
INFO 01/04-19:40:25.514 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/naming/discovery/discovery.go:631 discovery: successfully polls(http://127.0.0.1:7171/discovery/polls?appid=infra.discovery&env=dev&hostname=DESKTOP-NUEKD5O&latest_timestamp=0) instances ({"infra.discovery":{"instances":{"sh001":[{"region":"sh","zone":"sh001","env":"dev","appid":"infra.discovery","hostname":"test1","addrs":["http://127.0.0.1:7171"],"version":"","latest_timestamp":1578122538945305700,"metadata":null,"status":1}]},"latest_timestamp":1578122538945305700,"scheduler":null}})
INFO 01/04-19:40:25.527 I:/VSProject/go/pkg/mod/github.com/bilibili/kratos@v0.3.2-0.20191224125553-6e1180f53a8e/pkg/naming/discovery/discovery.go:414 discovery: register client.Get(http://127.0.0.1:7171/discovery/register) env(dev) appid(demo.service) addrs([grpc://127.0.0.1:9000]) success
服務註冊邏輯
如今咱們跟着日誌走一遍。
如圖理解，服務註冊邏輯應該是register -> renew ->cancel 註冊 而後 不停給心跳 最後取消註冊。
截取一條本地服務註冊日誌
操做大概是：
一、啓動discovery服務
二、啓動demo.server 註冊demo.server appid 服務
三、過一小會等待心跳，關閉demo.server
接着能夠看到整個日誌的過程大體上是 ：
一、 0 : 啓動dicovery服務
二、 2/3/4 : 服務初始化
三、 5 : polls 長輪循 infra.discovery 服務自發現
四、 6/7: 新的鏈接 & 服務註冊、這時候咱們起動的demo.server服務註冊上來了
五、 9 : polls 長輪循 infra.discovery 服務自發現
六、 10 : renew心跳
七、 12 : 最後我殺掉了註冊的服務，出現了cancel請求。
從日誌看邏輯理解基本上也沒有太多誤差，接着看看服務發現。
0：discovery -conf discovery-example.toml -log.v=0 1： 2：INFO 01/10-10:31:19.575 C:/server/src/go/src/discovery/discovery/syncup.go:160 discovery 3：changed nodes:[127.0.0.1:7171] zones:map[] 4：INFO 01/10-10:31:19.575 C:/server/src/go/pkg/mod/github.com/bilibili/kratos@v0.1.0/pkg/net/http/blademaster/server.go:98 blademaster: start http listen addr: 127.0.0.1:7171 INFO 01/10-10:31:19.575 C:/server/src/go/src/discovery/registry/registry.go:219 Polls from(test1) new connection(1) 5:INFO 01/10-10:31:31.796 http-access-log ts=0 method=GET ip=127.0.0.1 traceid= user=no_user params=appid=infra.discovery&env=dev&hostname=DESKTOP-9NFHKD0&latest_timestamp=0 msg=0 stack=<nil> err= timeout_quota=39.98 path=/discovery/polls ret=0 6:INFO 01/10-10:31:31.798 C:/server/src/go/src/discovery/registry/registry.go:219 Polls from(DESKTOP-9NFHKD0) new connection(1) 7:INFO 01/10-10:31:31.799 http-access-log method=POST user=no_user path=/discovery/register err= ts=0 params=addrs=grpc%3A%2F%2F127.0.0.1%3A9000&appid=demo.service&env=dev&hostname=DESKTOP-9NFHKD0&metadata=®ion=region01&status=1&version=&zone=zone01 stack=<nil> ret=0 timeout_quota=39.98 ip=127.0.0.1 msg=0 traceid= 8:INFO 01/10-10:32:01.799 C:/server/src/go/src/discovery/registry/registry.go:370 DelConns from(DESKTOP-9NFHKD0) delete(1) 9:ERROR 01/10-10:32:01.799 http-access-log method=GET ip=127.0.0.1 err=-304 timeout_quota=39.98 user=no_user path=/discovery/polls params=appid=infra.discovery&env=dev&hostname=DESKTOP-9NFHKD0&latest_timestamp=1578623479566211700 ret=-304 msg=-304 stack=-304 ts=30.0011342 traceid= 10:INFO 01/10-10:32:01.799 http-access-log msg=0 err= timeout_quota=39.98 method=POST ip=127.0.0.1 user=no_user ret=0 path=/discovery/renew traceid= params=appid=demo.service&env=dev&hostname=DESKTOP-9NFHKD0®ion=region01&zone=zone01 stack=<nil> ts=0 11:INFO 01/10-10:32:01.800 C:/server/src/go/src/discovery/registry/registry.go:219 Polls from(DESKTOP-9NFHKD0) new connection(1) 12:INFO 01/10-10:32:08.499 http-access-log timeout_quota=39.98 path=/discovery/cancel ret=0 stack=<nil> ip=127.0.0.1 msg=0 traceid= ts=0 method=POST user=no_user err= params=appid=demo.service&env=dev&hostname=DESKTOP-9NFHKD0®ion=region01&zone=zone01
服務發現
一樣先配置discovert節點 set DISCOVERY_NODES=127.0.0.1:7171
NewClient()改爲以下方式
package dao
import (
"context"
"github.com/bilibili/kratos/pkg/naming/discovery"
"github.com/bilibili/kratos/pkg/net/rpc/warden"
"github.com/bilibili/kratos/pkg/net/rpc/warden/resolver"
"google.golang.org/grpc"
)
// AppID your appid, ensure unique.
const AppID = "demo.service" // NOTE: example
func init(){
// NOTE: 注意這段代碼，表示要使用discovery進行服務發現
// NOTE: 還需注意的是，resolver.Register是全局生效的，因此建議該代碼放在進程初始化的時候執行
// NOTE: ！！！切記不要在一個進程內進行多個不一樣中間件的Register！！！
// NOTE: 在啓動應用時，能夠經過flag(-discovery.nodes) 或者 環境配置(DISCOVERY_NODES)指定discovery節點
resolver.Register(discovery.Builder())
}
// NewClient new member grpc client
func NewClient(cfg *warden.ClientConfig, opts ...grpc.DialOption) (DemoClient, error) {
client := warden.NewClient(cfg, opts...)
conn, err := client.Dial(context.Background(), "discovery://default/"+AppID)
if err != nil {
return nil, err
}
// 注意替換這裏：
// NewDemoClient方法是在"api"目錄下代碼生成的
// 對應proto文件內自定義的service名字，請使用正確方法名替換
return NewDemoClient(conn), nil
}
同時嵌入dao結構裏面、和上次warden direct方式同樣作SayHello接口測試調用。
// dao dao.
type dao struct {
db *sql.DB
redis *redis.Redis
mc *memcache.Memcache
demoClient demoapi.DemoClient
cache *fanout.Fanout
demoExpire int32
}
// New new a dao and return.
func New(r *redis.Redis, mc *memcache.Memcache, db *sql.DB) (d Dao, err error) {
var cfg struct{
DemoExpire xtime.Duration
}
if err = paladin.Get("application.toml").UnmarshalTOML(&cfg); err != nil {
return
}
grpccfg := &warden.ClientConfig{
Dial: xtime.Duration(time.Second * 10),
Timeout: xtime.Duration(time.Millisecond * 250),
Subset: 50,
KeepAliveInterval: xtime.Duration(time.Second * 60),
KeepAliveTimeout: xtime.Duration(time.Second * 20),
}
//paladin.Get("grpc.toml").UnmarshalTOML(grpccfg)
var grpcClient demoapi.DemoClient
grpcClient, err = NewClient(grpccfg)
d = &dao{
db: db,
redis: r,
mc: mc,
demoClient : grpcClient,
cache: fanout.New("cache"),
demoExpire: int32(time.Duration(cfg.DemoExpire) / time.Second),
}
return
}
測試調用
操做流程
一、啓動discovery服務
二、啓動demo.server 註冊爲 demo.server 服務
三、啓動demo.client、
四、最後從demo.client的SayHello http接口 調到demo.server的grpc SayHello 接口。
簡單看看官方grpc服務發現邏輯
context deadline exceeded
我發現個別時候調用作服務發現，會發現client起不來， context deadline exceeded。
由於我把new client加在了dao裏面，超時的話，demo.client就直接pannic了
根據client日誌能夠發現
warden client: dial discovery://default/demo.service?subset=50 error context deadline exceeded!panic: context deadline exceeded
client : host:127.0.0.1:7171, url:http://127.0.0.1:7171/discovery/polls?appid=infra.discovery&env=dev&hostname=DESKTOP-9NFHKD0&latest_timestamp=1578902420717217500
在調用discovery polls的時候超時了，我配置的grpc dial 期限爲10s， 在官方discovery文檔介紹中寫到discovery在作服務節點自發現的時候，若是server節點實例沒有變動，則接口會阻塞直到30s返回-304。(poll(polls) 接口爲長輪訓接口)
關於服務自發現的話，這裏不細看了，本節只關注應用發現邏輯，感興趣能夠去discovery上看看。
INFO 01/10-15:22:34.436 http-access-log method=GET path=/discovery/polls user=no_user params=appid=infra.discovery&env=dev&hostname=CLII&latest_timestamp=0 stack=<nil> err= timeout_quota=39.98 ts=0 msg=0 traceid= ip=127.0.0.1 ret=0 INFO 01/10-15:22:34.438 C:/server/src/go/src/discovery/registry/registry.go:222 Polls from(CLII) new connection(1) INFO 01/10-15:22:34.440 C:/server/src/go/src/discovery/registry/registry.go:228 Polls from(CLII) reuse connection(2) INFO 01/10-15:22:44.219 C:/server/src/go/src/discovery/registry/registry.go:373 DelConns from(DESKTOP-9NFHKD0) delete(1) ERROR 01/10-15:22:44.219 http-access-log path=/discovery/polls ret=-304 msg=-304 timeout_quota=39.98 ip=127.0.0.1 params=appid=infra.discovery&env=dev&hostname=DESKTOP-9NFHKD0&latest_timestamp=1578637331623587200 user=no_user ts=39.9808023 err=-304 traceid= method=GET stack=-304 INFO 01/10-15:22:44.221 C:/server/src/go/src/discovery/registry/registry.go:222 Polls from(DESKTOP-9NFHKD0) new connection(1) INFO 01/10-15:22:44.525 http-access-log ts=0 method=POST ip=127.0.0.1 user=no_user stack=<nil> path=/discovery/renew err= traceid= ret=0 msg=0 timeout_quota=39.98 params=appid=demo.service&env=dev&hostname=DESKTOP-9NFHKD0®ion=region01&zone=zone01 INFO 01/10-15:23:04.438 C:/server/src/go/src/discovery/registry/registry.go:370 DelConns from(CLII) count decr(2) ERROR 01/10-15:23:04.438 http-access-log msg=-304 ts=30.0002154 method=GET err=-304 stack=-304 timeout_quota=39.98 ip=127.0.0.1 user=no_user path=/discovery/polls params=appid=infra.discovery&env=dev&hostname=CLII&latest_timestamp=1578637331623587200 ret=-304 traceid= INFO 01/10-15:23:04.440 C:/server/src/go/src/discovery/registry/registry.go:373 DelConns from(CLII) delete(1) ERROR 01/10-15:23:04.440 http-access-log ts=30.0013758 traceid= user=no_user path=/discovery/polls ret=-304 err=-304 method=GET ip=127.0.0.1 params=appid=infra.discovery&appid=demo.service&env=dev&hostname=CLII&latest_timestamp=1578637331623587200&latest_timestamp=0 msg=-304 stack=-304 timeout_quota=39.98
結合discovery 日誌
15:22:34的client發dial
15:22:45左右client panic
15:23:04dicovery纔回復一個-304 (實例信息無變動)
這其實是由於 client.Dial() 裏面封裝了grpc官方的服務發現，固然最終走的是kratos warden裏面的實現的grpc官方服務發現邏輯。
下面簡單看看這層邏輯，很繞，我也沒看懂，只能簡單看看，有機會接觸再補個詳細的。
簡單看看官方grpc服務發現邏輯
// NewClient new grpc client
func NewClient(cfg *warden.ClientConfig, opts ...grpc.DialOption) (demoapi.DemoClient, error) {
client := warden.NewClient(cfg, opts...)
cc, err := client.Dial(context.Background(), fmt.Sprintf("discovery://default/%s", AppID))
if err != nil {
return nil, err
}
return demoapi.NewDemoClient(cc), nil
}
實際上 client.Dial() 裏面會有會有這麼一個流程 :
client.Dial() - > grpc裏面DialContext() -> parser target 的 scheme 而後獲取 (這裏是discovery) 對應的Builder
if cc.dopts.resolverBuilder == nil {
// Only try to parse target when resolver builder is not already set.
cc.parsedTarget = parseTarget(cc.target)
grpclog.Infof("parsed scheme: %q", cc.parsedTarget.Scheme)
cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
if cc.dopts.resolverBuilder == nil {
// If resolver builder is still nil, the parsed target's scheme is
// not registered. Fallback to default resolver and set Endpoint to
// the original target.
grpclog.Infof("scheme %q not registered, fallback to default scheme", cc.parsedTarget.Scheme)
cc.parsedTarget = resolver.Target{
Scheme: resolver.GetDefaultScheme(),
Endpoint: target,
}
cc.dopts.resolverBuilder = resolver.Get(cc.parsedTarget.Scheme)
}
} else {
cc.parsedTarget = resolver.Target{Endpoint: target}
}
DialContext() 成功會獲得 -> 結構體ClientConn -> ClientConn.resolverWrapper 初始化 -> 調用build()
defer ccr.resolverMu.Unlock()
ccr.resolver, err = rb.Build(cc.parsedTarget, ccr, rbo)
// ClientConn represents a virtual connection to a conceptual endpoint, to
// perform RPCs.
//
// A ClientConn is free to have zero or more actual connections to the endpoint
// based on configuration, load, etc. It is also free to determine which actual
// endpoints to use and may change it every RPC, permitting client-side load
// balancing.
//
// A ClientConn encapsulates a range of functionality including name
// resolution, TCP connection establishment (with retries and backoff) and TLS
// handshakes. It also handles errors on established connections by
// re-resolving the name and reconnecting.
type ClientConn struct {
ctx context.Context
cancel context.CancelFunc
target string
parsedTarget resolver.Target
authority string
dopts dialOptions
csMgr *connectivityStateManager
balancerBuildOpts balancer.BuildOptions
blockingpicker *pickerWrapper
mu sync.RWMutex
resolverWrapper *ccResolverWrapper
sc *ServiceConfig
conns map[*addrConn]struct{}
// Keepalive parameter can be updated if a GoAway is received.
mkp keepalive.ClientParameters
curBalancerName string
balancerWrapper *ccBalancerWrapper
retryThrottler atomic.Value
firstResolveEvent *grpcsync.Event
channelzID int64 // channelz unique identification number
czData *channelzData
}
用戶Builder的實現進行UpdateState —> ClientConn的updateResolverState -> updateResolverState -> Address初始化等grpc官方邏輯
// Builder creates a resolver that will be used to watch name resolution updates.
type Builder interface {
// Build creates a new resolver for the given target.
//
// gRPC dial calls Build synchronously, and fails if the returned error is
// not nil.
Build(target Target, cc ClientConn, opts BuildOptions) (Resolver, error)
// Scheme returns the scheme supported by this resolver.
// Scheme is defined at https://github.com/grpc/grpc/blob/master/doc/naming.md.
Scheme() string
}
// ClientConn contains the callbacks for resolver to notify any updates
// to the gRPC ClientConn.
//
// This interface is to be implemented by gRPC. Users should not need a
// brand new implementation of this interface. For the situations like
// testing, the new implementation should embed this interface. This allows
// gRPC to add new methods to this interface.
type ClientConn interface {
// UpdateState updates the state of the ClientConn appropriately.
UpdateState(State)
// ReportError notifies the ClientConn that the Resolver encountered an
// error. The ClientConn will notify the load balancer and begin calling
// ResolveNow on the Resolver with exponential backoff.
ReportError(error)
// NewAddress is called by resolver to notify ClientConn a new list
// of resolved addresses.
// The address list should be the complete list of resolved addresses.
//
// Deprecated: Use UpdateState instead.
NewAddress(addresses []Address)
// NewServiceConfig is called by resolver to notify ClientConn a new
// service config. The service config should be provided as a json string.
//
// Deprecated: Use UpdateState instead.
NewServiceConfig(serviceConfig string)
// ParseServiceConfig parses the provided service config and returns an
// object that provides the parsed config.
ParseServiceConfig(serviceConfigJSON string) *serviceconfig.ParseResult
}
kratos discovery
warden包裝了gRPC的整個服務發現實現邏輯，代碼分別位於pkg/naming/naming.go和warden/resolver/resolver.go中
naming.go定義了用於描述業務實例的Instance結構、用於服務註冊的Registry接口、用於服務發現的Resolver接口。
// Resolver resolve naming service
type Resolver interface {
Fetch(context.Context) (*InstancesInfo, bool)
Watch() <-chan struct{}
Close() error
}
// Registry Register an instance and renew automatically.
type Registry interface {
Register(ctx context.Context, ins *Instance) (cancel context.CancelFunc, err error)
Close() error
}
// InstancesInfo instance info.
type InstancesInfo struct {
Instances map[string][]*Instance `json:"instances"`
LastTs int64 `json:"latest_timestamp"`
Scheduler *Scheduler `json:"scheduler"`
}
resolver.go內實現了gRPC官方的resolver.Builder和resolver.Resolver接口，同時也暴露了naming.go內的naming.Builder和naming.Resolver接口
// Resolver resolve naming service
type Resolver interface {
Fetch(context.Context) (*InstancesInfo, bool)
Watch() <-chan struct{}
Close() error
}
// Builder resolver builder.
type Builder interface {
Build(id string) Resolver
Scheme() string
}
kratos對grpc的Build作了包裝，只須要傳對應的服務的appid便可：warden/resolver/resolver.go在gRPC進行調用後，會根據Scheme方法查詢對應的naming.Builder實現並調用Build將id傳入。而實現naming.Resolver便可經過appid去對應的服務發現中間件(這裏是discovery服務)進行實例信息的查詢(Fetch接口)、除了簡單進行Fetch操做外還多了Watch方法，用於監聽服務發現中間件的節點變化狀況，可以實時的進行服務實例信息的更新。
在naming/discovery內實現了基於discovery爲中間件的服務註冊與發現邏輯。大體上也能夠在這裏面看到作了對discovery服務中間件的polls請求。
// Build disovery resovler builder.
func (d *Discovery) Build(appid string, opts ...naming.BuildOpt) naming.Resolver {
r := &Resolve{
id: appid,
d: d,
event: make(chan struct{}, 1),
opt: new(naming.BuildOptions),
}
for _, opt := range opts {
opt.Apply(r.opt)
}
d.mutex.Lock()
app, ok := d.apps[appid]
if !ok {
app = &appInfo{
resolver: make(map[*Resolve]struct{}),
}
d.apps[appid] = app
cancel := d.cancelPolls
if cancel != nil {
cancel()
}
}
app.resolver[r] = struct{}{}
d.mutex.Unlock()
if ok {
select {
case r.event <- struct{}{}:
default:
}
}
log.Info("disocvery: AddWatch(%s) already watch(%v)", appid, ok)
d.once.Do(func() {
go d.serverproc()
})
return r
}
func (d *Discovery) serverproc() {
var (
retry int
ctx context.Context
cancel context.CancelFunc
)
ticker := time.NewTicker(time.Minute * 30)
defer ticker.Stop()
for {
if ctx == nil {
ctx, cancel = context.WithCancel(d.ctx)
d.mutex.Lock()
d.cancelPolls = cancel
d.mutex.Unlock()
}
select {
case <-d.ctx.Done():
return
case <-ticker.C:
d.switchNode()
default:
}
apps, err := d.polls(ctx)
if err != nil {
d.switchNode()
if ctx.Err() == context.Canceled {
ctx = nil
continue
}
time.Sleep(time.Second)
retry++
continue
}
retry = 0
d.broadcast(apps)
}
}
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