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Support multiple k8s api servers specification and load balance among api servers (#820)

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* Support multiple k8s api servers specification and load balance among api servers

This fix adds supports for multiple k8s api servers specification,
load balance among api servers.

When two or more api servers are specified in kubernetes block (endpoint ...),
a proxy is created locally (with randomly generately port). The coredns
will points to the generated proxy so that load balancing could be achieved.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Setup initial healthcheck at the beginning

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Update README.md for kubernetes middleware and remove whitespaces.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Use middleware/pkg/healthcheck in middleware/kubernetes

for api proxy

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
This commit is contained in:
Yong Tang 2017-08-10 17:14:56 -07:00 • committed by GitHub
parent acfa6501e0
commit 26d8680a11
6 changed files with 171 additions and 5 deletions
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63
middleware/kubernetes/kubernetes.go
View file

@ -7,11 +7,13 @@ import (
"log"
"net"
"strings"
"sync/atomic"
"time"
"github.com/coredns/coredns/middleware"
"github.com/coredns/coredns/middleware/etcd/msg"
"github.com/coredns/coredns/middleware/pkg/dnsutil"
"github.com/coredns/coredns/middleware/pkg/healthcheck"
dnsstrings "github.com/coredns/coredns/middleware/pkg/strings"
"github.com/coredns/coredns/middleware/proxy"
"github.com/coredns/coredns/request"
@ -32,7 +34,8 @@ type Kubernetes struct {
Zones []string
primaryZone int
Proxy proxy.Proxy // Proxy for looking up names during the resolution process
APIEndpoint string
APIServerList []string
APIProxy *apiProxy
APICertAuth string
APIClientCert string
APIClientKey string
@ -173,8 +176,62 @@ func (k *Kubernetes) getClientConfig() (*rest.Config, error) {
overrides := &clientcmd.ConfigOverrides{}
clusterinfo := clientcmdapi.Cluster{}
authinfo := clientcmdapi.AuthInfo{}
if len(k.APIEndpoint) > 0 {
clusterinfo.Server = k.APIEndpoint
if len(k.APIServerList) > 0 {
endpoint := k.APIServerList[0]
if len(k.APIServerList) > 1 {
// Use a random port for api proxy, will get the value later through listener.Addr()
listener, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
return nil, fmt.Errorf("failed to create kubernetes api proxy: %v", err)
}
k.APIProxy = &apiProxy{
listener: listener,
handler: proxyHandler{
HealthCheck: healthcheck.HealthCheck{
FailTimeout: 3 * time.Second,
MaxFails: 1,
Future: 10 * time.Second,
Path: "/",
Interval: 5 * time.Second,
},
},
}
k.APIProxy.handler.Hosts = make([]*healthcheck.UpstreamHost, len(k.APIServerList))
for i, entry := range k.APIServerList {
uh := &healthcheck.UpstreamHost{
Name: strings.TrimPrefix(entry, "http://"),
CheckDown: func(upstream *proxyHandler) healthcheck.UpstreamHostDownFunc {
return func(uh *healthcheck.UpstreamHost) bool {
down := false
uh.CheckMu.Lock()
until := uh.OkUntil
uh.CheckMu.Unlock()
if !until.IsZero() && time.Now().After(until) {
down = true
}
fails := atomic.LoadInt32(&uh.Fails)
if fails >= upstream.MaxFails && upstream.MaxFails != 0 {
down = true
}
return down
}
}(&k.APIProxy.handler),
}
k.APIProxy.handler.Hosts[i] = uh
}
k.APIProxy.Handler = &k.APIProxy.handler
// Find the random port used for api proxy
endpoint = fmt.Sprintf("http://%s", listener.Addr())
}
clusterinfo.Server = endpoint
} else {
cc, err := rest.InClusterConfig()
if err != nil {