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Fix comparison of EtcdClient to nil so that it does not run into the pointer vs. interface issue

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This is a partial rollback of commit 6e6f465a36 ("Fix a crash for
kubelet when without EtcdClient") in which we used the `reflect` module
to inspect that the pointer stored inside the interface was `nil`, but
as pointed out by @lavalamp, the correct solution is to make the
function return the interface type, in which case a `return nil` will
return the interface nil and not a nil pointer that turns into a non-nil
value when coerced into an interface.

For more details, see http://golang.org/doc/faq#nil_error and the
discussion in PR #3356.

Tested by installing a kubelet built from head with this patch into a
containervm instance and confirming it did not crash on standalone.go.
Confirmed that by only removing the `reflect.IsNil()` comparison but not
changing the return type of `EtcdClientOrDie()` did indeed cause that
same crash, so changing the return type does indeed fix the issue.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>
This commit is contained in:
Filipe Brandenburger 2015-01-16 16:38:09 -08:00
parent 3c370d0b1b
commit 79ff06ffa1
2 changed files with 4 additions and 4 deletions
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3
pkg/kubelet/util.go
View File

@ -25,6 +25,7 @@ import (
"github.com/GoogleCloudPlatform/kubernetes/pkg/client" "github.com/GoogleCloudPlatform/kubernetes/pkg/client"
"github.com/GoogleCloudPlatform/kubernetes/pkg/client/record" "github.com/GoogleCloudPlatform/kubernetes/pkg/client/record"
"github.com/GoogleCloudPlatform/kubernetes/pkg/health" "github.com/GoogleCloudPlatform/kubernetes/pkg/health"
"github.com/GoogleCloudPlatform/kubernetes/pkg/tools"
"github.com/GoogleCloudPlatform/kubernetes/pkg/util" "github.com/GoogleCloudPlatform/kubernetes/pkg/util"
"github.com/coreos/go-etcd/etcd" "github.com/coreos/go-etcd/etcd"
"github.com/golang/glog" "github.com/golang/glog"
@ -55,7 +56,7 @@ func InitHealthChecking(k *Kubelet) {
} }
// TODO: move this into a pkg/tools/etcd_tools // TODO: move this into a pkg/tools/etcd_tools
func EtcdClientOrDie(etcdServerList util.StringList, etcdConfigFile string) *etcd.Client { func EtcdClientOrDie(etcdServerList util.StringList, etcdConfigFile string) tools.EtcdClient {
if len(etcdServerList) > 0 { if len(etcdServerList) > 0 {
return etcd.NewClient(etcdServerList) return etcd.NewClient(etcdServerList)
} else if etcdConfigFile != "" { } else if etcdConfigFile != "" {

5
pkg/standalone/standalone.go
View File

@ -20,7 +20,6 @@ import (
"fmt" "fmt"
"net" "net"
"net/http" "net/http"
"reflect"
"time" "time"
"github.com/GoogleCloudPlatform/kubernetes/pkg/api" "github.com/GoogleCloudPlatform/kubernetes/pkg/api"
@ -229,11 +228,11 @@ func makePodSourceConfig(kc *KubeletConfig) *config.PodConfig {
glog.Infof("Adding manifest url: %v", kc.ManifestURL) glog.Infof("Adding manifest url: %v", kc.ManifestURL)
config.NewSourceURL(kc.ManifestURL, kc.HttpCheckFrequency, cfg.Channel(kubelet.HTTPSource)) config.NewSourceURL(kc.ManifestURL, kc.HttpCheckFrequency, cfg.Channel(kubelet.HTTPSource))
} }
if kc.EtcdClient != nil && !reflect.ValueOf(kc.EtcdClient).IsNil() { if kc.EtcdClient != nil {
glog.Infof("Watching for etcd configs at %v", kc.EtcdClient.GetCluster()) glog.Infof("Watching for etcd configs at %v", kc.EtcdClient.GetCluster())
config.NewSourceEtcd(config.EtcdKeyForHost(kc.Hostname), kc.EtcdClient, cfg.Channel(kubelet.EtcdSource)) config.NewSourceEtcd(config.EtcdKeyForHost(kc.Hostname), kc.EtcdClient, cfg.Channel(kubelet.EtcdSource))
} }
if kc.KubeClient != nil && !reflect.ValueOf(kc.KubeClient).IsNil() { if kc.KubeClient != nil {
glog.Infof("Watching apiserver") glog.Infof("Watching apiserver")
config.NewSourceApiserver(kc.KubeClient, kc.Hostname, cfg.Channel(kubelet.ApiserverSource)) config.NewSourceApiserver(kc.KubeClient, kc.Hostname, cfg.Channel(kubelet.ApiserverSource))
} }