kubernetes集群问题排查

水深无声 2022-06-16 05:42 311阅读 0赞

#  #

本文个人博客地址为：[http://www.huweihuang.com/article/kubernetes/kubernetes-troubleshooting/][http_www.huweihuang.com_article_kubernetes_kubernetes-troubleshooting]

本文个人博客地址为：[https://huweihuang.net/article/kubernetes/kubernetes-troubleshooting/][https_huweihuang.net_article_kubernetes_kubernetes-troubleshooting]

# 1. 查看系统Event事件 #

kubectl describe pod <PodName> --namespace=<NAMESPACE>

该命令可以显示Pod创建时的配置定义、状态等信息和最近的Event事件，事件信息可用于排错。例如当Pod状态为Pending，可通过查看Event事件确认原因，一般原因有几种：

*  没有可用的Node可调度
 *  开启了资源配额管理并且当前Pod的目标节点上恰好没有可用的资源
 *  正在下载镜像（镜像拉取耗时太久）或镜像下载失败。

kubectl describe还可以查看其它k8s对象：NODE,RC,Service,Namespace,Secrets。

## 1.1. Pod ##

kubectl describe pod <PodName> --namespace=<NAMESPACE>

以下是容器的启动命令非阻塞式导致容器挂掉，被k8s频繁重启所产生的事件。

kubectl describe pod  --namespace=  
    
    Events:
      FirstSeen LastSeen    Count   From            SubobjectPath       Reason      Message
      ───────── ────────    ─────   ────            ─────────────       ──────      ───────
      7m        7m      1   {scheduler }                    Scheduled   Successfully assigned yangsc-1-0-0-index0 to 10.8.216.19
      7m        7m      1   {kubelet 10.8.216.19}   containers{infra}   Pulled      Container image "gcr.io/kube-system/pause:0.8.0" already present on machine
      7m        7m      1   {kubelet 10.8.216.19}   containers{infra}   Created     Created with docker id 84f133c324d0
      7m        7m      1   {kubelet 10.8.216.19}   containers{infra}   Started     Started with docker id 84f133c324d0
      7m        7m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 3f9f82abb145
      7m        7m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 3f9f82abb145
      7m        7m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id fb112e4002f4
      7m        7m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id fb112e4002f4
      6m        6m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 613b119d4474
      6m        6m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 613b119d4474
      6m        6m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 25cb68d1fd3d
      6m        6m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 25cb68d1fd3d
      5m        5m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 7d9ee8610b28
      5m        5m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 7d9ee8610b28
      3m        3m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 88b9e8d582dd
      3m        3m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 88b9e8d582dd
      7m        1m      7   {kubelet 10.8.216.19}   containers{yangsc0} Pulling     Pulling image "gcr.io/test/tcp-hello:1.0.0"
      1m        1m      1   {kubelet 10.8.216.19}   containers{yangsc0} Started     Started with docker id 089abff050e7
      1m        1m      1   {kubelet 10.8.216.19}   containers{yangsc0} Created     Created with docker id 089abff050e7
      7m        1m      7   {kubelet 10.8.216.19}   containers{yangsc0} Pulled      Successfully pulled image "gcr.io/test/tcp-hello:1.0.0"
      6m        7s      34  {kubelet 10.8.216.19}   containers{yangsc0} Backoff     Back-off restarting failed docker container

## 1.2. NODE ##

kubectl describe node 10.8.216.20

[root@FC-43745A-10 ~]# kubectl describe node 10.8.216.20
    Name:			10.8.216.20
    Labels:			kubernetes.io/hostname=10.8.216.20,namespace/bcs-cc=true,namespace/myview=true
    CreationTimestamp:	Mon, 17 Apr 2017 11:32:52 +0800
    Phase:			
    Conditions:
      Type		Status	LastHeartbeatTime			LastTransitionTime			Reason				Message
      ────		──────	─────────────────			──────────────────			──────				───────
      Ready 	True 	Fri, 18 Aug 2017 09:38:33 +0800 	Tue, 02 May 2017 17:40:58 +0800 	KubeletReady 			kubelet is posting ready status
      OutOfDisk 	False 	Fri, 18 Aug 2017 09:38:33 +0800 	Mon, 17 Apr 2017 11:31:27 +0800 	KubeletHasSufficientDisk 	kubelet has sufficient disk space available
    Addresses:	10.8.216.20,10.8.216.20
    Capacity:
     cpu:		32
     memory:	67323039744
     pods:		40
    System Info:
     Machine ID:			723bafc7f6764022972b3eae1ce6b198
     System UUID:			4C4C4544-0042-4210-8044-C3C04F595631
     Boot ID:			da01f2e3-987a-425a-9ca7-1caaec35d1e5
     Kernel Version:		3.10.0-327.28.3.el7.x86_64
     OS Image:			CentOS Linux 7 (Core)
     Container Runtime Version:	docker://1.13.1
     Kubelet Version:		v1.1.1-xxx-13.1+79c90c68bfb72f-dirty
     Kube-Proxy Version:		v1.1.1-xxx-13.1+79c90c68bfb72f-dirty
    ExternalID:			10.8.216.20
    Non-terminated Pods:		(6 in total)
      Namespace			Name					CPU Requests	CPU Limits	Memory Requests	Memory Limits
      ─────────			────					────────────	──────────	───────────────	─────────────
      bcs-cc			bcs-cc-api-0-0-1364-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
      bcs-cc			bcs-cc-api-0-0-1444-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
      fw				fw-demo2-0-0-1519-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
      myview			myview-api-0-0-1362-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
      myview			myview-api-0-0-1442-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
      qa-ts-dna			ts-dna-console3-0-0-1434-index0		1 (3%)		1 (3%)		4294967296 (6%)	4294967296 (6%)
    Allocated resources:
      (Total limits may be over 100%, i.e., overcommitted. More info: http://releases.k8s.io/HEAD/docs/user-guide/compute-resources.md)
      CPU Requests	CPU Limits	Memory Requests		Memory Limits
      ────────────	──────────	───────────────		─────────────
      6 (18%)	6 (18%)		25769803776 (38%)	25769803776 (38%)
    No events.

## 1.3. RC ##

kubectl describe rc mytest-1-0-0 --namespace=test

[root@FC-43745A-10 ~]# kubectl describe rc mytest-1-0-0 --namespace=test
    Name:		mytest-1-0-0
    Namespace:	test
    Image(s):	gcr.io/test/mywebcalculator:1.0.1
    Selector:	app=mytest,appVersion=1.0.0
    Labels:		app=mytest,appVersion=1.0.0,env=ts,zone=inner
    Replicas:	1 current / 1 desired
    Pods Status:	1 Running / 0 Waiting / 0 Succeeded / 0 Failed
    No volumes.
    Events:
      FirstSeen	LastSeen	Count	From				SubobjectPath	Reason			Message
      ─────────	────────	─────	────				─────────────	──────			───────
      20h		19h		9	{replication-controller }			FailedCreate		Error creating: Pod "mytest-1-0-0-index0" is forbidden: limited to 10 pods
      20h		17h		7	{replication-controller }			FailedCreate		Error creating: pods "mytest-1-0-0-index0" already exists
      20h		17h		4	{replication-controller }			SuccessfulCreate	Created pod: mytest-1-0-0-index0

## 1.4. NAMESPACE ##

kubectl describe namespace test

[root@FC-43745A-10 ~]# kubectl describe namespace test
    Name:	test
    Labels:	<none>
    Status:	Active
    
    Resource Quotas
     Resource		Used		Hard
     ---			---		---
     cpu			5		20
     memory			1342177280	53687091200
     persistentvolumeclaims	0		10
     pods			4		10
     replicationcontrollers	8		20
     resourcequotas		1		1
     secrets		3		10
     services		8		20
    
    No resource limits.

## 1.5. Service ##

kubectl describe service xxx-containers-1-1-0 --namespace=test

[root@FC-43745A-10 ~]# kubectl describe service xxx-containers-1-1-0 --namespace=test
    Name:			xxx-containers-1-1-0
    Namespace:		test
    Labels:			app=xxx-containers,appVersion=1.1.0,env=ts,zone=inner
    Selector:		app=xxx-containers,appVersion=1.1.0
    Type:			ClusterIP
    IP:			10.254.46.42
    Port:			port-dna-tcp-35913	35913/TCP
    Endpoints:		10.0.92.17:35913
    Port:			port-l7-tcp-8080	8080/TCP
    Endpoints:		10.0.92.17:8080
    Session Affinity:	None
    No events.

# 2. 查看容器日志 #

**1、查看指定pod的日志**

kubectl logs <pod\_name>

kubectl logs -f <pod\_name> \#类似tail -f的方式查看

**2、查看上一个pod的日志**

kubectl logs -p <pod\_name>

**3、查看指定pod中指定容器的日志**

kubectl logs <pod\_name> -c <container\_name>

**4、kubectl logs的更多使用请参考kubectl logs --help**

[root@node5 ~]# kubectl logs --help
    Print the logs for a container in a pod. If the pod has only one container, the container name is optional.
    Usage:
      kubectl logs [-f] [-p] POD [-c CONTAINER] [flags]
    Aliases:
      logs, log
     
    Examples:
    # Return snapshot logs from pod nginx with only one container
    $ kubectl logs nginx
    # Return snapshot of previous terminated ruby container logs from pod web-1
    $ kubectl logs -p -c ruby web-1
    # Begin streaming the logs of the ruby container in pod web-1
    $ kubectl logs -f -c ruby web-1
    # Display only the most recent 20 lines of output in pod nginx
    $ kubectl logs --tail=20 nginx
    # Show all logs from pod nginx written in the last hour
    $ kubectl logs --since=1h nginx

**5、docker logs**

**如果有Node机器（即宿主机）的登录权限，可以到出问题的pod所调度到的机器上，通过docker logs的命令查看对应容器的问题原因。**

例如：

**docker ps -a |grep <container>**

**docker logs <container\_id>**

[root@kube-master ~]# docker ps -a |grep redis
    ee7398bba500        docker.io/redis@sha256:bb47379e6e0101441dbb1fe585171521e4ee2ebe1ae23f663232f56ac41551de   "docker-entrypoint.sh"   About a minute ago   Exited (1) About a minute ago                       k8s_kubernetes-log-tail-bigdatalog-testappkey_test-add-plugins-403621826-bskfz_test-7da2c1_a5412774-d43f-11e7-98c3-a2642aaa3458_6
    5360d15344fb        docker.io/redis@sha256:bb47379e6e0101441dbb1fe585171521e4ee2ebe1ae23f663232f56ac41551de   "docker-entrypoint.sh"   7 minutes ago        Up 7 minutes                                        k8s_kubernetes-log-tail-testagent_test-add-plugins-403621826-bskfz_test-7da2c1_a5412774-d43f-11e7-98c3-a2642aaa3458_0
    [root@kube-master ~]#
    [root@kube-master ~]# docker logs ee7398bba500
    1:C 28 Nov 13:32:29.352 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
    1:C 28 Nov 13:32:29.354 # Redis version=4.0.6, bits=64, commit=00000000, modified=0, pid=1, just started
    1:C 28 Nov 13:32:29.354 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
    1:M 28 Nov 13:32:29.355 # Creating Server TCP listening socket *:6379: bind: Address already in use

以上报错是因为端口冲突问题：bind: Address already in use

# 3. 查看k8s服务日志 #

## 3.1. journalctl ##

在Linux系统上systemd系统来管理kubernetes服务，并且journal系统会接管服务程序的输出日志，可以通过**systemctl status <xxx>或journalctl -u <xxx> -f**来查看kubernetes服务的日志。

其中kubernetes组件包括：

<table style="border-collapse:collapse;margin:0px;"> 
 <thead> 
  <tr> 
   <th style="border:1px solid rgb(221,221,221);padding:7px 15px 7px 10px;vertical-align:top;text-align:left;background:rgb(240,240,240) no-repeat right center;color:rgb(51,51,51);"> 
    <div style="margin:0px;padding:0px;">
      k8s组件 
    </div></th> 
   <th style="border:1px solid rgb(221,221,221);padding:7px 15px 7px 10px;vertical-align:top;text-align:left;background:rgb(240,240,240) no-repeat right center;color:rgb(51,51,51);"> 
    <div style="margin:0px;padding:0px;">
      涉及日志内容 
    </div></th> 
   <th style="border:1px solid rgb(221,221,221);padding:7px 15px 7px 10px;vertical-align:top;text-align:left;background:rgb(240,240,240) no-repeat right center;color:rgb(51,51,51);"> 
    <div style="margin:0px;padding:0px;">
      备注 
    </div></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">kube-apiserver</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
  </tr> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">kube-controller-manager</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">Pod扩容相关或RC相关</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
  </tr> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">kube-scheduler</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">Pod扩容相关或RC相关</td> 
   <td style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
  </tr> 
  <tr> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">kubelet</td> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">Pod生命周期相关：创建、停止等</td> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
  </tr> 
  <tr> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">etcd</td> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
   <td colspan="1" style="border:1px solid rgb(221,221,221);padding:7px 10px;vertical-align:top;">&nbsp;</td> 
  </tr> 
 </tbody> 
</table>

## 3.2. 日志文件 ##

也可以通过指定日志存放目录来保存和查看日志

*  \--logtostderr=false：不输出到stderr
 *  \--log-dir=/var/log/kubernetes:日志的存放目录
 *  \--alsologtostderr=false:设置为true表示日志输出到文件也输出到stderr
 *  \--v=0:glog的日志级别
 *  \--vmodule=gfs\*=2,test\*=4：glog基于模块的详细日志级别

# 4. 常见问题 #

## 4.1. Pod状态一直为Pending ##

kubectl describe <pod\_name> --namespace=<NAMESPACE>

查看该POD的事件。

*  正在下载镜像但拉取不下来（镜像拉取耗时太久）\[一般都是该原因\]
 *  没有可用的Node可调度
 *  开启了资源配额管理并且当前Pod的目标节点上恰好没有可用的资源

解决方法：

1.  查看该POD所在宿主机与镜像仓库之间的网络是否有问题，可以手动拉取镜像
2.  删除POD实例，让POD调度到别的宿主机上

## 4.2. Pod创建后不断重启 ##

kubectl get pods中Pod状态一会running，一会不是，且RESTARTS次数不断增加。

一般原因为容器启动命令不是阻塞式命令，导致容器运行后马上退出。

非阻塞式命令：

*  本身CMD指定的命令就是非阻塞式命令
 *  将服务启动方式设置为后台运行

解决方法：

1、将命令改为阻塞式命令（前台运行），例如：**zkServer.sh start-foreground**

2、java运行程序的启动脚本将 nohup xxx &的nobup和&去掉，例如：

nohup $JAVA\_HOME/bin/java $JAVA\_OPTS -cp $CLASSPATH com.cnc.open.processor.Main &

改为：

$JAVA\_HOME/bin/java $JAVA\_OPTS -cp $CLASSPATH com.cnc.open.processor.Main

文章参考《Kubernetes权威指南》

[http_www.huweihuang.com_article_kubernetes_kubernetes-troubleshooting]: http://www.huweihuang.com/article/kubernetes/kubernetes-troubleshooting/
[https_huweihuang.net_article_kubernetes_kubernetes-troubleshooting]: https://huweihuang.net/article/kubernetes/kubernetes-troubleshooting/