应用自测与调试
运行应用时,不可避免的需要定位问题。 前面我们介绍了如何使用 kubectl get pods
来查询 pod 的简单信息。 除此之外,还有一系列的方法来获取应用的更详细信息。
使用 kubectl describe pod
命令获取 Pod 详情
与之前的例子类似,我们使用一个 Deployment 来创建两个 Pod。
application/nginx-with-request.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 2
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx
resources:
limits:
memory: "128Mi"
cpu: "500m"
ports:
- containerPort: 80
使用如下命令创建 Deployment:
kubectl apply -f https://k8s.io/examples/application/nginx-with-request.yaml
deployment.apps/nginx-deployment created
使用如下命令查看 Pod 状态:
kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-1006230814-6winp 1/1 Running 0 11s
nginx-deployment-1006230814-fmgu3 1/1 Running 0 11s
我们可以使用 kubectl describe pod
命令来查询每个 Pod 的更多信息,比如:
kubectl describe pod nginx-deployment-1006230814-6winp
Name: nginx-deployment-1006230814-6winp
Namespace: default
Node: kubernetes-node-wul5/10.240.0.9
Start Time: Thu, 24 Mar 2016 01:39:49 +0000
Labels: app=nginx,pod-template-hash=1006230814
Annotations: kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicaSet","namespace":"default","name":"nginx-deployment-1956810328","uid":"14e607e7-8ba1-11e7-b5cb-fa16" ...
Status: Running
IP: 10.244.0.6
Controllers: ReplicaSet/nginx-deployment-1006230814
Containers:
nginx:
Container ID: docker://90315cc9f513c724e9957a4788d3e625a078de84750f244a40f97ae355eb1149
Image: nginx
Image ID: docker://6f62f48c4e55d700cf3eb1b5e33fa051802986b77b874cc351cce539e5163707
Port: 80/TCP
QoS Tier:
cpu: Guaranteed
memory: Guaranteed
Limits:
cpu: 500m
memory: 128Mi
Requests:
memory: 128Mi
cpu: 500m
State: Running
Started: Thu, 24 Mar 2016 01:39:51 +0000
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-5kdvl (ro)
Conditions:
Type Status
Initialized True
Ready True
PodScheduled True
Volumes:
default-token-4bcbi:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-4bcbi
Optional: false
QoS Class: Guaranteed
Node-Selectors: <none>
Tolerations: <none>
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
54s 54s 1 {default-scheduler } Normal Scheduled Successfully assigned nginx-deployment-1006230814-6winp to kubernetes-node-wul5
54s 54s 1 {kubelet kubernetes-node-wul5} spec.containers{nginx} Normal Pulling pulling image "nginx"
53s 53s 1 {kubelet kubernetes-node-wul5} spec.containers{nginx} Normal Pulled Successfully pulled image "nginx"
53s 53s 1 {kubelet kubernetes-node-wul5} spec.containers{nginx} Normal Created Created container with docker id 90315cc9f513
53s 53s 1 {kubelet kubernetes-node-wul5} spec.containers{nginx} Normal Started Started container with docker id 90315cc9f513
这里可以看到容器和 Pod 的标签、资源需求等配置信息,还可以看到状态、就绪态、 重启次数、事件等状态信息。
容器状态是 Waiting、Running 和 Terminated 之一。 根据状态的不同,还有对应的额外的信息 —— 在这里你可以看到, 对于处于运行状态的容器,系统会告诉你容器的启动时间。
Ready 指示是否通过了最后一个就绪态探测。 (在本例中,容器没有配置就绪态探测;如果没有配置就绪态探测,则假定容器已经就绪。)
Restart Count 告诉你容器已重启的次数; 这些信息对于定位配置了 “Always” 重启策略的容器持续崩溃问题非常有用。
目前,唯一与 Pod 有关的状态是 Ready 状况,该状况表明 Pod 能够为请求提供服务, 并且应该添加到相应服务的负载均衡池中。
最后,你还可以看到与 Pod 相关的近期事件。 系统通过指示第一次和最后一次看到事件以及看到该事件的次数来压缩多个相同的事件。 “From” 标明记录事件的组件, “SubobjectPath” 告诉你引用了哪个对象(例如 Pod 中的容器), “Reason” 和 “Message” 告诉你发生了什么。
例子: 调试 Pending 状态的 Pod
可以使用事件来调试的一个常见的场景是,你创建 Pod 无法被调度到任何节点。 比如,Pod 请求的资源比较多,没有任何一个节点能够满足,或者它指定了一个标签,没有节点可匹配。 假定我们创建之前的 Deployment 时指定副本数是 5(不再是 2),并且请求 600 毫核(不再是 500), 对于一个 4 个节点的集群,若每个节点只有 1 个 CPU,这时至少有一个 Pod 不能被调度。 (需要注意的是,其他集群插件 Pod,比如 fluentd、skydns 等等会在每个节点上运行, 如果我们需求 1000 毫核,将不会有 Pod 会被调度。)
kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-1006230814-6winp 1/1 Running 0 7m
nginx-deployment-1006230814-fmgu3 1/1 Running 0 7m
nginx-deployment-1370807587-6ekbw 1/1 Running 0 1m
nginx-deployment-1370807587-fg172 0/1 Pending 0 1m
nginx-deployment-1370807587-fz9sd 0/1 Pending 0 1m
为了查找 Pod nginx-deployment-1370807587-fz9sd 没有运行的原因,我们可以使用 kubectl describe pod
命令描述 Pod,查看其事件:
kubectl describe pod nginx-deployment-1370807587-fz9sd
Name: nginx-deployment-1370807587-fz9sd
Namespace: default
Node: /
Labels: app=nginx,pod-template-hash=1370807587
Status: Pending
IP:
Controllers: ReplicaSet/nginx-deployment-1370807587
Containers:
nginx:
Image: nginx
Port: 80/TCP
QoS Tier:
memory: Guaranteed
cpu: Guaranteed
Limits:
cpu: 1
memory: 128Mi
Requests:
cpu: 1
memory: 128Mi
Environment Variables:
Volumes:
default-token-4bcbi:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-4bcbi
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
1m 48s 7 {default-scheduler } Warning FailedScheduling pod (nginx-deployment-1370807587-fz9sd) failed to fit in any node
fit failure on node (kubernetes-node-6ta5): Node didn't have enough resource: CPU, requested: 1000, used: 1420, capacity: 2000
fit failure on node (kubernetes-node-wul5): Node didn't have enough resource: CPU, requested: 1000, used: 1100, capacity: 2000
这里你可以看到由调度器记录的事件,它表明了 Pod 不能被调度的原因是 FailedScheduling
(也可能是其他值)。 其 message 部分表明没有任何节点拥有足够多的资源。
要纠正这种情况,可以使用 kubectl scale
更新 Deployment,以指定 4 个或更少的副本。 (或者你可以让 Pod 继续保持这个状态,这是无害的。)
你在 kubectl describe pod
结尾处看到的事件都保存在 etcd 中, 并提供关于集群中正在发生的事情的高级信息。 如果需要列出所有事件,可使用命令:
kubectl get events
但是,需要注意的是,事件是区分名字空间的。 如果你对某些名字空间域的对象(比如 my-namespace
名字下的 Pod)的事件感兴趣, 你需要显式地在命令行中指定名字空间:
kubectl get events --namespace=my-namespace
查看所有 namespace 的事件,可使用 --all-namespaces
参数。
除了 kubectl describe pod
以外,另一种获取 Pod 额外信息(除了 kubectl get pod
)的方法 是给 kubectl get pod
增加 -o yaml
输出格式参数。 该命令将以 YAML 格式为你提供比 kubectl describe pod
更多的信息 —— 实际上是系统拥有的关于 Pod 的所有信息。 在这里,你将看到注解(没有标签限制的键值元数据,由 Kubernetes 系统组件在内部使用)、 重启策略、端口和卷等。
kubectl get pod nginx-deployment-1006230814-6winp -o yaml
apiVersion: v1
kind: Pod
metadata:
annotations:
kubernetes.io/created-by: |
{"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicaSet","namespace":"default","name":"nginx-deployment-1006230814","uid":"4c84c175-f161-11e5-9a78-42010af00005","apiVersion":"extensions","resourceVersion":"133434"}}
creationTimestamp: 2016-03-24T01:39:50Z
generateName: nginx-deployment-1006230814-
labels:
app: nginx
pod-template-hash: "1006230814"
name: nginx-deployment-1006230814-6winp
namespace: default
resourceVersion: "133447"
uid: 4c879808-f161-11e5-9a78-42010af00005
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: nginx
ports:
- containerPort: 80
protocol: TCP
resources:
limits:
cpu: 500m
memory: 128Mi
requests:
cpu: 500m
memory: 128Mi
terminationMessagePath: /dev/termination-log
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-4bcbi
readOnly: true
dnsPolicy: ClusterFirst
nodeName: kubernetes-node-wul5
restartPolicy: Always
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
volumes:
- name: default-token-4bcbi
secret:
secretName: default-token-4bcbi
status:
conditions:
- lastProbeTime: null
lastTransitionTime: 2016-03-24T01:39:51Z
status: "True"
type: Ready
containerStatuses:
- containerID: docker://90315cc9f513c724e9957a4788d3e625a078de84750f244a40f97ae355eb1149
image: nginx
imageID: docker://6f62f48c4e55d700cf3eb1b5e33fa051802986b77b874cc351cce539e5163707
lastState: {}
name: nginx
ready: true
restartCount: 0
state:
running:
startedAt: 2016-03-24T01:39:51Z
hostIP: 10.240.0.9
phase: Running
podIP: 10.244.0.6
startTime: 2016-03-24T01:39:49Z
示例:调试宕机或无法联系的节点
有时候,在调试时,查看节点的状态是很有用的 —— 例如,因为你已经注意到节点上运行的 Pod 的奇怪行为, 或者想了解为什么 Pod 不会调度到节点上。 与 Pod 一样,你可以使用 kubectl describe node
和 kubectl get node -o yaml
来查询节点的详细信息。 例如,如果某个节点宕机(与网络断开连接,或者 kubelet 挂掉无法重新启动等等),你将看到以下情况。 请注意显示节点未就绪的事件,也请注意 Pod 不再运行(它们在5分钟未就绪状态后被驱逐)。
kubectl get nodes
NAME STATUS ROLES AGE VERSION
kubernetes-node-861h NotReady <none> 1h v1.13.0
kubernetes-node-bols Ready <none> 1h v1.13.0
kubernetes-node-st6x Ready <none> 1h v1.13.0
kubernetes-node-unaj Ready <none> 1h v1.13.0
kubectl describe node kubernetes-node-861h
Name: kubernetes-node-861h
Role
Labels: kubernetes.io/arch=amd64
kubernetes.io/os=linux
kubernetes.io/hostname=kubernetes-node-861h
Annotations: node.alpha.kubernetes.io/ttl=0
volumes.kubernetes.io/controller-managed-attach-detach=true
Taints: <none>
CreationTimestamp: Mon, 04 Sep 2017 17:13:23 +0800
Phase:
Conditions:
Type Status LastHeartbeatTime LastTransitionTime Reason Message
---- ------ ----------------- ------------------ ------ -------
OutOfDisk Unknown Fri, 08 Sep 2017 16:04:28 +0800 Fri, 08 Sep 2017 16:20:58 +0800 NodeStatusUnknown Kubelet stopped posting node status.
MemoryPressure Unknown Fri, 08 Sep 2017 16:04:28 +0800 Fri, 08 Sep 2017 16:20:58 +0800 NodeStatusUnknown Kubelet stopped posting node status.
DiskPressure Unknown Fri, 08 Sep 2017 16:04:28 +0800 Fri, 08 Sep 2017 16:20:58 +0800 NodeStatusUnknown Kubelet stopped posting node status.
Ready Unknown Fri, 08 Sep 2017 16:04:28 +0800 Fri, 08 Sep 2017 16:20:58 +0800 NodeStatusUnknown Kubelet stopped posting node status.
Addresses: 10.240.115.55,104.197.0.26
Capacity:
cpu: 2
hugePages: 0
memory: 4046788Ki
pods: 110
Allocatable:
cpu: 1500m
hugePages: 0
memory: 1479263Ki
pods: 110
System Info:
Machine ID: 8e025a21a4254e11b028584d9d8b12c4
System UUID: 349075D1-D169-4F25-9F2A-E886850C47E3
Boot ID: 5cd18b37-c5bd-4658-94e0-e436d3f110e0
Kernel Version: 4.4.0-31-generic
OS Image: Debian GNU/Linux 8 (jessie)
Operating System: linux
Architecture: amd64
Container Runtime Version: docker://1.12.5
Kubelet Version: v1.6.9+a3d1dfa6f4335
Kube-Proxy Version: v1.6.9+a3d1dfa6f4335
ExternalID: 15233045891481496305
Non-terminated Pods: (9 in total)
Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits
--------- ---- ------------ ---------- --------------- -------------
......
Allocated resources:
(Total limits may be over 100 percent, i.e., overcommitted.)
CPU Requests CPU Limits Memory Requests Memory Limits
------------ ---------- --------------- -------------
900m (60%) 2200m (146%) 1009286400 (66%) 5681286400 (375%)
Events: <none>
kubectl get node kubernetes-node-861h -o yaml
apiVersion: v1
kind: Node
metadata:
creationTimestamp: 2015-07-10T21:32:29Z
labels:
kubernetes.io/hostname: kubernetes-node-861h
name: kubernetes-node-861h
resourceVersion: "757"
selfLink: /api/v1/nodes/kubernetes-node-861h
uid: 2a69374e-274b-11e5-a234-42010af0d969
spec:
externalID: "15233045891481496305"
podCIDR: 10.244.0.0/24
providerID: gce://striped-torus-760/us-central1-b/kubernetes-node-861h
status:
addresses:
- address: 10.240.115.55
type: InternalIP
- address: 104.197.0.26
type: ExternalIP
capacity:
cpu: "1"
memory: 3800808Ki
pods: "100"
conditions:
- lastHeartbeatTime: 2015-07-10T21:34:32Z
lastTransitionTime: 2015-07-10T21:35:15Z
reason: Kubelet stopped posting node status.
status: Unknown
type: Ready
nodeInfo:
bootID: 4e316776-b40d-4f78-a4ea-ab0d73390897
containerRuntimeVersion: docker://Unknown
kernelVersion: 3.16.0-0.bpo.4-amd64
kubeProxyVersion: v0.21.1-185-gffc5a86098dc01
kubeletVersion: v0.21.1-185-gffc5a86098dc01
machineID: ""
osImage: Debian GNU/Linux 7 (wheezy)
systemUUID: ABE5F6B4-D44B-108B-C46A-24CCE16C8B6E
接下来
了解更多的调试工具: