---
title: 应用故障排查
content_type: concept
---
<!--
title: Troubleshoot Applications
content_type: concept
-->

<!-- overview -->

<!--
This guide is to help users debug applications that are deployed into Kubernetes and not behaving correctly.
This is *not* a guide for people who want to debug their cluster.  For that you should check out
[this guide](/docs/admin/cluster-troubleshooting).
-->

本指南帮助用户调试那些部署到 Kubernetes 上后没有正常运行的应用。
本指南 *并非* 指导用户如何调试集群。
如果想调试集群的话，请参阅[这里](/zh/docs/tasks/debug-application-cluster/debug-cluster/)。


<!-- body -->

<!--
## Diagnosing the problem

The first step in troubleshooting is triage.  What is the problem?  Is it your Pods, your Replication Controller or
your Service?

   * [Debugging Pods](#debugging-pods)
   * [Debugging Replication Controllers](#debugging-replication-controllers)
   * [Debugging Services](#debugging-services)
-->
## 诊断问题   {#diagnosing-the-problem}

故障排查的第一步是先给问题分类。问题是什么？是关于 Pods、Replication Controller 还是 Service？

* [调试 Pods](#debugging-pods)
* [调试副本控制器](#debugging-replication-controllers)
* [调试服务](#debugging-services)

<!--
### Debugging Pods

The first step in debugging a Pod is taking a look at it.  Check the current state of the Pod and recent events with the following command:
-->
### 调试 Pods   {#debugging-pods}

调试 Pod 的第一步是查看 Pod 信息。用如下命令查看 Pod 的当前状态和最近的事件：

```shell
kubectl describe pods ${POD_NAME}
```

<!--
Look at the state of the containers in the pod.  Are they all `Running`?  Have there been recent restarts?

Continue debugging depending on the state of the pods.
-->
查看一下 Pod 中的容器所处的状态。这些容器的状态都是 `Running` 吗？最近有没有重启过？

后面的调试都是要依靠 Pod 的状态的。

<!--
#### My pod stays pending

If a Pod is stuck in `Pending` it means that it can not be scheduled onto a node.  Generally this is because
there are insufficient resources of one type or another that prevent scheduling.  Look at the output of the
`kubectl describe ...` command above.  There should be messages from the scheduler about why it can not schedule
your pod.  Reasons include:
-->
#### Pod 停滞在 Pending 状态

如果一个 Pod 停滞在 `Pending` 状态，表示 Pod 没有被调度到节点上。通常这是因为
某种类型的资源不足导致无法调度。
查看上面的 `kubectl describe ...` 命令的输出，其中应该显示了为什么没被调度的原因。
常见原因如下：

<!--
* **You don't have enough resources**:  You may have exhausted the supply of CPU or Memory in your cluster, in this case
you need to delete Pods, adjust resource requests, or add new nodes to your cluster. See [Compute Resources document](/docs/user-guide/compute-resources/#my-pods-are-pending-with-event-message-failedscheduling) for more information.

* **You are using `hostPort`**:  When you bind a Pod to a `hostPort` there are a limited number of places that pod can be
scheduled.  In most cases, `hostPort` is unnecessary, try using a Service object to expose your Pod.  If you do require
`hostPort` then you can only schedule as many Pods as there are nodes in your Kubernetes cluster.
-->
* **资源不足**:
  你可能耗尽了集群上所有的 CPU 或内存。此时，你需要删除 Pod、调整资源请求或者为集群添加节点。
  更多信息请参阅[计算资源文档](/zh/docs/concepts/configuration/manage-resources-containers/)

* **使用了 `hostPort`**:
  如果绑定 Pod 到 `hostPort`，那么能够运行该 Pod 的节点就有限了。
  多数情况下，`hostPort` 是非必要的，而应该采用 Service 对象来暴露 Pod。
  如果确实需要使用 `hostPort`，那么集群中节点的个数就是所能创建的 Pod
  的数量上限。

<!--
#### My pod stays waiting

If a Pod is stuck in the `Waiting` state, then it has been scheduled to a worker node, but it can't run on that machine.
Again, the information from `kubectl describe ...` should be informative.  The most common cause of `Waiting` pods is a failure to pull the image.  There are three things to check:

* Make sure that you have the name of the image correct.
* Have you pushed the image to the repository?
* Run a manual `docker pull <image>` on your machine to see if the image can be pulled.
-->
#### Pod 停滞在 Waiting 状态

如果 Pod 停滞在 `Waiting` 状态，则表示 Pod 已经被调度到某工作节点，但是无法在该节点上运行。
同样，`kubectl describe ...` 命令的输出可能很有用。
`Waiting` 状态的最常见原因是拉取镜像失败。要检查的有三个方面：

* 确保镜像名字拼写正确
* 确保镜像已被推送到镜像仓库
* 用手动命令 `docker pull <镜像>` 试试看镜像是否可拉取

<!--
#### My pod is crashing or otherwise unhealthy

Once your pod has been scheduled, the methods described in [Debug Running Pods](
/docs/tasks/debug-application-cluster/debug-running-pod/) are available for debugging.
-->
#### Pod 处于 Crashing 或别的不健康状态

一旦 Pod 被调度，就可以采用
[调试运行中的 Pod](/zh/docs/concepts/configuration/manage-resources-containers/)
中的方法来进一步调试。

<!--
#### My pod is running but not doing what I told it to do

If your pod is not behaving as you expected, it may be that there was an error in your
pod description (e.g. `mypod.yaml` file on your local machine), and that the error
was silently ignored when you created the pod.  Often a section of the pod description
is nested incorrectly, or a key name is typed incorrectly, and so the key is ignored.
For example, if you misspelled `command` as `commnd` then the pod will be created but
will not use the command line you intended it to use.
-->
#### Pod 处于 Running 态但是没有正常工作

如果 Pod 行为不符合预期，很可能 Pod 描述（例如你本地机器上的 `mypod.yaml`）中有问题，
并且该错误在创建 Pod 时被忽略掉，没有报错。
通常，Pod 的定义中节区嵌套关系错误、字段名字拼错的情况都会引起对应内容被忽略掉。
例如，如果你误将 `command` 写成 `commnd`，Pod 虽然可以创建，但它不会执行
你期望它执行的命令行。

<!--
The first thing to do is to delete your pod and try creating it again with the `--validate` option.
For example, run `kubectl apply --validate -f mypod.yaml`.
If you misspelled `command` as `commnd` then will give an error like this:
-->
可以做的第一件事是删除你的 Pod，并尝试带有 `--validate` 选项重新创建。
例如，运行 `kubectl apply --validate -f mypod.yaml`。
如果 `command`  被误拼成 `commnd`，你将会看到下面的错误信息：

```
I0805 10:43:25.129850   46757 schema.go:126] unknown field: commnd
I0805 10:43:25.129973   46757 schema.go:129] this may be a false alarm, see https://github.com/kubernetes/kubernetes/issues/6842
pods/mypod
```

<!-- TODO: Now that #11914 is merged, this advice may need to be updated -->

<!--
The next thing to check is whether the pod on the apiserver
matches the pod you meant to create (e.g. in a yaml file on your local machine).
For example, run `kubectl get pods/mypod -o yaml > mypod-on-apiserver.yaml` and then
manually compare the original pod description, `mypod.yaml` with the one you got
back from apiserver, `mypod-on-apiserver.yaml`.  There will typically be some
lines on the "apiserver" version that are not on the original version.  This is
expected.  However, if there are lines on the original that are not on the apiserver
version, then this may indicate a problem with your pod spec.
-->
接下来就要检查的是 API 服务器上的 Pod 与你所期望创建的是否匹配
（例如，你原本使用本机上的一个 YAML 文件来创建 Pod）。
例如，运行 `kubectl get pods/mypod -o yaml > mypod-on-apiserver.yaml`，之后
手动比较 `mypod.yaml` 与从 API 服务器取回的 Pod 描述。
从 API 服务器处获得的 YAML 通常包含一些创建 Pod 所用的 YAML 中不存在的行，这是正常的。
不过，如果如果源文件中有些行在 API 服务器版本中不存在，则意味着
Pod 规约是有问题的。

<!--
### Debugging Replication Controllers

Replication controllers are fairly straightforward.  They can either create Pods or they can't.  If they can't
create pods, then please refer to the [instructions above](#debugging-pods) to debug your pods.

You can also use `kubectl describe rc ${CONTROLLER_NAME}` to introspect events related to the replication
controller.
-->
### 调试副本控制器  {#debugging-replication-controllers}

副本控制器相对比较简单直接。它们要么能创建 Pod，要么不能。
如果不能创建 Pod，请参阅[上述说明](#debugging-pods)调试 Pod。

你也可以使用 `kubectl describe rc ${CONTROLLER_NAME}` 命令来检视副本控制器相关的事件。

<!--
### Debugging Services

Services provide load balancing across a set of pods.  There are several common problems that can make Services
not work properly.  The following instructions should help debug Service problems.

First, verify that there are endpoints for the service. For every Service object, the apiserver makes an `endpoints` resource available.

You can view this resource with:
-->
### 调试服务   {#debugging-services}

服务支持在多个 Pod 间负载均衡。
有一些常见的问题可以造成服务无法正常工作。
以下说明将有助于调试服务的问题。

首先，验证服务是否有端点。对于每一个 Service 对象，API 服务器为其提供
对应的 `endpoints` 资源。

通过如下命令可以查看 endpoints 资源：

```shell
kubectl get endpoints ${SERVICE_NAME}
```

<!--
Make sure that the endpoints match up with the number of pods that you expect to be members of your service.
For example, if your Service is for an nginx container with 3 replicas, you would expect to see three different
IP addresses in the Service's endpoints.
-->
确保 Endpoints 与服务成员 Pod 个数一致。
例如，如果你的 Service 用来运行 3 个副本的 nginx 容器，你应该会在服务的 Endpoints
中看到 3 个不同的 IP 地址。

<!--
#### My service is missing endpoints

If you are missing endpoints, try listing pods using the labels that Service uses.  Imagine that you have
a Service where the labels are:
-->
#### 服务缺少 Endpoints

如果没有 Endpoints，请尝试使用 Service 所使用的标签列出 Pod。
假定你的服务包含如下标签选择算符：

```yaml
...
spec:
  - selector:
     name: nginx
     type: frontend
```

<!--
You can use:
```shell
kubectl get pods --selector=name=nginx,type=frontend
```

to list pods that match this selector.  Verify that the list matches the Pods that you expect to provide your Service.
-->

你可以使用如下命令列出与选择算符相匹配的 Pod，并验证这些 Pod 是否归属于创建的服务：

```shell
kubectl get pods --selector=name=nginx,type=frontend
```

<!--
If the list of pods matches expectations, but your endpoints are still empty, it's possible that you don't
have the right ports exposed.  If your service has a `containerPort` specified, but the Pods that are
selected don't have that port listed, then they won't be added to the endpoints list.

Verify that the pod's `containerPort` matches up with the Service's `targetPort`
-->
如果 Pod 列表符合预期，但是 Endpoints 仍然为空，那么可能暴露的端口不正确。
如果服务指定了 `containerPort`，但是所选中的 Pod 没有列出该端口，这些 Pod
不会被添加到 Endpoints 列表。

验证 Pod 的 `containerPort` 与服务的 `targetPort` 是否匹配。

<!--
#### Network traffic is not forwarded

If you can connect to the service, but the connection is immediately dropped, and there are endpoints
in the endpoints list, it's likely that the proxy can't contact your pods.

There are three things to
check:

   * Are your pods working correctly?  Look for restart count, and [debug pods](#debugging-pods).
   * Can you connect to your pods directly?  Get the IP address for the Pod, and try to connect directly to that IP.
   * Is your application serving on the port that you configured?  Kubernetes doesn't do port remapping, so if your application serves on 8080, the `containerPort` field needs to be 8080.
-->
#### 网络流量未被转发

如果你可以连接到服务上，但是连接立即被断开了，并且在 Endpoints 列表中有末端表项，
可能是代理无法连接到 Pod。

要检查的有以下三项：

* Pod 工作是否正常？ 看一下重启计数，并参阅[调试 Pod](#debugging-pods)；
* 是否可以直接连接到 Pod？获取 Pod 的 IP 地址，然后尝试直接连接到该 IP；
* 应用是否在配置的端口上进行服务？Kubernetes 不进行端口重映射，所以如果应用在
  8080 端口上服务，那么 `containerPort` 字段就要设定为 8080。

## {{% heading "whatsnext" %}}

<!--
If none of the above solves your problem, follow the instructions in [Debugging Service document](/docs/user-guide/debugging-services) to make sure that your `Service` is running, has `Endpoints`, and your `Pods` are actually serving; you have DNS working, iptables rules installed, and kube-proxy does not seem to be misbehaving.

You may also visit [troubleshooting document](/docs/troubleshooting/) for more information.
-->
如果上述方法都不能解决你的问题，请按照
[调试服务文档](/zh/docs/tasks/debug-application-cluster/debug-service/)中的介绍，
确保你的 `Service` 处于 Running 态，有 `Endpoints` 被创建，`Pod` 真的在提供服务；
DNS 服务已配置并正常工作，iptables 规则也以安装并且 `kube-proxy` 也没有异常行为。

你也可以访问[故障排查文档](/zh/docs/tasks/debug-application-cluster/troubleshooting/ )来获取更多信息。
