# 介绍一个小工具：Kubedog

[Kubedog](https://github.com/flant/kubedog) 是一个开源的 Golang 项目，使用 watch 方式对 Kubernetes 资源进行跟踪，能够方便的用于日常运维和 CI/CD 过程之中，项目中除了一个 CLI 小工具之外，还提供了一组 SDK，用户可以将其中的 Watch 功能集成到自己的系统之中。安装过程非常简单，在项目网页直接下载即可。

Kubedog CLI 有两个功能：`rollout track` 和 `follow`。

## rollout track

在 Kubernetes 上运行应用时，通常的做法是使用 `kubectl apply` 提交 YAML 之后，使用 `kubectl get -w` 或者 `watch kubectl get` 之类的命令等待 Pod 启动。如果启动成功，则进行测试等后续动作；如果启动失败，就需要用 `kubectl logs`、`kubectl describe` 等命令来查看失败原因。kubedog 能在一定程度上简化这一过程。

例如使用 `kubectl run` 命令创建一个新的 Deployment 资源，并使用 `kubedog` 跟进创建进程：

~~~shell
$ kubectl run nginx --image=nginx22
...
deployment.apps/nginx created

$ kubedog rollout track deployment nginx
# deploy/nginx added
# deploy/nginx rs/nginx-6cc78cbf64 added
# deploy/nginx po/nginx-6cc78cbf64-8pnjz added
# deploy/nginx po/nginx-6cc78cbf64-8pnjz nginx error: ImagePullBackOff: Back-off pulling image "nginx22"
deploy/nginx po/nginx-6cc78cbf64-8pnjz nginx failed: ImagePullBackOff: Back-off pulling image "nginx22"

$ echo $?
130
~~~

很方便的看出，运行失败的状态及其原因，并且可以使用返回码来进行判断，方便在 Pipeline 中的运行。接下来可以使用 `kubectl edit` 命令编辑 Deployment，修改正确的镜像名称。然后再次进行验证：

~~~shell
$ kubectl edit deployment nginx
deployment.extensions/nginx edited
$ kubedog rollout track deployment nginx
# deploy/nginx added
# deploy/nginx rs/nginx-dbddb74b8 added
# deploy/nginx po/nginx-dbddb74b8-x4nkm added
# deploy/nginx event: po/nginx-dbddb74b8-x4nkm Pulled: Successfully pulled image "nginx"
# deploy/nginx event: po/nginx-dbddb74b8-x4nkm Created: Created container
# deploy/nginx event: po/nginx-dbddb74b8-x4nkm Started: Started container
# deploy/nginx event: ScalingReplicaSet: Scaled down replica set nginx-6cc78cbf64 to 0
# deploy/nginx become READY
$ echo $?
0
~~~

修改完成，重新运行 kubedog，会看到成功运行的情况，并且返回值也变成了 0。

## follow

follow 命令的功能和 [kubetail](https://github.com/johanhaleby/kubetail) 的功能有少量重叠，可以用 Deployment/Job/Daemonset 等为单位，查看其中所有 Pod 的日志，例如前面用的 Nginx，如果有访问的话，就会看到如下结果：

~~~shell
$ kubedog follow deployment nginx
# deploy/nginx appears to be ready
# deploy/nginx rs/nginx-6cc78cbf64 added
# deploy/nginx new rs/nginx-dbddb74b8 added
# deploy/nginx rs/nginx-dbddb74b8(new) po/nginx-dbddb74b8-x4nkm added
# deploy/nginx rs/nginx-6cc54845d9 added
# deploy/nginx event: ScalingReplicaSet: Scaled up replica set nginx-6cc54845d9 to 1
# deploy/nginx rs/nginx-6cc54845d9(new) po/nginx-6cc54845d9-nhlvs added
# deploy/nginx event: po/nginx-6cc54845d9-nhlvs Pulling: pulling image "nginx:alpine"
# deploy/nginx event: po/nginx-6cc54845d9-nhlvs Pulled: Successfully pulled image "nginx:alpine"
# deploy/nginx event: po/nginx-6cc54845d9-nhlvs Created: Created container
# deploy/nginx event: po/nginx-6cc54845d9-nhlvs Started: Started container
# deploy/nginx event: ScalingReplicaSet: Scaled down replica set nginx-dbddb74b8 to 0
# deploy/nginx become READY
# deploy/nginx event: po/nginx-dbddb74b8-x4nkm Killing: Killing container with id docker://nginx:Need to kill Pod
>> deploy/nginx rs/nginx-dbddb74b8 po/nginx-dbddb74b8-x4nkm nginx

>> deploy/nginx rs/nginx-6cc54845d9(new) po/nginx-6cc54845d9-nhlvs nginx
127.0.0.1 - - [02/Jun/2019:11:35:08 +0000] "GET / HTTP/1.1" 200 612 "-" "Wget" "-"
127.0.0.1 - - [02/Jun/2019:11:35:11 +0000] "GET / HTTP/1.1" 200 612 "-" "Wget" "-"
~~~

## 项目地址

`https://github.com/flant/kubedog`