coredns kubernetes插件，对指定分区namespace做域名解析

川长思鸟来 2023-07-16 03:53 10阅读 0赞

### 文章目录 ###

*   *  使用namespace\_label表达式
     *  使用label表达式
     *  参考

kubernetes [ZONES...] { 
        endpoint URL
        tls CERT KEY CACERT
        kubeconfig KUBECONFIG CONTEXT
        namespaces NAMESPACE...
        labels EXPRESSION
        pods POD-MODE
        endpoint_pod_names
        ttl TTL
        noendpoints
        transfer to ADDRESS...
        fallthrough [ZONES...]
        ignore empty_service
    }

在`zjjpt-es`的`namespace`分区下有如下的服务：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70]  
在`zjjpt-redis`的`namespace`分区下有如下的服务：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 1]  
在`mysql`的`namespace`分区下有如下的服务：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 2]

## 使用namespace\_label表达式 ##

> namespaces NAMESPACE \[NAMESPACE…\] only exposes the k8s namespaces listed. If this option is omitted all namespaces are exposed

> namespace\_labels EXPRESSION only expose the records for Kubernetes namespaces that match this label selector. The label selector syntax is described in the Kubernetes User Guide - Labels. An example that only exposes namespaces labeled as “istio-injection=enabled”, would use: labels istio-injection=enabled.

> labels EXPRESSION only exposes the records for Kubernetes objects that match this label selector. The label selector syntax is described in the Kubernetes User Guide - Labels. An example that only exposes objects labeled as “application=nginx” in the “staging” or “qa” environments, would use: labels environment in (staging, qa),application=nginx.

label表达式语法：[k8s官方文档：label语法][k8s_label]

给`zjjpt-redis`和`zjjpt-es`的namespace上打label：

kubectl label ns zjjpt-redis coredns=middleware
    kubectl label ns zjjpt-es coredns=middleware

![在这里插入图片描述][20200317223303708.png]  
在`coredns`的`Corefile`配置文件`configmaps`中加入`namespace_label`配置：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 3]  
重启`coredns` pod后测试，nslookup指定域名解析IP为`coredns`的podIP，可以看到`mysql`分区下的域名不能解析。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 4]

使用`coredns!=middleware`标签报错：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 5]  
使用`coredns notin (middleware)`标签：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 6]

## 使用label表达式 ##

如果使用label的方式，配置如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 7]  
此时只需要给指定的`svc`配置上改label即可：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 8]  
选择包含标签`middleware`的svc：会匹配到`middleware=redis`、`middleware=mysql`等key是`middleware`的对象。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 9]

## 参考 ##

[coredns kubernetes plugin describe][]

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[k8s_label]: https://kubernetes.io/docs/user-guide/labels/
[20200317223303708.png]: /images/20230528/f8d14acf575441a79a411a9120311df7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 3]: /images/20230528/43a15674b45f4d2596e23868c4fa5e2e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 4]: /images/20230528/84e7f49e6e6b4fe0bb26f51fa613e9a4.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xsODM3NDQ4Nzky_size_16_color_FFFFFF_t_70 8]: /images/20230528/ed30f6afae8d4e13b8ef6b373eac67b4.png
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[coredns kubernetes plugin describe]: https://github.com/coredns/coredns/tree/master/plugin/kubernetes