问题

I am trying to set up a Grafana dashboard, pulling information from Prometheus, that is scraping data from a Kubernetes cluster. I'm running into issues that seem related to dashboard level variables.

Dashboard variable query syntax

There is very little information regarding how to build queries to populate the available values for a given dashboard variable. I've based what I've done so far on the few examples I've found in other dashboards. While this is helpful, it gives a very limited view into how this works. As an example, there is a function (label_values) that appears to get the available values for a given label in the scraped data. I cannot find documentation for this function anywhere. I also do not know what other functions may exist. Where is there documentation that explains how to use all of this? I think this is probably the main issue.

Dashboard variable filtering

I've been reading the Grafana documentation and am under the impression that dashboard level variables can be filtered so that, for example, if I select a node, the other variable values can be filtered to only show the values available on that selected node. I can't get this to work - if I select a node, the other variable available values are not being filtered. I assume I'm not writing the variable queries correctly, but I can't tell for sure. The Grafana documentation is a little vague or too high-level in some areas.

Example dashboard variable definitions:

type: query name: nemspace query: label_values(namespace) ```

**Note**: I also tried setting the query for `namespace` to `label_values(node="$node", namespace)` but this did not work either. I have not been able to find good information on the correct query syntax, functions, etc. Again, I refer back to the first bullet item.

## Dashboard variable "include all" option

I'm under the impression that if you configure a variable to allow the "all" option, that this essentially turns off filtering for this variable. However, if I do this, I get no data at all in the view. I've tried setting the associated "custom all value" to "All" and wildcard ("*"), but neither makes any difference. What am I doing wrong?

## Conclusion

I think of all of these issues stem from the fact that I do not have information on how to properly configure Grafana dashboard variables. It would be so helpful if there was a detailed comprehensive guide - alas, I have not been able to find one.

<details>
<summary>英文:</summary>

I am trying to set up a Grafana dashboard, pulling information from Prometheus, that is scraping data from a Kubernetes cluster. I&#39;m running into issues that seem related to dashboard level variables.

## Dashboard variable query syntax

There is very little information regarding how to build queries to populate the available values for a given dashboard variable. I&#39;ve based what I&#39;ve done so far on the few examples I&#39;ve found in other dashboards. While this is helpful, it gives a very limited view into how this works. As an example, there is a function (`label_values`) that appears to get the available values for a given label in the scraped data. I cannot find documentation for this function anywhere. I also do not know what other functions may exist. Where is there documentation that explains how to use all of this? I think this is probably the main issue.

## Dashboard variable filtering

I&#39;ve been reading the Grafana documentation and am under the impression that dashboard level variables can be filtered so that, for example, if I select a node, the other variable values can be filtered to only show the values available on that selected node. I can&#39;t get this to work - if I select a node, the other variable available values are not being filtered. I assume I&#39;m not writing the variable queries correctly, but I can&#39;t tell for sure. The Grafana documentation is a little vague or too high-level in some areas.

Example dashboard variable definitions:

type: query
name: node
query: label_values(node)

type: query
name: nemspace
query: label_values(namespace)

**Note**: I also tried setting the query for `namespace` to `label_values(node="$node", namespace)` but this did not work either. I have not been able to find good information on the correct query syntax, functions, etc. Again, I refer back to the first bullet item.

## Dashboard variable "include all" option

I'm under the impression that if you configure a variable to allow the "all" option, that this essentially turns off filtering for this variable. However, if I do this, I get no data at all in the view. I've tried setting the associated "custom all value" to "All" and wildcard ("*"), but neither makes any difference. What am I doing wrong?

## Conclusion

I think of all of these issues stem from the fact that I do not have information on how to properly configure Grafana dashboard variables. It would be so helpful if there was a detailed comprehensive guide - alas, I have not been able to find one.


</details>


# 答案1
**得分**: 1

&gt; 这里有解释如何使用所有这些的文档吗？

我不知道是否有关于 `label_values` 的文档，但它非常简单：您提供指标选择器和要提取的标签，它会提取该标签的不同值。

例如
```shell
label_values(up{instance=~".*prod.*"}, job)

执行查询 up{instance=~".*prod.*"} 并提取 job 指标的不同值。

关于没有指标选择器的 label_values 的情况，我不确定，但我认为它在语义上等同于类似于 label_values({__name__=~".+"}, job) 这样的东西。

请注意，label_values 函数不支持查询，如果您需要从一些更复杂的查询中提取标签，请使用带有适当正则表达式的 query_result，参考此示例。

> 我假设我没有正确编写变量查询，但我无法确定。

根据您的描述，我假设您需要为第二个变量编写如下的查询：

label_values({node=~"$node"}, namespace)

它选择所有具有标签 node 的值等于当前选择的变量 node 名称的值的指标。但如果可能的话，我建议考虑使用某个特定的指标以降低此查询的性能影响。例如，类似于 label_values(up{node=~"$node"}, namespace) 的查询应该更快。对于第一个变量的查询也适用：考虑类似于 label_values(up, node) 的查询。

> 我的印象是，如果您配置一个变量以允许 "all" 选项，这基本上会关闭此变量的筛选。

这不完全正确。 "包括全部" 基本上会用所有可能的变量值替换变量。替换发生的方式取决于数据源。

例如，如果您的值节点有三个可能的值：node1.com，node2.com，node3.com，那么在将此值替换为 Prometheus 查询值时将使用 (node1.com|node2.com|node3.com)。

注意：如果您计划使用带有选项 "多个值" 或 "包括全部" 的变量，预计您将使用正则表达式选择器，例如 up{node=~"$node"}，以适应通过变量提供的多个值的查询。

> 如果有详细全面的指南将非常有帮助

您可以在 Grafana 的 GitHub 问题 中提出这个问题。那里的人相当响应，如果您向他们传达了需要更详细描述如何使用 label_values，那么它有很大机会被添加到 Grafana 的官方文档中。

label_values(up{instance=~".*prod.*"}, job)

label_values({node=~"$node"}, namespace)