# Using the Prometheus data source
## Prometheus settings
| Name | Description |
| --- | --- |
| Name | The data source name. This is how you see the data source in panels and queries. |
| Default | Default data source means that it will be pre-selected for new panels. |
| Url | The URL of your Prometheus server; for example, https://prometheus.example.org:9090. |
| Access | Server (default) = URL must be accessible from the Grafana backend/server. |
| Basic Auth | Enable basic authentication to the Prometheus data source. |
| User | User name for basic authentication. |
| Password | Password for basic authentication. |
| Scrape interval | Set this to the typical scrape and evaluation interval configured in Prometheus. Defaults to 15s. |
| Disable metrics lookup | Checking this option will disable the metrics chooser and metric/label support in the query field’s autocomplete. This helps if you have performance issues with bigger Prometheus instances. |
| Custom Query Parameters | Add custom parameters to the Prometheus query URL. For example timeout, partial\$1response, dedup, or max\$1source\$1resolution. Multiple parameters should be concatenated together with an "&". |
## Prometheus query editor
The following sections provide information and options for Prometheus query editor in the dashboard and in Explore.
### Query editor in dashboards
Open a graph in edit mode by choosing the title and then choosing **Edit** (or by pressing **e** key while pausing on the panel).
| Name | Description |
| --- | --- |
| Query expression | For more information about Prometheus query expressions, see the [Prometheus documentation](https://prometheus.io/docs/querying/basics/). |
| Legend format | Controls the name of the time series, using name or pattern. For example \$1\$1hostname\$1\$1 is replaced with the label value for the label hostname. |
| Min step | An additional lower limit for the [`step` parameter of Prometheus range queries](https://prometheus.io/docs/prometheus/latest/querying/api/#range-queries) and for the \$1\$1\$1interval and \$1\$1\$1rate\$1interval variables. The limit is absolute and not modified by the Resolution setting. |
| Resolution | 1/1 sets both the \$1\$1\$1interval variable and the [`step` parameter of Prometheus range queries](https://prometheus.io/docs/prometheus/latest/querying/api/#range-queries) such that each pixel corresponds to one data point. For better performance, use lower resolutions. 1/2 only retrieves a data point for every other pixel, and 1/10 retrieves one data point per 10 pixels. Note that both Min time interval and Min step limit the final value of \$1\$1\$1interval and step. |
| Metric lookup | Search for metric names in this input field. |
| Format as | Switch between Table, Time series, or Heatmap. Table works only in the table panel. Heatmap is suitable for displaying metrics of the histogram type on a heatmap panel. It converts cumulative histograms to regular ones and sorts series by the bucket bound. |
| Instant | Perform an "instant" query, to return only the latest value that Prometheus has scraped for the requested time series. Instant queries return results much faster than normal range queries. Use them to look up label sets. |
| Min time interval | This value multiplied by the denominator from the Resolution setting sets a lower limit to both the \$1\$1\$1interval variable and the [`step` parameter of Prometheus range queries](https://prometheus.io/docs/prometheus/latest/querying/api/#range-queries). Defaults to Scrape interval as set in the data source options. |
**Note**
Amazon Managed Grafana modifies the request dates for queries to align them with the dynamically calculated step. This ensures consistent display of metrics data, but it can result in a small gap of data at the right edge of a graph.
#### Instant queries in dashboards
The Prometheus data source allows you to run instant queries, which query only the latest value. You can visualize the results in a table panel to see all available labels of a time series.
Instant query results are made up of only one data point per series. They can be shown in the graph panel with the help of series overrides. To show them in the graph as a latest value point, add a series override and select `Points > true`. To show a horizontal line across the whole graph, add a series override and select `Transform > constant` For more information about series overrides, see [Series overrides](graph-panel.md#graph-panel-series-overrides).
### Query editor in Explore
| Name | Description |
| --- | --- |
| Query expression | For more information about Prometheus query expression, see the [Prometheus documentation](https://prometheus.io/docs/querying/basics/). |
| Step | [`Step` parameter of Prometheus range queries](https://prometheus.io/docs/prometheus/latest/querying/api/#range-queries). Time units can be used here, for example: 5s, 1m, 3h, 1d, 1y. Default unit if no unit specified is s (seconds). |
| Query type | Range, Instant, or Both. When running Range query, the result of the query is displayed in graph and table. Instant query returns only the latest value that Prometheus has scraped for the requested time series and it is displayed in the table. When Both is selected, both instant query and range query is run. Result of range query is displayed in graph and the result of instant query is displayed in the table. |
## Metrics browser
The metrics browser allows you to quickly find metrics and select relevant labels to build basic queries. When you open the browser you will see all available metrics and labels. If supported by your Prometheus instance, each metric will show its HELP and TYPE as a tooltip.
When you select a metric, the browser narrows down the available labels to show only the ones applicable to the metric. You can then select one or more labels for which the available label values are shown in lists in the bottom section. Select one or more values for each label to tighten your query scope.
**Note**
If you do not remember a metric name to start with, you can also select a few labels first, to narrow down the list and then find relevant label values.
All lists in the metrics browser have a search field above them to quickly filter for metrics or labels that match a certain string. The values section only has one search field. Its filtering applies to all labels to help you find values across labels once they have been selected, for example, among your labels app, job, job\$1name only one might with the value you are looking for.
Once you are satisfied with your query, click “Use query” to run the query. The **Use as rate query** button adds a rate(...)[\$1\$1\$1interval] around your query to help write queries for counter metrics. The “Validate selector” button will check with Prometheus how many time series are available for that selector.
### Limitations
The metrics browser has a hard limit of 10,000 labels (keys) and 50,000 label values (including metric names). If your Prometheus instance returns more results, the browser will continue functioning. However, the result sets will be cut off above those maximum limits.
## Templating
Instead of hardcoding things such as server, application and sensor name in your metric queries, you can use variables in their place. Variables are shown as dropdown select boxes at the top of the dashboard. You can use these dropdown boxes to change the data being displayed in your dashboard.
For more information about templating and template variables, see [Templates and variables](templates-and-variables.md).
### Query variable
Variable of the type *Query* allows you to query Prometheus for a list of metrics, labels, or label values. The Prometheus data source plugin provides the following functions you can use in the **Query** input field.
| Name | Description |
| --- | --- |
| label\$1names() | Returns a list of label names. |
| label\$1values(label) | Returns a list of label values for the label in every metric. |
| label\$1values(metric, label) | Returns a list of label values for the label in the specified metric. |
| metrics(metric) | Returns a list of metrics matching the specified metric regex. |
| query\$1result(query) | Returns a list of Prometheus query result for the query. |
For information about what *metric names*, *label names* and *label values* are, see the [Prometheus documentation](https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels).
#### Using interval and range variables
**Note**
Support for `$__range`, `$__range_s`, and `$__range_ms` are available only from Grafana v5.3.
You can use some global variables in query variables: `$__interval`, `$__interval_ms`, `$__range`, `$__range_s`, and `$__range_ms`. For more information, see [Global variables](variables-types.md#global-variables). These can be convenient to use with the `query_result` function when you must filter variable queries because the `label_values` function doesn’t support queries.
To get the correct instances when changing the time range on the dashboard, make sure to set the variable’s `refresh` trigger to be `On Time Range Change`.
The following code example shows how to populate a variable with the busiest five request instances based on average QPS over the time range shown in the dashboard.
```
Query: query_result(topk(5, sum(rate(http_requests_total[$__range])) by (instance)))
Regex: /"([^"]+)"/
```
The following code example shows how to populate a variable with the instances having a certain state over the time range shown in the dashboard, using `$__range_s`.
```
Query: query_result(max_over_time([${__range_s}s]) != )
Regex:
```
### Using `$__rate_interval` variable
The `$__rate_interval` variable is meant to be used in the rate function. It is defined as max( `$__interval` \$1 *Scrape interval*, 4 \$1 *Scrape interval*). *Scrape interval* is the Min step setting (AKA query\$1interval, a setting per PromQL query), if any is set, and otherwise the *Scrape interval* as set in the Prometheus data source (but ignoring any Min interval setting in the panel, because the latter is modified by the resolution setting).
### Using variables in queries
There are two syntaxes:
+ `$` Example: rate(http\$1requests\$1total\$1job=\$1"\$1job"\$1[5m])
+ `[[varname]]` Example: rate(http\$1requests\$1total\$1job=\$1"[[job]]"\$1[5m])
Why two ways? The first syntax is easier to read and write but does not allow you to use a variable in the middle of a word. When the *Multi-value* or *Include all value* options are enabled, Grafana converts the labels from plaintext to a regex compatible string. Which means you have to use `=~` instead of `=`.
## Annotations
You can use annotations to overlay rich event information on top of graphs. You add annotation queries using the Dashboard menu or Annotations view. For more information, see [Annotations](dashboard-annotations.md).
Prometheus supports two ways to query annotations.
+ A regular metric query
+ A Prometheus query for pending and firing alerts. For more information, see [Inspecting alerts during runtime](https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/#inspecting-alerts-during-runtime)).
The step option is useful to limit the number of events returned from your query.