Using Prometheus in Grafana

Grafana includes built-in support for Prometheus.

Adding the data source to Grafana

  1. Open the side menu by clicking the Grafana icon in the top header.
  2. In the side menu under the Dashboards link you should find a link named Data Sources.
  3. Click the + Add data source button in the top header.
  4. Select Prometheus from the Type dropdown.

NOTE: If you’re not seeing the Data Sources link in your side menu it means that your current user does not have the Admin role for the current organization.

Data source options

NameDescription
NameThe data source name. This is how you refer to the data source in panels & queries.
DefaultDefault data source means that it will be pre-selected for new panels.
UrlThe http protocol, ip and port of you Prometheus server (default port is usually 9090)
AccessProxy = access via Grafana backend, Direct = access directly from browser.
Basic AuthEnable basic authentication to the Prometheus data source.
UserName of your Prometheus user
PasswordDatabase user’s password

Query editor

Open a graph in edit mode by click the title > Edit (or by pressing e key while hovering over panel).

NameDescription
Query expressionPrometheus query expression, check out the Prometheus documentation.
Legend formatControls the name of the time series, using name or pattern. For example {{hostname}} will be replaced with label value for the label hostname.
Min stepSet a lower limit for the Prometheus step option. Step controls how big the jumps are when the Prometheus query engine performs range queries. Sadly there is no official prometheus documentation to link to for this very important option.
ResolutionControls the step option. Small steps create high-resolution graphs but can be slow over larger time ranges, lowering the resolution can speed things up. 1/2 will try to set step option to generate 1 data point for every other pixel. A value of 1/10 will try to set step option so there is a data point every 10 pixels.Metric lookup
Format as(New in v4.3) Switch between Table & Time series. Table format will only work in the Table panel.

Templating

Instead of hard-coding things like server, application and sensor name in you metric queries you can use variables in their place. Variables are shown as dropdown select boxes at the top of the dashboard. These dropdowns makes it easy to change the data being displayed in your dashboard.

Checkout the Templating documentation for an introduction to the templating feature and the different types of template variables.

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.

NameDescription
label_values(label)Returns a list of label values for the label in every metric.
label_values(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_result(query)Returns a list of Prometheus query result for the query.

For details of metric names, label names and label values are please refer to the Prometheus documentation.

Using variables in queries

There are two syntaxes:

  • $<varname> Example: rate(http_requests_total{job=~“$job”}[5m])
  • [[varname]] Example: rate(http_requests_total{job=“my[[job]]“}[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 plain text to a regex compatible string. Which means you have to use =~ instead of =.

Annotations

Annotations allows you to overlay rich event information on top of graphs. You add annotation queries via the Dashboard menu / Annotations view.

Prometheus supports two ways to query annotations.

The step option is useful to limit the number of events returned from your query.