Using 'or' logical operators in Prometheus or Grafana is a common requirement, especially when querying data that satisfies one of multiple conditions. The following provides a detailed explanation of how to implement this in both tools.
Prometheus
In Prometheus, you can use the logical OR operator or to combine the results of two queries, provided that both queries have the same vector structure. Here is a simple example:
Suppose you have two monitoring metrics: http_requests_total (HTTP request total) and http_errors_total (HTTP error total). You want to query cases where the total requests exceed 1000 or the error requests exceed 100. You can write the query as:
(http_requests_total > 1000) or (http_errors_total > 100)
This query returns all label combinations where http_requests_total is greater than 1000 or http_errors_total is greater than 100.
Grafana
In Grafana, using 'or' logic is typically implemented by adding multiple queries in the Query Editor and displaying them in the panel view. Grafana does not handle logical operations directly; instead, it relies on the query language of the data source to process logic.
If your data source is Prometheus, you can directly use the Prometheus Query Language (PromQL) in Grafana's Query Editor, just as in Prometheus. Here is a step-by-step example:
- Open Grafana and select the panel you want to edit.
- In the "Query" section, choose "Prometheus" as the data source.
- In the first query box, enter the first condition, for example:
http_requests_total > 1000 - Click the "Add Query" button to add another query.
- In the new query box, enter the second condition, for example:
http_errors_total > 100 - Grafana will automatically display the results of both conditions.
Additionally, you can use variables and other Grafana features to dynamically construct these queries for more complex logic.
By doing this, even though Grafana does not directly handle 'or' operations, you can effectively merge and display data that meets either condition visually.