Metric-based SLOs

Overview

Metric-based SLOs are useful for a count-based stream of data where you are differentiating good and bad events. A metric query uses the sum of the good events divided by the sum of total events over time to calculate a Service Level Indicator (or SLI).

example metric-based SLO

Setup

On the SLO status page, select New SLO +. Then select Metric.

Define queries

  1. There are two queries to define. The numerator query defines the sum of the good events, while the denominator query defines the sum of the total events. Your queries must use COUNT, RATE, or percentile-enabled DISTRIBUTION metrics to ensure the SLO calculation behaves correctly.
  2. Use the FROM field to include or exclude specific groups using tags.
  3. For percentile-enabled DISTRIBUTION metrics, you must use the count values... aggregator to specify a numerical threshold for the metric to count. This feature is called Threshold Queries and allows you to count the number of raw values that match a numerical threshold to produce counts for your numerator and denominator. For more information, see Threshold Queries.
  4. Optionally, for percentile-enabled DISTRIBUTION metrics, use the dropdown immediately to the right of the count values.. aggregator to break your SLI out by specific groups.
  5. Optionally, for COUNT or RATE metrics, use the sum by aggregator to break your SLI out by specific groups.

Example: If you are tracking HTTP return codes, and your metric includes a tag like code:2xx || code:3xx || code:4xx. The sum of good events would be sum:httpservice.hits{code:2xx} + sum:httpservice.hits{code:4xx}. And the total events would be sum:httpservice.hits{!code:3xx}.

Why is HTTP 3xx excluded? - These are typically redirects and should not count for or against the SLI, but other non-3xx based error codes should. In the total case, you want all types minus HTTP 3xx, in the numerator, you only want OK type status codes.

Multi-group for metric-based SLIs

Metric-based SLIs allow you to focus on the most important attributes of your SLIs. You can add groups to your metric-based SLIs in the editor by using tags like datacenter, partition, availability-zone, resource, or any other relevant group:

grouped metric-based SLO editor

By grouping these SLIs you can visualize each individual group’s status, good request counts, and remaining error budget on the detail panel:

metric-based SLO group results

By default, the bar graph shows the overall counts of good and bad requests for the entire SLO. You can scope the bar graph down to an individual group’s good and bad requests counts by clicking on its corresponding row in the table. In addition, you can also choose to show or hide good request counts or bad request counts by selecting the appropriate option in the legend directly below the bar graph.

Note: If you are using monitor-based SLIs, you can also view monitor groups.

Set your SLO targets

An SLO target is comprised of the target percentage and the time window. When you set a target for a metric-based SLO the target percentage specifies what portion of the total events specified in the denominator of the SLO should be good events, while the time window specifies the rolling time period over which the target should be tracked.

Example: 99% of requests should be error-free over the past 7 days.

While the SLO remains above the target percentage, the SLO’s status will be displayed in green font. When the target percentage is violated, the SLO’s status will be displayed in red font. You can also optionally include a warning percentage that is greater than the target percentage to indicate when you are approaching an SLO breach. When the warning percentage is violated (but the target percentage is not violated), the SLO status will be displayed in yellow font.

Note: Up to three decimal places are allowed for metric-based SLO targets. The precision shown in the details UI of the SLO will be up to num_target_decimal_places + 1 = 4 decimal places. The exact precision shown will be dependent on the magnitude of the values in your denominator query. The higher the magnitude of the denominator, the higher the precision that can be shown up to the four decimal place limit.

Identify this indicator

Here you can add contextual information about the purpose of the SLO, including any related information or resources in the description and tags you would like to associate with the SLO.

Further Reading

Additional helpful documentation, links, and articles: