Calculating Aggregate Statistics with Splunk Eval

As you delve into the world of Splunk, one of the most powerful and versatile commands is eval. This command allows you to calculate aggregate statistics over your results set, such as average, count, and sum. In this article, we will explore how to use eval to calculate the sum of entries in a time range.

Understanding Eval

The eval command evaluates mathematical, string, and boolean expressions. It creates new fields in your events by using existing fields and an expression. You can chain multiple eval expressions in one search using a comma to separate subsequent expressions. The search processes multiple eval expressions left-to-right and lets you reference previously evaluated fields in subsequent expressions.

Example: Calculating Sum of Entries

Let's say we want to calculate the sum of active power for all PDUs in our server room. We can use the following query:

```

splunk eval sum(metric_name='st4InputCordActivePower' OR metric_name='systemTotalPower') host_name='pdu01r1*' OR 'pdu02r1*'

```

This query uses the `sum` function to calculate the total active power for all PDUs. The `host_name` field is used to filter the results by a specific range of PDU host names.

Calculating Success Rate

In addition to calculating sums, eval can also be used to calculate success rates. For example, let's say we have a variable called 'state' that has three values: success, aborted, and chargeback. We want to calculate the success rate, which is the number of successes divided by the total number of states combined.

We can use the following query:

```

eval (success_count = sum(state='success'), total_count = sum(state IN ('success', 'aborted', 'chargeback')), success_rate = success_count / total_count)

```

This query uses the `sum` function to calculate the count of successes and the total number of states. It then calculates the success rate by dividing the success count by the total count.

In this article, we have seen how to use eval to calculate aggregate statistics in Splunk. Whether you need to calculate sums, averages, or counts, eval provides a powerful way to manipulate your data and extract insights from it. With its flexible syntax and ability to chain multiple expressions, eval is an essential command for any Splunk user.

Splunk eval sum