This processor samples your logging traffic for a representative subset at the rate that you define, dropping the remaining logs. As an example, you can use this processor to sample 20% of logs from a noisy non-critical service.

The sampling only applies to logs that match your filter query and does not impact other logs. If a log is dropped at this processor, none of the processors below receives that log.

To set up the sample processor:

1. Define a filter query. Only logs that match the specified filter query are sampled at the specified retention rate below. The sampled logs and the logs that do not match the filter query are sent to the next step in the pipeline.
2. Set the retain field with your desired sampling rate expressed as a percentage. For example, entering 2 means 2% of logs are retained out of all the logs that match the filter query.

Filter query syntax

Each processor has a corresponding filter query in their fields. Processors only process logs that match their filter query. And for all processors except the filter processor, logs that do not match the query are sent to the next step of the pipeline. For the filter processor, logs that do not match the query are dropped.

For any attribute, tag, or key:value pair that is not a reserved attribute, your query must start with @. Conversely, to filter reserved attributes, you do not need to append @ in front of your filter query.

For example, to filter out and drop status:info logs, your filter can be set as NOT (status:info). To filter out and drop system-status:info, your filter must be set as NOT (@system-status:info).

Filter query examples:

• NOT (status:debug): This filters for only logs that do not have the status DEBUG.
• status:ok service:flask-web-app: This filters for all logs with the status OK from your flask-web-app service.
  • This query can also be written as: status:ok AND service:flask-web-app.
• host:COMP-A9JNGYK OR host:COMP-J58KAS: This filter query only matches logs from the labeled hosts.
• @user.status:inactive: This filters for logs with the status inactive nested under the user attribute.

Learn more about writing filter queries in Datadog’s Log Search Syntax.