[[resiliency]] == Data Resiliency As data flows through the event processing pipeline, Logstash may encounter situations that prevent it from delivering events to the configured output. For example, the data might contain unexpected data types, or Logstash might terminate abnormally. To guard against data loss and ensure that events flow through the pipeline without interruption, Logstash provides the following data resiliency features. * <> protect against data loss by storing events in an internal queue on disk. * <> provide on-disk storage for events that Logstash is unable to process. You can easily reprocess events in the dead letter queue by using the `dead_letter_queue` input plugin. //TODO: Make dead_letter_queue an active link after the plugin docs are published. These resiliency features are disabled by default. To turn on these features, you must explicitly enable them in the Logstash <>.