In May 2015, Aaron Mildenstein introduced the heartbeat input plugin for Logstash 1.5, designed to monitor the flow of events through Logstash's single pipeline by sending periodic heartbeat messages. The plugin helps identify when the pipeline's flow slows or stops, which can occur if any output becomes backed up, halting the entire pipeline. Users can configure the heartbeat messages to include a string value, an epoch timestamp, or a sequence number, and these messages can be used to monitor system performance, track event timing, or detect pipeline delays. The heartbeat plugin provides a straightforward method for ensuring Logstash's operational status and offers basic monitoring capabilities, with future plans to expand its functionality to include an API for comprehensive pipeline visibility and performance metrics.