Using MQTT and Node-RED to monitor the ATLAS Metadata Interface (AMI) stack and define metadata aggregation tasks in a pipelined way.

ATLAS Metadata Interface (AMI) is a generic ecosystem for metadata aggregation, transformation and cataloging. Benefiting from more than 20 years of feedback in the LHC context, the second major version was released in 2018. Each sub-system of the stack has recently be improved in order to acquire messaging/telemetry capabilities. This poster describes the whole stack monitoring with the Message Queuing Telemetry Transport (MQTT) protocol, Node-RED, a tool for wiring together hardware/software devices and Elasticsearch. Finally, this poster shows how Node-RED is used to graphically define metadata aggregation tasks, in a pipelined way, without introducing additional single point of failure.