Mule is an open source Enterprise Service Bus (ESB) that enables existing systems to communicate with each other regardless of transport protocol or location, acting as a transit system for connecting services and applications. It is Java based and supports the New Relic APM Java agent from version 3.4 up to the latest version, 3.8. Mule ESB provides an environment where applications can run, called "flows," which can perform various duties such as acting as an intermediary between systems, providing database access, handling HTTP requests, and interacting with data stores, external systems, and web services. The New Relic APM Java agent allows users to see flows run through their entire life cycle, view interactions with data stores, and see external calls and cross application tracing. It provides insight into the behavior and performance of flows, including transaction traces that show app name, flow name, endpoint, HTTP request with headers, response, and execution time for each part of the transaction. The agent also supports technologies like JDBC, JMS, Apache HttpClient, and other libraries used inside Mule ESB, providing a seamless experience drilling down the entire stack from request to response.