Why is APM Server a separate component?

The APM Server is kept as a separate component for the following reasons:

  • It helps keep the agents as light as possible and since the APM Server is a stateless separate component, it can be scaled independently.
  • For real-user-monitoring (beta), data is being collected in agents running in browsers. APM Server prevents browsers from interacting directly with Elasticsearch (which poses a security risk), and controls the amount of data flowing into Elasticsearch.
  • In cases where Elasticsearch becomes unresponsive, APM Server can buffer data temporarily (configurable) without adding overhead to the agents.
  • APM Server serves as a middleware for source mapping for javascript in the browser.
  • The APM Server provides a JSON API for agents to use thereby improving compatibility across different versions of agents and the Elastic Stack.