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Basic concepts

Application Programming Interface (API)

An API is a well-defined interface that can be called from a remote process. There are many styles and protocols available to enable calls to APIs. The most popular at the moment is the REST API style that piggy-backs on top of the HTTP protocol that powers the Internet. Egeria makes extensive use of REST APIs.

Further information

Details of the different types of APIs provided by Egeria can be found in the developer guide. In addition, it is possible to automatically catalog details of the APIs that your organization uses:

Event

An event is a message that describes a specific situation, or more typically a change in situation. It is sent on a topic to share its information with other servers.

Further information

Details of the different types of events used by Egeria

In addition, it is possible to automatically catalog details of the types of events that your organization uses:

Event Broker

An event broker is an infrastructure service that provides a publish-subscribe capability through topics.

There are many different event broker implementations with greater or lesser reliability and performance. Egeria's default event broker is Apache Kafka . This is an open source event broker with a high level of performance, scalability and reliability.

Many organizations establish a standard choice of their event broker service which is why Egeria uses connectors to connect to the event broker so that Apache Kafka can be swapped out for a different event broker implementation. As such, each topic is accessed through an open metadata topic connector.

Further information

Topic

A topic is a service provided by an event broker that offers a publish-subscribe capability for a specific type of event.

Multiple servers can read and write events to a topic. Each topic maintains information about the events that a server has not read so that it can receive each event even if it restarts. Typically the events are processed in a first-in-first-out (FIFO) order, but that is not necessarily guaranteed since it depends on the type and configuration of the event broker.

Further information

Details of the different types of topics used by Egeria

  • OMRSTopic - for open metadata repository cohorts
  • InTopic - for sending events to an Open Metadata Access Service (OMAS)
  • OutTopic - for receiving events from an Open Metadata Access Service (OMAS)

In addition, it is possible to automatically catalog details of the event brokers that your organization uses:

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