Glossary
A
AMQP
Advanced Message Queuing Protocol - An open standard application layer protocol for message-oriented middleware.
ACL
Access Control List - A list of permissions attached to an object, specifying which users or system processes have access to objects.
B
Broker
The central node in a message queue system that handles routing of messages between publishers and subscribers.
Backpressure
A mechanism to handle overflow of data when the incoming rate exceeds the processing rate.
C
Client ID
A unique identifier for each client connecting to the message broker.
Cluster
A group of message brokers working together to provide high availability and scalability.
M
MQTT
Message Queuing Telemetry Transport - A lightweight messaging protocol designed for constrained devices and low-bandwidth, high-latency networks.
Message Retention
The ability to store messages for future delivery to subscribers.
P
Publisher
A client that sends messages to topics in the message broker.
Persistence
The storage of messages and client session data to disk for reliability.
Q
QoS
Quality of Service - The level of assurance for message delivery:
- QoS 0: At most once
- QoS 1: At least once
- QoS 2: Exactly once
Queue
A data structure that stores messages in a FIFO (First In, First Out) order.
R
Retained Message
A message that the broker stores for a topic and sends to new subscribers.
REST API
Representational State Transfer API - HTTP-based API for managing the message broker.
S
Subscriber
A client that receives messages from topics they have subscribed to.
SSL/TLS
Security protocols for establishing encrypted links between networked computers.
T
Topic
A string that the broker uses to filter messages for each connected client.
Topic Wildcard
Special characters used in topic subscription to match multiple topics:
- '+': Single level wildcard
- '#': Multi level wildcard
W
WebSocket
A computer communications protocol providing full-duplex communication channels over a single TCP connection.
Will Message
A message that is published automatically by the broker when a client disconnects unexpectedly.