参考：
https://docs.solace.com/PubSub-ConceptMaps/Event-Stream-Maps.htm
Persistence refers to the Quality-of-Service (QoS) of event messages, and they can be classified as Persistent (Guaranteed) or Non-Persistent
Durable endpoints operate whether or not consumers are active.
The concept of persistence applies to event messages, and durability applies to endpoints.
Non-persistent events are ephemeral. These events provide a QoS for consumers where loss of messages is acceptable, and use a design pattern where consumers only receive messages starting from the time of connection.
When event messages arrive at the broker with Persistent Delivery Mode set to Direct, the message is placed at the tail of the Non-Persistent Event Stream.
Each Direct message has an assigned priority. The consumer’s egress queue ensures higher priority Direct messages are processed before lower priority ones.
Persistent events are persistent. Event messages are considered to be persistent if they are placed onto non-volatile storage media after they arrive on the broker. They are suitable to application design patterns where events are required to be:
There are three pieces to the puzzle, which we‘ll examine in detail in the upcoming sections:
【消息中间件123】Solace PubSub+ Event Broker介绍
原文：https://www.cnblogs.com/cathygx/p/12869643.html