Consumers

Consumers can either be based where JetStream will deliver the messages as fast as possible to a subject of your choice or pull based to have control by asking the server for messages. The rate of message delivery in both cases is subject to ReplayPolicy. A ReplayInstant Consumer will receive all messages as fast as possible while a ReplayOriginal Consumer will receive messages at the rate they were received, which is great for replaying production traffic in staging.

Consumers track their progress, they know what messages were delivered, acknowledged, etc., and will redeliver messages they sent that were not acknowledged. When first created, the Consumer has to know what message to send as the first one. You can configure either a specific message in the set (StreamSeq), specific time (StartTime), all () or last (DeliverLast). This is the starting point and from there, they all behave the same - delivering all of the following messages with optional Acknowledgement.

Some messages may cause your applications to crash and cause a never ending loop forever poisoning your system. The MaxDeliver setting allow you to set a upper bound to how many times a message may be delivered.

When defining Consumers the items below make up the entire configuration of the Consumer: