Headers
Message headers are used in a variety of JetStream contexts, such de-duplication, auto-purging of messages, metadata from republished messages, and more.
Headers that can be set by a client when a message being published.
Name | Description | Example | Version |
---|---|---|---|
Nats-Msg-Id | Client-defined unique identifier for a message that will be used by the server apply de-duplication within the configured Duplicate Window . | 9f01ccf0-8c34-4789-8688-231a2538a98b | 2.2.0 |
Nats-Expected-Stream | Used to assert the published message is received by some expected stream. | my-stream | 2.2.0 |
Nats-Expected-Last-Msg-Id | Used to apply optimistic concurrency control at the stream-level. The value is the last expected Nats-Msg-Id and the server will reject a publish if the current ID does not match. | 9f01ccf0-8c34-4789-8688-231a2538a98b | 2.2.0 |
Nats-Expected-Last-Sequence | Used to apply optimistic concurrency control at the stream-level. The value is the last expected sequence and the server will reject a publish if the current sequence does not match. | 328 | 2.2.0 |
Nats-Expected-Last-Subject-Sequence | Used to apply optimistic concurrency control at the subject-level. The value is the last expected sequence and the server will reject a publish if the current sequence does not match for the message's subject. | 38 | 2.3.1 |
Nats-Rollup | Used to apply a purge of all prior messages in the stream or at the subject-level. | all for stream, sub for subject | 2.6.2 |
Headers set messages that are republished.
Name | Description | Example | Version |
---|---|---|---|
Nats-Stream | Name of the stream the message was republished from. | Nats-Stream: my-stream | 2.8.3 |
Nats-Subject | The original subject of the message. | events.mouse_clicked | 2.8.3 |
Nats-Sequence | The original sequence of the message. | 193 | 2.8.3 |
Nats-Last-Sequence | The last sequence of the message having the same subject, otherwise zero if this is the first message for the subject. | 190 | 2.8.3 |
Nats-Time-Stamp | The original timestamp of the message. | 2023-08-23T19:53:05.762416Z | 2.10.0 |
Headers that are implicitly added to messages sourced from other streams.
Name | Description | Example | Version |
---|---|---|---|
Nats-Stream-Source | Specifies the origin stream name, the subject and the sequence number plus the subject filter and destination transform of the message being sourced. | my-stream | 2.2.0 |
Headers added to messages when the consumer is configured to be "headers only" omitting the body.
Name | Description | Example | Version |
---|---|---|---|
Nats-Msg-Size | Indicates the message size in bytes. | 1024 | 2.6.2 |
Headers used for internal flow-control messages for a mirror.
Name | Description | Example | Version |
---|---|---|---|
Nats-Last-Consumer | | | 2.2.1 |
Nats-Last-Stream | | | 2.2.1 |
Nats-Consumer-Stalled | | | 2.4.0 |
Nats-Response-Type | | | 2.6.4 |