Head stream

bucketpathstringrequired

Bucket ID.

streampathstringrequired

Stream ID within the bucket.

Stream-Incarnationheaderstring

Optional precondition: the stream's incarnation token, as a previous response's Stream-Incarnation header returned it. The HEAD answers 200 only if the stream is still that incarnation; otherwise 412, with the current token in Stream-Incarnation. Without the header, the request behaves exactly as described here. A malformed value answers 400. See Stream-Incarnation.

Response

Status	Meaning
`200`	Stream found.
`307`	In a cluster, this node could not answer as the stream's group leader. `Location` is the same request on the leader.
`404`	Stream not found or expired.
`412`	`Stream-Incarnation` did not match. The response's `Stream-Incarnation` is the current token.
`503`	The group has no known leader, or the leader could not confirm its leadership in time. Retry after `Retry-After`.

HEAD is linearizable: the leader confirms with a majority of voters that it still leads before it answers, so the response reflects every append acknowledged before the request started. See Durability and consistency.

Response headers include:

Header	Description
`Content-Type`	The stream's content type.
`Stream-Next-Offset`	The stream's tail: the offset the next append starts at.
`Stream-Closed`	Present and `true` if the stream is closed.
`Stream-Retained-Offset`	The earliest offset still readable. Reads below it answer `410 Gone`. Before any retention advance, it is the start of the stream.
`Stream-Snapshot-Offset`	The offset of the latest snapshot. Absent when the stream has no snapshot. Read the snapshot with `GET …/snapshot/{offset}`.
`Stream-Snapshot-Digest`	The digest of the latest snapshot's content type and body, as its publish returned it. Present with `Stream-Snapshot-Offset`.
`Stream-Incarnation`	An opaque token for this incarnation of the stream. It changes when the stream is deleted and recreated at the same URL; compare it only for equality.
`Ursula-Protocol`	`2`. Present on every answer to a `HEAD`, `404`, `307` and `503` included. See Server metadata.
`Ursula-Cluster-Id`	The deployment that served the request, as `server.cluster_id` names it. Present on every answer to a `HEAD`. A different id means another deployment, not a new history of the stream.
`Ursula-Max-Request-Bytes`	The largest request body any request to the stream may carry: 33554432 (32 MiB) from a node, lowered by a gateway with a smaller limit. A larger request answers `413`. A larger snapshot goes up in parts. See Server metadata.
`Ursula-Max-Snapshot-Bytes`	The largest snapshot the node accepts in parts: 1073741824 (1 GiB), in at most 4,096 parts. Present only on a node with a cold backend. A gateway passes it unchanged: each part is a request under its own limit.
`Stream-TTL`	The configured TTL in seconds (if a TTL was set). This is the sliding window length, not the time remaining. `HEAD` does not renew it.
`Stream-Expires-At`	Expiration timestamp (if set).
`Cache-Control`	`no-store`.
`Stream-Cold-Hot-Start-Offset`	Diagnostic and unstable: may change or disappear in any release. Data below this offset has been flushed to cold storage.

curl -I http://127.0.0.1:4437/demo/hello