Allow joining FETCH for PUBLISH and SUBSCRIBE_UPDATE forward=1 #1335
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This also restricts joining fetch to subscriptions in Forward State=1, since joining a subscription in Forward State 0 does not have the intended "no gaps" effect.
This means that subscriptions initiated in Forward=0 need to update the join point when Forward transitions to 1. Possible flow:
```
P->S: PUBLISH, Forward=0, Largest Object={10, 5}
P: Object 11,0
S->P: PUBLISH_OK, Forward=1
S->P: Joining FETCH
P->S: FETCH_OK, End=11,0 (inclusive)
P->S (fetch stream): 11,0
P->S (subscribe stream): Object 11,1
```
Note in the above flow, a standalone FETCH to Largest Object would miss 11,0.
This PR also allows re-joining a track that was temporarily in Forward=0:
```
S->P: SUBSCRIBE, Forward=1
S->P: Joining FETCH
...
S->P: SUBSCRIBE_UDPATE, Forward=0
...
S->P: SUBSCRIBE_UDPATE, Forward=1
S->P: Joining FETCH
P->S: REQUEST_OK, Largest={21,0}
P->S (fetch stream): Object 21,0
```
afrind
added
Design
yekuiwang
reviewed
Oct 23, 2025
suhasHere
reviewed
Oct 30, 2025
suhasHere
approved these changes
Oct 30, 2025
Co-authored-by: Suhas Nandakumar <[email protected]> Co-authored-by: Ye-Kui Wang <[email protected]>
Collaborator
|
Based on my initial review, I think this PR looks sensible and it's definitely a use case worth solving, but this feels bad. |
afrind
commented
Nov 6, 2025
| * Joining Request ID: The Request ID of the `Established` subscription to be | ||
| joined. If a publisher receives a Joining Fetch with a Request ID that does | ||
| not correspond to an existing Subscribe in the same session, it MUST return | ||
| not correspond to an `Established` subscription in the same session, it MUST return |
Collaborator
Author
There was a problem hiding this comment.
Some other states are valid. Pending (subscriber)
afrind
changed the title
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This also restricts joining fetch to subscriptions in Forward State=1, since joining a subscription in Forward State 0 does not have the intended "no gaps" effect.
This means that subscriptions initiated in Forward=0 need to update the join point when Forward transitions to 1. Possible flow:
Note in the above flow, a standalone FETCH to Largest Object would miss 11,0.
This PR also allows re-joining a track that was temporarily in Forward=0:
Addresses an issue raised in #1313