Update elastic scaling documentation by sandreim · Pull Request #9677 · paritytech/polkadot-sdk

sandreim · 2025-09-08T14:54:47Z

Closes #9677

Add docs and remove MVP.

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

sandreim · 2025-09-09T13:09:53Z

/cmd prdoc generate --bump major

…p major'

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

…/polkadot-sdk into sandreim/elastic_scaling_docs

eskimor

Well written. Thank you!

eskimor · 2025-09-09T13:18:35Z

docs/sdk/src/guides/enable_elastic_scaling.rs

+//! This commitment is implemented via `UMP` signals, which rely on the upward message passing channel that
+//! is used by parachains to send messages to the relay chain.
+//! 
+//! The only required change for the runtime is enabling the `experimental-ump-signals` feature of the `parachain-system`


Why is this still experimental? When will we no longer make it experimental?

Because it is not enabled on Polkadot yet. I plan to remove this feature completely as soon as RFC103 is enabled on Polkadot.

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

Sajjon

Nice! I left some suggestions for improvement. There is a minor lack of consistency between 6s and 6 seconds also I think it is good practice to use Three cores instead of 3 cores, I think the "threshold" is numbers less than 10 one typically writes as words?

Good job! :)

docs/sdk/src/guides/enable_elastic_scaling.rs

Co-authored-by: Alexander Cyon <Sajjon@users.noreply.github.com>

sandreim · 2025-09-10T11:37:19Z

Addressed all feedback. @alindima @skunert can I get some ✅ ?

skunert

Niice!

alindima · 2025-09-10T11:54:57Z

We should also add a note about customizing the block authoring duration on the collator

sandreim · 2025-09-10T12:04:53Z

We should also add a note about customizing the block authoring duration on the collator

What is customisable that is requirement ?

alindima · 2025-09-10T12:14:35Z

We should also add a note about customizing the block authoring duration on the collator

What is customisable that is requirement ?

polkadot-sdk/cumulus/client/consensus/aura/src/collators/slot_based/mod.rs

Line 132 in 6060499

pub authoring_duration: Duration,

The omni node hardcodes this to 2 seconds. If a parachain wants to have 12 cores with 500ms block times, they need to lower this. We probably need to add this parameter to the omni node CLI. WDYT @skunert ?

sandreim · 2025-09-10T12:45:50Z

We should also add a note about customizing the block authoring duration on the collator

What is customisable that is requirement ?

polkadot-sdk/cumulus/client/consensus/aura/src/collators/slot_based/mod.rs

Line 132 in 6060499

pub authoring_duration: Duration,

The omni node hardcodes this to 2 seconds. If a parachain wants to have 12 cores with 500ms block times, they need to lower this. We probably need to add this parameter to the omni node CLI. WDYT @skunert ?

AFAIK this authoring duration gets adjusted based on this, you don't need to change it.

LE: However it seems to be used only to compute the block production interval, still 2s getting passed to proposer.

skunert · 2025-09-10T13:00:43Z

This is a good point, we currently don't have any description of the timings and how they need to be adjusted. I know that @bkchr is working on dynamic timings and weight adjustments in the runtime. Until that is done, we only have shitty solutions.

For any number of cores, you would need to adjust the weight in your runtime right? Otherwise, how would we know when to stop authoring. This is the proper way to do it. But at the same time, its a problem if someone wants to have these 12 cores. Do we want people to set their runtime weight to 500ms? Probably not. So we would indeed need to handle everything node-side and adjust this authoring_duration. But my gut feeling still says that we should discourage this 12 core use-case and wait with recommending this until we have a proper dynamic approach.

bkchr · 2025-09-10T13:21:06Z

The omni node hardcodes this to 2 seconds. If a parachain wants to have 12 cores with 500ms block times, they need to lower this.

They will need to change their weight. This is basically an upper bound on what the node will use. When the block finishes after 500ms, the block production stops before.

This is a good point, we currently don't have any description of the timings and how they need to be adjusted. I know that @bkchr is working on dynamic timings and weight adjustments in the runtime. Until that is done, we only have shitty solutions.

Yes this will be fixed by my work. If anyone right now really needs this, they need to go with the 500ms weight route. There are a lot of considerations to be done, they also need to ensure if they set the weight to 500ms, that they don't prevent e.g. doing runtime upgrades or similar.

sandreim · 2025-09-10T13:38:55Z

The omni node hardcodes this to 2 seconds. If a parachain wants to have 12 cores with 500ms block times, they need to lower this.

They will need to change their weight. This is basically an upper bound on what the node will use. When the block finishes after 500ms, the block production stops before.

For elastic scaling, when we have a full core to fill, wouldn't it be better if we don't limit the weight ? Parachains can run faster collators and fill in more than 500ms ref time with 500ms authorship duration.

sandreim · 2025-09-10T14:22:50Z

/cmd fmt

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

…/polkadot-sdk into sandreim/elastic_scaling_docs Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

paritytech-workflow-stopper · 2025-09-10T15:37:43Z

All GitHub workflows were cancelled due to failure one of the required jobs.
Failed workflow url: https://github.com/paritytech/polkadot-sdk/actions/runs/17618872655
Failed job name: fmt

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

paritytech-release-backport-bot · 2025-09-10T17:31:48Z

Successfully created backport PR for stable2509:

[stable2509] Backport #9677 #9704

Closes #9677 Add docs and remove MVP. --------- Signed-off-by: Andrei Sandu <andrei-mihail@parity.io> Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Alexander Cyon <Sajjon@users.noreply.github.com> Co-authored-by: Sebastian Kunert <skunert49@gmail.com> Co-authored-by: Alin Dima <alin@parity.io> (cherry picked from commit 7af791f)

Backport #9677 into `stable2509` from sandreim. See the [documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md) on how to use this bot.  Signed-off-by: Andrei Sandu <andrei-mihail@parity.io> Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com> Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Alexander Cyon <Sajjon@users.noreply.github.com> Co-authored-by: Sebastian Kunert <skunert49@gmail.com> Co-authored-by: Alin Dima <alin@parity.io>

Follow-up to #9677 . I think it would be good to add our view on the slot duration, as it is often confused with the actual block production interval. This short addition should clarify things a bit. --------- Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com> Co-authored-by: Bastian Köcher <git@kchr.de>

Follow-up to #9677 . I think it would be good to add our view on the slot duration, as it is often confused with the actual block production interval. This short addition should clarify things a bit. --------- Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com> Co-authored-by: Bastian Köcher <git@kchr.de> (cherry picked from commit fbf98c8)

Follow-up to #9677 . I think it would be good to add our view on the slot duration, as it is often confused with the actual block production interval. This short addition should clarify things a bit. --------- Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com> Co-authored-by: Bastian Köcher <git@kchr.de>

Closes #9677 Add docs and remove MVP. --------- Signed-off-by: Andrei Sandu <andrei-mihail@parity.io> Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Alexander Cyon <Sajjon@users.noreply.github.com> Co-authored-by: Sebastian Kunert <skunert49@gmail.com> Co-authored-by: Alin Dima <alin@parity.io>

Follow-up to #9677 . I think it would be good to add our view on the slot duration, as it is often confused with the actual block production interval. This short addition should clarify things a bit. --------- Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com> Co-authored-by: Bastian Köcher <git@kchr.de>

sandreim added 5 commits September 8, 2025 12:16

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sandreim added the T11-documentation This PR/Issue is related to documentation. label Sep 9, 2025

sandreim added 6 commits September 9, 2025 14:43

remove the need for async backing to be enabled first

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rephrase / format

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fix build

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Update from github-actions[bot] running command 'prdoc generate --bum…

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…p major'

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Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

Merge branch 'master' into sandreim/elastic_scaling_docs

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sandreim marked this pull request as ready for review September 9, 2025 13:16

sandreim added 2 commits September 9, 2025 16:20

add rfc103 link

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Merge branch 'sandreim/elastic_scaling_docs' of github.com:paritytech…

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…/polkadot-sdk into sandreim/elastic_scaling_docs

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sandreim added the A4-backport-stable2509 Pull request must be backported to the stable2509 release branch label Sep 9, 2025

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sandreim changed the title ~~[WIP] Update elastic scaling documentation~~ Update elastic scaling documentation Sep 9, 2025

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sandreim and others added 5 commits September 9, 2025 17:39

Update docs/sdk/src/guides/enable_elastic_scaling.rs

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Update docs/sdk/src/guides/enable_elastic_scaling.rs

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Update docs/sdk/src/guides/enable_elastic_scaling.rs

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sandreim deleted the sandreim/elastic_scaling_docs branch September 10, 2025 17:31

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[stable2509] Backport #9677 #9704

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Elastic-scaling-guide: Mention slot duration #9713

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