Validators missing votes Polkadot AH parachain since Elastic Scaling ?

[florentina57]

@sandreim Since yesterday, from session 12431, after elastic scaling was enabled on Polkadot Asset Hub, my Polkadot validators in LATAM are missing votes with PAH parachain. Their performance on turboflakes for the given sessions has lowered from A+ to A.

I had observed this same issue on Kusama a few months ago, specifically with parachains 3392 and 2281(kreivo), and had anecdotally documented on the forum, and it seems to have recently improved after ref 628 was executed and config schedulerParams.lookahead was changed from 3 to 5.

[m-saxemberg]

+1 to this problem
Latin America node most impacted
https://apps.turboflakes.io/?chain=polkadot#/validator/153YD8ZHD9dRh82U419bSCB5SzWhbdAFzjj4NtA5pMazR2yC?mode=history
US validator also has a slight impact
https://apps.turboflakes.io/?chain=polkadot#/validator/12ryLNrg44r7Qv7oWZa2wK6PuzUmAMueyVHRBsyR5N6anEaV?mode=history

Pur Thailand RPC is also having connectivity issues.

Only Europe nodes seem safe/efficient at the moment.

[bkchr]

CC @sandreim

[sandreim]

I believe this is caused by block confidence issues when Elastic Scaling is used - a chain of parablocks need to be backed in a RC block.

Let me give you an example: if we have the following chain of blocks (A,B,C) and your validator backed block C, but somehow block A was not backed (due to some other issues), then B and C will not be backed on-chain resulting in loosing some votes.

We are working on improving this in 2026. One notable improvement was done via https://kusama.subsquare.io/referenda/628 and I'll soon submit a referendum for Polkadot with the same change.

[m-saxemberg]

Based on the Kusama data which already includes the parameter schedulerParams.lookahead to 5 and despite the high variance, the South America and Asia validators seem to still be heavily penalized when compared to others in Europe.

South America + Asia
https://apps.turboflakes.io/?chain=kusama#/validator/FELETDtt5cdxYmqTudCkeqLPGqbM8VRU37fgxB4ctoXARgh?mode=history
https://apps.turboflakes.io/?chain=kusama#/validator/JMB89sS8GfRN4ebiQ8xMVVowwnzQ6oD1iXrxPP6WjsXTJXb?mode=history
https://apps.turboflakes.io/?chain=kusama#/validator/ESSZefozpZYVLbLF1vaGtabthQYg8PVXiTytVm6YiiwAnee?mode=history

Spain, Lithuania, Switzerland
https://apps.turboflakes.io/?chain=kusama#/validator/DSA55HQ9uGHE5MyMouE8Geasi2tsDcu3oHR4aFkJ3VBjZG5?mode=history
https://apps.turboflakes.io/?chain=kusama#/validator/DSA55HQ9uGHE5MyMouE8Geasi2tsDcu3oHR4aFkJ3VBjZG5?mode=history
https://apps.turboflakes.io/?chain=kusama#/validator/Dfg9gbTwG6aghwLYTfYoV4dXyhCRBLbRyFwENADHmg4zfDF?mode=history
https://apps.turboflakes.io/?chain=kusama#/validator/J9KLy6nouPoj5rA2RWX8C9wrmrg84Mv3hpB7mZTN7Jvww7C?mode=history

it was always expected to have a slight difference but now the more remote nodes' performance have started to diverge significantly when compared to the ones located in Europe. It seems like even the ones in the US are impacted to some extent and miss votes (not as often as in other locations however).