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statement-store: allow light clients to specify topic affinity#11329

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alexggh merged 25 commits into
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alexggh/explicit_affinity
Apr 14, 2026
Merged

statement-store: allow light clients to specify topic affinity#11329
alexggh merged 25 commits into
masterfrom
alexggh/explicit_affinity

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@alexggh

@alexggh alexggh commented Mar 10, 2026 •
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Description

Add explicit topic affinity support to the statement protocol, allowing nodes to advertise at P2P level which statement topics they're interested in. When a peer's affinity changes, relevant statements are re-sent.

The topic affinity is specified as a BloomFilter, all statements that match the filter are forwarded to new peers.

Currently, this is meant to be used by light clients like smoldot to receive only the statements they are interested in. In the future, this can also be used by statement store full nodes, but some other changes will also be needed.

Changes

  • Change the format of the message and introduce a new protocol "statement/2".
enum StatementMessage {
	Statements(Vec<Statement>),
	/// Bloom filter bytes representing the topics this peer is interested in.
	ExplicitTopicAffinity(AffinityFilter),
}
  • Light client nodes connected on the new protocol need to also advertise a topic affinity before they are receiving any statements.
  • If node define a topic affinity send them only the statements matching that affinity.

TODO

  • Integration testing of the new flow, tested with modify node
  • E2E integrations tests with smoldot: e9a20b6.
  • Rate limit Explicit Affinity

alexggh added 12 commits February 26, 2026 16:27
@alexggh
explicit affinity
c2486c7 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
make topic affinity change re-send statements
fa3cf9d 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
std support
cf92102 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
switch to using fastbloom
809d9ef 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
move to fast bloom
f0f9f84 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
Merge remote-tracking branch 'origin/master' into explicit_affinity
bcd405a
@alexggh
filter them first
1045375 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
add more tests
8670f97 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
keep formatting
8729b40 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
document protocol purpose
1d01f84 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
cleanup
38fa5a5 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
make the affinity filter bounded
625a4ae 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
P1sar
P1sar reviewed Mar 10, 2026
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Comment thread substrate/client/network/statement/src/affinity.rs
AndreiEres
AndreiEres requested changes Mar 11, 2026
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Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs
Comment thread substrate/client/network/statement/src/lib.rs
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs Outdated
Comment thread substrate/client/network/statement/src/lib.rs
P1sar
P1sar reviewed Mar 11, 2026
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Comment thread substrate/client/network/statement/src/lib.rs
@AndreiEres

AndreiEres commented Mar 13, 2026

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@alexggh please consider merging this PR to your branch
#11372

@AndreiEres @alexggh
statement-store: Fix affinity filter (#11372)
2e7634e 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
Co-authored-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
review comments
b33eb85 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh alexggh marked this pull request as ready for review March 18, 2026 13:18
@alexggh alexggh added the T8-polkadot This PR/Issue is related to/affects the Polkadot network. label Mar 18, 2026
@alexggh
add rate limiting
1eecfd6 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh alexggh requested review from AndreiEres and P1sar March 18, 2026 15:47
@alexggh
fix taplo
c939b84 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
AndreiEres
AndreiEres approved these changes Mar 20, 2026
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Good job!

Comment thread substrate/client/network/statement/src/lib.rs
Comment thread substrate/client/network/statement/src/lib.rs
Comment thread substrate/client/network/statement/src/lib.rs Outdated
@alexggh
address review feedback
93f1f7f 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh alexggh mentioned this pull request Mar 24, 2026
Closed
alexggh added 3 commits March 24, 2026 13:35
@alexggh
add prdoc
033fec9 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
fix prdoc
f22d5b5 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@alexggh
reject if can't determine peer role
85d86c4 
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
@AndreiEres AndreiEres mentioned this pull request Mar 26, 2026
Merged
P1sar
P1sar approved these changes Mar 31, 2026
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Looks good now!

@socket-security

socket-security Bot commented Apr 7, 2026 •
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Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff Package Supply Chain
Security		 Vulnerability Quality Maintenance License
Addedcargo/​fastbloom@​0.17.010010093100100

View full report

@alexggh alexggh enabled auto-merge April 14, 2026 11:37
@alexggh alexggh added this pull request to the merge queue Apr 14, 2026
Merged via the queue into master with commit 54108b3 Apr 14, 2026
280 of 283 checks passed
@alexggh alexggh deleted the alexggh/explicit_affinity branch April 14, 2026 13:34
dmitry-markin
dmitry-markin reviewed Apr 15, 2026
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Comment thread substrate/client/network/statement/src/affinity.rs
/// Maximum number of bits allowed in a bloom filter received from the network.
/// Derived from [`MAX_STATEMENT_NOTIFICATION_SIZE`] so the affinity filter can never exceed the
/// protocol's notification budget. 1 MiB = 8_388_608 bits.
const MAX_BLOOM_BITS: usize = MAX_STATEMENT_NOTIFICATION_SIZE as usize * 8;

@dmitry-markin dmitry-markin Apr 15, 2026 •
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nit: We unlikely ever encounter a 1 MiB filter, but should this also account for the v2 envelope size and other data sent on the wire?

@dmitry-markin dmitry-markin Apr 15, 2026

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Actually, may be set a way lower cap on the filter size? For example, Bitcoin caps a transaction Bloom filter size to 36 kB: https://github.com/bitcoin/bips/blob/master/bip-0037.mediawiki

Given the false positive rate of 1% and 10000 topics (which is already a lot), we only need a 12 kB filter.

@dmitry-markin dmitry-markin Apr 15, 2026 •
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Actually, realized that 10k topics for a chat of 1m daily users is not enough :D

@dmitry-markin dmitry-markin Apr 15, 2026

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Edit: 1m users should be irrelevant to a single client/filter, if I am not mistaking something.

@alexggh alexggh Apr 16, 2026

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1m users should be irrelevant to a single client/filter, if I am not mistaking something.

No it is not irelevant, the number bits is related to the total number of topics in the system, not just the ones a client subscribes to, because if the system has 10M topics that get check against your filter then 1% means you still get 100K topics(which is not what you want), so you would have to have a lower FP rate let's say 0.001% and that automatically translate in more bits.

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@dmitry-markin dmitry-markin dmitry-markin left review comments
@AndreiEres AndreiEres AndreiEres approved these changes
@P1sar P1sar P1sar approved these changes
@s0me0ne-unkn0wn s0me0ne-unkn0wn Awaiting requested review from s0me0ne-unkn0wn
@DenzelPenzel DenzelPenzel Awaiting requested review from DenzelPenzel

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