[Peras 9] More type definitions and plumbing #1784

agustinmista · 2025-11-28T12:11:44Z

This PR introduces some general changes and QoL improvements in anticipation to the introduction of the Peras voting rules. These are separated into hopefully digestible atomic commits:

Introduce Ouroboros.Consensus.Peras.Params module to keep track of Peras protocol parameters in a single place,
Add small helper function onPerasRoundNo,
Tweak HasPerasCertX field projection typeclasses,
Introduce WithArrivalTime combinator to wrap values with a RelativeTime,
Wrap validated Peras certs with their arrival time (and adapt tests).
Store latest certificate seen in the PerasCertDB and add a getLatestCertSeen method to retrieve it.

Please refer to the corresponding commit messages for more information.

This commits introduces the module: Ouroboros.Consensus.Peras.Params To consolidate all the protocol parameters related to Peras in one place. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

This commit adds a small helper to compute over Peras round numbers. Will be needed later on to implement the Peras voting rules. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

This commit simplifies the interface of the HasPerasCertX typeclasses, removing the StandardHash superclass constraint, and splitting them into several smaller typeclasses. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

This commit defines a generic WithArrivalTime combinator to wrap a value with its arrival time (as a Relative time). This is needed by Peras in several places, e.g., to evaluate the voting rules. Notably, we store a raw Relative time instead of a (arguably more apt) SlotNo or PerasRoundNo to defer as much as possible having to deal with the case where making this translation (timestamp -> slot/round) is not possible due to the HFC time translation horizon. Instead, the client will need to perform this translation in a context where such a failure cannot occur or can be more easily dealt with. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

This commit wraps the existing ValidatedPerasCerts stored in the PerasCertDB with their corresponding arrival time. In addition, it adapts tests to use either a randomly generated arrival time, or (when appropriate) one generated by a monotonically increasing SystemTime. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

This commit adds a method to the PerasCertDB API to retrieve the latest certificate seen. This is certificate needed to implement the Peras voting and must be kept around even after garbage collection. Because of this, we extend the internal state of the PerasCertDB to store this special certificate on the side, and (potentially) update it after new certificates are added to the database. Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

Co-authored-by: Agustin Mista <agustin.mista@moduscreate.com> Co-authored-by: Alexander Esgen <alexander.esgen@iohk.io> Co-authored-by: Georgy Lukyanov <georgy.lukyanov@iohk.io> Co-authored-by: Thomas BAGREL <thomas.bagrel@tweag.io> Co-authored-by: Nicolas BACQUEY <nicolas.bacquey@tweag.io>

tbagrel1

LGTM!

I think we may change the title of the PR though (and maybe part of its description) to better reflect that most changes are related to adding timestamps on certs and propagate the necessary stuff to make it work.

tbagrel1 · 2025-12-01T14:29:56Z

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Peras/Params.hs

+  deriving stock Generic
+  deriving newtype (Enum, Eq, Ord, NoThunks)
+
+-- | Maximum number of slots to after the start of a round to consider a


Slight typo here: "Maximum number of slots to after"

tbagrel1 · 2025-12-01T14:30:59Z

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Peras/Params.hs

+  deriving stock Generic
+  deriving newtype (Enum, Eq, Ord, NoThunks)
+
+-- | Minimum age (in slots) of a block to be voted on at the beginning of a


This description is not entierely clear to me

nbacquey

Besides my comments, it seems ok to undraft

nbacquey · 2025-12-01T17:51:39Z

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Peras/Params.hs

There are other parameters that could have their place here, for instance:

Weight boost

Round length

Quorum size

Do we plan to put those here at a later date?

Now that I'm thinking about it, we have PerasCfg blk as part of SupportPeras.hs / BlockSupportsPeras typeclass. Do we have a clear line on what should be part of this PerasCfg vs what should be part of PerasParams?

nbacquey · 2025-12-01T17:53:48Z

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/PerasCertDB/API.hs

+  -- the db since it has been opened. This certificate is not affected by garbage
+  -- collection, but it's forgotten when the db is closed.
+  --
+  -- NOTE: having seen a certificate is a precondition to start voting in every


Maybe this ought to be a TODO or even a FIXME, lest we forget about it and render Peras unusable for lack of bootstrapping

nbacquey · 2025-12-01T18:05:47Z

...consensus/test/consensus-test/Test/Consensus/MiniProtocol/ObjectDiffusion/PerasCert/Smoke.hs

 instance WithId (PerasCert blk) PerasRoundNo where
  getId = pcCertRound

+mockSystemTime :: IOLike m => m (SystemTime m)


IOLike is MonadTime, I'm not sure this mocking is necessary

nbacquey · 2025-12-01T18:08:45Z

ouroboros-consensus/test/storage-test/Test/Ouroboros/Storage/ChainDB/StateMachine.hs

+  genSystemTime :: Gen (SystemTime Gen)
+  genSystemTime = do
+    current <- RelativeTime . fromIntegral <$> arbitrary @Word64
+    pure $ SystemTime{systemTimeCurrent = return current, systemTimeWait = pure ()}


This may cause problems: maybe we rely on the fact that successive calls to systemTimeCurrent return strictly increasing values

nbacquey · 2025-12-01T18:10:07Z

ouroboros-consensus/test/storage-test/Test/Ouroboros/Storage/PerasCertDB/StateMachine.hs

          ]
    | otherwise = pure $ Some OpenDB
   where
+    genSystemTime :: Gen (SystemTime Gen)


Sane remark. Also, maybe we could share that piece of code somewhere, since it's used twice?

agustinmista added the peras label Nov 28, 2025

agustinmista mentioned this pull request Nov 28, 2025

[Peras 10] Add pure voting rules #1785

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agustinmista force-pushed the peras/main-pr/new-defs-and-plumbing branch 4 times, most recently from 8d5c8a4 to 84a8f29 Compare December 1, 2025 11:15

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agustinmista force-pushed the peras/main-pr/new-defs-and-plumbing branch from 84a8f29 to 14229b9 Compare December 1, 2025 11:48

agustinmista and others added 4 commits December 1, 2025 12:49

agustinmista force-pushed the peras/main-pr/new-defs-and-plumbing branch from 14229b9 to 85e4b39 Compare December 1, 2025 11:49

agustinmista requested review from nbacquey and tbagrel1 December 1, 2025 12:37

tbagrel1 approved these changes Dec 1, 2025

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[Peras 9] More type definitions and plumbing #1784

[Peras 9] More type definitions and plumbing #1784

agustinmista commented Nov 28, 2025 •

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agustinmista commented Nov 28, 2025 •

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