Model max_uncommitted_tx_count of raft.h in abs.tla

[lemmy]

Align spec with CCF by replacing global upper bound MaxLogLength with MaxUncommittedCount (see max_uncommitted_tx_count in raft.h) that restricts the length by which a log may be extended in each step.

These two commits were previously part of #6475. @heidihoward approved them in #6475 (comment).

[achamayou]

This constraint is too simplistic, and does not accurately represent what max uncommitted tx count does.

The current behaviour is that new user and governance transactions are rejected, but signatures and nodes frontend transactions (joins, jwt refresh...) do not count towards that limit. Applying that cap to the overall committed growth per step is incorrect.

I can see that it is necessary to have a cap for model checking to work, but conflating it with max uncommitted tx is not accurate, and may result in confusion and trace validation failures.

[lemmy]

This constraint is too simplistic, and does not accurately represent what max uncommitted tx count does.

The current behaviour is that new user and governance transactions are rejected, but signatures and nodes frontend transactions (joins, jwt refresh...) do not count towards that limit. Applying that cap to the overall committed growth per step is incorrect.

The documentation of max_uncommitted_tx_count documentation could mention this behavior:

"Maximum number of uncommitted transactions allowed before the primary refuses new transactions. Unlimited if set to 0."

Regarding ccfraft, is it correct to assume that max_uncommitted_tx_count applies to TypeEntry, but does not apply to TypeSignature, TypeReconfiguration, or TypeRetired?

I can see that it is necessary to have a cap for model checking to work, but conflating it with max uncommitted tx is not accurate, and may result in confusion and trace validation failures.

Actually, unbounded sequences create one less constraint in the (pending) axiomatic definitions in abs.tla.

[lemmy]

Implementation-level issues and PRs:
#5692
#3871
#5690