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Consensus Team Update

· 3 min read
Damian Nadales

High level summary​

During the past two weeks we got the results from the system level benchmarks for UTxO HD. They showed a substantial performance regression, so we spent some time analyzing the results. We found out the frequency at which ledger snapshots were taken was too high, so we requested the benchmarking team a new run with a more realistic snapshotting policy. We continued refactoring and improving the prototype, and we released UTxO-HD related packages to CHaP.

We met with IOG researchers and networking specialists to discuss the Genesis design, which was well received. We continued working on testing and benchmarking different Genesis prototypes.

We are also working on solving a test failure related to iterators. This work derived in several improvements such as better documentation, a framework for writing unit (and regression) tests, and the possibility of debugging QuickCheck counter examples in the REPL.

Finally, we released ouroboros-consensus 0.2.0.0 and ouroboros-consensus-cardano 0.3.0.0 to CHaP

Workstreams​

UTxO HD Prototype​

We got the results of the first system level benchmarks for UTxO HD. They seemed to indicate a significant regression in performance. After looking into the benchmark logs we found that the benchmark runs took ledger state snapshots too often, due to the default snapshotting policy depending on k, and k being so small in the benchmark runs. Therefore, the next step is to re-run the benchmarks with a snapshotting policy that more closely resembles the one from mainnet.

At the same time, we continued refactoring and cleaning up the prototype.

Also, we prepared the anti-diff packages (fingertree-rm, diff-containers, simple-semigroupoids) and the lmdb related packages (cardano-lmdb and cardano-lmdb-simple) to CHaP.

Genesis​

The Genesis design was presented to the IOG researchers and Peter Thompson from NSol. It was well received. They pointed out one blindspot, but we think it'll be relatively simple to mitigate.

In parallel, we continued developing test and benchmarks for the Genesis prototypes. I particular we tested and implemented a potential fix for increased ChainDB dequeue timings, which partly behaved as we expected, but still needs further investigation. Also we obtained new benchmarking data for the prototype.

Technical debt​

Related to #4183, we developed a DSL for specifying ChainDB unit tests. This will allow us to better understand the counter-examples returned by QuickCheck tests, and to write regression tests for them. Also, we added a module to enable QuickCheck counter-examples to be run on the REPL, allowing for faster debugging feedback. Also, we improved the documentation related to followers (#4372).

We are also working on a design for optimizing the way we handle blocks from the future.

Support​

We released ouroboros-consensus 0.2.0.0 and ouroboros-consensus-cardano 0.3.0.0 to CHaP. Remember that we decided to split the packages related to Consensus into two bundles, one with the core functionality, Cardano-agnostic code, and another bundle with instantiations specific to Cardano.