On decentralized software updates for blockchain systems

This repository contains research output (papers, specifications, models, and executable software) about decentralized software updates for blockchain systems. Our research focuses on defining a protocol that covers the life cycle of software updates, which consists of:

• Ideation: the definition and specification of an update proposal, similar to Bitcoin or Ethereum improvement proposals.
• Implementation: the actual implementation of improvement proposals.
• Activation: the activation of new software version across nodes in the blockchain.

This work was funded by the Priviledge project. This project ended on July 2021, and therefore the work on this repository has stopped as well. The deliverables we produced can be found here.

The work carried out in this project helped to prepare the ledger layer of Cardano to accommodate future work on the Voltaire era. Other results might be incorporated later on.

The research roadmap can be found here.

Design specification

The design specification is written in LaTeX. It can be found in the design-spec folder. A compiled pdf can be found here.

We use nix to achieve not only reproducible software builds, but also reproducible document builds across developers machines. This means that anybody who clones this code should be able to build the software and documents without requiring any additional setup other than having nix installed. However, the use of nix is not required.

When using nix it is recommended that you setup the cache, so that it can reuse built artifacts, reducing the compilation times dramatically:

If you are using NixOS add the snippet below to your /etc/nixos/configuration.nix:

nix.binaryCaches = [
  "https://cache.nixos.org"
  "https://hydra.iohk.io"
];

nix.binaryCachePublicKeys = [
  "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="
];

If you are using the nix package manager next to another operating system put the following in /etc/nix/nix.conf if you have a system-wide nix installation , or in ~/.config/nix/nix.conf if you have a local installation:

substituters        = https://hydra.iohk.io https://cache.nixos.org/
trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=

The PDF corresponding to the formal specification can be built by running:

nix-build -A specs -o spec.decentralized-updates

The above command will create a spec.decentralized-updates folder that contains the compiled document.

To get a shell where you have access to all the necessary tools for building the document run:

nix-shell default.nix -A specs.decentralized-updates

Once in the nix-shell the document can be built by running make inside the design-spec directory. When editing the document it is also useful to recompile on file changes. To this end use make watch.

Implementation

The ./cardano-ledger-update directory contains the implementation of the update protocol described in the design specification. This implementation does not include delegation to experts. This is an orthogonal concept that can be incorporated later on, without needing to alter the prototype. See cardano-ledger-update/README.md for more details.

If using nix, to test the executable specifications enter a nix shell and use cabal:

nix-shell
cabal test all

Additionally, you can setup lorri so that cabal is available without needing to enter the nix shell.

Integration with Cardano

The update protocol implemented in this repository was integrated into Cardano, although this was not merged into the master branch of any of its components (due to the experimental nature of this work). However, as a result of this integration the ledger layer of Cardano was made parametric in the update protocol. This was a significant change that did get merged into the master branch of cardano-ledger-specs.

The update protocol integration with Cardano took place across several components:

• Ledger.
• Consensus.
• Node and Cardano command line interface.
• Devops infrastructure.

The cardano-node repository, commit 61e44a22f73969054070edb4668b5b922de94107, contains the references to all the components and their corresponding commits in the cabal.project file:

source-repository-package
  type: git
  location: https://github.com/input-output-hk/decentralized-software-updates
  tag: e8325a440782a9c362a121340cea64a37e876e2a
-- ...

source-repository-package
  type: git
  location: https://github.com/input-output-hk/cardano-ledger-specs
  tag: 3626206b45e68499d7869a4aeeac6ed5889a490d
-- ...

source-repository-package
  type: git
  location: https://github.com/input-output-hk/ouroboros-network
  tag: 035e65bdfc2d79ccd4a204e1735c16e8307991cb
-- ...

The Cardano DevOps infrastructure repository cardano-ops, in commit 5c630ba534d0211a12f3a98fb8796b630b7a56e1 contains a script for testing the integration, and a script for benchmarking a run of the update protocol. Both scripts require a system with nix installed. We mention how to run them later on.

The integration testing script setups a testnet consisting of OBFT nodes that produce blocks, and pool nodes which register stake pools and participate in the update protocol.

In this test, an update proposal to double the maximum block size is activated, after going through the ideation and approval phases. The following steps take place:

0. Initially each pool node registers a stake pool. This is required since only active stake, i.e., stake delegated to stake pools, is considered in the stake distribution snapshot that the ledger computes and our update mechanism uses.
1. An SIP is submitted by one of the pool nodes.
2. All the pool nodes vote for the SIP.
3. After the SIP is approved, one of the pool nodes submits the implementation.
4. All the pool nodes vote for the implementation.
5. After the implementation is approved, all the pool nodes endorse it.
6. Once the proposal is endorsed, the update is activated at an epoch change.

In parallel with the steps above, two processes are run:

0. A process that submits random amounts of Lovelace to newly created keys. The goal of this process is to show that other transactions can take place during and after an update.
1. A process that monitors the update state of the ledger, printing the results on screen. This process terminates when the protocol version changes to the protocol version of the update proposal submitted in this script.

A recording of the demo can be found here.

To run this demo check out cardano-ops, and inside the root directory of this project start a tmux session and run:

./examples/priviledge-demo.sh redeploy

In the cardano-ops repository (commit 5c630ba534d0211a12f3a98fb8796b630b7a56e1) the number of nodes can be changed by editing the lists bftNodeRegionNames and poolRegionNames in topologies/pivo.nix. This repository also:

• provides additional details on how to manipulate the testnet infrastructure in examples/shelley-testnet/README.md, in the cardano-ops repository.
• explains how the tesnet can be run on an AWS cluster, also in examples/shelley-testnet/README.md.

The examples/pivo-version-change/aws-integration-test.patch patch contains an example of the changes necessary to run the integration tests with 10 pool nodes on AWS. Besides modifying the poolRegionNames this patch delays blockchain start time so that it takes place after all the nodes are deployed.

The benchmarking script implements the same logic as the test script, but it uses a larger number of transaction submission threads and voting keys. In the test script we used 10 voting keys, in the benchmarks we used a maximum of 12K voting keys instead. Also different network parameters are used so that the network can accommodate the additional load.

The benchmarks were run on AWS only because a large number of nodes needed to be deployed. To run on AWS, the examples/pivo-version-change/aws-benchmarks.patch must be applied. This patch sets a different set of network parameters for the testnet w.r.t. the integration tests, and uses a different number of nodes. Due to a quirk in the AWS testnet setup, to guarantee that everything runs smoothly first the network must be deployed and redeployed after some delay. To do this first enter the nix shell:

nix-shell

and then run:

nixops destroy --confirm && nixops  deploy -k \
  && sleep 120; ./examples/pivo-benchmark.sh redeploy

The voting process can be followed by monitoring the script's logs:

tail -f voting-process.log

Upon completion the script copies the relevant logs from the nodes so that they can be analyzed.

There is a program that processes the node logs and outputs (among other information):

• average UTxO transactions submitted during the voting period
• average latency during the voting period

The log analyzer program can be found in the menl directory, in the cardano-ops repository. It expects the node logs to be in the root directory of the cardano-ops repository. The log analyzer can be run using stack:

stack run

inside the menl directory. This program assumes that the following log files are stored in the root directory of cardano-ops:

• bft-node.log
• bft-nodes-tx-submission.log
• voting-timing.log

These log files are produced by the benchmarking script. When run on an AWS cluster, they should be copied to the machine where the logs will be analyzed.

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