Project

Amaru

An alternative Rust node client for the Cardano blockchain. Aimed as an entrypoint for client applications initially, it aspires to become a full block-producing node running side-by-side the Haskell nodes to further increase the decentralisation of the platform while fostering its rich open source ecosystem.

Goal

Build a new fully interoperable block-producing Cardano node.

One of the core objectives is to achieve a full block-producing Cardano node which can run side-by-side the existing Haskell nodes in a fully interoperable manner. The project is ambitious and spans over many areas such as networking, cryptography or language theory. It is developed from several parts each covering a different aspect of the node and its surrounding ecosystem.

Besides, Amaru is also geared towards developer experience and aims at providing easy to grasp interfaces using widely spread technologies such as gRPC while maintaining compatibility with the strong ecosystem of middlewares, such as Ogmios or Oura, that constitutes the backbone of Cardano services.

Maintainers

Matthias Benkort Technical Director @ Cardano Foundation

Santiago Carmuega CEO @ TxPipe

Journey

An incremental roadmap in 4-phases.

Phase 1 Q1 2024 April May June/July Phase 2 Q3 2024 December Phase 3 Q2 2025 Phase 4

Client node

A node capable of synchronizing the chain from a (remote) trusted peer, and serve the data to client applications through an API query layer.

Such a node is most useful for decentralised applications building on the blockchain. It doesn't however take part in the consensus nor help to propagate blocks on the network.

A full relay node as an entrypoint to the network is still required at this point.

Workshop at Buidler Fest

Organize workshop(s) during the Buidler Fest second day to gather builders feedback and insights about what they would expect from an alternative node.

Chain-Synchronization PoC

Perform basic chain-synchronization of the latest Cardano era through Dolos to demonstrate the capabilities of the base Rust primitives.

(Partial) validator

Apply a subset of the ledger rules to partially validate transactions sent through the node in an attempt to provide better user feedback, and in the longer run, prepare the ground for a relay node.

Chain synchronization (single relay)

Chain synchronization (single relay)

We must ensure that data can be synchronized from another source and made accessible to client applications.

At this point, we assume that all data comes from a single trusted relay (i.e. a Haskell node).

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Read-only client APIs

Read-only client APIs

The primary goal of a client node is to be a read-only entrypoint for client applications. So it must provide an API for accessing the stored data.

We aim to support the legacy Ouroboros node-to-client mini-protocols to ensure interoperability with the existing ecosystem as well as the new utxoRPC specification.

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Transaction Submission Proxy

Transaction Submission Proxy

A read-only node is useful but relatively limited to observing the chain. Having easy ways to alter the blockchain state by accepting transaction is thus a necessary feature.

We intend to let client applications submit through the client node, by proxying transactions to its underlying trusted peer, while performing extra validation upfront to improve the user experience associated with transaction submission.

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Minimal Viable Ledger

Minimal Viable Ledger

In order to provide some useful transaction submission capabilities, we must perform some ledger validation upfront. More specifically, we are interested in validation that only requires protocol parameters but not a full ledger state yet.

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Packaging & distribution

Packaging & distribution

A software is meant to be used. Which means that we must ensure prompt delivery and make it easy to consume and operate.

This work packages covers anything from build artifacts to monitoring.

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Companion dApp examples

Companion dApp examples

The best way to ensure that we build the right software is by using it. With the alternative node, we want to build applications that make use of it and witness the product of our making.

Such example applications also serve a double-purpose of being useful documentation pieces.

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Relay node

A node capable of validating (at least partially) blocks seen on the network and propagate them by taking part in the p2p gossiping between nodes. It can also seemingly follow the chain from multiple peers by performing adequate chain selection.

Such node doesn't yet take part in the consensus and cannot produce blocks. It can however fully replace any relay and is, from the perspective of any external observer, a Cardano relay node.

Hybrid Testnet

While a relay node isn't capable of producing blocks on its own, it should perfectly blend in a hybrid testnet comprises of classic Haskell nodes acting as block producers and Amaru relay nodes.

If you are a stake pool operator on Cardano, we welcome you to reach out and help us launch this into orbit.

Dynamic peer management

Dynamic peer management

A peer-to-peer and Byzantine fault tolerant decentralised network requires some specific peer management. Cardano currently uses a hot/warm/cold peer management system where each node maintain active connection with peers based on their stake and how they perform in their networking activities.
Consensus chain selection

Consensus chain selection

In a decentralised network where anyone can propose not only addition, but past history of the chain, an algorithm for choosing which chain to follow is crucial.

While relatively simple in the PoW world, it has proven a significant challenge in PoS systems like Cardano.
(partial) Transaction stage-1 validations

(partial) Transaction stage-1 validations

In order to validate blocks, one must first validate transactions (since blocks are mostly made of transactions). There is a variety of ledger rules covering all aspects of transactions from fees to authorized governance actions.

At first, since we will initially operate on short-lived testnets, we are mostly interested in validating in actions other than governance and protocol changes.
Transaction stage-2 validations

Transaction stage-2 validations

Transaction validation in Cardano is done in two stages. The first stage ensures that transactions are structurally valid and can be fully executed (e.g. they spend valid inputs and provide the right amount of fees).

If the 1st stage passes, we move on to the second validation stage which evaluates any scripts present in the transaction. This happens by running Plutus Core programs in the Plutus Virtual Machine.
Reward calculations

Reward calculations

The ledger in the node builds and maintains a state of the blockchain which is commonly referred to as the ledger state. In an eUTxO blockchain like Cardano, this includes the current UTxO set and protocol parameters.

It also includes the state of each reward account that are passively gathering rewards on every epoch. The tracking of rewards is a challenging task, hence why it deserves its own work package.
TestNet(s)

TestNet(s)

Let's test things, together. The idea behind the development of Amaru is to onboard as many developers and enthusiasts on the journey. This is only possible if we allow people to run their own node and interact with Amaru directly.

While still in development, many parts may be considered unstable and we wouldn't want to disrupt the activities of the Cardano mainnet, or even the PreProd testnet. We will thus favor having isolated short-lived testnets at first.

Full node

A node that can produce blocks and take part to the consensus. It can monitor the leader schedule, manage a mempool, forge blocks and follow protocol updates (hard-forks).

A full node is not however capable of validating the historical chain. Instead, it always bootstrap from a snapshot constructed from an archive node.

(full) Transaction stage-1 validations

(full) Transaction stage-1 validations

Any ledger rules and validations that we left aside for the Relay phase should be implemented, if any.

This should mostly include protocol updates and hard-fork-related elements that were deemed unnecessary for relays and preliminary testnets.
Hard-fork combinator

Hard-fork combinator

Cardano's upgrade system is built around the well-known Hard-Fork Combinator. Behind this fancy term lies a piece of software which ensures that multiple protocols (a.k.a eras) can be combined into one sequence.

This is done in such way that prevents elements from previous eras do not conflict with new eras. It also allows the switch to happen smoothly at runtime and works across the uncertainty that comes with a Byzantine fault-tolerant system.
Block forging

Block forging

The main purpose of a block-producing node is to produce blocks! This is also referred to as block forging and includes various tasks such as mempool management and validation, as well as authentication through signing and VRF proving.
Full block validation & propagation

Full block validation & propagation

At this point in the development, we should be able to fully validate block headers and ensure their validity against the leader schedule computed at the beginning of each epoch.

Archive node

A node that can validate any historical part of the chain, including the Byron era of Cardano. Its purpose is to produce ledger and blockchain snapshot usable by full nodes.

At this point, it is unclear whether we want to build this, for the current Haskell nodes already fullfil that role and there's at this point no clear benefits in building an alternative.

Historical validations

Historical validations

A working block-producing node only needs to be able to validate blocks of the current network era (up to a few blocks in the past). Yet, Cardano is live since September 2017 and has already gone through many eras.

While not necessary (because software such as the Haskell node can already do so), being able to re-validate the entire chain is an interesting task that would bring a nice sense of completion to the project.
Snapshots aggregation & creation

Snapshots aggregation & creation

A direct application of historical validation is the ability to produce configuration snapshot to bootstrap block producing and relay node.

Snapshots can in the long-run be fully authenticated by Mithril which provides a robust stake-based threshold multi-signature mechanism.

Getting started