Important

Ethereum Synchronization Domain¶

Introduction¶

Daml Enterprise includes a Canton Ethereum Sequencer integration, which interacts via an Ethereum client with a smart contract Sequencer.sol deployed on an external Ethereum network. It uses the blockchain as a source of truth for sequenced events and is currently tested with the Ethereum client Hyperledger Besu. The architecture document contains more details on the architecture of the integration.

The Ethereum Demo¶

Prerequisites¶

To run the demo, you will need access to a Daml Enterprise release, the Canton docker repository, as well as having docker, docker-compose, and Hyperledger Besu (instructions here) installed.

Introduction¶

The demo Ethereum deployment can be found inside the examples directory of the Canton Enterprise release. Unpack the Canton Enterprise release and then cd into examples/e03-ethereum-sequencer.

The script ./run.sh from the folder examples will create a new Besu testnet for the demo deployment and then start the demo. It has two scenarios: a simple and an advanced scenario. Both scenarios will start several dockerised services:

An Ethereum testnet, using four Besu nodes with the QBFT consensus protocol. This is the same for the simple and advanced scenario.
An instance of Canton. This includes two participants and a sync domain with one Ethereum sequencer for the simple scenario and two Ethereum sequencers for the advanced scenario. The respective Canton configurations are in canton-conf/simple and canton-conf/advanced.

The environment variable CANTON_VERSION is used to select the version of Canton to use for the demo deployment. This should normally be set to the version of Canton being used, but can alternatively be set to a different version or dev for the latest main build of Canton.

Simple Scenario¶

The simple scenario uses one Canton sequencer whose corresponding Sequencer.sol contract is deployed using a script before startup. It uses mutual TLS between Canton and Besu.

Advanced Scenario¶

The advanced scenario uses two Canton sequencers, mutual TLS, Ethereum wallets and uses the same script deploying Sequencer.sol.

Running a scenario¶

To start the simple or advanced demo scenario run:

<<canton-release>>/examples/e03-ethereum-sequencer$ CANTON_VERSION=<your version> ./run.sh simple

or

<<canton-release>>/examples/e03-ethereum-sequencer$ CANTON_VERSION=<your version> ./run.sh advanced

A new Besu testnet will be created and the demo will begin running with the created testnet. Once the demo is initialized and running, it will print out

******************************
Successfully initialized Canton-on-Ethereum
******************************

You will then be able to interact with the two participants via their ledger APIs (or their admin APIs) respectively running on ports 5011 and 5021 (or 5012 and 5022).

For example, you can start an instance of the Canton console to connect to the two remote participants. You can find the Canton binary in bin/canton of the Canton Enterprise release artifact.

<<canton-release>>/examples/e03-ethereum-sequencer$ ../../bin/canton -c canton-conf/remote.conf

You can then perform various commands in the Canton console:

@ remoteParticipant1.id
res5: ParticipantId = ParticipantId(
  UniqueIdentifier(Identifier("participant1"), Namespace(Fingerprint("01e69a39e2c821fc98eaeb22994b47084162122a01ebcb16dfb2514ccafcedd43d")))
)

@ remoteParticipant2.id
res6: ParticipantId = ParticipantId(
  UniqueIdentifier(Identifier("participant2"), Namespace(Fingerprint("014aeb29dddff83678bc6f1194c363c6f0d18d3a6c9655927a7fb5adc84ec0532c")))
)

@ remoteParticipant1.domains.list_connected
res7: Seq[(com.digitalasset.canton.DomainAlias, com.digitalasset.canton.DomainId)] = List(
  (Domain 'mydomain', mydomain::01537eb8...)
)

@ remoteParticipant1.health.ping(remoteParticipant2)
res8: concurrent.duration.Duration = 968 milliseconds

To shutdown and remove all Docker containers, you can execute stop-with-purge.sh:

<<canton-release>>/examples/e03-ethereum-sequencer$ ./stop-with-purge.sh

Generating a Clean Testnet¶

The directory examples/e03-ethereum-sequencer/qbft-testnet contains the script generate-testnet.sh. This automatically generates a clean Besu network in a testnet directory, including new randomized private keys. generate-testnet.sh is automatically called by run.sh but you may want to understand and edit it to create your own custom Besu deployment.

When generate-testnet.sh is run:

The state from any previous runs of generate-testnet.sh is deleted and a new directory testnet is created.
A genesis file, a set of keys for four Besu nodes and TLS certificates for Canton and Besu are automatically generated. These can be found in the folders testnet/nodei (where i has values 1 to 4) and testnet/tls. respectively.
The four Besu nodes are started via calling start-node.sh.

If the script finds Besu keys or TLS certificates in the same directory as the script, it will attempt to reuse them. This significantly reduces startup time if you want to test different network configurations.

The generated Besu testnet has been configured largely following these tutorials:

Note that the RPC HTTP APIs ETH, TXPOOL, and WEB3 of Besu need to be enabled when using the Besu driver.

Customization of the Besu network¶

The parameters of the generated testnet can be changed by modifying the genesis.json file defined inline in generate-testnet.sh. Similarly, the CLI options with which the Besu nodes are started can be configured by modifying start-node.sh

Customization of the Demo Configuration¶

You can also modify the Canton configurations and bootstrap scripts for the demo if, for example, you want to add persistence to the participants. The Canton configurations are found in

canton-conf/simple and
canton-conf/advanced

for the simple and advanced scenarios, respectively. If you want to change Ethereum-specific configuration options, (e.g. to configure a different wallet) please refer to the documentation section on this page and the corresponding scaladoc configuration option.

Note that if you change port mappings in the Canton config file you may also need to update the corresponding docker compose files in directory docker-compose/.

Error Codes¶

The Ethereum Sequencer application auto-detects many common configuration and deployment issues and logs them as warnings or errors with error codes. If you see such a warning or error, please refer to the respective error code explanation and resolution.

TLS Configuration¶

Canton supports mutual TLS between Canton and Ethereum client nodes and the demo contains an example of how to configure this. Concretely, the TLS configuration for Canton expects a key store and the path to the Ethereum TLS certificates:

_tls {
  canton-key-store {
    path="/canton/testnet-working/tls/canton_store.p12"
    password="password"
  }
  ethereum-certificate-path = "/canton/testnet-working/tls/besu_cert.pem"
}

canton.sequencers.ethereumSequencer1.sequencer.config.tls = ${_tls}

The demo also contains the utility script qbft-testnet/generate-tls.sh which is called by generate-testnet.sh and writes the TLS certificates to qbft-testnet/testnet/tls. These certificates are then used by start-node.sh.

If Canton is not configured to use TLS with an Ethereum node, it will attempt to communicate via a HTTP endpoint on the Ethereum node (and HTTPS for TLS).

For more details on the Canton configuration, please see the scaladocs of the TLS configuration. For more details on how to configure Besu to accept TLS connections (as done in the demo, see especially file start-node.sh), please see the Besu documentation.

Ethereum Accounts and Wallets¶

Canton allows you to configure an Ethereum wallet (and therefore an Ethereum account) to be used by an Ethereum sequencer application. The configured Ethereum account is used for all interactions of the Ethereum sequencer with the Ethereum blockchain. If no Ethereum account is explicitly configured, a random Ethereum account is used.

Note

When multiple Ethereum sequencer applications interact with the same Sequencer.sol instance, each Ethereum Sequencer process needs to use a separate Ethereum account. Otherwise, transactions may get stuck due to nonce mismatches.

Canton allows configuring a wallet in UTC JSON and BIP 39 format.

The Ethereum demo includes examples of mix-in wallet configuration files for both formats; the UTC JSON-based wallet mix-in looks as follows:

canton.sequencers.ethereumSequencer2.sequencer.config.wallet {
  type = "utc-json-wallet"
  password = "password"
  wallet-path = "/canton/advanced/utc-wallet.json"
}

with following utc-wallet.json:

canton.sequencers.ethereumSequencer2.sequencer.config.wallet {
  type = "utc-json-wallet"
  password = "password"
  wallet-path = "/canton/advanced/utc-wallet.json"
}

The BIP39-based wallet mix-in looks as follows:

canton.sequencers.ethereumSequencer2.sequencer.config.wallet {
  type = "utc-json-wallet"
  password = "password"
  wallet-path = "/canton/advanced/utc-wallet.json"
}

For more details, please refer to the Canton scaladoc documentation.

Deployment of the Sequencer Contract¶

Manual deployment¶

If you want to manually deploy Sequencer.sol to your Ethereum network, the file <<canton-release/examples/e03-ethereum-sequencer/qbft-testnet/Sequencer-binary contains the compiled Solidity code you need to deploy. For Besu, for example, you will need to specify the contents of Sequencer-binary in "code": "..." as documented here.

Requirements for the Ethereum Network¶

The Canton Ethereum integration is currently tested with the QBFT consensus protocol as illustrated in the demo. Other setups are possible, but they should fulfill the following requirements:

The Ethereum client Hyperledger Besu (version in release notes tested, but any sibling subminor version should be OK) should be used and expose the RPC HTTP APIs ETH, TXPOOL, and WEB3.
Currently, a free gas network is required. This means setting the gas price to zero.
The block size limit (often measured in gas, and sometimes referred to as the ‘gas limit’) must be larger than any message to be sequenced. It is recommended to set this parameter as high as possible.
The contract size limit must be big enough for the Canton Ethereum sync domain to store all required states for sequencing messages. It is recommended to set this parameter as high as possible.
Proof of authority protocols are recommended over proof of work.
Currently, consensus protocols must have immediate finality. This means that ledger forks should not occur with the chosen consensus protocol.

Furthermore, we also have some suggestions to improve throughput and latency irrespective of the choice of Ethereum client.

Throughput¶

Generally, the throughput of a Canton system using Ethereum-based sequencers is limited by the throughput of the Ethereum client. Thus, if an Ethereum-based sequencer does not deliver the desired throughput, the throughput and deployment of the Ethereum clients should be optimized in the first instance. For Besu performance optimization, some recommendations can be found in the Besu documentation - in particular, it is crucial to use a fast storage media.

Latency¶

Within a Canton transaction, there are three sequential sequencing steps, that is, a single Canton transaction leads to at least three sequential messages sent to the sequencer. This is illustrated, e.g., in the message sequence diagram of the Canton 101 section. As a result, a Canton transaction also leads to at least three Ethereum transactions within three different blocks. Thus, to achieve relatively low latencies, the Ethereum network networks must be configured with a frequent block mining frequency (configured via blockperiodseconds in Besu) and ideally co-located with the Canton sequencer node. A block mining frequency of at least one block per second is recommended.

Trust Properties of the Ethereum Sequencer Integration¶

The demo integration uses two participants and two different Ethereum Sequencer nodes. Each participant chooses its preferred Ethereum Sequencer node, and this node performs reads and writes on behalf of the participant. Therefore, each participant must trust its chosen Ethereum Sequencer node. Additionally, each participant must trust some proportion of the nodes in the Ethereum network as determined by the consensus protocol.

High Availability¶

The Ethereum sequencer currently supports connecting to just one Ethereum client node. The sequencer node monitors its dependencies and signals to its users any potential issue that would prevent it from operating correctly.

The health information is exposed as a Grpc Health service; sequencer clients use this in order to determine whether a sequencer is usable or or not. The health state is also included in the sequencer status accessible on the Admin API. In order to benefit from higher availability, clients must connect to multiple sequencers such that they can fail over automatically to healthy sequencers once some of them become unhealthy.

The following health checks are implemented:

Can the sequencer node connect and read from the Ethereum RPC API by calling the eth_synching method and check whether a result can be obtained?
Can the sequencer node connect to its database?