This feature is only available in Canton Enterprise
The Canton-on-Fabric integration runs a Canton domain where events are sequenced using the Hyperledger Fabric ledger.
To run the demo Canton Fabric deployment, you will need access to the following:
- a Canton Enterprise release for the example files and the Canton enterprise binary
- Canton Enterprise docker repository access, in order to have access to the Canton docker image
Also make sure to have docker and docker-compose installed.
The following example explains how to set up Canton on Fabric using a topology with 2 sequencer nodes, (belonging to two different organizations) a domain manager, a mediator, and two participants nodes.
The demo can be found in the examples directory of the Canton Enterprise release.
Unpack the Canton Enterprise release and then
Run the script
The script will start the following:
- A Fabric ledger with 2 peers and one orderer node.
- Two Canton Sequencer nodes that interact with the Fabric ledger.
- A Canton process running a Canton domain manager, a mediator, and 2 participants. The configuration for this Canton process is in
Once the script has finished setting up (you should see the
canton service print “Successfully initialized Canton-on-Fabric” together with the Canton console startup message), you will be able to interact with the two participants using the config at
You can start an instance of the Canton console to connect to the two remote participants (provided you have also installed Canton):
<<canton-release>>/examples/e01-fabric-domain/canton-on-fabric$ ../../../bin/canton -c config/remote/demo.conf
You can then perform various commands in the Canton console:
@ remoteParticipant1.id res1: ParticipantId = PAR::participant1::012c7af9... @ remoteParticipant1.domains.list_connected res2: Seq[(com.digitalasset.canton.DomainAlias, com.digitalasset.canton.DomainId)] = List((Domain 'myDomain', myDomain::01dafa04...)) @ remoteParticipant1.health.ping(remoteParticipant2) res3: concurrent.duration.Duration = 946 milliseconds
The example files located at
examples/e01-fabric-domain/canton-on-fabric provide you with more flexibility than to run the basic demo just shown.
You will find in this directory our main script called
run.sh. If you run the script, it will show you the help instructions with all the options that you can choose to run the deployment with.
The demo deployment will by default use the Canton version from the release.
If you wish to use a different version, you can specify it with the
environment variable. For example,
export CANTON_VERSION=2.0.0 to use Canton v2.0.0.
You can choose
dev for the latest main build of Canton.
Depending on which options you choose, it will run a docker-compose command using a different subset of the following docker-compose files below:
docker-compose-ledger.yaml: Sets up the Fabric ledger. You can see that there is a service in it called
ledger-setupthat is a service responsible for creating the crypto materials, setting up the channel and deploying the chaincode. It uses a customized and simplified version of the
test-networkfrom fabric-samples inside a docker container.
docker-compose-blockchain-explorer.yaml: Runs a blockchain explorer that allows visualizing the Fabric ledger on the browser.
docker-compose-canton.yaml: Runs all canton components: a domain manager, a mediator, the two Fabric sequencer(s) and two participants.
The bootstrapping process of the distributed domain is done by the
docker-compose-canton.yaml docker-compose file which uses the
If you wish to learn more about this process please refer to domain bootstrapping.
Run with Docker Compose¶
run.sh works by running
docker-compose using a different combination of the
files shown above, depending on the arguments given to the script.
As was shown, to run Canton with two Fabric Sequencers in a multi-sequencer setup, run
That is equivalent to running the following docker-compose command:
<<canton-release>>/examples/e01-fabric-domain/canton-on-fabric$ COMPOSE_PROJECT_NAME="fabric-sequencer-demo" docker-compose -f docker-compose-ledger.yaml -f docker-compose-canton.yaml up
Note that you can at this point connect the remote participants to this setup just like in demo from the tutorial.
When you’re done running the sequencer, make sure to run
This will clean up all docker resources so that the next run can happen smoothly.
Using the Canton Binary instead of docker¶
To run the full Canton setup separately outside of docker (with the canton binary or jar):
<<canton-release>>/examples/e01-fabric-domain/canton-on-fabric$ ./run.sh ledger
After a few seconds you should see the two peers and one orderer nodes are up by running
docker ps and
hyperledger/fabric-peer containers exposing ports 9051 and 7051 and one
exposing the port 7050. Next run the following:
<<canton-release>>/examples/e01-fabric-domain/canton-on-fabric$ ../../../bin/canton -c config/self-contained/demo.conf --bootstrap config/canton/demo.canton
To run the jar file instead of the canton binary, simply replace
../../../bin/canton above with
java -jar ../../../lib/canton-enterprise-*.jar.
If you wish to start the Hyperledger Blockchain Explorer
to browse activity on the running Fabric Ledger,
-e flag when running
Alternatively you can use docker-compose as shown before and add
You will then be able to see the explorer web UI in your browser if you go to
You can start the explorer separately after the ledger has been started by simply running the following command:
<<canton-release>>/examples/e01-fabric-domain/canton-on-fabric$ COMPOSE_PROJECT_NAME="fabric-sequencer-demo" docker-compose -f docker-compose-blockchain-explorer.yaml up
Note that even when the explorer is working perfectly, it might output some error messages like the following which can be safely ignored:
[ERROR] FabricGateway - Failed to get block 0 from channel undefined : TypeError: Cannot read property 'toString' of undefined
The Fabric Sequencer operates on top of the Fabric Ledger and uses it as the source of truth for the state of the sequencer (all the messages and the order of them).
In order for The Fabric Sequencer to successfully operate on a given Fabric Ledger, that ledger must have been set up with at least one channel where the Canton Sequencer chaincode has been installed and the sequencer needs to be configured properly to have access to the ledger.
As mentioned previously, for our demo setup we use a slightly modified version of
test-network scripts from fabric-samples inside a docker container
to setup a simple local docker-based Fabric network.
This script uses many of the Fabric CLI commands
to set up this network, such as configtxgen,
peer chaincode, and
In a real-life scenario one might use this CLI to set up the ledger or some specific UI provided by a cloud service provider
that hosts Blockchain services.
Regarding the chaincode setup, the Fabric Sequencer expects that the chaincode is initialized by calling the function
init (no arguments needed) and with the
--isInit flag turned on.
You can find the chaincode source at
In order to configure a Fabric Sequencer in Canton, make sure to set
canton.sequencers.<your sequencer>.sequencer.type = "fabric".
The rest of the Fabric sequencer-specific config will be under
Within this subconfig, you’ll need to set the
user key with Fabric client details so that the sequencer can invoke chaincode functions and read from the ledger.
You’ll also need to set
organizations details which include peers and orderers connection details that the sequencer will have access to.
The sequencer needs access to at least enough peers to fulfil the chaincode endorsement policy
that has been configured (more info below at High Availability).
It is possible to indicate the channel name with the
channel.name key and the chaincode name with the
channel.chaincode.name key (defaults to “sequencer”).
This is all exemplified, including extensive commentary, in the config file used for the first sequencer of the demo, which you
can find at
By default, the sequencer application will start reading blocks from the ledger from the genesis block.
We can signal a later starting point by setting
channel.chaincode.start-block-height to a specific number
in case the chaincode has been deployed much later than genesis.
Block Cutting Parameters and Performance¶
It is possible to configure the block cutting parameters of the ledger by changing the file at
The relevant parameters are the following:
Orderer.BatchTimeout: The amount of time to wait before creating a block.
Orderer.BatchSize.MaxMessageCount: The maximum number of transactions to permit in a block (block size).
Note: In other kinds of Fabric Ledger setups, one should be able to configure these parameters in different ways.
If your use case operates under high traffic, you may benefit from increasing the block size in order to increase your throughput at the expense of latency. If you care more about latency and don’t need to support high traffic, then decreasing block size will be of help.
Currently, we have set the values of 200ms for batch timeout and 50 for block size as it has empirically shown to be a good tradeoff after some rounds of long running tests, but feel free to pick parameters that fit your use-case best.
Note: See slide 17 of http://www.mscs.mu.edu/~mascots/Papers/blockchain.pdf for a discussion on block size influence on throughput and latency.
Fabric Policies can be used to define how members come to agreement on accepting or rejecting changes to the network, a channel or a smart contract.
Versatile policies can be written using combinations of
NOutOf (more detail here).
See other kinds of policies here.
See the section below on High Availability for more information on creating endorsement policies from the point of view of availability.
When configuring the Fabric sequencer, make sure to provide access to at least enough peers to fulfill the chaincode endorsement policy that has been configured.
Access to additional peers may also be configured, to make the setup more highly available and to avoid a scenario where the crash of one peer would cause transactions to stop going through due to lack of enough endorsements.
This article by the University of Groningen goes into some detail on how to define proper endorsement policies. The key takeaway for our purposes is: if the endorsement policy requires all organizations to provide endorsements, a risk of unavailability emerges since if just one organization doesn’t have any peers running, the whole transaction workflow is halted. On the other hand, if the endorsement policy is something like 2 organizations out of 10 need to provide endorsements, then there is an integrity risk, since only 2 malicious organizations are enough to collude and and endorse invalid transactions. Thus, there is an availability vs integrity tradeoff (the article talks about a confidentiality vs integrity tradeoff, but confidentiality is not relevant for our purposes). The right balance for a particular deployment depends on the trust assumptions for the different organizations and how available each organization is expected to be.
You can find more information on high availability for Hyperledger Fabric components on this blog post.
If a client is connected to more than one Fabric Sequencer and each sequencer defines a different set of connections to Fabric peers (and orderers), the client will benefit from another level of availability. If of the sequencers is not healthy, the client will simply fail over to the ones that are still healthy.