DAML SDK and Canton¶
In this tutorial, you will learn how to run the Create DAML App example on Canton. This guide (together with the DAML SDK getting started guide), will teach you
- The main concepts of DAML
- How to compile your own DAML Archive (DAR)
- How to run the Create DAML App example on Canton
- How to write your own DAML code
- How to integrate a conventional application with Canton
This tutorial builds on the DAML tutorial and mainly covers the difference of running the example on a distributed setup using Canton instead of running it on the DAML sandbox. This comes with a few known problems and this section explains how to work around them.
Please run through the original DAML getting-started guide to familiarise yourself with what you are going to do first. Then, come back here to get the same example running on Canton.
Please follow the DAML SDK installation guide to get the SDK locally installed.
Starting from the location where you unpacked the Canton distribution, fetch the create-daml-app example into a directory
create-daml-app (as the example configuration files of
examples/04-create-daml-app expect the files to be there):
daml new create-daml-app create-daml-app
Then, compile the DAML code into a DAR file (this will create the file
run the code generation step used by the UI:
cd create-daml-app daml build daml codegen js .daml/dist/create-daml-app-0.1.0.dar -o daml.js
You will also need to install the dependancies for the UI:
cd ui yarn install
Next, the original tutorial would ask you to start the Sandbox and the HTTP JSON API with
We will instead start Canton using the distributed setup
examples/04-create-daml-app, and will later start the HTTP JSON API separately.
Return to the directory where you unpacked the Canton distribution, and start canton with:
bin/canton -c examples/04-create-daml-app/canton.conf --bootstrap examples/04-create-daml-app/init.canton
You may have to make the canton binary executable with
chmod +x bin/canton
This will start two participant nodes, and will allocate the parties Alice and Bob. Each participant node will expose its own ledger API:
#. Alice will be hosted by participant1, with its ledger API on port
#. Bob will be hosted by participant2, with its ledger API on port
Note that the
examples/04-create-daml-app/init.canton script performs a few setup steps to permission the parties and upload the DAR.
Leave Canton running and switch to a new terminal window.
Running the Create DAML App example¶
Right now, the Create DAML App UI is configured to use the HTTP JSON API on port
7575. Each instance of the HTTP
JSON API connects to one participant so we’ll only be able to run one instance of the UI application at a time,
connected to one participant (assuming we don’t
want to tweak the UI application).
Once Canton is running, start the HTTP JSON API connected to the ledger api on port
12011 (corresponding to Alice’s participant),
and connected to the UI on the expected port
daml json-api \ --ledger-host localhost \ --ledger-port 12011 \ --http-port 7575 \ --allow-insecure-tokens
Leave this running. The UI can then be started from a 3rd terminal window with:
cd create-daml-app/ui export REACT_APP_LEDGER_ID=participant1 yarn start
Note that we have to configure the ledger ID used by the UI to match the name of the participant that we’re running against.
This is done using the environment variable
In order to login as Alice we need to know Alice’s party ID. Return to the running instance of Canton and enter the following command to the Canton console:
The result should look something like this:
res1: PartyId = PartyId( UniqueIdentifier( Identifier("Alice"), Namespace( Fingerprint( "016e41879bcbcfb629cfd26e8287a5fd4407ad06bd8f45cdd71d27bda401802a55" ) ) ) )
In this case, Alice’s party ID is
Alice::016e41879bcbcfb629cfd26e8287a5fd4407ad06bd8f45cdd71d27bda401802a55, but your
Fingerprint will differ. Enter Alice’s party ID in the UI to login as Alice.
The Sandbox performs party allocation implicitly, which is why you didn’t need this step when running the Create DAML App example against Sandbox. Canton, as well as other production ledgers, requires explicit party allocation. See the Provisioning Identities section of the Ledger API documentation for more information.
You can login as Bob using
participant2 by following essentially the same process:
- Stop the UI and HTTP JSON API
- Restart the HTTP JSON API, this time using the option
- Restart the UI, with the ledger ID re-configured using the environment variable
- Fetch Bob’s party ID from
participant2using the Canton console
- Login using Bob’s party ID
Now that you have glimpsed at DAML and what a full DAML based solution looks like, it is maybe time for you to build your own first DAML application.
- Use the DAML language reference docs to master DAML.
- Build your own application that drives the models using one of the ledger clients.
- Create a simple UI following the example of the Create DAML App template used in this tutorial.
- Read up on how to write good DAML.
- See how to compose workflows across multiple domains.