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Run back-end in Host Mode

When developing an application, it is often important to easily test and debug it. For that matter, it is possible to run the Cartesi Rollups environment in host mode, so that the dApp's back-end can be executed directly on the host machine, allowing it to be debugged using regular development tools such as an IDE.



When running in host mode, localhost port 5004 will be used by default to allow the dApp's back-end to communicate with the Cartesi Rollups framework.

Step 1: Run the environment

The first step is to run the environment in host mode:

docker compose -f ../docker-compose.yml -f ./docker-compose.override.yml -f ../docker-compose-host.yml up

If you are using macOS, please add the line platform: linux/amd64 under the server_manager service in the file, located in the root of the cloned rollups-examples repository.


If you have PostgreSQL and Redis already installed on your system, you may encounter port conflicts when the Docker containers attempt to start services on ports that are already in use. To resolve these conflicts, edit the ports for Redis and PostgreSQL in the docker-compose.yml file located in the root directory of your dApp.

Step 2: Run the application back-end

The next step is to run the application back-end in your machine. Before proceeding, ensure that you have installed the dependencies and libraries required for your selected language. For example, if the code is written in Python, you will need to have python3 installed.

If you are using the echo-python example, in order to start the back-end, run the following commands in a dedicated terminal:

cd echo-python/
python3 -m venv .venv
. .venv/bin/activate
pip install -r requirements.txt

Step 3: Check output

After the back-end successfully starts, it should print an output like the following:

INFO:__main__:HTTP rollup_server url is
INFO:__main__:Sending finish

Step 4: Interact with the application

With the infrastructure in place, you can use our frontend-console application to interact with your dApp by following the steps:

  1. Open a separate terminal window
  2. From the rollups-examples base directory, navigate to the frontend-console one:
cd frontend-console
  1. Build the frontend console application:
yarn build
  1. Send an input to the current locally deployed dApp:
yarn start input send --payload "Hello, Cartesi."
  1. For instance, the echo-python dApp "echoes" each input it receives by generating a corresponding output notice based on your input. To check these notices, run the following command:
yarn start notice list

After completing all the steps above, you should get a response with the payload of the notice:

"Hello, Cartesi."


Although we used the echo-python dApp as a specific example, it's important to understand that not all dApps generate notices in the same manner. Your dApp may have different behaviors or responses related to notices. However, we hope this example provides a clear understanding and a helpful starting point.


How to automatically restart the back-end

The final command will effectively run the back-end and send corresponding outputs to port 5004. It can optionally be configured in an IDE to allow interactive debugging using features like breakpoints.

You can also use a tool like entr to restart the back-end automatically when the code changes. For example:

ls *.py | ROLLUP_HTTP_SERVER_URL="" entr -r python3

How to stop containers

Stop the containers using ctrl+c then remove the containers and the volumes: Stop the containers using ctrl+c then remove the containers and the volumes:

docker compose -f ../docker-compose.yml -f ./docker-compose.override.yml -f ../docker-compose-host.yml down -v

Every time you stop the docker compose ... up command with ctrl+c, you need to run the docker compose ... down -v command to remove the volumes and containers. Ignoring this will preserve outdated information in those volumes, causing unexpected behaviors, such as failure to reset the hardhat localchain.

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The Cartesi Project is commissioned by the Cartesi Foundation.

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