Command-line Arguments

Canton supports a variety of command line arguments. Please run bin/canton --help to see all of them. Here, we explain the most relevant ones.

Selecting a Configuration

Canton requires a configuration file to run. There is no default topology configuration built in and therefore, the user needs to at least define what kind of node (domain or participant) and how many they want to run in the given process. Sample configuration files can be found in our release package, under the examples directory.

When starting Canton, configuration files can be provided using

bin/canton --config conf_filename -c conf_filename2

which will start Canton by merging the content of conf_filename2 into conf_filename. Both options -c and --config are equivalent. If several configuration files assign values to the same key, the last value is taken. The section on static configuration explains how to write a configuration file.

You can also specify config parameters on the command line, alone or along with configuration files, to specify missing parameters or to overwrite others. This can be useful for providing simple short config info. Config parameters can be provided using -C:

bin/canton --config conf_filename -C canton.participants.participant1.storage.type=memory

Run Modes

Canton can run in three different modes, depending on the desired environment and task.

Interactive Console

The default method to run Canton is in the interactive mode. The process will start a command line interface (REPL) which allows to conveniently operate, modify and inspect the Canton application.

In this mode, all errors will be reported as CommandExecutionException to the console, but Canton will remain running.

The interactive console can be started together with a script, using the --boostrap-script=... option. The script uses the same syntax as the console.

The interactive mode is useful for development, education and expert use.

Daemon

If the console is undesired such as in server operation, Canton can be started in daemon mode

bin/canton daemon --config ...

All configured entities will be automatically started and will resume operation.

A failure to connect to the database storage will lead the process to exit with a non-zero exit code. This can be turned off using:

canton.participants.participant1.storage.parameters.fail-fast-on-startup = "no"

Any failures encountered while running the bootstrap script will immediately shutdown the Canton process with a non-zero exit code.

Nodes started in daemon mode can be administrated by setting up a remote console that provides the interactive user experience, while the nodes run in a separate process.

Headless Script Mode

For testing and scripting purposes, Canton can also start in headless script mode:

bin/canton run <script-path> --config ...

In this case, commands are specified in a script rather than executed interactively. Any errors with the script or during command execution should cause the Canton process to exit with a non-zero exit code.

Interactive Server Process using Screen

In some situations, we find it convenient to run even a server process interactively. For server use on Linux / OSX, this can be accomplished by using the screen command:

screen -S canton -d -m ./bin/canton -c ...

will start the Canton process in a screen session named canton which does not terminate on user-logout and therefore allows to inspect the Canton process whenever necessary.

A previously started process can be joined using

screen -r canton

and an active screen session can be detached using CTRL-A + D (in sequence). Be careful and avoid typing CTRL-D, as it will terminate the session. The screen session will continue to run even if you log out of the machine.

Java Virtual Machine Arguments

The bin/canton application is a convenient wrapper to start a Java virtual machine running the Canton process. The wrapper supports providing additional JVM options using the JAVA_OPTS environment variable or using the -D command line option.

For example, you can configure the heap size as follows:

JAVA_OPTS="-Xmx2G" ./bin/canton --config ...

There are several log related options that can be specified. Refer to Logging for more details.