Re: [PATCH v2 2/7] dts: add blocking dpdk app class

[Nicholas Pratte <npratte@iol.unh.edu>]

This is perfect for my TREX implementation!

Reviewed-by: Nicholas Pratte <npratte@iol.unh.edu>

On Fri, Mar 14, 2025 at 9:19 AM Luca Vizzarro <luca.vizzarro@arm.com> wrote:
>
> Add BlockingDPDKApp class. Some non-interactive applications are
> blocking and run until the user interrupts them. As their main intended
> usage is to be kept running in the background, this class exploits
> InteractiveShell to spawn a dedicated shell to keep the blocking
> application running, while detaching from it.
>
> This class works by providing the `wait_until_ready` and `close`
> methods. The former starts up the application and returns only when the
> application readiness output ends in the string provided as an argument
> to the same method. Whereas the latter works by simulating a Ctrl+C
> keystroke, therefore sending a SIGINT to the app.
>
> Signed-off-by: Luca Vizzarro <luca.vizzarro@arm.com>
> Reviewed-by: Paul Szczepanek <paul.szczepanek@arm.com>
> ---
>  dts/framework/remote_session/dpdk_app.py      | 73 +++++++++++++++++++
>  dts/framework/remote_session/dpdk_shell.py    |  3 +-
>  .../single_active_interactive_shell.py        | 12 ++-
>  dts/framework/remote_session/testpmd_shell.py |  2 +-
>  4 files changed, 85 insertions(+), 5 deletions(-)
>  create mode 100644 dts/framework/remote_session/dpdk_app.py
>
> diff --git a/dts/framework/remote_session/dpdk_app.py b/dts/framework/remote_session/dpdk_app.py
> new file mode 100644
> index 0000000000..c9945f302d
> --- /dev/null
> +++ b/dts/framework/remote_session/dpdk_app.py
> @@ -0,0 +1,73 @@
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2025 Arm Limited
> +
> +"""Class to run blocking DPDK apps in the background.
> +
> +The class won't automatically start the app. The start-up is done as part of the
> +:meth:`BlockingDPDKApp.wait_until_ready` method, which will return execution to the caller only
> +when the desired stdout has been returned by the app. Usually this is used to detect when the app
> +has been loaded and ready to be used.
> +
> +Example:
> +    ..code:: python
> +
> +        pdump = BlockingDPDKApp(
> +            PurePath("app/dpdk-pdump"),
> +            app_params="--pdump 'port=0,queue=*,rx-dev=/tmp/rx-dev.pcap'"
> +        )
> +        pdump.wait_until_ready("65535") # start app
> +
> +        # pdump is now ready to capture
> +
> +        pdump.close() # stop/close app
> +"""
> +
> +from pathlib import PurePath
> +
> +from framework.params.eal import EalParams
> +from framework.remote_session.dpdk_shell import DPDKShell
> +
> +
> +class BlockingDPDKApp(DPDKShell):
> +    """Class to manage blocking DPDK apps."""
> +
> +    def __init__(
> +        self,
> +        path: PurePath,
> +        name: str | None = None,
> +        privileged: bool = True,
> +        app_params: EalParams | str = "",
> +    ) -> None:
> +        """Constructor.
> +
> +        Overrides :meth:`~.dpdk_shell.DPDKShell.__init__`.
> +
> +        Args:
> +            path: Path relative to the DPDK build to the executable.
> +            name: Name to identify this application.
> +            privileged: Run as privileged user.
> +            app_params: The application parameters. If a string or an incomplete :class:`EalParams`
> +                object are passed, the EAL params are computed based on the current context.
> +        """
> +        if isinstance(app_params, str):
> +            eal_params = EalParams()
> +            eal_params.append_str(app_params)
> +            app_params = eal_params
> +
> +        super().__init__(name, privileged, path, app_params)
> +
> +    def wait_until_ready(self, end_token: str) -> None:
> +        """Start app and wait until ready.
> +
> +        Args:
> +            end_token: The string at the end of a line that indicates the app is ready.
> +        """
> +        self._start_application(end_token)
> +
> +    def close(self) -> None:
> +        """Close the application.
> +
> +        Sends a SIGINT to close the application.
> +        """
> +        self.send_command("\x03")
> +        self._close()
> diff --git a/dts/framework/remote_session/dpdk_shell.py b/dts/framework/remote_session/dpdk_shell.py
> index 0962414876..f7ea2588ca 100644
> --- a/dts/framework/remote_session/dpdk_shell.py
> +++ b/dts/framework/remote_session/dpdk_shell.py
> @@ -65,13 +65,14 @@ def __init__(
>          self,
>          name: str | None = None,
>          privileged: bool = True,
> +        path: PurePath | None = None,
>          app_params: EalParams = EalParams(),
>      ) -> None:
>          """Extends :meth:`~.interactive_shell.InteractiveShell.__init__`."""
>          app_params = compute_eal_params(app_params)
>          node = get_ctx().sut_node
>
> -        super().__init__(node, name, privileged, app_params)
> +        super().__init__(node, name, privileged, path, app_params)
>
>      def _update_real_path(self, path: PurePath) -> None:
>          """Extends :meth:`~.interactive_shell.InteractiveShell._update_real_path`.
> diff --git a/dts/framework/remote_session/single_active_interactive_shell.py b/dts/framework/remote_session/single_active_interactive_shell.py
> index c1369ef77e..2257b6156b 100644
> --- a/dts/framework/remote_session/single_active_interactive_shell.py
> +++ b/dts/framework/remote_session/single_active_interactive_shell.py
> @@ -92,6 +92,7 @@ def __init__(
>          node: Node,
>          name: str | None = None,
>          privileged: bool = False,
> +        path: PurePath | None = None,
>          app_params: Params = Params(),
>          **kwargs,
>      ) -> None:
> @@ -105,6 +106,7 @@ def __init__(
>              name: Name for the interactive shell to use for logging. This name will be appended to
>                  the name of the underlying node which it is running on.
>              privileged: Enables the shell to run as superuser.
> +            path: Path to the executable. If :data:`None`, then the class' path attribute is used.
>              app_params: The command line parameters to be passed to the application on startup.
>              **kwargs: Any additional arguments if any.
>          """
> @@ -116,7 +118,7 @@ def __init__(
>          self._privileged = privileged
>          self._timeout = SETTINGS.timeout
>          # Ensure path is properly formatted for the host
> -        self._update_real_path(self.path)
> +        self._update_real_path(path or self.path)
>          super().__init__(**kwargs)
>
>      def _setup_ssh_channel(self):
> @@ -133,7 +135,7 @@ def _make_start_command(self) -> str:
>              start_command = self._node.main_session._get_privileged_command(start_command)
>          return start_command
>
> -    def _start_application(self) -> None:
> +    def _start_application(self, prompt: str | None = None) -> None:
>          """Starts a new interactive application based on the path to the app.
>
>          This method is often overridden by subclasses as their process for starting may look
> @@ -141,6 +143,10 @@ def _start_application(self) -> None:
>          `self._init_attempts` - 1 times. This is done because some DPDK applications need slightly
>          more time after exiting their script to clean up EAL before others can start.
>
> +        Args:
> +            prompt: When starting up the application, expect this string at the end of stdout when
> +                the application is ready. If :data:`None`, the class' default prompt will be used.
> +
>          Raises:
>              InteractiveCommandExecutionError: If the application fails to start within the allotted
>                  number of retries.
> @@ -151,7 +157,7 @@ def _start_application(self) -> None:
>          self.is_alive = True
>          for attempt in range(self._init_attempts):
>              try:
> -                self.send_command(start_command)
> +                self.send_command(start_command, prompt)
>                  break
>              except InteractiveSSHTimeoutError:
>                  self._logger.info(
> diff --git a/dts/framework/remote_session/testpmd_shell.py b/dts/framework/remote_session/testpmd_shell.py
> index 1f291fcb68..db1bfaa9d1 100644
> --- a/dts/framework/remote_session/testpmd_shell.py
> +++ b/dts/framework/remote_session/testpmd_shell.py
> @@ -1540,7 +1540,7 @@ def __init__(
>          """Overrides :meth:`~.dpdk_shell.DPDKShell.__init__`. Changes app_params to kwargs."""
>          if "port_topology" not in app_params and get_ctx().topology.type is TopologyType.one_link:
>              app_params["port_topology"] = PortTopology.loop
> -        super().__init__(name, privileged, TestPmdParams(**app_params))
> +        super().__init__(name, privileged, app_params=TestPmdParams(**app_params))
>          self.ports_started = not self._app_params.disable_device_start
>          self._ports = None
>
> --
> 2.43.0
>