[lttng-dev] [babeltrace2]about python self-defined plugin loading

[Wu, Yannan]

ok thanks for the help. I will try it later

Amanda

________________________________
From: Simon Marchi <simark at simark.ca>
Sent: Friday, April 26, 2024 10:57:59 PM
To: Wu, Yannan; Kienan Stewart; lttng-dev at lists.lttng.org
Subject: RE: [EXTERNAL] [lttng-dev] [babeltrace2]about python self-defined plugin loading

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On 2024-04-26 09:56, Wu, Yannan via lttng-dev wrote:
> Hihi, Kienan,
>
> I finally find a workaround. I could success with the following code:
> file_name = "bt_plugin_latency_filter.py"
> current_directory=os.getcwd()
>
> file_path = os.path.join(current_directory, file_name)
> pset=bt2.find_plugins_in_path(file_path)
>
> forplugininpset:
> if plugin.name=="latency_filter"andhasattr(plugin,"filter_component_classes"):
>
>     latency_filter_comp_cls=plugin.filter_component_classes['LatencyFilter']
>
> But loading the whole directory, it just doesnt work from command line.
> Amanda

So, since this works, it confirms that your babeltrace build has support
for Python plugins.  Then there's no reason for your original example
using babeltrace-fun-plugins/my-first-components not to work.

When running the command:

  babeltrace2 --plugin-path . -c source.demo.MyFirstSource -c sink.demo.MyFirstSink

is your working directory babeltrace-fun-plugins/my-first-component?
`--plugin-path .` refers to the current working directory, so it must be
the directory that directly contains the `bt_plugin_*.py` file.

I made an example with docker to show it working, hopefully this can
help you figure out what's wrong on your side.  Put this inside a
`Dockerfile` file:

```
FROM debian:12

RUN apt-get -y update
RUN apt-get -y full-upgrade
RUN apt-get -y install babeltrace2 git
RUN git clone https://github.com/simark/babeltrace-fun-plugins.git
WORKDIR /babeltrace-fun-plugins/my-first-components
ENTRYPOINT babeltrace2 --plugin-path . -c source.demo.MyFirstSource -c sink.demo.MyFirstSink
```

Then, do either (whatever works for you):

  $ docker buildx build -t bt2-example .
  $ docker build -t bt2-example .

And finally:

  $ docker run -it bt2-example
  Stream beginning
  event my-event, timestamp 123
  Stream end

This last command runs babeltrace2, loading the Python plugin from
babeltrace-fun-plugins/my-first-components.

Finally, to investigate more in depth, you can increase the log level of
babeltrace2, like so:

  $ babeltrace2 --log-level DEBUG --plugin-path . -c source.demo.MyFirstSource -c sink.demo.MyFirstSink

This will output all sorts of things about babeltrace looking for
plugins and trying to load them.

Simon
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