On Sun, Aug 14, 2022 at 4:48 AM zenan <dantefu9...@163.com> wrote: > > In command line, I use “babeltrace2 net://somehost/some-session” to read live > lttng session trace, and I want to use python bindings to do the same, is it > possible? > > here is my code:
Almost there. Some `src.ctf.lttng-live` component and message iterator methods may return a "try again" status code (I don't remember exactly under which circumstances). This propagates to bt_graph_run() [1] (in C) eventually which itself returns `BT_GRAPH_RUN_STATUS_AGAIN`. The Python bt2.Graph.run() method translates this status code to throwing `bt2.TryAgain`. Just catch those `bt2.TryAgain`, wait a bit, and call `graph.run()` again: # Run the trace processing graph. while True: try: graph.run() except bt2.TryAgain: time.sleep(.1) Works for me. If you ever need to access the messages themselves instead of forwarding them to a `sink.text.pretty` component, then use a `bt2.TraceCollectionMessageIterator` instance [2]. Hope it helps, Phil [1]: https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#gad2e1c1ab20d1400af1b552e70b3d567c [2]: https://babeltrace.org/docs/v2.0/python/bt2/examples.html#iterate-trace-events > > import bt2 > import sys > > # Create an empty graph. > graph = bt2.Graph() > > # Add a `source.text.dmesg` component. > # > # graph.add_component() returns the created and added component. > # > # Such a component reads Linux kernel ring buffer messages (see > # `dmesg(1)`) from the standard input and creates corresponding event > # messages. See `babeltrace2-source.text.dmesg(7)`. > # > # `my source` is the unique name of this component within `graph`. > > # the original source code here in the example is: > # comp_cls = bt2.find_plugin('text').source_component_classes['dmesg'] > # src_comp = graph.add_component(comp_cls,'my source') > comp_cls = bt2.find_plugin('ctf').source_component_classes['lttng-live'] > src_comp = graph.add_component(comp_cls, 'my source', params = { > 'inputs': [sys.argv[1]], > }) > > # Add a `sink.text.pretty` component. > # > # Such a component pretty-prints event messages on the standard output > # (one message per line). See `babeltrace2-sink.text.pretty(7)`. > # > # The `babeltrace2 convert` CLI command uses a `sink.text.pretty` > # sink component by default. > comp_cls = bt2.find_plugin('text').sink_component_classes['pretty'] > sink_comp = graph.add_component(comp_cls, 'my sink') > > # Connect the `out` output port of the `source.text.dmesg` component > # to the `in` input port of the `sink.text.pretty` component. > graph.connect_ports(src_comp.output_ports['out'], sink_comp.input_ports['in']) > > # Run the trace processing graph. > graph.run() > > > > > > 发件人: Philippe Proulx > 发送时间: 2022年8月10日 22:08 > 收件人: zenan > 抄送: lttng-dev@lists.lttng.org > 主题: Re: [lttng-dev] babeltrace2 python api related question > > > > On Wed, Aug 10, 2022 at 9:54 AM zenan via lttng-dev > > <lttng-dev@lists.lttng.org> wrote: > > > > > > > > > > > > Hi there, > > > > > > I’m trying to use babeltrace2 python bindings to track live lttng trace, as > > shown in some examples in the documents, I tried to use ctf.lttng-live( > > ctf.fs in the documents) plugin as source, and use text.pretty as sink, but > > it didn’t work out as I expected. So does the api support tracking live > > lttng trace and print them out yet? > > > > > > > > > > What did you try exactly? > > > > I need command lines and/or some code (keep it minimal) to help you. > > > > Philippe > > > > > > > > > > > > > > Yours sincerely > > > > > > _______________________________________________ > > > lttng-dev mailing list > > > lttng-dev@lists.lttng.org > > > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev