Re: Python CTF writer example

Re: Python CTF writer example

[Jonathan Rajotte-Julien]

Hi,

On Fri, Sep 13, 2019 at 07:03:59PM -0400, Francis Giraldeau wrote:
> Hello!
> 
> It looks like there are some issues with the Python CTF writer example with
> babeltrace stable-1.5.

I will infer that you are looking at this doc:

  https://diamon.org/babeltrace/docs/python/examples/#ctf-writer-api-examples

This doc is currently outdated(invalid). We are in the process of
revamping it/removing it.

If you need an example for bt 1.5 use:

  https://github.com/efficios/babeltrace/blob/stable-1.5/bindings/python/babeltrace/examples/ctf_writer.py

This example works as expected.

> 
> * Import error, should replace "import babeltrace.writer as btw" by "from
> babeltrace import CTFWriter as btw"
> * The FloatingPointDeclaration does not exists and should be replaced
> by FloatFieldDeclaration
> * babeltrace.common.CTFStringEncoding.UTF8 is
> instead babeltrace.CTFStringEncoding.UTF8
> * The variant still had issue that I cannot fix (ValueError("Invalid tag
> provided.") babeltrace.py:2221)

If you still wish to follow the documentation, please make sure to read the
green notice here:
  https://diamon.org/babeltrace/docs/python/examples/#examples

> 
> Events with simple fields are working okay with these changes. I thought
> that the clock would be updated automatically when appending the event, but
> that would be nice also to add it to the example.
> 
> I tried babeltrace 2.0.0-pre6, but the writer API seems to have
> disappeared. I was looking at how to create a ctf.fs.sink, but I was not
> successful. Is writing CTF traces with the Python bindings still possible?

The ctf-writer capability are not part of the bindings anymore.
 https://review.lttng.org/c/babeltrace/+/1392

What can be done is writing a source plugin using the bindings and use a ctf
sink on the cli to generate a ctf trace.

A quick source plugin: http://paste.ubuntu.com/p/8CBqTt8cSj/

Note that babeltrace 1.5 and babeltrace 2 can coexist on the same system.
Allowing you to still use the bindings from bt1.5 to generate traces.

I recommend that you stick with the babeltrace 1.5 bindings (import babeltrace).

Cheers

-- 
Jonathan Rajotte-Julien
EfficiOS

Python CTF writer example

[Francis Giraldeau]

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Hello!

It looks like there are some issues with the Python CTF writer example with
babeltrace stable-1.5.

* Import error, should replace "import babeltrace.writer as btw" by "from
babeltrace import CTFWriter as btw"
* The FloatingPointDeclaration does not exists and should be replaced
by FloatFieldDeclaration
* babeltrace.common.CTFStringEncoding.UTF8 is
instead babeltrace.CTFStringEncoding.UTF8
* The variant still had issue that I cannot fix (ValueError("Invalid tag
provided.") babeltrace.py:2221)

Events with simple fields are working okay with these changes. I thought
that the clock would be updated automatically when appending the event, but
that would be nice also to add it to the example.

I tried babeltrace 2.0.0-pre6, but the writer API seems to have
disappeared. I was looking at how to create a ctf.fs.sink, but I was not
successful. Is writing CTF traces with the Python bindings still possible?

Regards,

-- 
Francis

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#!/usr/bin/env python3

#import babeltrace.writer as btw
#import babeltrace.common

import babeltrace
from babeltrace import CTFWriter as btw
import tempfile
import time

trace_path = tempfile.mkdtemp()

print('trace path: {}'.format(trace_path))


writer = btw.Writer(trace_path)

clock = btw.Clock('my_clock')
clock.description = 'this is my clock'
writer.add_clock(clock)

stream_class = btw.StreamClass('my_stream')
stream_class.clock = clock

event_class = btw.EventClass('my_event')

# 32-bit signed integer field declaration
int32_field_decl = btw.IntegerFieldDeclaration(32)
int32_field_decl.signed = True

# string field declaration
string_field_decl = btw.StringFieldDeclaration()
string_field_decl.encoding = babeltrace.CTFStringEncoding.UTF8

# IEEE 754 single precision floating point number field declaration
float_field_decl = btw.FloatFieldDeclaration()
float_field_decl.exponent_digits = btw.FloatFieldDeclaration.FLT_EXP_DIG
float_field_decl.mantissa_digits = btw.FloatFieldDeclaration.FLT_MANT_DIG

event_class.add_field(int32_field_decl, 'val1')
event_class.add_field(string_field_decl, 'val2')
event_class.add_field(float_field_decl, 'val3')

stream_class.add_event_class(event_class)

stream = writer.create_stream(stream_class)

for i in range(10):
    event = btw.Event(event_class)
    event.payload('val1').value = 42 + i
    event.payload('val2').value = "foo {}".format(i)
    event.payload('val3').value = i * 0.1
    clock.time = time.time_ns()
    stream.append_event(event)

stream.flush()

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