gstreamer/tracer/gsttr-tsplot.py

#!/usr/bin/env python3
'''
Plot buffer pts and events in relation to the wall clock. The plots can be used
to spot anomalies, such as processing gaps.

How to run:
1) generate a log
GST_DEBUG="GST_TRACER:7" GST_TRACERS=stats GST_DEBUG_FILE=trace.log <application>

2) generate the images
python3 gsttr-tsplot.py trace.log <outdir>
eog <outdir>/*.png
'''

# TODO:
# - the event labels are still way too dense
#   - ideally each event is a vertical line
#     http://stackoverflow.com/questions/35105672/vertical-lines-from-data-in-file-in-time-series-plot-using-gnuplot
#   - this won't work well if the event is e.g. 'qos'
#   - we could sort them by event type and separarate them by double new-lines,
#     we'd then use 'index <x>' to plot them in different colors with
#   - instead of just skipping duplicates, we could count them, store min/max ts
#     and draw segments (is there something like labeled horizontal error bars?)

import logging
import os
from subprocess import Popen, PIPE, DEVNULL
from string import Template
from tracer.analysis_runner import AnalysisRunner
from tracer.analyzer import Analyzer
from tracer.parser import Parser
from tracer.structure import Structure


logging.basicConfig(level=logging.WARNING)
logger = logging.getLogger('gsttr-tsplot')

_HANDLED_CLASSES = ('buffer', 'event', 'new-pad', 'new-element')

_GST_BUFFER_FLAG_DISCONT = (1<<6)

_PLOT_SCRIPT_HEAD = Template(
    '''set term png truecolor size $width,$height
    ''')
_PLOT_SCRIPT_BODY = Template(
    '''set output '$png_file_name'
       plot '$buf_file_name' using 1:2 with linespoints title '$pad_name', \
            '$ev_file_name' using 1:(0):2 with labels rotate center font ',7' notitle')
       ''')

class TsPlot(Analyzer):
    '''Generate a timestamp plots from a tracer log.

    These show the buffer pts on the y-axis and the wall-clock time the buffer
    was produced on the x-axis. This helps to spot timing issues, such as
    stalled elements.
    '''

    def __init__(self, outdir, show_ghost_pads, size):
        super(TsPlot, self).__init__()
        self.outdir = outdir
        self.show_ghost_pads = show_ghost_pads
        self.params = {
            'width': size[0],
            'height': size[1],
        }
        self.buf_files = {}
        self.ev_files = {}
        self.element_names = {}
        self.pad_names = {}
        self.ev_labels = {}

    def _get_data_file(self, files, key, name_template):
        data_file = files.get(key)
        if not data_file:
            pad_name = self.pad_names.get(key)
            if pad_name:
                file_name = name_template % (self.outdir, key, pad_name)
                data_file = open(file_name, 'w')
                files[key] = data_file
        return data_file

    def handle_tracer_entry(self, event):
        if event[Parser.F_FUNCTION]:
            return

        msg = event[Parser.F_MESSAGE]
        p = msg.find(',')
        if p == -1:
            return
        entry_name = msg[:p]
        if entry_name not in _HANDLED_CLASSES:
            return

        try:
            s = Structure(msg)
        except ValueError:
            logger.warning("failed to parse: '%s'", msg)
            return

        if entry_name == 'new-element':
            ix = int(s.values['ix'])
            self.element_names[ix] = s.values['name']
        elif entry_name == 'new-pad':
            pad_type = s.values['type']
            if pad_type not in ['GstGhostPad', 'GstProxyPad']:
                parent_ix = int(s.values['parent-ix'])
                parent_name = self.element_names.get(parent_ix, '')
                ix = int(s.values['ix'])
                self.pad_names[ix] = "%s.%s" % (parent_name, s.values['name'])
        elif entry_name == 'event':
            # build a [ts, event-name] data file
            ix = int(s.values['pad-ix'])
            pad_file = self._get_data_file(self.ev_files, ix, '%s/ev_%d_%s.dat')
            if pad_file:
                # convert timestamps to seconds
                x = int(s.values['ts']) / 1e9
                l = s.values['name']
                if l == self.ev_labels.get(ix):
                    # omit repeated labels for readability
                    pad_file.write('%f ""\n' % x)
                else:
                    pad_file.write('%f "%s"\n' % (x, l))
                    self.ev_labels[ix] = l
        else:  # 'buffer'
            if int(s.values['have-buffer-pts']):
                # build a [ts, buffer-pts] data file
                ix = int(s.values['pad-ix'])
                pad_file = self._get_data_file(self.buf_files, ix, '%s/buf_%d_%s.dat')
                if pad_file:
                    flags = int(s.values['buffer-flags'])
                    if flags & _GST_BUFFER_FLAG_DISCONT:
                        pad_file.write('\n')
                    # convert timestamps to e.g. seconds
                    x = int(s.values['ts']) / 1e9
                    y = int(s.values['buffer-pts']) / 1e9
                    pad_file.write('%f %f\n' % (x, y))

    def report(self):
        for ix, pad_file in self.ev_files.items():
            pad_file.close()

        script = _PLOT_SCRIPT_HEAD.substitute(self.params)
        for ix, pad_file in self.buf_files.items():
            pad_file.close()
            name = self.pad_names[ix]
            buf_file_name = '%s/buf_%d_%s.dat' % (self.outdir, ix, name)
            ev_file_name = '%s/ev_%d_%s.dat' % (self.outdir, ix, name)
            png_file_name = '%s/%d_%s.png' % (self.outdir, ix, name)
            script += _PLOT_SCRIPT_BODY.substitute(self.params, pad_name=name,
                buf_file_name=buf_file_name, ev_file_name=ev_file_name,
                png_file_name=png_file_name)
        # plot PNGs
        p = Popen(['gnuplot'], stdout=DEVNULL, stdin=PIPE)
        p.communicate(input=script.encode('utf-8'))

        # cleanup
        for ix, pad_file in self.buf_files.items():
            name = self.pad_names[ix]
            buf_file_name = '%s/buf_%d_%s.dat' % (self.outdir, ix, name)
            os.unlink(buf_file_name)
        for ix, pad_file in self.ev_files.items():
            name = self.pad_names[ix]
            ev_file_name = '%s/ev_%d_%s.dat' % (self.outdir, ix, name)
            os.unlink(ev_file_name)


if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('file', nargs='?', default='debug.log')
    parser.add_argument('outdir', nargs='?', default='tsplot')
    parser.add_argument('-g', '--ghost-pads', action='store_true',
                        help='also plot data for ghost-pads')
    parser.add_argument('-s', '--size', action='store', default='1600x300',
                        help='graph size as WxH')
    args = parser.parse_args()

    os.makedirs(args.outdir, exist_ok=True)
    size = [int(s) for s in args.size.split('x')]

    with Parser(args.file) as log:
        tsplot = TsPlot(args.outdir, args.ghost_pads, size)
        runner = AnalysisRunner(log)
        runner.add_analyzer(tsplot)
        runner.run()

        tsplot.report()