Python stacktracer

stacktracer.py

# -*- coding: utf-8 -*-

"""Stack tracer for multi-threaded applications.

This code is a copy of https://pypi.python.org/pypi/stacktracer/0.1.2
with minor modifications.


Usage:

import stacktracer

stacktracer.trace_start("trace.html", interval=5, auto=True)
# Set auto flag to always update file!
....
stacktracer.trace_stop()
"""

# pylint: disable=protected-access


import os
import sys
import time
import threading
import traceback


try:
    from pygments import highlight
    from pygments.lexers import PythonLexer
    from pygments.formatters import HtmlFormatter
    HAS_PYGMENTS = True
except ImportError:
    HAS_PYGMENTS = False


def get_stacktraces():
    """Get the stack traces from each thread."""
    id_to_name = {}
    for thread in threading.enumerate():
        id_to_name[thread.ident] = thread.name

    code = []
    for thread_id, stack in sys._current_frames().items():
        code.append("\n# Thread {}, ID {}"
                    .format(id_to_name[thread_id], thread_id))
        for filename, lineno, name, line in traceback.extract_stack(stack):
            code.append('File: "{}", line {}, in {}'
                        .format(filename, lineno, name))
            if line:
                code.append("  %s" % (line.strip()))

    if HAS_PYGMENTS:
        return highlight("\n".join(code),
                         PythonLexer(),
                         HtmlFormatter(full=False,
                                       # style="native",
                                       noclasses=True))

    return "\n".join(code)


class TraceDumper(threading.Thread):

    """Dump stack traces into a given file periodically."""

    def __init__(self, fpath, interval, auto):
        """
        :param fpath: File path to output HTML (stack trace file)
        :param auto: Set flag (True) to update trace continuously.
            Clear flag (False) to update only if file not exists.
            (Then delete the file to force update.)
        :param interval: In seconds: how often to update the trace file.
        """
        assert interval > 0.1
        self.auto = auto
        self.interval = interval
        self.fpath = os.path.abspath(fpath)
        self.stop_requested = threading.Event()
        threading.Thread.__init__(self, name="stackTracer")

    def run(self):
        while not self.stop_requested.isSet():
            time.sleep(self.interval)
            if self.auto or not os.path.isfile(self.fpath):
                self.dump_stacktraces()

    def stop(self):
        self.stop_requested.set()
        self.join()
        try:
            if os.path.isfile(self.fpath):
                os.unlink(self.fpath)
        except:  # pylint: disable=bare-except
            pass

    def dump_stacktraces(self):
        with open(self.fpath, "w+", encoding="utf-8") as fout:
            fout.write(get_stacktraces())


###############################################################################

_TRACER = None


def trace_start(fpath, interval=5, auto=True):
    """Start tracing into the given file."""
    global _TRACER  # pylint: disable=global-statement
    if _TRACER is None:
        _TRACER = TraceDumper(fpath, interval, auto)
        _TRACER.setDaemon(True)
        _TRACER.start()
    else:
        raise Exception("Already tracing to %s" % _TRACER.fpath)


def trace_stop():
    """Stop tracing."""
    global _TRACER  # pylint: disable=global-statement
    if _TRACER is None:
        raise Exception("Not tracing, cannot stop.")
    else:
        _TRACER.stop()
        _TRACER = None