How I Built a Power Debugger Out of the Standard Library and Things I Found on the Internet

How I Built a Power Debugger Out of the Standard Library and Things I Found on the Internet

Doug Hellmann PyCon US 2016

I Built a Power Debugger!Doug Hellmann PyCon US 2016

How I Built a Power Debugger!

Doug Hellmann PyCon US 2016

github.com/dhellmann/smiley

smiley.readthedocs.org

Features

• Record calls with data

• Remote monitoring, local analysis

• Browse history

• Learn new tools

flickr/Kangrex

class Publisher(object):

def __init__(self, endpoint, high_water_mark=10000): self.context = zmq.Context() self.pub_socket = \ self.context.socket(zmq.PUSH) self.pub_socket.bind(endpoint) self.pub_socket.identity = 'publisher' self.pub_socket.hwm = high_water_mark

def send(self, msg_type, data): msg = [ msg_type, json.dumps(data, default=self._json_special_types), ] self.pub_socket.send_multipart(msg)

def trace_calls(self, frame, event, arg): co = frame.f_code filename = co.co_filename if filename in (__file__,): # Ignore ourself return self._send_notice(frame, event, arg) return self.trace_calls

def _send_notice(self, frame, event, arg): co = frame.f_code func_name = co.co_name line_no = frame.f_lineno filename = os.path.abspath(co.co_filename) for d in IGNORE_DIRS: if filename.startswith(d): return # …

# … interesting_locals = { n: v for n, v in frame.f_locals.items() if (not inspect.ismodule(v) and not inspect.isfunction(v) and not inspect.ismethod(v) and (n[:2] != '__' and n[-2:] != '__')) } # …

# … self.publisher.send( event, {'func_name': func_name, 'line_no': line_no, 'filename': filename, 'arg': arg, 'locals': interesting_locals, 'timestamp': time.time(), 'run_id': self.run_id, })

$ smiley help usage: smiley [--version] [-v] [--log-file LOG_FILE] [-q] [-h] [--debug]

smiley spies on your apps as they run

optional arguments: --version show program's version number and exit -v, --verbose Increase verbosity of output. --log-file LOG_FILE Specify a file to log output. -q, --quiet suppress output except warnings -h, --help show this help message and exit --debug show tracebacks on errors

Commands: complete print bash completion command help print detailed help for another command monitor Listen for running programs and show their progress. run Run another program with monitoring enabled.

$ smiley help run

usage: smiley run [-h] [--socket SOCKET] command [command ...]

Run another program with monitoring enabled.

positional arguments: command the command to spy on

optional arguments: -h, --help show this help message and exit --socket SOCKET URL for the socket where the listener will be (tcp://127.0.0.1:5556)

$ smiley help monitor

usage: smiley monitor [-h] [--socket SOCKET]

Listen for running programs and show their progress.

optional arguments: -h, --help show this help message and exit --socket SOCKET URL for the socket where to monitor on (tcp://127.0.0.1:5556)

def _process_message(self, msg): print 'MESSAGE:', msg msg_type, msg_payload = msg if msg_type == 'start_run': print (‘Starting new run:', msg_payload.get(‘command_line')) elif msg_type == 'end_run': print 'Finished run' else: line = linecache.getline(msg_payload['filename'], msg_payload['line_no']).rstrip() if msg_type == 'return': print '%s:%4s: return>>> %s' % ( msg_payload['filename'], msg_payload[‘line_no'], msg_payload['arg']) else: print '%s:%4s: %s' % ( msg_payload['filename'], msg_payload[‘line_no'], line) if msg_payload.get('locals'): for n, v in sorted(msg_payload['locals'].items()): print '%s %s = %s' % ( ' ' * len(msg_payload['filename']), n, v, ) print

def gen(m): for i in xrange(m): yield i

def c(input): print 'input =', input data = list(gen(input)) print 'Leaving c()'

def b(arg): val = arg * 5 c(val) print 'Leaving b()' return val

def a(): print 'args:', sys.argv b(2) print 'Leaving a()'

a()

$ smiley monitor Waiting for incoming data MESSAGE: ['start_run', {u'command_line': [u'simple.py'], u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e'}] Starting new run: [u'simple.py'] MESSAGE: ['call', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.142863, u'line_no': 1, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg': None, u'locals': {u'self': u'<smiley.tracer.Tracer object at 0x103caff10>', u'command_line': [u'simple.py']}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 1: import sys command_line = [u'simple.py'] self = <smiley.tracer.Tracer object at 0x103caff10>

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.143175, u'line_no': 1, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg': None, u'locals': {u'self': u'<smiley.tracer.Tracer object at 0x103caff10>', u'command_line': [u'simple.py']}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 1: import sys command_line = [u'simple.py'] self = <smiley.tracer.Tracer object at 0x103caff10>

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.143499, u'line_no': 3, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg':

$ smiley monitor Waiting for incoming data MESSAGE: ['start_run', {u'command_line': [u'simple.py'], u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e'}] Starting new run: [u'simple.py'] MESSAGE: ['call', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.142863, u'line_no': 1, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg': None, u'locals': {u'self': u'<smiley.tracer.Tracer object at 0x103caff10>', u'command_line': [u'simple.py']}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 1: import sys command_line = [u'simple.py'] self = <smiley.tracer.Tracer object at 0x103caff10>

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.143175, u'line_no': 1, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg': None, u'locals': {u'self': u'<smiley.tracer.Tracer object at 0x103caff10>', u'command_line': [u'simple.py']}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 1: import sys command_line = [u'simple.py'] self = <smiley.tracer.Tracer object at 0x103caff10>

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.143499, u'line_no': 3, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'<module>', u'arg':

MESSAGE: ['call', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.144927, u'line_no': 21, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 21: def a():

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.145128, u'line_no': 22, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 22: print 'args:', sys.argv

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.145343, u'line_no': 23, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 23: b(2)

def start_run(self, run_id, cwd, description, start_time): "Record the beginning of a run." with transaction(self.conn) as c: c.execute( """ INSERT INTO run (id, cwd, description, start_time) VALUES (:id, :cwd, :description, :start_time) """, {'id': run_id, 'cwd': cwd, 'description': description, 'start_time': start_time} )

def _process_message(self, msg): msg_type, msg_payload = msg

if msg_type == 'start_run': command_line = ' ‘.join( msg_payload.get('command_line', []))

self._cwd = msg_payload.get('cwd', '') if self._cwd: self._cwd = (self._cwd.rstrip(os.sep) + os.sep) self.db.start_run( run_id=msg_payload.get('run_id'), cwd=self._cwd, description=command_line, start_time=msg_payload.get('timestamp'), )

elif msg_type == 'end_run': self.log.info('Finished run') self.db.end_run( run_id=msg_payload['run_id'], end_time=msg_payload.get('timestamp'), message=msg_payload.get('message'), traceback=msg_payload.get('traceback'), )

else: self.db.trace( run_id=msg_payload['run_id'], event=msg_type, func_name=msg_payload.get('func_name'), line_no=msg_payload.get('line_no'), filename=msg_payload.get('filename'), trace_arg=msg_payload.get('arg'), locals=msg_payload.get('locals'), timestamp=msg_payload.get('timestamp'), )

• Replay past runs

• Complex data types

flickr/Chris Marquardt

import json import traceback import types

def _json_special_types(obj): if isinstance(obj, types.TracebackType): return traceback.extract_tb(obj) if isinstance(obj, type): # We don't want to return classes return repr(obj) try: data = dict(vars(obj)) data['__class__'] = obj.__class__.__name__ data['__module__'] = obj.__class__.__module__ except Exception as err: data = repr(obj) return data

def dumps(data): return json.dumps(data, default=_json_special_types)

?

class EventProcessor(object): __metaclass__ = abc.ABCMeta

@abc.abstractmethod def start_run(self, run_id, cwd, description, start_time): """Called when a 'start_run' event is seen. """

@abc.abstractmethod def end_run(self, run_id, end_time, message, traceback): """Called when an 'end_run' event is seen. """

@abc.abstractmethod def trace(self, run_id, event, func_name, line_no, filename, trace_arg, local_vars, timestamp): """Called when any other event type is seen. """

def get_runs(self): "Return the runs available to browse." with transaction(self.conn) as c: c.execute( """ SELECT id, cwd, description, start_time, end_time, error_message FROM run """ ) return c.fetchall()

def take_action(self, parsed_args): self.out = output.OutputFormatter( linecache.getline) self.db = db.DB(parsed_args.database)

run_details = self.db.get_run(parsed_args.run_id) self.out.start_run( run_details.id, run_details.cwd, run_details.description, run_details.start_time, ) for t in self.db.get_trace(parsed_args.run_id): self.out.trace( t.run_id, t.event, t.func_name, t.line_no, t.filename, t.trace_arg, t.local_vars, t.timestamp, ) self.out.end_run( run_details.id, run_details.end_time, run_details.error_message, None) # run_details.traceback

MESSAGE: ['call', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.144927, u'line_no': 21, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 21: def a():

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.145128, u'line_no': 22, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 22: print 'args:', sys.argv

MESSAGE: ['line', {u'run_id': u'e87302b2-402a-4243-bb27-69a467d4bd8e', u'timestamp': 1436367235.145343, u'line_no': 23, u'filename': u'/Users/dhellmann/Devel/smiley/scratch/simple.py', u'func_name': u'a', u'arg': None, u'locals': {}}] /Users/dhellmann/Devel/smiley/scratch/simple.py: 23: b(2)

class DBLineCache(object):

def __init__(self, db, run_id): self._db = db self._run_id = run_id self._files = {}

def getline(self, filename, line_no): if filename not in self._files: body = self._db.get_cached_file( self._run_id, filename) self._files[filename] = body.splitlines() try: return self._files[filename][line_no] except IndexError: # Line number is out of range return ''

def take_action(self, parsed_args): # Fix import path cwd = os.getcwd() if (cwd not in sys.path and os.curdir not in sys.path): sys.path.insert(0, cwd)

# Fix command line args sys.argv = parsed_args.command

# Run the app p = publisher.Publisher(parsed_args.socket) t = tracer.Tracer(p) t.run(parsed_args.command)

def take_action(self, parsed_args): # Fix import path cwd = os.getcwd() if (cwd not in sys.path and os.curdir not in sys.path): sys.path.insert(0, cwd)

# Fix command line args sys.argv = parsed_args.command

# Run the app if parsed_args.mode == 'remote': p = publisher.Publisher(parsed_args.socket) else: p = db.DB(parsed_args.database) t = tracer.Tracer(p) t.run(parsed_args.command)

1.ZMQ

2.Tracing

3.Command line interface

4.Database

5.Complex objects

6.EventProcessor API

7.Replay command

8.Store source files

9.Local database

1.ZMQ

2.Tracing

3.Command line interface

4.Database

5.Complex objects

6.EventProcessor API

7.Replay command

8.Store source files

9.Local database

UI Tools

class FileController(RestController):

@expose(generic=True, template='file.html') @nav.active_section('runs') def get_one(self, run_id, file_id): filename, body = \ request.db.get_cached_file_by_id(run_id, file_id) run = request.db.get_run(run_id)

lexer = guess_lexer_for_filename(filename, body) formatter = HtmlFormatter(linenos=True) styled_body = highlight(body, lexer, formatter)

return { 'run_id': run_id, 'run': run, 'filename': filename, 'body': body, 'styled_body': styled_body, }

class StyledLineCache(object):

def __init__(self, db, run_id): self._db = db self._run_id = run_id self._files = {}

EXPECTED_PREFIX = '<div class="highlight"><pre>' EXPECTED_SUFFIX = '</pre></div>'

def getline(self, filename, line_no): if filename not in self._files: body = self._db.get_cached_file(self._run_id, filename) styled_body = apply_style(filename, body, linenos=False) start = len(self.EXPECTED_PREFIX) end = -1 * (len(self.EXPECTED_SUFFIX) + 1) middle_body = styled_body[start:end].rstrip('\n') self._files[filename] = middle_body.splitlines() try: return self._files[filename][line_no-1] except IndexError: # Line number is out of range return ''

✓ Web UI

✓ Profiling Data

✓ Call Graph

✓ Syntax Highlighting

• Only Changed Variables

• Comments

def _mk_seq(d): return sorted( (k, pformat(v, width=20)) for k, v in d.iteritems() )

def get_variable_changes(older, newer): s_a = _mk_seq(older) s_b = _mk_seq(newer) matcher = difflib.SequenceMatcher(None, s_a, s_b)

for tag, i1, i2, j1, j2 in matcher.get_opcodes(): if tag in {'insert', 'replace'}: for i in s_b[j1:j2]: yield i

Other Features

Tracing Threaded

Applications

Static HTML

Reports

DB Export/ Import

Pagination in

Web UI

Other Features

Tracing Threaded

Applications

Static HTML

Reports

DB Export/ Import

Pagination in

Web UI

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• Performance• Standard I/O• GUI• Compare runs

flickr/Mike Mozart

Freenode: dhellmann doug@doughellmann.com github.com/dhellmann/smiley smiley.readthedocs.org