3 # © Copyright 2021-2022, Scott Gasch
5 """Global configuration driven by commandline arguments, environment variables,
6 saved configuration files, and zookeeper-based dynamic configurations. This
7 works across several modules.
15 parser = config.add_commandline_args(
17 "Args related to module doing the thing.",
20 "--module_do_the_thing",
23 help="Should the module do the thing?"
30 parser = config.add_commandline_args(
32 "A program that does the thing.",
38 help="Should we really do the thing?"
42 config.parse() # Very important, this must be invoked!
44 If you set this up and remember to invoke config.parse(), all commandline
45 arguments will play nicely together. This is done automatically for you
46 if you're using the :meth:`bootstrap.initialize` decorator on
47 your program's entry point. See :meth:`python_modules.bootstrap.initialize`
56 if __name__ == '__main__':
59 Either way, you'll get this behavior from the commandline::
63 [--module_do_the_thing MODULE_DO_THE_THING]
67 Args related to module doing the thing.
69 --module_do_the_thing MODULE_DO_THE_THING
70 Should the module do the thing?
73 A program that does the thing
76 Should we really do the thing?
78 Arguments themselves should be accessed via
79 :code:`config.config['arg_name']`. e.g.::
81 if not config.config['dry_run']:
91 from typing import Any, Dict, List, Optional, Tuple
93 from kazoo.client import KazooClient
94 from kazoo.protocol.states import WatchedEvent
98 # This module is commonly used by others in here and should avoid
99 # taking any unnecessary dependencies back on them.
101 # Make a copy of the original program arguments immediately upon module load.
102 PROGRAM_NAME: str = os.path.basename(sys.argv[0])
103 ORIG_ARGV: List[str] = sys.argv.copy()
106 class OptionalRawFormatter(argparse.HelpFormatter):
107 """This formatter has the same bahavior as the normal argparse text
108 formatter except when the help text of an argument begins with
109 "RAW|". In that case, the line breaks are preserved and the text
112 Use this, for example, when you need the helptext of an argument
113 to have its spacing preserved exactly, e.g.::
119 choices=['CHEAT', 'AUTOPLAY', 'SELFTEST', 'PRECOMPUTE', 'PLAY'],
121 help='''RAW|Our mode of operation. One of:
123 PLAY = play wordle with me! Pick a random solution or
124 specify a solution with --template.
126 CHEAT = given a --template and, optionally, --letters_in_word
127 and/or --letters_to_avoid, return the best guess word;
129 AUTOPLAY = given a complete word in --template, guess it step
130 by step showing work;
132 SELFTEST = autoplay every possible solution keeping track of
133 wins/losses and average number of guesses;
135 PRECOMPUTE = populate hash table with optimal guesses.
140 def _split_lines(self, text, width):
141 if text.startswith('RAW|'):
142 return text[4:].splitlines()
143 return argparse.HelpFormatter._split_lines(self, text, width)
146 # A global argparser that we will collect arguments in. Each module (including
147 # us) will add arguments to a separate argument group.
148 ARGS = argparse.ArgumentParser(
150 formatter_class=OptionalRawFormatter,
151 fromfile_prefix_chars="@",
152 epilog=f'{PROGRAM_NAME} uses config.py ({__file__}) for global, cross-module configuration setup and parsing.',
153 # I don't fully understand why but when loaded by sphinx sometimes
154 # the same module is loaded many times causing any arguments it
155 # registers via module-level code to be redefined. Work around
156 # this iff the program is 'sphinx-build'
157 conflict_handler='resolve' if PROGRAM_NAME == 'sphinx-build' else 'error',
160 # Arguments specific to config.py. Other users should get their own group by
161 # invoking config.add_commandline_args.
162 GROUP = ARGS.add_argument_group(
163 f'Global Config ({__file__})',
164 'Args that control the global config itself; how meta!',
170 help='Config file (populated via --config_savefile) from which to read args in lieu or in addition to those passed via the commandline. Note that if the given path begins with "zk:" then it is interpreted as a zookeeper path instead of as a filesystem path. When loading config from zookeeper, any argument with the string "dynamic" in the name (e.g. --module_dynamic_url) may be modified at runtime by changes made to zookeeper (using --config_savefile=zk:path). You should therefore either write your code to handle dynamic argument changes or avoid naming arguments "dynamic" if you use zookeeper configuration paths.',
176 help='Display the global configuration (possibly derived from multiple sources) on STDERR at program startup time.',
183 help='Populate a config file (compatible with --config_loadfile) with the given path for later use. If the given path begins with "zk:" it is interpreted as a zookeeper path instead of a filesystem path. When updating zookeeper-based configs, all running programs that read their configuration from zookeeper (via --config_loadfile=zk:path) at startup time will see their configuration dynamically updated; flags with "dynamic" in their names (e.g. --my_dynamic_flag) may have their values changed. You should therefore either write your code to handle dynamic argument changes or avoid naming arguments "dynamic" if you use zookeeper configuration paths.',
186 '--config_rejects_unrecognized_arguments',
189 help='If present, config will raise an exception if it doesn\'t recognize an argument. The default behavior is to ignore unknown arguments so as to allow interoperability with programs that want to use their own argparse calls to parse their own, separate commandline args.',
195 Everything in the config module used to be module-level functions and
196 variables but it made the code ugly and harder to maintain. Now, this
197 class does the heavy lifting. We still rely on some globals, though:
199 ARGS and GROUP to interface with argparse
200 PROGRAM_NAME stores argv[0] close to program invocation
201 ORIG_ARGV stores the original argv list close to program invocation
202 CONFIG and config: hold the (singleton) instance of this class.
207 # Has our parse() method been invoked yet?
208 self.config_parse_called = False
210 # A configuration dictionary that will contain parsed
211 # arguments. This is the data that is most interesting to our
212 # callers as it will hold the configuration result.
213 self.config: Dict[str, Any] = {}
215 # Defer logging messages until later when logging has been
217 self.saved_messages: List[str] = []
219 # A zookeeper client that is lazily created so as to not incur
220 # the latency of connecting to zookeeper for programs that are
221 # not reading or writing their config data into zookeeper.
222 self.zk: Optional[KazooClient] = None
224 # Per known zk file, what is the max version we have seen?
225 self.max_version: Dict[str, int] = {}
227 def __getitem__(self, key: str) -> Optional[Any]:
228 """If someone uses []'s on us, pass it onto self.config."""
229 return self.config.get(key, None)
231 def __setitem__(self, key: str, value: Any) -> None:
232 self.config[key] = value
234 def __contains__(self, key: str) -> bool:
235 return key in self.config
238 def add_commandline_args(title: str, description: str = "") -> argparse._ArgumentGroup:
239 """Create a new context for arguments and return a handle.
242 title: A title for your module's commandline arguments group.
243 description: A helpful description of your module.
246 An argparse._ArgumentGroup to be populated by the caller.
248 return ARGS.add_argument_group(title, description)
251 def overwrite_argparse_epilog(msg: str) -> None:
252 """Allows your code to override the default epilog created by
256 msg: The epilog message to substitute for the default.
261 def is_flag_already_in_argv(var: str) -> bool:
262 """Returns true if a particular flag is passed on the commandline
266 var: The flag to search for.
274 def print_usage() -> None:
275 """Prints the normal help usage message out."""
282 program usage help text as a string.
284 return ARGS.format_usage()
287 def _reorder_arg_action_groups_before_help(entry_module: Optional[str]):
288 """Internal. Used to reorder the arguments before dumping out a
289 generated help string such that the main program's arguments come
293 reordered_action_groups = []
294 for grp in ARGS._action_groups:
295 if entry_module is not None and entry_module in grp.title: # type: ignore
296 reordered_action_groups.append(grp)
297 elif PROGRAM_NAME in GROUP.title: # type: ignore
298 reordered_action_groups.append(grp)
300 reordered_action_groups.insert(0, grp)
301 return reordered_action_groups
304 def _parse_arg_into_env(arg: str) -> Optional[Tuple[str, str, List[str]]]:
305 """Internal helper to parse commandling args into environment vars."""
308 if not arg.startswith('['):
311 if not arg.endswith(']'):
321 # Environment vars the same as flag names without
322 # the initial -'s and in UPPERCASE.
326 return arg, env, chunks
328 def _augment_sys_argv_from_environment_variables(self):
329 """Internal. Look at the system environment for variables that match
330 commandline arg names. This is done via some munging such that:
332 :code:`--argument_to_match`
336 :code:`ARGUMENT_TO_MATCH`
338 This allows users to set args via shell environment variables
339 in lieu of passing them on the cmdline.
342 usage_message = Config.usage()
346 # Foreach valid optional commandline option (chunk) generate
347 # its analogous environment variable.
348 for chunk in usage_message.split():
355 _ = Config._parse_arg_into_env(arg)
358 if env in os.environ:
359 if not Config.is_flag_already_in_argv(var):
360 value = os.environ[env]
361 self.saved_messages.append(
362 f'Initialized from environment: {var} = {value}'
364 from string_utils import to_bool
366 if len(chunks) == 1 and to_bool(value):
368 elif len(chunks) > 1:
370 sys.argv.append(value)
373 def _process_dynamic_args(self, event: WatchedEvent):
375 logger = logging.getLogger(__name__)
376 contents, meta = self.zk.get(event.path, watch=self._process_dynamic_args)
377 logger.debug('Update for %s at version=%d.', event.path, meta.version)
379 'Max known version for %s is %d.', event.path, self.max_version.get(event.path, 0)
381 if meta.version > self.max_version.get(event.path, 0):
382 self.max_version[event.path] = meta.version
383 contents = contents.decode()
385 for arg in contents.split():
387 temp_argv.append(arg)
388 logger.info("Updating %s from zookeeper async config change.", arg)
389 if len(temp_argv) > 0:
392 known, _ = ARGS.parse_known_args()
394 self.config.update(vars(known))
396 def _augment_sys_argv_from_loadfile(self):
397 """Internal. Augment with arguments persisted in a saved file."""
400 saw_other_args = False
401 grab_next_arg = False
402 for arg in sys.argv[1:]:
403 if 'config_loadfile' in arg:
404 pieces = arg.split('=')
412 saw_other_args = True
414 if loadfile is not None:
416 if loadfile[:3] == 'zk:':
419 self.zk = KazooClient(
420 hosts=scott_secrets.ZOOKEEPER_NODES,
423 keyfile=scott_secrets.ZOOKEEPER_CLIENT_CERT,
424 keyfile_password=scott_secrets.ZOOKEEPER_CLIENT_PASS,
425 certfile=scott_secrets.ZOOKEEPER_CLIENT_CERT,
428 zkpath = loadfile[3:]
429 if not zkpath.startswith('/config/'):
430 zkpath = '/config/' + zkpath
431 zkpath = re.sub(r'//+', '/', zkpath)
432 if not self.zk.exists(zkpath):
434 f'ERROR: --config_loadfile argument must be a file, {loadfile} not found (in zookeeper)'
436 except Exception as e:
438 f'ERROR: Error talking with zookeeper while looking for {loadfile}'
440 elif not os.path.exists(loadfile):
442 f'ERROR: --config_loadfile argument must be a file, {loadfile} not found.'
446 msg = f'Augmenting commandline arguments with those from {loadfile}.'
448 msg = f'Reading commandline arguments from {loadfile}.'
449 print(msg, file=sys.stderr)
450 self.saved_messages.append(msg)
456 contents, meta = self.zk.get(zkpath, watch=self._process_dynamic_args)
457 contents = contents.decode()
460 for arg in contents.split('\n')
461 if 'config_savefile' not in arg
463 self.saved_messages.append(f'Setting {zkpath}\'s max_version to {meta.version}')
464 self.max_version[zkpath] = meta.version
465 except Exception as e:
466 raise Exception(f'Error reading {zkpath} from zookeeper.') from e
467 self.saved_messages.append(f'Loaded config from zookeeper from {zkpath}')
469 with open(loadfile, 'r') as rf:
470 newargs = rf.readlines()
471 newargs = [arg.strip('\n') for arg in newargs if 'config_savefile' not in arg]
474 def dump_config(self):
475 """Print the current config to stdout."""
476 print("Global Configuration:", file=sys.stderr)
477 pprint.pprint(self.config, stream=sys.stderr)
480 def parse(self, entry_module: Optional[str]) -> Dict[str, Any]:
481 """Main program should call this early in main(). Note that the
482 :code:`bootstrap.initialize` wrapper takes care of this automatically.
483 This should only be called once per program invocation.
486 if self.config_parse_called:
489 # If we're about to do the usage message dump, put the main
490 # module's argument group last in the list (if possible) so that
491 # when the user passes -h or --help, it will be visible on the
492 # screen w/o scrolling.
494 if arg in ('--help', '-h'):
495 if entry_module is not None:
496 entry_module = os.path.basename(entry_module)
497 ARGS._action_groups = Config._reorder_arg_action_groups_before_help(entry_module)
499 # Examine the environment for variables that match known flags.
500 # For a flag called --example_flag the corresponding environment
501 # variable would be called EXAMPLE_FLAG. If found, hackily add
502 # these into sys.argv to be parsed.
503 self._augment_sys_argv_from_environment_variables()
505 # Look for loadfile and read/parse it if present. This also
506 # works by jamming these values onto sys.argv.
507 self._augment_sys_argv_from_loadfile()
509 # Parse (possibly augmented, possibly completely overwritten)
510 # commandline args with argparse normally and populate config.
511 known, unknown = ARGS.parse_known_args()
512 self.config.update(vars(known))
514 # Reconstruct the argv with unrecognized flags for the benefit of
515 # future argument parsers. For example, unittest_main in python
516 # has some of its own flags. If we didn't recognize it, maybe
519 if config['config_rejects_unrecognized_arguments']:
521 f'Encountered unrecognized config argument(s) {unknown} with --config_rejects_unrecognized_arguments enabled; halting.'
523 self.saved_messages.append(
524 f'Config encountered unrecognized commandline arguments: {unknown}'
526 sys.argv = sys.argv[:1] + unknown
528 # Check for savefile and populate it if requested.
529 savefile = config['config_savefile']
530 if savefile and len(savefile) > 0:
531 data = '\n'.join(ORIG_ARGV[1:])
532 if savefile[:3] == 'zk:':
533 zkpath = savefile[3:]
534 if not zkpath.startswith('/config/'):
535 zkpath = '/config/' + zkpath
536 zkpath = re.sub(r'//+', '/', zkpath)
539 self.zk = KazooClient(
540 hosts=scott_secrets.ZOOKEEPER_NODES,
543 keyfile=scott_secrets.ZOOKEEPER_CLIENT_CERT,
544 keyfile_password=scott_secrets.ZOOKEEPER_CLIENT_PASS,
545 certfile=scott_secrets.ZOOKEEPER_CLIENT_CERT,
549 if len(data) > 1024 * 1024:
550 raise Exception(f'Saved args are too large! ({len(data)} bytes)')
551 if not self.zk.exists(zkpath):
552 self.zk.create(zkpath, data)
553 self.saved_messages.append(
554 f'Just created {zkpath}; setting its max_version to 0'
556 self.max_version[zkpath] = 0
558 meta = self.zk.set(zkpath, data)
559 self.saved_messages.append(
560 f'Setting {zkpath}\'s max_version to {meta.version}'
562 self.max_version[zkpath] = meta.version
563 except Exception as e:
564 raise Exception(f'Failed to create zookeeper path {zkpath}') from e
565 self.saved_messages.append(f'Saved config to zookeeper in {zkpath}')
567 with open(savefile, 'w') as wf:
570 # Also dump the config on stderr if requested.
571 if config['config_dump']:
574 self.config_parse_called = True
577 def has_been_parsed(self) -> bool:
578 """Returns True iff the global config has already been parsed"""
579 return self.config_parse_called
581 def late_logging(self):
582 """Log messages saved earlier now that logging has been initialized."""
583 logger = logging.getLogger(__name__)
584 logger.debug('Original commandline was: %s', ORIG_ARGV)
585 for _ in self.saved_messages:
589 # A global singleton instance of the Config class.
592 # A lot of client code uses config.config['whatever'] to lookup
593 # configuration so to preserve this we make this, config.config, with
594 # a __getitem__ method on it.
597 # Config didn't use to be a class; it was a mess of module-level
598 # functions and data. The functions below preserve the old interface
599 # so that existing clients do not need to be changed. As you can see,
600 # they mostly just thunk into the config class.
603 def add_commandline_args(title: str, description: str = "") -> argparse._ArgumentGroup:
604 """Create a new context for arguments and return a handle. An alias
605 for config.config.add_commandline_args.
608 title: A title for your module's commandline arguments group.
609 description: A helpful description of your module.
612 An argparse._ArgumentGroup to be populated by the caller.
614 return CONFIG.add_commandline_args(title, description)
617 def parse(entry_module: Optional[str]) -> Dict[str, Any]:
618 """Main program should call this early in main(). Note that the
619 :code:`bootstrap.initialize` wrapper takes care of this automatically.
620 This should only be called once per program invocation. Subsequent
621 calls do not reparse the configuration settings but rather just
622 return the current state.
624 return CONFIG.parse(entry_module)
627 def has_been_parsed() -> bool:
628 """Returns True iff the global config has already been parsed"""
629 return CONFIG.has_been_parsed()
632 def late_logging() -> None:
633 """Log messages saved earlier now that logging has been initialized."""
634 CONFIG.late_logging()
637 def dump_config() -> None:
638 """Print the current config to stdout."""
642 def overwrite_argparse_epilog(msg: str) -> None:
643 """Allows your code to override the default epilog created by
647 msg: The epilog message to substitute for the default.
649 Config.overwrite_argparse_epilog(msg)
652 def is_flag_already_in_argv(var: str) -> bool:
653 """Returns true if a particular flag is passed on the commandline
657 var: The flag to search for.
659 return Config.is_flag_already_in_argv(var)
662 def print_usage() -> None:
663 """Prints the normal help usage message out."""
670 program usage help text as a string.
672 return Config.usage()