# -*- coding: utf-8 -*- """ @author: Fabio Erculiani @contact: lxnay@sabayon.org @copyright: Fabio Erculiani @license: GPL-2 B{Entropy Framework cache module}. This module contains the Entropy, asynchronous caching logic. It is not meant to handle cache pollution management, because this is either handled implicitly when cached items are pulled in or by using entropy.dump or cache cleaners (see entropy.client.interfaces.cache mixin methods) """ import os import errno import sys import tempfile import atexit from entropy.const import etpConst, etpUi, const_debug_write, \ const_pid_exists, const_setup_perms from entropy.core import Singleton from entropy.misc import TimeScheduled, Lifo import time import threading import copy import entropy.dump import entropy.tools class EntropyCacher(Singleton): CACHE_IDS = { 'db_match': 'match/db', 'dep_tree': 'deptree/dep_tree_', 'atom_match': 'atom_match/atom_match_', 'atom_search': 'atom_search/atom_search_', 'world_update': 'world_update/world_cache_', 'critical_update': 'critical_update/critical_cache_', 'world_available': 'world_available/available_cache_', 'world_masked': 'world_available/masked_cache_', 'check_package_update': 'check_update/package_update_', 'depends_tree': 'depends/depends_tree_', 'filter_satisfied_deps': 'depfilter/filter_satisfied_deps_', 'library_breakage': 'libs_break/library_breakage_', 'mask_filter': 'match/mask_filter', } # Max amount of processes to spawn _PROC_LIMIT = 10 # Max number of cache objects written at once _OBJS_WRITTEN_AT_ONCE = 250 # Number of seconds between cache writeback to disk WRITEBACK_TIMEOUT = 5 """ Entropy asynchronous and synchronous cache writer and reader. This class is a Singleton and contains a thread doing the cache writes asynchronously, thus it must be stopped before your application is terminated calling the stop() method. Sample code: >>> # import module >>> from entropy.cache import EntropyCacher ... >>> # first EntropyCacher load, start it >>> cacher = EntropyCacher() >>> cacher.start() ... >>> # now store something into its cache >>> cacher.push('my_identifier1', [1, 2, 3]) >>> # now store something synchronously >>> cacher.push('my_identifier2', [1, 2, 3], async = False) ... >>> # now flush all the caches to disk, and make sure all >>> # is written >>> cacher.sync() ... >>> # now fetch something from the cache >>> data = cacher.pop('my_identifier1') [1, 2, 3] ... >>> # now discard all the cached (async) writes >>> cacher.discard() ... >>> # and stop EntropyCacher >>> cacher.stop() """ class SemaphoreTimeScheduled(TimeScheduled): def __init__(self, sem, *args, **kwargs): self._sem = sem TimeScheduled.__init__(self, *args, **kwargs) def kill(self): self._sem.release() return TimeScheduled.kill(self) def init_singleton(self): """ Singleton overloaded method. Equals to __init__. This is the place where all the properties initialization takes place. """ self.__exit_registered = False self.__copy = copy self.__alive = False self.__cache_writer = None self.__cache_buffer = Lifo() self.__stashing_cache = {} self.__inside_with_stmt = 0 self.__proc_pids = set() self.__proc_pids_lock = threading.Lock() self.__dump_data_lock = threading.Lock() self.__worker_sem = threading.Semaphore(0) # this lock ensures that all the writes are hold while it's acquired self.__enter_context_lock = threading.RLock() def __enter__(self): """ When used with the with statement, pause cacher on-disk writes. """ self.__enter_context_lock.acquire() self.__inside_with_stmt += 1 def __exit__(self, exc_type, exc_value, traceback): """ When used with the with statement, pause cacher on-disk writes. """ self.__inside_with_stmt -= 1 self.__enter_context_lock.release() def __copy_obj(self, obj): """ Return a copy of an object done by the standard library "copy" module. @param obj: object to copy @type obj: any Python object @rtype: copied object @return: copied object """ return self.__copy.deepcopy(obj) def __clean_pids(self): with self.__proc_pids_lock: dead_pids = set() for pid in self.__proc_pids: try: dead = os.waitpid(pid, os.WNOHANG)[0] except OSError as err: if err.errno != errno.ECHILD: raise dead = True if dead: dead_pids.add(pid) elif not const_pid_exists(pid): dead_pids.add(pid) if dead_pids: self.__proc_pids.difference_update(dead_pids) def __wait_cacher_semaphore(self): self.__clean_pids() while len(self.__proc_pids) > EntropyCacher._PROC_LIMIT: if etpUi['debug']: const_debug_write(__name__, "EntropyCacher.__wait_cacher_semaphore: too many pids") time.sleep(0.1) self.__clean_pids() def __cacher(self, run_until_empty = False, sync = False, _loop=False): """ This is where the actual asynchronous copy takes place. __cacher runs on a different threads and all the operations done by this are atomic and thread-safe. It just loops over and over until __alive becomes False. """ try: if self.__inside_with_stmt != 0: return except AttributeError: # interpreter shutdown pass # make sure our set delay is respected try: self.__cache_writer.set_delay(EntropyCacher.WRITEBACK_TIMEOUT) except AttributeError: # can be None pass # sleep if there's nothing to do if _loop: try: # CANBLOCK self.__worker_sem.acquire() except AttributeError: pass while self.__alive or run_until_empty: if etpUi['debug']: const_debug_write(__name__, "EntropyCacher.__cacher: loop, alive: %s, empty: %s" % ( self.__alive, run_until_empty,)) with self.__enter_context_lock: massive_data = [] try: massive_data_count = EntropyCacher._OBJS_WRITTEN_AT_ONCE except AttributeError: # interpreter shutdown break while massive_data_count > 0: massive_data_count -= 1 try: data = self.__cache_buffer.pop() except (ValueError, TypeError,): # TypeError is when objects are being destroyed break # stack empty massive_data.append(data) # this must stay before massive_data to make sure to clean # every defunct process self.__wait_cacher_semaphore() if not massive_data: break pid = os.fork() if pid == 0: # make sure there's nothing weird bound to exception hook sys.excepthook = sys.__excepthook__ for (key, cache_dir), data in massive_data: d_o = entropy.dump.dumpobj if d_o is not None: d_o(key, data, dump_dir = cache_dir) os._exit(0) else: if etpUi['debug']: const_debug_write(__name__, "EntropyCacher.__cacher [%s], writing %s objs" % ( pid, len(massive_data),)) with self.__proc_pids_lock: self.__proc_pids.add(pid) if sync: try: os.waitpid(pid, 0) except OSError as err: if err.errno != errno.ECHILD: raise for (key, cache_dir), data in massive_data: try: del self.__stashing_cache[(key, cache_dir)] except (AttributeError, KeyError,): continue del massive_data[:] del massive_data def __del__(self): self.stop() @staticmethod def current_directory(): """ Return the path to current EntropyCacher cache storage directory. """ return entropy.dump.D_DIR def start(self): """ This is the method used to start the asynchronous cache writer but also the whole cacher. If this method is not called, the instance will always trash and cache write request. @return: None """ # If EntropyCacher is started, its thread could hang a the process # termination phase. So, register an exit handler against Python if not self.__exit_registered: def _stop_cacher(): EntropyCacher().stop() atexit.register(_stop_cacher) self.__exit_registered = True self.__cache_buffer.clear() self.__cache_writer = EntropyCacher.SemaphoreTimeScheduled( self.__worker_sem, EntropyCacher.WRITEBACK_TIMEOUT, self.__cacher, _loop=True) self.__cache_writer.daemon = True self.__cache_writer.setName("EntropyCacher") self.__cache_writer.set_delay_before(True) self.__cache_writer.start() while not self.__cache_writer.isAlive(): continue self.__alive = True def is_started(self): """ Return whether start is called or not. This equals to checking if the cacher is running, thus is writing cache to disk. @return: None """ return self.__alive def stop(self): """ This method stops the execution of the cacher, which won't accept cache writes anymore. The thread responsible of writing to disk is stopped here and the Cacher will be back to being inactive. A watchdog will avoid the thread to freeze the call if the write buffer is overloaded. @return: None """ self.__alive = False if self.__cache_writer is not None: self.__cache_writer.kill() self.__cache_writer.join() self.__cache_writer = None self.sync() def sync(self): """ This method can be called anytime and forces the instance to flush all the cache writes queued to disk. If wait == False a watchdog prevents this call to get stuck in case of write buffer overloads. """ self.__cacher(run_until_empty = True, sync = True) def discard(self): """ This method makes buffered cache to be discarded synchronously. @return: None """ self.__cache_buffer.clear() self.__stashing_cache.clear() def save(self, key, data, cache_dir = None): """ Save data object to cache asynchronously and in any case. This method guarantees that cached data is stored even if cacher is not started. If data cannot be stored, IOError will be raised. @param key: cache data identifier @type key: string @param data: picklable object @type data: any picklable object @keyword cache_dir: alternative cache directory @type cache_dir: string """ if cache_dir is None: cache_dir = EntropyCacher.current_directory() try: with self.__dump_data_lock: entropy.dump.dumpobj(key, data, dump_dir = cache_dir, ignore_exceptions = False) except (EOFError, IOError, OSError) as err: raise IOError("cannot store %s to %s. err: %s" % ( key, cache_dir, repr(err))) def push(self, key, data, async = True, cache_dir = None): """ This is the place where data is either added to the write queue or written to disk (if async == False) only and only if start() method has been called. @param key: cache data identifier @type key: string @param data: picklable object @type data: any picklable object @keyword async: store cache asynchronously or not @type async: bool @keyword cache_dir: alternative cache directory @type cache_dir: string """ if not self.__alive: return if cache_dir is None: cache_dir = EntropyCacher.current_directory() if async: try: obj_copy = self.__copy_obj(data) self.__cache_buffer.push(((key, cache_dir,), obj_copy,)) self.__worker_sem.release() self.__stashing_cache[(key, cache_dir)] = obj_copy except TypeError: # sometimes, very rarely, copy.deepcopy() is unable # to properly copy an object (blame Python bug) sys.stdout.write("!!! cannot cache object with key %s\n" % ( key,)) sys.stdout.flush() #if etpUi['debug']: # const_debug_write(__name__, # "EntropyCacher.push, async push %s, into %s" % ( # key, cache_dir,)) else: #if etpUi['debug']: # const_debug_write(__name__, # "EntropyCacher.push, sync push %s, into %s" % ( # key, cache_dir,)) with self.__dump_data_lock: entropy.dump.dumpobj(key, data, dump_dir = cache_dir) def pop(self, key, cache_dir = None): """ This is the place where data is retrieved from cache. You must know the cache identifier used when push() was called. @param key: cache data identifier @type key: string @keyword cache_dir: alternative cache directory @type cache_dir: string @rtype: Python object @return: object stored into the stack or None (if stack is empty) """ if cache_dir is None: cache_dir = EntropyCacher.current_directory() # object is being saved on disk, it's in RAM atm ram_obj = self.__stashing_cache.get((key, cache_dir)) if ram_obj is not None: return ram_obj l_o = entropy.dump.loadobj if not l_o: return return l_o(key, dump_dir = cache_dir) @staticmethod def clear_cache_item(cache_item, cache_dir = None): """ Clear Entropy Cache item from on-disk cache. @param cache_item: Entropy Cache item identifier @type cache_item: string @keyword cache_dir: alternative cache directory @type cache_dir: string """ if cache_dir is None: cache_dir = EntropyCacher.current_directory() dump_path = os.path.join(cache_dir, cache_item) dump_dir = os.path.dirname(dump_path) for currentdir, subdirs, files in os.walk(dump_dir): path = os.path.join(dump_dir, currentdir) for item in files: if item.endswith(entropy.dump.D_EXT): item = os.path.join(path, item) try: os.remove(item) except (OSError, IOError,): pass try: if not os.listdir(path): os.rmdir(path) except (OSError, IOError,): pass @staticmethod def clear_cache(excluded_items = None, cache_dir = None): """ Clear all the on-disk cache items included in EntropyCacher.CACHE_IDS. @keyword excluded_items: list of items to exclude from cleaning @type excluded_items: list @keyword cache_dir: alternative cache directory @type cache_dir: string """ if excluded_items is None: excluded_items = [] for key, value in EntropyCacher.CACHE_IDS.items(): if key in excluded_items: continue EntropyCacher.clear_cache_item(value, cache_dir = cache_dir) class MtimePingus(object): """ This class can be used to store on-disk mtime of executed calls. This can be handy for cache expiration validation. Example of usage: >>> from entropy.cache import MtimePingus >>> pingus = MtimePingus() >>> pingus.ping("my_action_string") >>> pingus.pong("my_action_string) 19501230123.0 >>> pingus.hours_passed("my_action_string", 3) False >>> pingus.minutes_passed("my_action_string", 60) False >>> pingus seconds_passed("my_action_string", 15) False """ PINGUS_DIR = os.path.join(etpConst['entropyworkdir'], "pingus_cache") def __init__(self): object.__init__(self) self.__dump_lock = threading.Lock() try: if not os.path.isdir(MtimePingus.PINGUS_DIR): os.makedirs(MtimePingus.PINGUS_DIR, 0o775) const_setup_perms(MtimePingus.PINGUS_DIR, etpConst['entropygid']) except (OSError, IOError,): MtimePingus.PINGUS_DIR = tempfile.mkdtemp() # what else can I do? def _hash_key(self, key): """ Create a hash representation of string. """ return str(hash(key)) def ping(self, action_string): """ Actually store a ping action mtime. @param action_string: action identifier @type action_string: string """ _hash = self._hash_key(action_string) with self.__dump_lock: entropy.dump.dumpobj(_hash, time.time(), dump_dir = MtimePingus.PINGUS_DIR) def pong(self, action_string): """ Actually retrieve a ping action mtime. @param action_string: action identifier @type action_string: string @return: mtime (float) or None @rtype: float or None """ _hash = self._hash_key(action_string) with self.__dump_lock: return entropy.dump.loadobj(_hash, dump_dir = MtimePingus.PINGUS_DIR) def seconds_passed(self, action_string, seconds): """ Determine whether given seconds are passed since last ping against action_string. This also returns True if action_string does not exist. @param action_string: action identifier @type action_string: string @param seconds: seconds passed @type seconds: int @return: True, if seconds are passed @rtype: bool """ mtime = self.pong(action_string) if mtime is None: return True return time.time() > (mtime + seconds) def minutes_passed(self, action_string, minutes): """ Determine whether given minutes are passed since last ping against action_string. This also returns True if action_string does not exist. @param action_string: action identifier @type action_string: string @param minutes: minutes passed @type minutes: int @return: True, if minutes are passed @rtype: bool """ mtime = self.pong(action_string) if mtime is None: return True return time.time() > (mtime + minutes*60) def hours_passed(self, action_string, hours): """ Determine whether given hours are passed since last ping against action_string. This also returns True if action_string does not exist. @param action_string: action identifier @type action_string: string @param hours: minutes passed @type hours: int @return: True, if hours are passed @rtype: bool """ mtime = self.pong(action_string) if mtime is None: return True return time.time() > (mtime + hours*3600)