Note

You are reading an old version of the Evennia documentation. The latest version is here

.

# Source code for evennia.utils.idmapper.models

    """
    Django ID mapper

    Modified for Evennia by making sure that no model references
    leave caching unexpectedly (no use of WeakRefs).

    Also adds `cache_size()` for monitoring the size of the cache.
    """

    import gc
    import os
    import threading
    import time
    from weakref import WeakValueDictionary

    from django.core.exceptions import FieldError, ObjectDoesNotExist
    from django.db.models.base import Model, ModelBase
    from django.db.models.signals import post_migrate, post_save, pre_delete
    from django.db.transaction import atomic
    from django.db.utils import DatabaseError
    from twisted.internet.reactor import callFromThread

    from evennia.utils import logger
    from evennia.utils.utils import dbref, get_evennia_pids, to_str

    from .manager import SharedMemoryManager

    AUTO_FLUSH_MIN_INTERVAL = 60.0 * 5  # at least 5 mins between cache flushes

    _GA = object.__getattribute__
    _SA = object.__setattr__
    _DA = object.__delattr__
    _MONITOR_HANDLER = None

    # References to db-updated objects are stored here so the
    # main process can be informed to re-cache itself.
    PROC_MODIFIED_COUNT = 0
    PROC_MODIFIED_OBJS = WeakValueDictionary()

    # get info about the current process and thread; determine if our
    # current pid is different from the server PID (i.e.  # if we are in a
    # subprocess or not)
    _SELF_PID = os.getpid()
    _SERVER_PID, _PORTAL_PID = get_evennia_pids()
    _IS_SUBPROCESS = (_SERVER_PID and _PORTAL_PID) and _SELF_PID not in (_SERVER_PID, _PORTAL_PID)
    _IS_MAIN_THREAD = threading.current_thread().name == "MainThread"

    class SharedMemoryModelBase(ModelBase):
        # CL: upstream had a __new__ method that skipped ModelBase's __new__ if
        # SharedMemoryModelBase was not in the model class's ancestors. It's not
        # clear what was the intended purpose, but skipping ModelBase.__new__
        # broke things; in particular, default manager inheritance.

        def __call__(cls, *args, **kwargs):
            """
            this method will either create an instance (by calling the default implementation)
            or try to retrieve one from the class-wide cache by inferring the pk value from
            `args` and `kwargs`. If instance caching is enabled for this class, the cache is
            populated whenever possible (ie when it is possible to infer the pk value).

            """

            def new_instance():
                return super(SharedMemoryModelBase, cls).__call__(*args, **kwargs)

            instance_key = cls._get_cache_key(args, kwargs)
            # depending on the arguments, we might not be able to infer the PK, so in that case we
            # create a new instance
            if instance_key is None:
                return new_instance()
            cached_instance = cls.get_cached_instance(instance_key)
            if cached_instance is None:
                cached_instance = new_instance()
                cls.cache_instance(cached_instance, new=True)
            return cached_instance

        def _prepare(cls):
            """
            Prepare the cache, making sure that proxies of the same db base
            share the same cache.

            """
            # the dbmodel is either the proxy base or ourselves
            dbmodel = cls._meta.concrete_model if cls._meta.proxy else cls
            cls.__dbclass__ = dbmodel
            if not hasattr(dbmodel, "__instance_cache__"):
                # we store __instance_cache__ only on the dbmodel base
                dbmodel.__instance_cache__ = {}
            super()._prepare()

        def __new__(cls, name, bases, attrs):
            """
            Field shortcut creation:

            Takes field names `db_*` and creates property wrappers named
            without the `db_` prefix. So db_key -> key

            This wrapper happens on the class level, so there is no
            overhead when creating objects.  If a class already has a
            wrapper of the given name, the automatic creation is skipped.

            Notes:
                Remember to document this auto-wrapping in the class
                header, this could seem very much like magic to the user
                otherwise.
            """

            attrs["typename"] = cls.__name__
            attrs["path"] = "%s.%s" % (attrs["__module__"], name)
            attrs["_is_deleted"] = False

            # set up the typeclass handling only if a variable _is_typeclass is set on the class
            def create_wrapper(cls, fieldname, wrappername, editable=True, foreignkey=False):
                "Helper method to create property wrappers with unique names (must be in separate call)"

                def _get(cls, fname):
                    "Wrapper for getting database field"
                    if _GA(cls, "_is_deleted"):
                        raise ObjectDoesNotExist(
                            "Cannot access %s: Hosting object was already deleted." % fname
                        )
                    return _GA(cls, fieldname)

                def _get_foreign(cls, fname):
                    "Wrapper for returning foreignkey fields"
                    if _GA(cls, "_is_deleted"):
                        raise ObjectDoesNotExist(
                            "Cannot access %s: Hosting object was already deleted." % fname
                        )
                    return _GA(cls, fieldname)

                def _set_nonedit(cls, fname, value):
                    "Wrapper for blocking editing of field"
                    raise FieldError("Field %s cannot be edited." % fname)

                def _set(cls, fname, value):
                    "Wrapper for setting database field"
                    if _GA(cls, "_is_deleted"):
                        raise ObjectDoesNotExist(
                            "Cannot set %s to %s: Hosting object was already deleted!" % (fname, value)
                        )
                    _SA(cls, fname, value)
                    # only use explicit update_fields in save if we actually have a
                    # primary key assigned already (won't be set when first creating object)
                    update_fields = (
                        [fname] if _GA(cls, "_get_pk_val")(_GA(cls, "_meta")) is not None else None
                    )
                    _GA(cls, "save")(update_fields=update_fields)

                def _set_foreign(cls, fname, value):
                    "Setter only used on foreign key relations, allows setting with #dbref"
                    if _GA(cls, "_is_deleted"):
                        raise ObjectDoesNotExist(
                            "Cannot set %s to %s: Hosting object was already deleted!" % (fname, value)
                        )
                    if isinstance(value, (str, int)):
                        value = to_str(value)
                        if value.isdigit() or value.startswith("#"):
                            # we also allow setting using dbrefs, if so we try to load the matching
                            # object. (we assume the object is of the same type as the class holding
                            # the field, if not a custom handler must be used for that field)
                            dbid = dbref(value, reqhash=False)
                            if dbid:
                                model = _GA(cls, "_meta").get_field(fname).model
                                try:
                                    value = model._default_manager.get(id=dbid)
                                except ObjectDoesNotExist:
                                    # maybe it is just a name that happens to look like a dbid
                                    pass
                    _SA(cls, fname, value)
                    # only use explicit update_fields in save if we actually have a
                    # primary key assigned already (won't be set when first creating object)
                    update_fields = (
                        [fname] if _GA(cls, "_get_pk_val")(_GA(cls, "_meta")) is not None else None
                    )
                    _GA(cls, "save")(update_fields=update_fields)

                def _del_nonedit(cls, fname):
                    "wrapper for not allowing deletion"
                    raise FieldError("Field %s cannot be edited." % fname)

                def _del(cls, fname):
                    "Wrapper for clearing database field - sets it to None"
                    _SA(cls, fname, None)
                    update_fields = (
                        [fname] if _GA(cls, "_get_pk_val")(_GA(cls, "_meta")) is not None else None
                    )
                    _GA(cls, "save")(update_fields=update_fields)

                # wrapper factories
                if not editable:

                    def fget(cls):
                        return _get(cls, fieldname)

                    def fset(cls, val):
                        return _set_nonedit(cls, fieldname, val)

                elif foreignkey:

                    def fget(cls):
                        return _get_foreign(cls, fieldname)

                    def fset(cls, val):
                        return _set_foreign(cls, fieldname, val)

                else:

                    def fget(cls):
                        return _get(cls, fieldname)

                    def fset(cls, val):
                        return _set(cls, fieldname, val)

                def fdel(cls):
                    return _del(cls, fieldname) if editable else _del_nonedit(cls, fieldname)

                # set docstrings for auto-doc
                fget.__doc__ = "A wrapper for getting database field `%s`." % fieldname
                fset.__doc__ = "A wrapper for setting (and saving) database field `%s`." % fieldname
                fdel.__doc__ = "A wrapper for deleting database field `%s`." % fieldname
                # assigning
                attrs[wrappername] = property(fget, fset, fdel)
                # type(cls).__setattr__(cls, wrappername, property(fget, fset, fdel))#, doc))

            # exclude some models that should not auto-create wrapper fields
            if cls.__name__ in ("ServerConfig", "TypeNick"):
                return
            # dynamically create the wrapper properties for all fields not already handled
            # (manytomanyfields are always handlers)
            for fieldname, field in (
                (fname, field)
                for fname, field in list(attrs.items())
                if fname.startswith("db_") and type(field).__name__ != "ManyToManyField"
            ):
                foreignkey = type(field).__name__ == "ForeignKey"
                wrappername = "dbid" if fieldname == "id" else fieldname.replace("db_", "", 1)
                if wrappername not in attrs:
                    # makes sure not to overload manually created wrappers on the model
                    create_wrapper(
                        cls, fieldname, wrappername, editable=field.editable, foreignkey=foreignkey
                    )

            return super().__new__(cls, name, bases, attrs)

    class SharedMemoryModel(Model, metaclass=SharedMemoryModelBase):
        """
        Base class for idmapped objects. Inherit from `this`.
        """

        objects = SharedMemoryManager()

        class Meta(object):
            abstract = True

        @classmethod
        def _get_cache_key(cls, args, kwargs):
            """
            This method is used by the caching subsystem to infer the PK
            value from the constructor arguments.  It is used to decide if
            an instance has to be built or is already in the cache.

            """
            result = None
            # Quick hack for my composites work for now.
            if hasattr(cls._meta, "pks"):
                pk = cls._meta.pks[0]
            else:
                pk = cls._meta.pk
            # get the index of the pk in the class fields. this should be calculated *once*, but isn't
            # atm
            pk_position = cls._meta.fields.index(pk)
            if len(args) > pk_position:
                # if it's in the args, we can get it easily by index
                result = args[pk_position]
            elif pk.attname in kwargs:
                # retrieve the pk value. Note that we use attname instead of name, to handle the case
                # where the pk is a a ForeignKey.
                result = kwargs[pk.attname]
            elif pk.name != pk.attname and pk.name in kwargs:
                # ok we couldn't find the value, but maybe it's a FK and we can find the corresponding
                # object instead
                result = kwargs[pk.name]

            if result is not None and isinstance(result, Model):
                # if the pk value happens to be a model instance (which can happen wich a FK), we'd
                # rather use its own pk as the key
                result = result._get_pk_val()
            return result

        @classmethod
        def get_cached_instance(cls, id):
            """
            Method to retrieve a cached instance by pk value. Returns None
            when not found (which will always be the case when caching is
            disabled for this class). Please note that the lookup will be
            done even when instance caching is disabled.

            """
            return cls.__dbclass__.__instance_cache__.get(id)

        @classmethod
        def cache_instance(cls, instance, new=False):
            """
            Method to store an instance in the cache.

            Args:
                instance (Class instance): the instance to cache.
                new (bool, optional): this is the first time this instance is
                    cached (i.e. this is not an update operation like after a
                    db save).

            """
            pk = instance._get_pk_val()
            if pk is not None:
                new = new or pk not in cls.__dbclass__.__instance_cache__
                cls.__dbclass__.__instance_cache__[pk] = instance
                if new:
                    try:
                        # trigger the at_init hook only
                        # at first initialization
                        instance.at_init()
                    except AttributeError:
                        # The at_init hook is not assigned to all entities
                        pass

        @classmethod
        def get_all_cached_instances(cls):
            """
            Return the objects so far cached by idmapper for this class.

            """
            return list(cls.__dbclass__.__instance_cache__.values())

        @classmethod
        def _flush_cached_by_key(cls, key, force=True):
            """
            Remove the cached reference.

            """
            try:
                if force or cls.at_idmapper_flush():
                    del cls.__dbclass__.__instance_cache__[key]
                else:
                    cls._dbclass__.__instance_cache__[key].refresh_from_db()
            except KeyError:
                # No need to remove if cache doesn't contain it already
                pass

        @classmethod
        def flush_cached_instance(cls, instance, force=True):
            """
            Method to flush an instance from the cache. The instance will
            always be flushed from the cache, since this is most likely
            called from delete(), and we want to make sure we don't cache
            dead objects.

            """
            cls._flush_cached_by_key(instance._get_pk_val(), force=force)

        # flush_cached_instance = classmethod(flush_cached_instance)

        @classmethod
        def flush_instance_cache(cls, force=False):
            """
            This will clean safe objects from the cache. Use `force`
            keyword to remove all objects, safe or not.

            """
            if force:
                cls.__dbclass__.__instance_cache__ = {}
            else:
                cls.__dbclass__.__instance_cache__ = dict(
                    (key, obj)
                    for key, obj in cls.__dbclass__.__instance_cache__.items()
                    if not obj.at_idmapper_flush()
                )

        # flush_instance_cache = classmethod(flush_instance_cache)

        # per-instance methods

        def __eq__(self, other):
            return super().__eq__(other)

        def __hash__(self):
            # this is required to maintain hashing
            return super().__hash__()

        def at_idmapper_flush(self):
            """
            This is called when the idmapper cache is flushed and
            allows customized actions when this happens.

            Returns:
                do_flush (bool): If True, flush this object as normal. If
                    False, don't flush and expect this object to handle
                    the flushing on its own.
            """
            return True

        def flush_from_cache(self, force=False):
            """
            Flush this instance from the instance cache. Use
            `force` to override the result of at_idmapper_flush() for the object.

            """
            pk = self._get_pk_val()
            if pk:
                if force or self.at_idmapper_flush():
                    self.__class__.__dbclass__.__instance_cache__.pop(pk, None)

        def delete(self, *args, **kwargs):
            """
            Delete the object, clearing cache.

            """
            self.flush_from_cache()
            self._is_deleted = True
            super().delete(*args, **kwargs)

        def save(self, *args, **kwargs):
            """
            Central database save operation.

            Notes:
                Arguments as per Django documentation.
                Calls `self.at_<fieldname>_postsave(new)`
                (this is a wrapper set by oobhandler:
                self._oob_at_<fieldname>_postsave())

            """
            global _MONITOR_HANDLER
            if not _MONITOR_HANDLER:
                from evennia.scripts.monitorhandler import (
                    MONITOR_HANDLER as _MONITOR_HANDLER,
                )

            if _IS_SUBPROCESS:
                # we keep a store of objects modified in subprocesses so
                # we know to update their caches in the central process
                global PROC_MODIFIED_COUNT, PROC_MODIFIED_OBJS
                PROC_MODIFIED_COUNT += 1
                PROC_MODIFIED_OBJS[PROC_MODIFIED_COUNT] = self

            if _IS_MAIN_THREAD:
                # in main thread - normal operation
                try:
                    with atomic():
                        super().save(*args, **kwargs)
                except DatabaseError:
                    # we handle the 'update_fields did not update any rows' error that
                    # may happen due to timing issues with attributes
                    ufields_removed = kwargs.pop("update_fields", None)
                    if ufields_removed:
                        with atomic():
                            super().save(*args, **kwargs)
                    else:
                        raise
            else:
                # in another thread; make sure to save in reactor thread
                def _save_callback(cls, *args, **kwargs):
                    super().save(*args, **kwargs)

                callFromThread(_save_callback, self, *args, **kwargs)

            if not self.pk:
                # this can happen if some of the startup methods immediately
                # delete the object (an example are Scripts that start and die immediately)
                return

            # update field-update hooks and eventual OOB watchers
            new = False
            if "update_fields" in kwargs and kwargs["update_fields"]:
                # get field objects from their names
                update_fields = (
                    self._meta.get_field(fieldname) for fieldname in kwargs.get("update_fields")
                )
            else:
                # meta.fields are already field objects; get them all
                new = True
                update_fields = self._meta.fields
            for field in update_fields:
                fieldname = field.name
                # trigger eventual monitors
                _MONITOR_HANDLER.at_update(self, fieldname)
                # if a hook is defined it must be named exactly on this form
                hookname = "at_%s_postsave" % fieldname
                if hasattr(self, hookname) and callable(_GA(self, hookname)):
                    _GA(self, hookname)(new)

            #            # if a trackerhandler is set on this object, update it with the
            #            # fieldname and the new value
            #            fieldtracker = "_oob_at_%s_postsave" % fieldname
            #            if hasattr(self, fieldtracker):
            #                _GA(self, fieldtracker)(fieldname)
            pass

    class WeakSharedMemoryModelBase(SharedMemoryModelBase):
        """
        Uses a WeakValue dictionary for caching instead of a regular one.

        """

        def _prepare(cls):
            super()._prepare()
            cls.__dbclass__.__instance_cache__ = WeakValueDictionary()

    class WeakSharedMemoryModel(SharedMemoryModel, metaclass=WeakSharedMemoryModelBase):
        """
        Uses a WeakValue dictionary for caching instead of a regular one

        """

        class Meta(object):
            abstract = True

    def flush_cache(**kwargs):
        """
        Flush idmapper cache. When doing so the cache will fire the
        at_idmapper_flush hook to allow the object to optionally handle
        its own flushing.

        Uses a signal so we make sure to catch cascades.

        """

        def class_hierarchy(clslist):
            """Recursively yield a class hierarchy"""
            for cls in clslist:
                subclass_list = cls.__subclasses__()
                if subclass_list:
                    for subcls in class_hierarchy(subclass_list):
                        yield subcls
                else:
                    yield cls

        for cls in class_hierarchy([SharedMemoryModel]):
            cls.flush_instance_cache()
        # run the python garbage collector
        return gc.collect()

    # request_finished.connect(flush_cache)
    post_migrate.connect(flush_cache)

    def flush_cached_instance(sender, instance, **kwargs):
        """
        Flush the idmapper cache only for a given instance.

        """
        # XXX: Is this the best way to make sure we can flush?
        if not hasattr(instance, "flush_cached_instance"):
            return
        sender.flush_cached_instance(instance, force=True)

    pre_delete.connect(flush_cached_instance)

    def update_cached_instance(sender, instance, **kwargs):
        """
        Re-cache the given instance in the idmapper cache.

        """
        if not hasattr(instance, "cache_instance"):
            return
        sender.cache_instance(instance)

    post_save.connect(update_cached_instance)

    LAST_FLUSH = None

    def conditional_flush(max_rmem, force=False):
        """
        Flush the cache if the estimated memory usage exceeds `max_rmem`.

        The flusher has a timeout to avoid flushing over and over
        in particular situations (this means that for some setups
        the memory usage will exceed the requirement and a server with
        more memory is probably required for the given game).

        Args:
            max_rmem (int): memory-usage estimation-treshold after which
                cache is flushed.
            force (bool, optional): forces a flush, regardless of timeout.
                Defaults to `False`.

        """
        global LAST_FLUSH

        def mem2cachesize(desired_rmem):
            """
            Estimate the size of the idmapper cache based on the memory
            desired. This is used to optionally cap the cache size.

            desired_rmem - memory in MB (minimum 50MB)

            The formula is empirically estimated from usage tests (Linux)
            and is
                Ncache = RMEM - 35.0 / 0.0157
            where RMEM is given in MB and Ncache is the size of the cache
            for this memory usage. VMEM tends to be about 100MB higher
            than RMEM for large memory usage.
            """
            vmem = max(desired_rmem, 50.0)
            Ncache = int(abs(float(vmem) - 35.0) / 0.0157)
            return Ncache

        if not max_rmem:
            # auto-flush is disabled
            return

        now = time.time()
        if not LAST_FLUSH:
            # server is just starting
            LAST_FLUSH = now
            return

        if ((now - LAST_FLUSH) < AUTO_FLUSH_MIN_INTERVAL) and not force:
            # too soon after last flush.
            logger.log_warn(
                "Warning: Idmapper flush called more than once in %s min interval. Check memory usage."
                % (AUTO_FLUSH_MIN_INTERVAL / 60.0)
            )
            return

        if os.name == "nt":
            # we can't look for mem info in Windows at the moment
            return

        # check actual memory usage
        Ncache_max = mem2cachesize(max_rmem)
        Ncache, _ = cache_size()
        actual_rmem = (
            float(os.popen("ps -p %d -o %s | tail -1" % (os.getpid(), "rss")).read()) / 1000.0
        )  # resident memory

        if Ncache >= Ncache_max and actual_rmem > max_rmem * 0.9:
            # flush cache when number of objects in cache is big enough and our
            # actual memory use is within 10% of our set max
            flush_cache()
            LAST_FLUSH = now

    def cache_size(mb=True):
        """
        Calculate statistics about the cache.

        Note: we cannot get reliable memory statistics from the cache -
        whereas we could do `getsizof` each object in cache, the result is
        highly imprecise and for a large number of objects the result is
        many times larger than the actual memory usage of the entire server;
        Python is clearly reusing memory behind the scenes that we cannot
        catch in an easy way here.  Ideas are appreciated. /Griatch

        Returns:
          total_num, {objclass:total_num, ...}

        """
        numtotal = [0]  # use mutable to keep reference through recursion
        classdict = {}

        def get_recurse(submodels):
            for submodel in submodels:
                subclasses = submodel.__subclasses__()
                if not subclasses:
                    num = len(submodel.get_all_cached_instances())
                    numtotal[0] += num
                    classdict[submodel.__dbclass__.__name__] = num
                else:
                    get_recurse(subclasses)

        get_recurse(SharedMemoryModel.__subclasses__())
        return numtotal[0], classdict

Note

You are reading an old version of the Evennia documentation. The latest version is here

.