Initial commit

venv/lib/python3.9/site-packages/diskcache/fanout.py

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+"""Fanout cache automatically shards keys and values."""
+
+import contextlib as cl
+import functools
+import itertools as it
+import operator
+import os.path as op
+import sqlite3
+import tempfile
+import time
+
+from .core import DEFAULT_SETTINGS, ENOVAL, Cache, Disk, Timeout
+from .persistent import Deque, Index
+
+
+class FanoutCache:
+    """Cache that shards keys and values."""
+
+    def __init__(
+        self, directory=None, shards=8, timeout=0.010, disk=Disk, **settings
+    ):
+        """Initialize cache instance.
+
+        :param str directory: cache directory
+        :param int shards: number of shards to distribute writes
+        :param float timeout: SQLite connection timeout
+        :param disk: `Disk` instance for serialization
+        :param settings: any of `DEFAULT_SETTINGS`
+
+        """
+        if directory is None:
+            directory = tempfile.mkdtemp(prefix='diskcache-')
+        directory = str(directory)
+        directory = op.expanduser(directory)
+        directory = op.expandvars(directory)
+
+        default_size_limit = DEFAULT_SETTINGS['size_limit']
+        size_limit = settings.pop('size_limit', default_size_limit) / shards
+
+        self._count = shards
+        self._directory = directory
+        self._disk = disk
+        self._shards = tuple(
+            Cache(
+                directory=op.join(directory, '%03d' % num),
+                timeout=timeout,
+                disk=disk,
+                size_limit=size_limit,
+                **settings,
+            )
+            for num in range(shards)
+        )
+        self._hash = self._shards[0].disk.hash
+        self._caches = {}
+        self._deques = {}
+        self._indexes = {}
+
+    @property
+    def directory(self):
+        """Cache directory."""
+        return self._directory
+
+    def __getattr__(self, name):
+        safe_names = {'timeout', 'disk'}
+        valid_name = name in DEFAULT_SETTINGS or name in safe_names
+        assert valid_name, 'cannot access {} in cache shard'.format(name)
+        return getattr(self._shards[0], name)
+
+    @cl.contextmanager
+    def transact(self, retry=True):
+        """Context manager to perform a transaction by locking the cache.
+
+        While the cache is locked, no other write operation is permitted.
+        Transactions should therefore be as short as possible. Read and write
+        operations performed in a transaction are atomic. Read operations may
+        occur concurrent to a transaction.
+
+        Transactions may be nested and may not be shared between threads.
+
+        Blocks until transactions are held on all cache shards by retrying as
+        necessary.
+
+        >>> cache = FanoutCache()
+        >>> with cache.transact():  # Atomically increment two keys.
+        ...     _ = cache.incr('total', 123.4)
+        ...     _ = cache.incr('count', 1)
+        >>> with cache.transact():  # Atomically calculate average.
+        ...     average = cache['total'] / cache['count']
+        >>> average
+        123.4
+
+        :return: context manager for use in `with` statement
+
+        """
+        assert retry, 'retry must be True in FanoutCache'
+        with cl.ExitStack() as stack:
+            for shard in self._shards:
+                shard_transaction = shard.transact(retry=True)
+                stack.enter_context(shard_transaction)
+            yield
+
+    def set(self, key, value, expire=None, read=False, tag=None, retry=False):
+        """Set `key` and `value` item in cache.
+
+        When `read` is `True`, `value` should be a file-like object opened
+        for reading in binary mode.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param value: value for item
+        :param float expire: seconds until the key expires
+            (default None, no expiry)
+        :param bool read: read value as raw bytes from file (default False)
+        :param str tag: text to associate with key (default None)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: True if item was set
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.set(key, value, expire, read, tag, retry)
+        except Timeout:
+            return False
+
+    def __setitem__(self, key, value):
+        """Set `key` and `value` item in cache.
+
+        Calls :func:`FanoutCache.set` internally with `retry` set to `True`.
+
+        :param key: key for item
+        :param value: value for item
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        shard[key] = value
+
+    def touch(self, key, expire=None, retry=False):
+        """Touch `key` in cache and update `expire` time.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param float expire: seconds until the key expires
+            (default None, no expiry)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: True if key was touched
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.touch(key, expire, retry)
+        except Timeout:
+            return False
+
+    def add(self, key, value, expire=None, read=False, tag=None, retry=False):
+        """Add `key` and `value` item to cache.
+
+        Similar to `set`, but only add to cache if key not present.
+
+        This operation is atomic. Only one concurrent add operation for given
+        key from separate threads or processes will succeed.
+
+        When `read` is `True`, `value` should be a file-like object opened
+        for reading in binary mode.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param value: value for item
+        :param float expire: seconds until the key expires
+            (default None, no expiry)
+        :param bool read: read value as bytes from file (default False)
+        :param str tag: text to associate with key (default None)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: True if item was added
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.add(key, value, expire, read, tag, retry)
+        except Timeout:
+            return False
+
+    def incr(self, key, delta=1, default=0, retry=False):
+        """Increment value by delta for item with key.
+
+        If key is missing and default is None then raise KeyError. Else if key
+        is missing and default is not None then use default for value.
+
+        Operation is atomic. All concurrent increment operations will be
+        counted individually.
+
+        Assumes value may be stored in a SQLite column. Most builds that target
+        machines with 64-bit pointer widths will support 64-bit signed
+        integers.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param int delta: amount to increment (default 1)
+        :param int default: value if key is missing (default 0)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: new value for item on success else None
+        :raises KeyError: if key is not found and default is None
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.incr(key, delta, default, retry)
+        except Timeout:
+            return None
+
+    def decr(self, key, delta=1, default=0, retry=False):
+        """Decrement value by delta for item with key.
+
+        If key is missing and default is None then raise KeyError. Else if key
+        is missing and default is not None then use default for value.
+
+        Operation is atomic. All concurrent decrement operations will be
+        counted individually.
+
+        Unlike Memcached, negative values are supported. Value may be
+        decremented below zero.
+
+        Assumes value may be stored in a SQLite column. Most builds that target
+        machines with 64-bit pointer widths will support 64-bit signed
+        integers.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param int delta: amount to decrement (default 1)
+        :param int default: value if key is missing (default 0)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: new value for item on success else None
+        :raises KeyError: if key is not found and default is None
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.decr(key, delta, default, retry)
+        except Timeout:
+            return None
+
+    def get(
+        self,
+        key,
+        default=None,
+        read=False,
+        expire_time=False,
+        tag=False,
+        retry=False,
+    ):
+        """Retrieve value from cache. If `key` is missing, return `default`.
+
+        If database timeout occurs then returns `default` unless `retry` is set
+        to `True` (default `False`).
+
+        :param key: key for item
+        :param default: return value if key is missing (default None)
+        :param bool read: if True, return file handle to value
+            (default False)
+        :param float expire_time: if True, return expire_time in tuple
+            (default False)
+        :param tag: if True, return tag in tuple (default False)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: value for item if key is found else default
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.get(key, default, read, expire_time, tag, retry)
+        except (Timeout, sqlite3.OperationalError):
+            return default
+
+    def __getitem__(self, key):
+        """Return corresponding value for `key` from cache.
+
+        Calls :func:`FanoutCache.get` internally with `retry` set to `True`.
+
+        :param key: key for item
+        :return: value for item
+        :raises KeyError: if key is not found
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        return shard[key]
+
+    def read(self, key):
+        """Return file handle corresponding to `key` from cache.
+
+        :param key: key for item
+        :return: file open for reading in binary mode
+        :raises KeyError: if key is not found
+
+        """
+        handle = self.get(key, default=ENOVAL, read=True, retry=True)
+        if handle is ENOVAL:
+            raise KeyError(key)
+        return handle
+
+    def __contains__(self, key):
+        """Return `True` if `key` matching item is found in cache.
+
+        :param key: key for item
+        :return: True if key is found
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        return key in shard
+
+    def pop(
+        self, key, default=None, expire_time=False, tag=False, retry=False
+    ):  # noqa: E501
+        """Remove corresponding item for `key` from cache and return value.
+
+        If `key` is missing, return `default`.
+
+        Operation is atomic. Concurrent operations will be serialized.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param default: return value if key is missing (default None)
+        :param float expire_time: if True, return expire_time in tuple
+            (default False)
+        :param tag: if True, return tag in tuple (default False)
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: value for item if key is found else default
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.pop(key, default, expire_time, tag, retry)
+        except Timeout:
+            return default
+
+    def delete(self, key, retry=False):
+        """Delete corresponding item for `key` from cache.
+
+        Missing keys are ignored.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param key: key for item
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: True if item was deleted
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        try:
+            return shard.delete(key, retry)
+        except Timeout:
+            return False
+
+    def __delitem__(self, key):
+        """Delete corresponding item for `key` from cache.
+
+        Calls :func:`FanoutCache.delete` internally with `retry` set to `True`.
+
+        :param key: key for item
+        :raises KeyError: if key is not found
+
+        """
+        index = self._hash(key) % self._count
+        shard = self._shards[index]
+        del shard[key]
+
+    def check(self, fix=False, retry=False):
+        """Check database and file system consistency.
+
+        Intended for use in testing and post-mortem error analysis.
+
+        While checking the cache table for consistency, a writer lock is held
+        on the database. The lock blocks other cache clients from writing to
+        the database. For caches with many file references, the lock may be
+        held for a long time. For example, local benchmarking shows that a
+        cache with 1,000 file references takes ~60ms to check.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param bool fix: correct inconsistencies
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: list of warnings
+        :raises Timeout: if database timeout occurs
+
+        """
+        warnings = (shard.check(fix, retry) for shard in self._shards)
+        return functools.reduce(operator.iadd, warnings, [])
+
+    def expire(self, retry=False):
+        """Remove expired items from cache.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: count of items removed
+
+        """
+        return self._remove('expire', args=(time.time(),), retry=retry)
+
+    def create_tag_index(self):
+        """Create tag index on cache database.
+
+        Better to initialize cache with `tag_index=True` than use this.
+
+        :raises Timeout: if database timeout occurs
+
+        """
+        for shard in self._shards:
+            shard.create_tag_index()
+
+    def drop_tag_index(self):
+        """Drop tag index on cache database.
+
+        :raises Timeout: if database timeout occurs
+
+        """
+        for shard in self._shards:
+            shard.drop_tag_index()
+
+    def evict(self, tag, retry=False):
+        """Remove items with matching `tag` from cache.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param str tag: tag identifying items
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: count of items removed
+
+        """
+        return self._remove('evict', args=(tag,), retry=retry)
+
+    def cull(self, retry=False):
+        """Cull items from cache until volume is less than size limit.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: count of items removed
+
+        """
+        return self._remove('cull', retry=retry)
+
+    def clear(self, retry=False):
+        """Remove all items from cache.
+
+        If database timeout occurs then fails silently unless `retry` is set to
+        `True` (default `False`).
+
+        :param bool retry: retry if database timeout occurs (default False)
+        :return: count of items removed
+
+        """
+        return self._remove('clear', retry=retry)
+
+    def _remove(self, name, args=(), retry=False):
+        total = 0
+        for shard in self._shards:
+            method = getattr(shard, name)
+            while True:
+                try:
+                    count = method(*args, retry=retry)
+                    total += count
+                except Timeout as timeout:
+                    total += timeout.args[0]
+                else:
+                    break
+        return total
+
+    def stats(self, enable=True, reset=False):
+        """Return cache statistics hits and misses.
+
+        :param bool enable: enable collecting statistics (default True)
+        :param bool reset: reset hits and misses to 0 (default False)
+        :return: (hits, misses)
+
+        """
+        results = [shard.stats(enable, reset) for shard in self._shards]
+        total_hits = sum(hits for hits, _ in results)
+        total_misses = sum(misses for _, misses in results)
+        return total_hits, total_misses
+
+    def volume(self):
+        """Return estimated total size of cache on disk.
+
+        :return: size in bytes
+
+        """
+        return sum(shard.volume() for shard in self._shards)
+
+    def close(self):
+        """Close database connection."""
+        for shard in self._shards:
+            shard.close()
+        self._caches.clear()
+        self._deques.clear()
+        self._indexes.clear()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *exception):
+        self.close()
+
+    def __getstate__(self):
+        return (self._directory, self._count, self.timeout, type(self.disk))
+
+    def __setstate__(self, state):
+        self.__init__(*state)
+
+    def __iter__(self):
+        """Iterate keys in cache including expired items."""
+        iterators = (iter(shard) for shard in self._shards)
+        return it.chain.from_iterable(iterators)
+
+    def __reversed__(self):
+        """Reverse iterate keys in cache including expired items."""
+        iterators = (reversed(shard) for shard in reversed(self._shards))
+        return it.chain.from_iterable(iterators)
+
+    def __len__(self):
+        """Count of items in cache including expired items."""
+        return sum(len(shard) for shard in self._shards)
+
+    def reset(self, key, value=ENOVAL):
+        """Reset `key` and `value` item from Settings table.
+
+        If `value` is not given, it is reloaded from the Settings
+        table. Otherwise, the Settings table is updated.
+
+        Settings attributes on cache objects are lazy-loaded and
+        read-only. Use `reset` to update the value.
+
+        Settings with the ``sqlite_`` prefix correspond to SQLite
+        pragmas. Updating the value will execute the corresponding PRAGMA
+        statement.
+
+        :param str key: Settings key for item
+        :param value: value for item (optional)
+        :return: updated value for item
+
+        """
+        for shard in self._shards:
+            while True:
+                try:
+                    result = shard.reset(key, value)
+                except Timeout:
+                    pass
+                else:
+                    break
+        return result
+
+    def cache(self, name, timeout=60, disk=None, **settings):
+        """Return Cache with given `name` in subdirectory.
+
+        If disk is none (default), uses the fanout cache disk.
+
+        >>> fanout_cache = FanoutCache()
+        >>> cache = fanout_cache.cache('test')
+        >>> cache.set('abc', 123)
+        True
+        >>> cache.get('abc')
+        123
+        >>> len(cache)
+        1
+        >>> cache.delete('abc')
+        True
+
+        :param str name: subdirectory name for Cache
+        :param float timeout: SQLite connection timeout
+        :param disk: Disk type or subclass for serialization
+        :param settings: any of DEFAULT_SETTINGS
+        :return: Cache with given name
+
+        """
+        _caches = self._caches
+
+        try:
+            return _caches[name]
+        except KeyError:
+            parts = name.split('/')
+            directory = op.join(self._directory, 'cache', *parts)
+            temp = Cache(
+                directory=directory,
+                timeout=timeout,
+                disk=self._disk if disk is None else Disk,
+                **settings,
+            )
+            _caches[name] = temp
+            return temp
+
+    def deque(self, name, maxlen=None):
+        """Return Deque with given `name` in subdirectory.
+
+        >>> cache = FanoutCache()
+        >>> deque = cache.deque('test')
+        >>> deque.extend('abc')
+        >>> deque.popleft()
+        'a'
+        >>> deque.pop()
+        'c'
+        >>> len(deque)
+        1
+
+        :param str name: subdirectory name for Deque
+        :param maxlen: max length (default None, no max)
+        :return: Deque with given name
+
+        """
+        _deques = self._deques
+
+        try:
+            return _deques[name]
+        except KeyError:
+            parts = name.split('/')
+            directory = op.join(self._directory, 'deque', *parts)
+            cache = Cache(
+                directory=directory,
+                disk=self._disk,
+                eviction_policy='none',
+            )
+            deque = Deque.fromcache(cache, maxlen=maxlen)
+            _deques[name] = deque
+            return deque
+
+    def index(self, name):
+        """Return Index with given `name` in subdirectory.
+
+        >>> cache = FanoutCache()
+        >>> index = cache.index('test')
+        >>> index['abc'] = 123
+        >>> index['def'] = 456
+        >>> index['ghi'] = 789
+        >>> index.popitem()
+        ('ghi', 789)
+        >>> del index['abc']
+        >>> len(index)
+        1
+        >>> index['def']
+        456
+
+        :param str name: subdirectory name for Index
+        :return: Index with given name
+
+        """
+        _indexes = self._indexes
+
+        try:
+            return _indexes[name]
+        except KeyError:
+            parts = name.split('/')
+            directory = op.join(self._directory, 'index', *parts)
+            cache = Cache(
+                directory=directory,
+                disk=self._disk,
+                eviction_policy='none',
+            )
+            index = Index.fromcache(cache)
+            _indexes[name] = index
+            return index
+
+
+FanoutCache.memoize = Cache.memoize  # type: ignore