feat(archive-cache): implemented eviction policy logic

rhodecode/lib/rc_cache/archive_cache/fanout_cache.py

@@ -1,278 +1,412 b''
 # Copyright (C) 2015-2024 RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 import codecs
 import contextlib
 import functools
 import os
 import logging
 import time
 import typing
 import zlib
+import sqlite3
 
 from rhodecode.lib.ext_json import json
 from .lock import GenerationLock
 
 log = logging.getLogger(__name__)
 
 cache_meta = None
 
 UNKNOWN = -241
 NO_VAL = -917
 
 MODE_BINARY = 'BINARY'
 
 
+EVICTION_POLICY = {
+    'none': {
+        'evict': None,
+    },
+    'least-recently-stored': {
+        'evict': 'SELECT {fields} FROM archive_cache ORDER BY store_time',
+    },
+    'least-recently-used': {
+        'evict': 'SELECT {fields} FROM archive_cache ORDER BY access_time',
+    },
+    'least-frequently-used': {
+        'evict': 'SELECT {fields} FROM archive_cache ORDER BY access_count',
+    },
+}
+
+
+class DB:
+
+    def __init__(self):
+        self.connection = sqlite3.connect(':memory:')
+        self._init_db()
+
+    def _init_db(self):
+        qry = '''
+            CREATE TABLE IF NOT EXISTS archive_cache (
+             rowid INTEGER PRIMARY KEY,
+             key_file TEXT,
+             key_file_path TEXT,
+             filename TEXT,
+             full_path TEXT,
+             store_time REAL,
+             access_time REAL,
+             access_count INTEGER DEFAULT 0,
+             size INTEGER DEFAULT 0
+             )
+        '''
+
+        self.sql(qry)
+        self.connection.commit()
+
+    @property
+    def sql(self):
+        return self.connection.execute
+
+    def bulk_insert(self, rows):
+        qry = '''
+            INSERT INTO archive_cache (
+             rowid,
+             key_file,
+             key_file_path,
+             filename,
+             full_path,
+             store_time,
+             access_time,
+             access_count,
+             size
+            )
+            VALUES (
+            ?, ?, ?, ?, ?, ?, ?, ?, ?
+            )
+        '''
+        cursor = self.connection.cursor()
+        cursor.executemany(qry, rows)
+        self.connection.commit()
+
+
 class FileSystemCache:
 
     def __init__(self, index, directory, **settings):
         self._index = index
         self._directory = directory
 
     def _write_file(self, full_path, iterator, mode, encoding=None):
         full_dir, _ = os.path.split(full_path)
 
         for count in range(1, 11):
             with contextlib.suppress(OSError):
                 os.makedirs(full_dir)
 
             try:
                 # Another cache may have deleted the directory before
                 # the file could be opened.
                 writer = open(full_path, mode, encoding=encoding)
             except OSError:
                 if count == 10:
                     # Give up after 10 tries to open the file.
                     raise
                 continue
 
             with writer:
                 size = 0
                 for chunk in iterator:
                     size += len(chunk)
                     writer.write(chunk)
                 return size
 
     def _get_keyfile(self, key):
         return os.path.join(self._directory, f'{key}.key')
 
     def store(self, key, value_reader, metadata):
         filename, full_path = self.random_filename()
         key_file = self._get_keyfile(key)
 
         # STORE METADATA
         _metadata = {
             "version": "v1",
             "filename": filename,
             "full_path": full_path,
             "key_file": key_file,
             "store_time": time.time(),
             "access_count": 1,
             "access_time": 0,
             "size": 0
         }
         if metadata:
             _metadata.update(metadata)
 
         reader = functools.partial(value_reader.read, 2**22)
 
         iterator = iter(reader, b'')
         size = self._write_file(full_path, iterator, 'xb')
         metadata['size'] = size
 
         # after archive is finished, we create a key to save the presence of the binary file
         with open(key_file, 'wb') as f:
             f.write(json.dumps(_metadata))
 
         return key, size, MODE_BINARY, filename, _metadata
 
     def fetch(self, key) -> tuple[typing.BinaryIO, dict]:
         if key not in self:
             raise KeyError(key)
 
         key_file = self._get_keyfile(key)
         with open(key_file, 'rb') as f:
             metadata = json.loads(f.read())
 
         filename = metadata['filename']
 
         try:
             return open(os.path.join(self._directory, filename), 'rb'), metadata
         finally:
             # update usage stats, count and accessed
             metadata["access_count"] = metadata.get("access_count", 0) + 1
             metadata["access_time"] = time.time()
 
             with open(key_file, 'wb') as f:
                 f.write(json.dumps(metadata))
 
     def random_filename(self):
         """Return filename and full-path tuple for file storage.
 
         Filename will be a randomly generated 28 character hexadecimal string
         with ".archive_cache" suffixed. Two levels of sub-directories will be used to
         reduce the size of directories. On older filesystems, lookups in
         directories with many files may be slow.
         """
 
         hex_name = codecs.encode(os.urandom(16), 'hex').decode('utf-8')
         sub_dir = os.path.join(hex_name[:2], hex_name[2:4])
         name = hex_name[4:] + '.archive_cache'
         filename = os.path.join(sub_dir, name)
         full_path = os.path.join(self._directory, filename)
         return filename, full_path
 
     def hash(self, key):
         """Compute portable hash for `key`.
 
         :param key: key to hash
         :return: hash value
 
         """
         mask = 0xFFFFFFFF
         return zlib.adler32(key.encode('utf-8')) & mask  # noqa
 
     def __contains__(self, key):
         """Return `True` if `key` matching item is found in cache.
 
         :param key: key matching item
         :return: True if key matching item
 
         """
         key_file = self._get_keyfile(key)
         return os.path.exists(key_file)
 
 
 class FanoutCache:
     """Cache that shards keys and values."""
 
     def __init__(
         self, directory=None, **settings
     ):
         """Initialize cache instance.
 
         :param str directory: cache directory
         :param settings: settings dict
 
         """
         if directory is None:
             raise ValueError('directory cannot be None')
 
         directory = str(directory)
         directory = os.path.expanduser(directory)
         directory = os.path.expandvars(directory)
         self._directory = directory
 
         self._count = settings.pop('cache_shards')
         self._locking_url = settings.pop('locking_url')
 
         self._eviction_policy = settings['cache_eviction_policy']
         self._cache_size_limit = settings['cache_size_limit']
 
         self._shards = tuple(
             FileSystemCache(
                 index=num,
                 directory=os.path.join(directory, 'shard_%03d' % num),
                 **settings,
             )
             for num in range(self._count)
         )
         self._hash = self._shards[0].hash
 
     def get_lock(self, lock_key):
         return GenerationLock(lock_key, self._locking_url)
 
     def _get_shard(self, key) -> FileSystemCache:
         index = self._hash(key) % self._count
         shard = self._shards[index]
         return shard
 
     def store(self, key, value_reader, metadata=None):
         shard = self._get_shard(key)
         return shard.store(key, value_reader, metadata)
 
     def fetch(self, key):
         """Return file handle corresponding to `key` from cache.
         """
         shard = self._get_shard(key)
         return shard.fetch(key)
 
     def has_key(self, key):
         """Return `True` if `key` matching item is found in cache.
 
         :param key: key for item
         :return: True if key is found
 
         """
         shard = self._get_shard(key)
         return key in shard
 
     def __contains__(self, item):
         return self.has_key(item)
 
-    def evict(self):
-        """Remove old items based on the conditions"""
-        # TODO: Implement this...
+    def evict(self, policy=None, size_limit=None):
+        """
+        Remove old items based on the conditions
+
+
+        explanation of this algo:
+        iterate over each shard, then for each shard iterate over the .key files
+        read the key files metadata stored. This gives us a full list of keys, cached_archived, their size and
+        access data, time creation, and access counts.
+
+        Store that into a memory DB so we can run different sorting strategies easily.
+        Summing the size is a sum sql query.
+
+        Then we run a sorting strategy based on eviction policy.
+        We iterate over sorted keys, and remove each checking if we hit the overall limit.
+        """
+
+        policy = policy or self._eviction_policy
+        size_limit = size_limit or self._cache_size_limit
+
+        select_policy = EVICTION_POLICY[policy]['evict']
+
+        if select_policy is None:
+            return 0
+
+        db = DB()
+
+        data = []
+        cnt = 1
+        for shard in self._shards:
+            for key_file in os.listdir(shard._directory):
+                if key_file.endswith('.key'):
+                    key_file_path = os.path.join(shard._directory, key_file)
+                    with open(key_file_path, 'rb') as f:
+                        metadata = json.loads(f.read())
+                        # in case we don't have size re-calc it...
+                        if not metadata.get('size'):
+                            fn = metadata.get('full_path')
+                            size = os.stat(fn).st_size
+
+                        data.append([
+                          cnt,
+                          key_file,
+                          key_file_path,
+                          metadata.get('filename'),
+                          metadata.get('full_path'),
+                          metadata.get('store_time', 0),
+                          metadata.get('access_time', 0),
+                          metadata.get('access_count', 0),
+                          metadata.get('size', size),
+                        ])
+                        cnt += 1
+
+        # Insert bulk data using executemany
+        db.bulk_insert(data)
+
+        ((total_size,),) = db.sql('SELECT COALESCE(SUM(size), 0) FROM archive_cache').fetchall()
+
+        select_policy_qry = select_policy.format(fields='key_file_path, full_path, size')
+        sorted_keys = db.sql(select_policy_qry).fetchall()
+
+        for key, cached_file, size in sorted_keys:
+            # simulate removal impact BEFORE removal
+            total_size -= size
+            if total_size <= size_limit:
+                # we obtained what we wanted...
+                break
+
+            os.remove(cached_file)
+            os.remove(key)
         return
 
 
 def get_archival_config(config):
 
     final_config = {
 
     }
 
     for k, v in config.items():
         if k.startswith('archive_cache'):
             final_config[k] = v
 
     return final_config
 
 
 def get_archival_cache_store(config):
 
     global cache_meta
     if cache_meta is not None:
         return cache_meta
 
     config = get_archival_config(config)
     backend = config['archive_cache.backend.type']
     if backend != 'filesystem':
         raise ValueError('archive_cache.backend.type only supports "filesystem"')
 
     archive_cache_locking_url = config['archive_cache.locking.url']
     archive_cache_dir = config['archive_cache.filesystem.store_dir']
     archive_cache_size_gb = config['archive_cache.filesystem.cache_size_gb']
     archive_cache_shards = config['archive_cache.filesystem.cache_shards']
     archive_cache_eviction_policy = config['archive_cache.filesystem.eviction_policy']
 
     log.debug('Initializing archival cache instance under %s', archive_cache_dir)
 
     # check if it's ok to write, and re-create the archive cache
     if not os.path.isdir(archive_cache_dir):
         os.makedirs(archive_cache_dir, exist_ok=True)
 
     d_cache = FanoutCache(
         archive_cache_dir,
         locking_url=archive_cache_locking_url,
         cache_shards=archive_cache_shards,
         cache_size_limit=archive_cache_size_gb * 1024 * 1024 * 1024,
         cache_eviction_policy=archive_cache_eviction_policy
     )
     cache_meta = d_cache
     return cache_meta