feat(archive-cache): implemented eviction policy logic

rhodecode/lib/rc_cache/archive_cache/fanout_cache.py

@@ -24,6 +24,7 @@ import logging
 import time
 import typing
 import zlib
+import sqlite3
 
 from rhodecode.lib.ext_json import json
 from .lock import GenerationLock
@@ -38,6 +39,72 @@ 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):
@@ -225,9 +292,76 @@ class FanoutCache:
     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