store big lru cache objects in files

lib/cache.py

@@ -5,12 +5,21 @@ LRU-Cache implementation for formatted (`format=`) answers
 import datetime
 import re
 import time
-import pylru
+import os
+import hashlib
+
 import pytz
+import pylru
+
+from globals import LRU_CACHE
 
 CACHE_SIZE = 10000
 CACHE = pylru.lrucache(CACHE_SIZE)
 
+# strings longer than this are stored not in ram
+# but in the file cache
+MIN_SIZE_FOR_FILECACHE = 80
+
 def _update_answer(answer):
     def _now_in_tz(timezone):
         return datetime.datetime.now(pytz.timezone(timezone)).strftime("%H:%M:%S%z")
@@ -26,9 +35,10 @@ def get_signature(user_agent, query_string, client_ip_address, lang):
     `lang`, and `client_ip_address`
     """
 
-    timestamp = int(time.time()) / 1000
+    timestamp = int(time.time() / 1000)
     signature = "%s:%s:%s:%s:%s" % \
         (user_agent, query_string, client_ip_address, lang, timestamp)
+    print(signature)
     return signature
 
 def get(signature):
@@ -38,13 +48,54 @@ def get(signature):
     the `_update_answer` function.
     """
 
-    if signature in CACHE:
-        return _update_answer(CACHE[signature])
+    value = CACHE.get(signature)
+    if value:
+        if value.startswith("file:"):
+            sighash = value[5:]
+            value = _read_from_file(signature, sighash=sighash)
+            if not value:
+                return None
+        return _update_answer(value)
     return None
 
 def store(signature, value):
     """
     Store in cache `value` for `signature`
     """
-    CACHE[signature] = value
+    if len(value) < MIN_SIZE_FOR_FILECACHE:
+        CACHE[signature] = value
+    else:
+        sighash = _store_in_file(signature, value)
+        CACHE[signature] = "file:%s" % sighash
     return _update_answer(value)
+
+def _hash(signature):
+    return hashlib.md5(signature.encode("utf-8")).hexdigest()
+
+def _store_in_file(signature, value):
+    """Store `value` for `signature` in cache file.
+    Return file name (signature_hash) as the result.
+    """
+
+    signature_hash = _hash(signature)
+    filename = os.path.join(LRU_CACHE, signature_hash)
+    if not os.path.exists(LRU_CACHE):
+        os.makedirs(LRU_CACHE)
+    with open(filename, "w") as f_cache:
+        f_cache.write(value)
+    return signature_hash
+
+def _read_from_file(signature, sighash=None):
+    """Read value for `signature` from cache file,
+    or return None if file is not found.
+    If `sighash` is specified, do not calculate file name
+    from signature, but use `sighash` instead.
+    """
+
+    signature_hash = sighash or _hash(signature)
+    filename = os.path.join(LRU_CACHE, signature_hash)
+    if not os.path.exists(filename):
+        return None
+
+    with open(filename, "r") as f_cache:
+        return f_cache.read()

lib/globals.py

@@ -14,6 +14,7 @@ from __future__ import print_function
 
 import logging
 import os
+import re
 
 MYDIR = os.path.abspath(os.path.dirname(os.path.dirname('__file__')))
 
@@ -31,6 +32,7 @@ _LOGDIR = "/wttr.in/log"
 CACHEDIR = os.path.join(_DATADIR, "cache/wego/")
 IP2LCACHE = os.path.join(_DATADIR, "cache/ip2l/")
 PNG_CACHE = os.path.join(_DATADIR, "cache/png")
+LRU_CACHE = os.path.join(_DATADIR, "cache/lru")
 
 LOG_FILE = os.path.join(_LOGDIR, 'main.log')