Thread safe requests

sqlite3dbm/dbm.py

@@ -97,6 +97,8 @@
 from __future__ import with_statement
 
 import os
+import time
+import functools
 import sqlite3
 
 __all__ = [
@@ -179,6 +181,28 @@ class SqliteMapException(Exception):
 # DBM interface
 error = SqliteMapException
 
+ATTEMPTS_COUNT = float("inf")
+
+def lockwait(f):
+    @functools.wraps(f)
+    def _lockwait(*args, **kwargs):
+        attempt = ATTEMPTS_COUNT
+        r = None
+        while attempt >= 0:
+            attempt -= 1
+            try:
+                r = f(*args, **kwargs)
+            except sqlite3.OperationalError, e:
+                if e.message != "database is locked" or \
+                   attempt == -1: # -1 is last attempt
+                    raise
+                else:
+                    time.sleep(0.01)
+            else:
+                break
+
+        return r
+    return _lockwait
 
 class SqliteMap(object):
     """Dictionary interface backed by a SQLite DB.
@@ -221,6 +245,7 @@ def __init__(self, path, flag='r', mode=0666):
         if flag == 'n':
             self.clear()
 
+    @lockwait
     def __setitem__(self, k, v):
         """x.__setitem__(k, v) <==> x[k] = v"""
         if self.readonly:
@@ -229,6 +254,7 @@ def __setitem__(self, k, v):
         self.conn.execute(_SET_QUERY, (k, v))
         self.conn.commit()
 
+    @lockwait
     def __getitem__(self, k):
         """x.__getitem__(k) <==> x[k]
 
@@ -247,6 +273,7 @@ def __getitem__(self, k):
             raise KeyError(k)
         return row[0]
 
+    @lockwait
     def __delitem__(self, k):
         """x.__delitem__(k) <==> del x[k]"""
         if self.readonly:
@@ -262,6 +289,7 @@ def __delitem__(self, k):
         self.conn.execute(_DEL_QUERY, (k,))
         self.conn.commit()
 
+    @lockwait
     def __contains__(self, k):
         """D.__contains__(k) -> True if D has a key k, else False"""
         try:
@@ -271,6 +299,7 @@ def __contains__(self, k):
         else:
             return True
 
+    @lockwait
     def clear(self):
         """D.clear() -> None. Remove all items from D."""
         if self.readonly:
@@ -359,6 +388,7 @@ def k_gen():
                 else:
                     yield arg
 
+        @lockwait
         def lookup(keys):
             """Reuse the slightly weird logic to lookup values"""
             # Do all the selects in a single transaction
@@ -406,6 +436,7 @@ def select(self, *args):
             raise KeyError('One of the requested keys is missing!')
         return vals
 
+    @lockwait
     def update(self, *args, **kwargs):
         """D.update(E, **F) -> None.  Update D from E and F: for k in E: D[k] = E[k]
         (if E has keys else: for (k, v) in E: D[k] = v) then: for k in F: D[k] = F[k]