Merge branch 'master' of https://code.grnet.gr/git/pithos

[pithos] / snf-pithos-backend / pithos / backends / util.py

diff --git a/snf-pithos-backend/pithos/backends/util.py b/snf-pithos-backend/pithos/backends/util.py
new file mode 100644 (file)
index 0000000..e8d9837
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+++ b/snf-pithos-backend/pithos/backends/util.py
@@ -0,0 +1,114 @@
+# Copyright 2011-2012 GRNET S.A. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or
+# without modification, are permitted provided that the following
+# conditions are met:
+#
+#   1. Redistributions of source code must retain the above
+#      copyright notice, this list of conditions and the following
+#      disclaimer.
+#
+#   2. Redistributions in binary form must reproduce the above
+#      copyright notice, this list of conditions and the following
+#      disclaimer in the documentation and/or other materials
+#      provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
+# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# The views and conclusions contained in the software and
+# documentation are those of the authors and should not be
+# interpreted as representing official policies, either expressed
+# or implied, of GRNET S.A.
+
+from synnefo.lib.pool import ObjectPool
+from new import instancemethod
+from select import select
+from traceback import print_exc
+from pithos.backends import connect_backend
+
+USAGE_LIMIT = 500
+
+
+class PithosBackendPool(ObjectPool):
+    def __init__(self, size=None, db_module=None, db_connection=None,
+                 block_module=None, block_path=None, block_umask=None,
+                 queue_module=None, queue_connection=None):
+        super(PithosBackendPool, self).__init__(size=size)
+        self.db_module = db_module
+        self.db_connection = db_connection
+        self.block_module = block_module
+        self.block_path = block_path
+        self.block_umask = block_umask
+        self.queue_module = queue_module
+        self.queue_connection = queue_connection
+
+    def _pool_create(self):
+        backend = connect_backend(db_module=self.db_module,
+                                  db_connection=self.db_connection,
+                                  block_module=self.block_module,
+                                  block_path=self.block_path,
+                                  block_umask=self.block_umask,
+                                  queue_module=self.queue_module,
+                                  queue_connection=self.queue_connection)
+
+        backend._real_close = backend.close
+        backend.close = instancemethod(_pooled_backend_close, backend,
+                                       type(backend))
+        backend._pool = self
+        backend._use_count = USAGE_LIMIT
+        return backend
+
+    def _pool_verify(self, backend):
+        wrapper = backend.wrapper
+        conn = wrapper.conn
+        if conn.closed:
+            return False
+
+        if conn.in_transaction():
+            conn.close()
+            return False
+
+        try:
+            fd = conn.connection.connection.fileno()
+            r, w, x = select([fd], (), (), 0)
+            if r:
+                conn.close()
+                return False
+        except:
+            print_exc()
+            return False
+
+        return True
+
+    def _pool_cleanup(self, backend):
+        c = backend._use_count - 1
+        if c < 0:
+            backend._real_close()
+            return True
+
+        backend._use_count = c
+        wrapper = backend.wrapper
+        if wrapper.trans is not None:
+            conn = wrapper.conn
+            if conn.closed:
+                wrapper.trans = None
+            else:
+                wrapper.rollback()
+        if backend.messages:
+            backend.messages = []
+        return False
+
+
+def _pooled_backend_close(backend):
+    backend._pool.pool_put(backend)