code.grnet.gr Git - pithos/blob - snf-pithos-backend/pithos/backends/util.py

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  33
  34 from synnefo.lib.pool import ObjectPool
  35 from new import instancemethod
  36 from select import select
  37 from traceback import print_exc
  38 from pithos.backends import connect_backend
  39
  40 USAGE_LIMIT = 500
  41
  42
  43 class PithosBackendPool(ObjectPool):
  44     def __init__(self, size=None, db_module=None, db_connection=None,
  45                  block_module=None, block_path=None, block_umask=None,
  46                  queue_module=None, queue_hosts=None,
  47                  queue_exchange=None, quotaholder_url=None,
  48                  free_versioning=True, block_params=None):
  49         super(PithosBackendPool, self).__init__(size=size)
  50         self.db_module = db_module
  51         self.db_connection = db_connection
  52         self.block_module = block_module
  53         self.block_path = block_path
  54         self.block_umask = block_umask
  55         self.queue_module = queue_module
  56         self.block_params = block_params
  57         self.queue_hosts = queue_hosts
  58         self.queue_exchange = queue_exchange
  59         self.quotaholder_url = quotaholder_url
  60         self.free_versioning = free_versioning
  61
  62     def _pool_create(self):
  63         backend = connect_backend(db_module=self.db_module,
  64                                   db_connection=self.db_connection,
  65                                   block_module=self.block_module,
  66                                   block_path=self.block_path,
  67                                   block_umask=self.block_umask,
  68                                   queue_module=self.queue_module,
  69                                   block_params=self.block_params,
  70                                   queue_hosts=self.queue_hosts,
  71                                   queue_exchange=self.queue_exchange,
  72                                   quotaholder_url=self.quotaholder_url,
  73                                   free_versioning=self.free_versioning)
  74
  75         backend._real_close = backend.close
  76         backend.close = instancemethod(_pooled_backend_close, backend,
  77                                        type(backend))
  78         backend._pool = self
  79         backend._use_count = USAGE_LIMIT
  80         return backend
  81
  82     def _pool_verify(self, backend):
  83         wrapper = backend.wrapper
  84         conn = wrapper.conn
  85         if conn.closed:
  86             return False
  87
  88         if conn.in_transaction():
  89             conn.close()
  90             return False
  91
  92         try:
  93             fd = conn.connection.connection.fileno()
  94             r, w, x = select([fd], (), (), 0)
  95             if r:
  96                 conn.close()
  97                 return False
  98         except:
  99             print_exc()
 100             return False
 101
 102         return True
 103
 104     def _pool_cleanup(self, backend):
 105         c = backend._use_count - 1
 106         if c < 0:
 107             backend._real_close()
 108             return True
 109
 110         backend._use_count = c
 111         wrapper = backend.wrapper
 112         if wrapper.trans is not None:
 113             conn = wrapper.conn
 114             if conn.closed:
 115                 wrapper.trans = None
 116             else:
 117                 wrapper.rollback()
 118         if backend.messages:
 119             backend.messages = []
 120         return False
 121
 122
 123 def _pooled_backend_close(backend):
 124     backend._pool.pool_put(backend)