examples: Add py-postgresql non-blocking adapter

Demonstrates how easy it is to make existing codebase non-blocking

examples/postgres.py

@@ -0,0 +1,128 @@
+##
+# Copyright (c) 2008-2012 Sprymix Inc.
+# License: Apache 2.0
+##
+
+
+"""A non-blocking adapter for py-postgresql library.
+WARNING: This is just an experiment; use in production is not recommended.
+"""
+
+
+import postgresql
+from postgresql.python import socket as pg_socket
+from postgresql.driver import pq3
+
+from greentulip import socket as greensocket
+
+
+class SocketConnector:
+    def create_socket_factory(self, **params):
+        params['socket_extra'] = {'async': self.async}
+        return SocketFactory(**params)
+
+    def __init__(self, async=False):
+        self.async = async
+
+
+class IPConnector(pq3.IPConnector, SocketConnector):
+    def __init__(self, *args, async=False, **kw):
+        pq3.IPConnector.__init__(self, *args, **kw)
+        SocketConnector.__init__(self, async=async)
+
+
+class IP4(IPConnector, pq3.IP4):
+    pass
+
+
+class IP6(IPConnector, pq3.IP6):
+    pass
+
+
+class Host(SocketConnector, pq3.Host):
+    def __init__(self, *args, async=False, **kw):
+        pq3.Host.__init__(self, *args, **kw)
+        SocketConnector.__init__(self, async=async)
+
+
+class Unix(SocketConnector, pq3.Unix):
+    def __init__(self, unix=None, async=False, **kw):
+        pq3.Unix.__init__(self, unix=unix, **kw)
+        SocketConnector.__init__(self, async=async)
+
+
+class SocketFactory(pg_socket.SocketFactory):
+    def __init__(self, *args, socket_extra=None, **kw):
+        super().__init__(*args, **kw)
+        self.async = socket_extra.get('async', False) if socket_extra else False
+
+    def __call__(self, timeout=None):
+        if self.async:
+            s = greensocket.socket(*self.socket_create)
+            s.connect(self.socket_connect)
+            return s
+        else:
+            return super().__call__(timeout)
+
+
+class Driver(pq3.Driver):
+    def ip4(self, **kw):
+        return IP4(driver=self, **kw)
+
+    def ip6(self, **kw):
+        return IP6(driver=self, **kw)
+
+    def host(self, **kw):
+        return Host(driver=self, **kw)
+
+    def unix(self, **kw):
+        return Unix(driver=self, **kw)
+
+
+driver = Driver()
+
+
+def connector_factory(iri, async=False):
+    params = postgresql.iri.parse(iri)
+    settings = params.setdefault('settings', {})
+    settings['standard_conforming_strings'] = 'on'
+    params['async'] = async
+    return driver.fit(**params)
+
+
+if __name__ == '__main__':
+    import greentulip
+    import time
+    import tulip
+
+    @tulip.task
+    def sleeper():
+        # show that we're not blocked
+        while True:
+            yield from tulip.sleep(0.4)
+            print('.')
+
+    @greentulip.task
+    def db():
+        connection = connector_factory('pq://postgres@localhost:5432', async=True)()
+        connection.connect()
+
+        try:
+            print('>> sleeping')
+            st = time.monotonic()
+            connection.execute('SELECT pg_sleep(2)')
+            en = time.monotonic() - st
+            assert en >= 2
+            print('<< sleeping {:.3f}s'.format(en))
+
+            ps = connection.prepare('SELECT 42')
+            print('"SELECT 42" -> {!r}'.format(ps()))
+        finally:
+            connection.close()
+
+    @tulip.task
+    def run():
+        yield from tulip.wait([db(), sleeper()], return_when=tulip.FIRST_COMPLETED)
+
+    tulip.set_event_loop_policy(greentulip.GreenEventLoopPolicy())
+    tulip.get_event_loop().run_until_complete(run())