Support timeouts in Connection.close() and Pool.release()

Connection.close() and Pool.release() each gained the new timeout
parameter.  The pool.acquire() context manager now applies the
passed timeout to __aexit__() as well.

Connection.close() is now actually graceful.  Instead of simply dropping
the connection, it attempts to cancel the running query (if any), asks
the server to terminate the connection and waits for the connection to
terminate.

To test all this properly, implement a TCP proxy, which emulates sudden
connectivity loss (i.e. packets not reaching the server).

Closes: #220

Author: elprans

.ci/appveyor.yml

@@ -32,7 +32,7 @@ build_script:
     - "%PYTHON% setup.py build_ext --inplace"
 
 test_script:
-    - "%PYTHON% -m unittest discover -s tests"
+    - "%PYTHON% setup.py test"
 
 after_test:
     - "%PYTHON% setup.py bdist_wheel"

.gitignore

@@ -5,6 +5,7 @@
 *.ymlc~
 *.scssc
 *.so
+*.pyd
 *~
 .#*
 .DS_Store

asyncpg/_testbase.py renamed to asyncpg/_testbase/__init__.py

@@ -21,6 +21,8 @@
 from asyncpg import connection as pg_connection
 from asyncpg import pool as pg_pool
 
+from . import fuzzer
+
 
 @contextlib.contextmanager
 def silence_asyncio_long_exec_warning():
@@ -36,7 +38,16 @@ def flt(log_record):
         logger.removeFilter(flt)
 
 
+def with_timeout(timeout):
+    def wrap(func):
+        func.__timeout__ = timeout
+        return func
+
+    return wrap
+
+
 class TestCaseMeta(type(unittest.TestCase)):
+    TEST_TIMEOUT = None
 
     @staticmethod
     def _iter_methods(bases, ns):
@@ -64,7 +75,16 @@ def __new__(mcls, name, bases, ns):
         for methname, meth in mcls._iter_methods(bases, ns):
             @functools.wraps(meth)
             def wrapper(self, *args, __meth__=meth, **kwargs):
-                self.loop.run_until_complete(__meth__(self, *args, **kwargs))
+                coro = __meth__(self, *args, **kwargs)
+                timeout = getattr(__meth__, '__timeout__', mcls.TEST_TIMEOUT)
+                if timeout:
+                    coro = asyncio.wait_for(coro, timeout, loop=self.loop)
+                try:
+                    self.loop.run_until_complete(coro)
+                except asyncio.TimeoutError:
+                    raise self.failureException(
+                        'test timed out after {} seconds'.format(
+                            timeout)) from None
             ns[methname] = wrapper
 
         return super().__new__(mcls, name, bases, ns)
@@ -169,7 +189,8 @@ def _start_default_cluster(server_settings={}, initdb_options=None):
 
 
 def _shutdown_cluster(cluster):
-    cluster.stop()
+    if cluster.get_status() == 'running':
+        cluster.stop()
     cluster.destroy()
 
 
@@ -238,6 +259,49 @@ def start_cluster(cls, ClusterCls, *,
             server_settings, _get_initdb_options(initdb_options))
 
 
+class ProxiedClusterTestCase(ClusterTestCase):
+    @classmethod
+    def get_server_settings(cls):
+        settings = dict(super().get_server_settings())
+        settings['listen_addresses'] = '127.0.0.1'
+        return settings
+
+    @classmethod
+    def get_proxy_settings(cls):
+        return {'fuzzing-mode': None}
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        conn_spec = cls.cluster.get_connection_spec()
+        host = conn_spec.get('host')
+        if not host:
+            host = '127.0.0.1'
+        elif host.startswith('/'):
+            host = '127.0.0.1'
+        cls.proxy = fuzzer.TCPFuzzingProxy(
+            backend_host=host,
+            backend_port=conn_spec['port'],
+        )
+        cls.proxy.start()
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.proxy.stop()
+        super().tearDownClass()
+
+    @classmethod
+    def get_connection_spec(cls, kwargs):
+        conn_spec = super().get_connection_spec(kwargs)
+        conn_spec['host'] = cls.proxy.listening_addr
+        conn_spec['port'] = cls.proxy.listening_port
+        return conn_spec
+
+    def tearDown(self):
+        self.proxy.reset()
+        super().tearDown()
+
+
 def with_connection_options(**options):
     if not options:
         raise ValueError('no connection options were specified')