Add query logging callbacks and context manager

asyncpg/connection.py

@@ -9,6 +9,7 @@
 import asyncpg
 import collections
 import collections.abc
+import contextlib
 import functools
 import itertools
 import inspect
@@ -51,7 +52,7 @@ class Connection(metaclass=ConnectionMeta):
                  '_intro_query', '_reset_query', '_proxy',
                  '_stmt_exclusive_section', '_config', '_params', '_addr',
                  '_log_listeners', '_termination_listeners', '_cancellations',
-                 '_source_traceback', '__weakref__')
+                 '_source_traceback', '_query_loggers', '__weakref__')
 
     def __init__(self, protocol, transport, loop,
                  addr,
@@ -84,6 +85,7 @@ def __init__(self, protocol, transport, loop,
         self._log_listeners = set()
         self._cancellations = set()
         self._termination_listeners = set()
+        self._query_loggers = set()
 
         settings = self._protocol.get_settings()
         ver_string = settings.server_version
@@ -221,6 +223,29 @@ def remove_termination_listener(self, callback):
         """
         self._termination_listeners.discard(_Callback.from_callable(callback))
 
+    def add_query_logger(self, callback):
+        """Add a logger that will be called when queries are executed.
+
+        :param callable callback:
+            A callable or a coroutine function receiving one argument:
+            **record**: a LoggedQuery containing `query`, `args`, `timeout`,
+                        `elapsed`, `addr`, `params`, and `exception`.
+
+        .. versionadded:: 0.29.0
+        """
+        self._query_loggers.add(_Callback.from_callable(callback))
+
+    def remove_query_logger(self, callback):
+        """Remove a query logger callback.
+
+        :param callable callback:
+            The callable or coroutine function that was passed to
+            :meth:`Connection.add_query_logger`.
+
+        .. versionadded:: 0.29.0
+        """
+        self._query_loggers.discard(_Callback.from_callable(callback))
+
     def get_server_pid(self):
         """Return the PID of the Postgres server the connection is bound to."""
         return self._protocol.get_server_pid()
@@ -314,7 +339,9 @@ async def execute(self, query: str, *args, timeout: float=None) -> str:
         self._check_open()
 
         if not args:
-            return await self._protocol.query(query, timeout)
+            with self._time_and_log(query, args, timeout):
+                result = await self._protocol.query(query, timeout)
+            return result
 
         _, status, _ = await self._execute(
             query,
@@ -1384,6 +1411,7 @@ def _cleanup(self):
         self._mark_stmts_as_closed()
         self._listeners.clear()
         self._log_listeners.clear()
+        self._query_loggers.clear()
         self._clean_tasks()
 
     def _clean_tasks(self):
@@ -1667,6 +1695,62 @@ async def _execute(
             )
         return result
 
+    @contextlib.contextmanager
+    def logger(self, callback):
+        """Context manager that adds `callback` to the list of query loggers,
+        and removes it upon exit.
+
+        :param callable callback:
+            A callable or a coroutine function receiving one argument:
+            **record**: a LoggedQuery containing `query`, `args`, `timeout`,
+                        `elapsed`, `addr`, `params`, and `exception`.
+
+        Example:
+
+        .. code-block:: pycon
+
+            >>> class QuerySaver:
+                    def __init__(self):
+                        self.queries = []
+                    def __call__(self, record):
+                        self.queries.append(record.query)
+            >>> with con.logger(QuerySaver()) as log:
+            >>>     await con.execute("SELECT 1")
+            >>> print(log.queries)
+            ['SELECT 1']
+
+        .. versionadded:: 0.29.0
+        """
+        self.add_query_logger(callback)
+        yield callback
+        self.remove_query_logger(callback)
+
+    @contextlib.contextmanager
+    def _time_and_log(self, query, args, timeout):
+        start = time.monotonic()
+        exception = None
+        try:
+            yield
+        except Exception as ex:
+            exception = ex
+            raise
+        finally:
+            elapsed = time.monotonic() - start
+            record = LoggedQuery(
+                query=query,
+                args=args,
+                timeout=timeout,
+                elapsed=elapsed,
+                addr=self._addr,
+                params=self._params,
+                exception=exception,
+            )
+            for cb in self._query_loggers:
+                if cb.is_async:
+                    self._loop.create_task(cb.cb(record))
+                else:
+                    self._loop.call_soon(cb.cb, record)
+
     async def __execute(
         self,
         query,
@@ -1681,20 +1765,23 @@ async def __execute(
         executor = lambda stmt, timeout: self._protocol.bind_execute(
             stmt, args, '', limit, return_status, timeout)
         timeout = self._protocol._get_timeout(timeout)
-        return await self._do_execute(
-            query,
-            executor,
-            timeout,
-            record_class=record_class,
-            ignore_custom_codec=ignore_custom_codec,
-        )
+        with self._time_and_log(query, args, timeout):
+            result, stmt = await self._do_execute(
+                query,
+                executor,
+                timeout,
+                record_class=record_class,
+                ignore_custom_codec=ignore_custom_codec,
+            )
+        return result, stmt
 
     async def _executemany(self, query, args, timeout):
         executor = lambda stmt, timeout: self._protocol.bind_execute_many(
             stmt, args, '', timeout)
         timeout = self._protocol._get_timeout(timeout)
         with self._stmt_exclusive_section:
-            result, _ = await self._do_execute(query, executor, timeout)
+            with self._time_and_log(query, args, timeout):
+                result, _ = await self._do_execute(query, executor, timeout)
         return result
 
     async def _do_execute(
@@ -2327,6 +2414,12 @@ class _ConnectionProxy:
     __slots__ = ()
 
 
+LoggedQuery = collections.namedtuple(
+    'LoggedQuery',
+    ['query', 'args', 'timeout', 'elapsed', 'exception', 'addr', 'params'])
+LoggedQuery.__doc__ = 'Log record of an executed query.'
+
+
 ServerCapabilities = collections.namedtuple(
     'ServerCapabilities',
     ['advisory_locks', 'notifications', 'plpgsql', 'sql_reset',

tests/test_logging.py

@@ -0,0 +1,48 @@
+import asyncio
+
+from asyncpg import _testbase as tb
+from asyncpg import exceptions
+
+
+class LogCollector:
+    def __init__(self):
+        self.records = []
+
+    def __call__(self, record):
+        self.records.append(record)
+
+
+class TestQueryLogging(tb.ConnectedTestCase):
+
+    async def test_logging_context(self):
+        queries = asyncio.Queue()
+
+        def query_saver(record):
+            queries.put_nowait(record)
+
+        with self.con.logger(query_saver):
+            self.assertEqual(len(self.con._query_loggers), 1)
+            await self.con.execute("SELECT 1")
+            with self.con.logger(LogCollector()) as log:
+                self.assertEqual(len(self.con._query_loggers), 2)
+                await self.con.execute("SELECT 2")
+
+        r1 = await queries.get()
+        r2 = await queries.get()
+        self.assertEqual(r1.query, "SELECT 1")
+        self.assertEqual(r2.query, "SELECT 2")
+        self.assertEqual(len(log.records), 1)
+        self.assertEqual(log.records[0].query, "SELECT 2")
+        self.assertEqual(len(self.con._query_loggers), 0)
+
+    async def test_error_logging(self):
+        with self.con.logger(LogCollector()) as log:
+            with self.assertRaises(exceptions.UndefinedColumnError):
+                await self.con.execute("SELECT x")
+
+        await asyncio.sleep(0)  # wait for logging
+        self.assertEqual(len(log.records), 1)
+        self.assertEqual(
+            type(log.records[0].exception),
+            exceptions.UndefinedColumnError
+        )