Support generating structured logs in addition to standard logs. (#8607)

This modifies the configuration of structured logging to be usable from
the standard Python logging configuration.

This also separates the formatting of logs from the transport allowing
JSON logs to files or standard logs to sockets.

1 files changed, 153 insertions, 0 deletions

diff --git a/tests/logging/test_remote_handler.py b/tests/logging/test_remote_handler.py
new file mode 100644
index 0000000000..58ee1f2f3c
--- /dev/null
+++ b/tests/logging/test_remote_handler.py
@@ -0,0 +1,153 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from twisted.test.proto_helpers import AccumulatingProtocol
+
+from synapse.logging import RemoteHandler
+
+from tests.logging import LoggerCleanupMixin
+from tests.server import FakeTransport, get_clock
+from tests.unittest import TestCase
+
+
+def connect_logging_client(reactor, client_id):
+    # This is essentially tests.server.connect_client, but disabling autoflush on
+    # the client transport. This is necessary to avoid an infinite loop due to
+    # sending of data via the logging transport causing additional logs to be
+    # written.
+    factory = reactor.tcpClients.pop(client_id)[2]
+    client = factory.buildProtocol(None)
+    server = AccumulatingProtocol()
+    server.makeConnection(FakeTransport(client, reactor))
+    client.makeConnection(FakeTransport(server, reactor, autoflush=False))
+
+    return client, server
+
+
+class RemoteHandlerTestCase(LoggerCleanupMixin, TestCase):
+    def setUp(self):
+        self.reactor, _ = get_clock()
+
+    def test_log_output(self):
+        """
+        The remote handler delivers logs over TCP.
+        """
+        handler = RemoteHandler("127.0.0.1", 9000, _reactor=self.reactor)
+        logger = self.get_logger(handler)
+
+        logger.info("Hello there, %s!", "wally")
+
+        # Trigger the connection
+        client, server = connect_logging_client(self.reactor, 0)
+
+        # Trigger data being sent
+        client.transport.flush()
+
+        # One log message, with a single trailing newline
+        logs = server.data.decode("utf8").splitlines()
+        self.assertEqual(len(logs), 1)
+        self.assertEqual(server.data.count(b"\n"), 1)
+
+        # Ensure the data passed through properly.
+        self.assertEqual(logs[0], "Hello there, wally!")
+
+    def test_log_backpressure_debug(self):
+        """
+        When backpressure is hit, DEBUG logs will be shed.
+        """
+        handler = RemoteHandler(
+            "127.0.0.1", 9000, maximum_buffer=10, _reactor=self.reactor
+        )
+        logger = self.get_logger(handler)
+
+        # Send some debug messages
+        for i in range(0, 3):
+            logger.debug("debug %s" % (i,))
+
+        # Send a bunch of useful messages
+        for i in range(0, 7):
+            logger.info("info %s" % (i,))
+
+        # The last debug message pushes it past the maximum buffer
+        logger.debug("too much debug")
+
+        # Allow the reconnection
+        client, server = connect_logging_client(self.reactor, 0)
+        client.transport.flush()
+
+        # Only the 7 infos made it through, the debugs were elided
+        logs = server.data.splitlines()
+        self.assertEqual(len(logs), 7)
+        self.assertNotIn(b"debug", server.data)
+
+    def test_log_backpressure_info(self):
+        """
+        When backpressure is hit, DEBUG and INFO logs will be shed.
+        """
+        handler = RemoteHandler(
+            "127.0.0.1", 9000, maximum_buffer=10, _reactor=self.reactor
+        )
+        logger = self.get_logger(handler)
+
+        # Send some debug messages
+        for i in range(0, 3):
+            logger.debug("debug %s" % (i,))
+
+        # Send a bunch of useful messages
+        for i in range(0, 10):
+            logger.warning("warn %s" % (i,))
+
+        # Send a bunch of info messages
+        for i in range(0, 3):
+            logger.info("info %s" % (i,))
+
+        # The last debug message pushes it past the maximum buffer
+        logger.debug("too much debug")
+
+        # Allow the reconnection
+        client, server = connect_logging_client(self.reactor, 0)
+        client.transport.flush()
+
+        # The 10 warnings made it through, the debugs and infos were elided
+        logs = server.data.splitlines()
+        self.assertEqual(len(logs), 10)
+        self.assertNotIn(b"debug", server.data)
+        self.assertNotIn(b"info", server.data)
+
+    def test_log_backpressure_cut_middle(self):
+        """
+        When backpressure is hit, and no more DEBUG and INFOs cannot be culled,
+        it will cut the middle messages out.
+        """
+        handler = RemoteHandler(
+            "127.0.0.1", 9000, maximum_buffer=10, _reactor=self.reactor
+        )
+        logger = self.get_logger(handler)
+
+        # Send a bunch of useful messages
+        for i in range(0, 20):
+            logger.warning("warn %s" % (i,))
+
+        # Allow the reconnection
+        client, server = connect_logging_client(self.reactor, 0)
+        client.transport.flush()
+
+        # The first five and last five warnings made it through, the debugs and
+        # infos were elided
+        logs = server.data.decode("utf8").splitlines()
+        self.assertEqual(
+            ["warn %s" % (i,) for i in range(5)]
+            + ["warn %s" % (i,) for i in range(15, 20)],
+            logs,
+        )