Add kernel independent logging

jupyter_server/serverapp.py

@@ -275,6 +275,7 @@ def init_settings(self, jupyter_app, kernel_manager, contents_manager,
             server_root_dir=root_dir,
             jinja2_env=env,
             terminals_available=False,  # Set later if terminals are available
+            kernel_logger=jupyter_app.kernel_logger,
             serverapp=self
         )
 
@@ -542,6 +543,7 @@ def start(self):
     'browser': 'ServerApp.browser',
     'pylab': 'ServerApp.pylab',
     'gateway-url': 'GatewayClient.url',
+    'kernel-logger': 'ServerApp.kernel_logger',
 })
 
 #-----------------------------------------------------------------------------
@@ -1214,6 +1216,33 @@ def _update_server_extensions(self, change):
          is not available.
          """))
 
+    kernel_logger = Unicode(u'', config=True,
+                        help="""The full path to a logging configuration file with a logger named
+                        kernel_logger. Allows the user to log all code messages to the kernel independent
+                        of the kernel type.
+                        """)
+
+    @validate('kernel_logger')
+    def _validate_kernel_logger(self, proposal):
+        import logging.config
+        from configparser import NoSectionError
+
+        value = proposal['value']
+
+        if not os.path.exists(value):
+            raise ValueError("Could not find logging configuration file {}".format(value))
+        try:
+            logging.config.fileConfig(value, disable_existing_loggers=False)
+            k_logger = logging.getLogger('kernel_logger')
+            if k_logger.handlers:
+                return value
+            else:
+                raise TraitError("Logging configuration file passed to --kernel-logger must have"
+                                 "a logger named kernel_logger.")
+        except (AttributeError, NoSectionError):
+            raise TraitError("Logging configuration file {} is not valid. Ensure that it has a kernel_logger specified"
+                             .format(value))
+
     def parse_command_line(self, argv=None):
 
         super(ServerApp, self).parse_command_line(argv)

jupyter_server/services/kernels/handlers.py

@@ -8,6 +8,7 @@
 
 import json
 import logging
+import logging.config
 from textwrap import dedent
 
 from tornado import web
@@ -116,6 +117,13 @@ def iopub_data_rate_limit(self):
     def rate_limit_window(self):
         return self.settings.get('rate_limit_window', 1.0)
 
+    @property
+    def kernel_logger(self):
+        logger_conf = self.settings.get('kernel_logger', None)
+        if logger_conf:
+            logging.config.fileConfig(logger_conf, disable_existing_loggers=False)
+            return logging.getLogger('kernel_logger')
+
     def __repr__(self):
         return "%s(%s)" % (self.__class__.__name__, getattr(self, 'kernel_id', 'uninitialized'))
 
@@ -307,6 +315,8 @@ def on_message(self, msg):
         else:
             stream = self.channels[channel]
             self.session.send(stream, msg)
+            if self.kernel_logger and msg['content'].get('code', None):
+                self.kernel_logger.info(msg['content']['code'].replace('\n', '\\n'))
 
     def _on_zmq_reply(self, stream, msg_list):
         idents, fed_msg_list = self.session.feed_identities(msg_list)