Add serialization of logging arguments

Author: mbirger

examples/serialize.py

@@ -0,0 +1,84 @@
+"""Simple usage example of kafka-logging-handler."""
+
+import json
+import logging
+import os
+import sys
+
+from kafka_logger.handlers import KafkaLoggingHandler
+
+REQUIRED_ENV_VARS = ['KAFKA_SERVER', 'KAFKA_CERT', 'KAFKA_TOPIC']
+
+
+class CustomClass:
+    """Dummy class to demo logging."""
+
+    def __init__(self, value):
+        """Initialize CustomClass object."""
+        self._value = value
+
+    def __str__(self):
+        """Convert CustomClass to string."""
+        return "CustomClass: {}".format(self._value)
+
+
+def main():
+    """Setup logger and test logging."""
+    # validate that Kafka configuration is available
+    assert all([(key in os.environ) for key in REQUIRED_ENV_VARS])
+
+    logger = logging.getLogger("test.logger")
+    logger.propagate = False
+    log_level = logging.DEBUG
+
+    log_format = logging.Formatter(
+        '%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
+        '%Y-%m-%dT%H:%M:%S')
+
+    # create handler to show logs at stdout
+    stdout_handler = logging.StreamHandler(sys.stdout)
+    stdout_handler.setLevel(log_level)
+    stdout_handler.setFormatter(log_format)
+    logger.addHandler(stdout_handler)
+
+    # create Kafka logging handler
+    kafka_handler = KafkaLoggingHandler(
+        os.environ['KAFKA_SERVER'],
+        os.environ['KAFKA_TOPIC'],
+        security_protocol='SSL',
+        ssl_cafile=os.environ['KAFKA_CERT'],
+        unhandled_exception_logger=logger,
+    )
+    kafka_handler.setFormatter(log_format)
+    logger.addHandler(kafka_handler)
+
+    logger.setLevel(log_level)
+
+    logger.info("Test log with int parameter: %d", 42)
+    logger.info("Test log with multiple parameters: %d %f", 42, 43.2)
+
+    logger.info("Test log with str parameter: %s", "test1")
+    logger.info("Test log with multiple str parameters: %s %s",
+                "test1", "test2")
+
+    custom_object = CustomClass('test')
+    logger.info("Test logging of custom obj: %s", custom_object)
+    # log record will contain the following values:
+    # args: <__main__.CustomClass object at 0x7f3147041c88>
+    # message: Test logging of custom obj: CustomClass: test
+
+    # extra values have to be JSON serializable
+    try:
+        json.dumps(custom_object)
+        # TypeError: Object of type 'CustomClass' is not JSON serializable
+    except TypeError:
+        logger.exception("Attempt to log non JSON serializable data")
+    # please transform extra values to JSON
+    logger.info("Test custom objects in extra argument", extra={
+        "custom_field_number": 42,
+        "custom_field_json": {"a": "test", "b": "test"}
+    })
+
+
+if __name__ == '__main__':
+    main()

kafka_logger/handlers.py

@@ -126,6 +126,12 @@ def emit(self, record):
         rec = self.additional_fields.copy()
         for key, value in record.__dict__.items():
             if key not in KafkaLoggingHandler.__LOGGING_FILTER_FIELDS:
+                if key == "args":
+                    # convert ALL argument to a str representation
+                    # Elasticsearch supports number datatypes
+                    # but it is not 1:1 - logging "inf" float
+                    # causes _jsonparsefailure error in ELK
+                    value = tuple(arg.__repr__() for arg in value)
                 rec[key] = "" if value is None else value
 
         with self.buffer_lock: