vdk-core: VdkBoundLogger (#2823)

This change introduces the VdkBoundLogger and addresses #2802.

Testing done: locally tested

Signed-off-by: Gabriel Georgiev <[email protected]>

projects/vdk-core/src/vdk/internal/core/logging.py

@@ -0,0 +1,51 @@
+# Copyright 2021-2023 VMware, Inc.
+# SPDX-License-Identifier: Apache-2.0
+import logging
+
+
+class VdkBoundLogger(logging.LoggerAdapter):
+    """
+    This class wraps around a Logger to append additional context to log records.
+    Logger-wide context can be included by providing it in the `context` parameter of the
+    `bind_logger` method.
+    Log statement-specific context can be included by including an `extra` kwarg to the log call and
+    providing a dictionary object (or any object which implements __getitem__ and __iter__) with the
+    required additional log fields.
+    It is intended to be instantiated using the `bind_logger` function and providing it with the current
+    log object and the additional context which will be included in dictionary form.
+
+    Example use::
+
+        import logging
+        from vdk.internal.builtin_plugins.config.log_config import bind_logger
+
+        bound_logger = bind_logger(logging.getLogger(__name__), {"logger_wide_bound_key": "logger_wide_bound_value"})
+        bound.warning("From vdk_initialize", extra={"first_key": "first_value"})
+        bound.warning("Something else from vdk_initialize")
+
+    Now, the LogRecord produced by the first log statement will have both
+    "logger_wide_bound_key": "logger_wide_bound_value" and "first_key": "first_value" included in its __dict__,
+    while the second one will only have "first_key": "first_value" in it.
+
+    Note that these will not be automatically included in the output log and must be processed downstream by
+    something like vdk-structlog.
+    """
+
+    def process(self, msg: str, kwargs: dict):
+        # merge bound extra dict with existing extra dict if any
+        if "extra" in kwargs:
+            kwargs["extra"] = {**self.extra, **kwargs["extra"]}
+        else:
+            kwargs["extra"] = self.extra
+        return msg, kwargs
+
+
+def bind_logger(log: logging.Logger, context: dict):
+    """
+    Instantiates a VdkBoundLogger object.
+
+    :param log: current log object
+    :param context: dictionary containing the additional context we want to include in log statements
+    :return: a VdkBoundLogger instance
+    """
+    return VdkBoundLogger(log, context)