fix: safely handle correlation ID lookup in non-web mode

CHANGELOG.md

@@ -6,6 +6,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ## Unreleased
 
+- fix: `json_logging.get_correlation_id()` returns `-` after `init_non_web()` instead of raising
+  `AttributeError`. Fixes #126
+
 - fix: Flask, Quart and Connexion no longer generate a new correlation ID for each log record emitted outside an
   active HTTP request; those records now get `-`, as documented. Connexion 3 error handlers and ASGI middleware,
   which run outside the Flask request context, still use the request's correlation header; without one they get

README.md

@@ -242,6 +242,9 @@ correlation_id_without_request_obj = json_logging.get_correlation_id()
 In request context, if one is not present, a new one might be generated depends on CREATE_CORRELATION_ID_IF_NOT_EXISTS
 setting value.
 
+Before initialization or after `init_non_web()`, `json_logging.get_correlation_id()` returns
+`json_logging.EMPTY_VALUE` (`"-"`) instead of raising an error or generating an HTTP correlation ID.
+
 
 ## 2.4 Log extra properties
 

json_logging/__init__.py

@@ -39,8 +39,13 @@ def get_correlation_id(request=None):
     Get current request correlation-id. If one is not present, a new one might be generated
     depends on CREATE_CORRELATION_ID_IF_NOT_EXISTS setting value.
 
+    After init_non_web(), or before any init, there is no HTTP request to read from, so this returns
+    EMPTY_VALUE.
+
     :return: correlation-id string
     """
+    if _request_util is None:
+        return EMPTY_VALUE
     return _request_util.get_correlation_id(request=request)
 
 

tests/test_non_web_correlation.py

@@ -0,0 +1,90 @@
+"""Public correlation-ID accessor in non-web mode (issue #126).
+
+init_non_web() does not create a request utility, so json_logging.get_correlation_id() used to raise
+AttributeError. Non-web logs have no HTTP request, so the accessor should return the documented empty
+value and must not generate an ID.
+"""
+import json
+import logging
+
+import pytest
+from helpers.handler import FormattedMessageCollectorHandler
+from helpers.imports import undo_imports_from_package
+
+
+@pytest.fixture(autouse=True)
+def restore_framework_logger_state():
+    """Restore process-global logging defaults and per-logger state changed by initialization."""
+    default_formatter = logging._defaultFormatter
+    names = ("flask-request-logger", "connexion-request-logger", "quart-request-logger",
+             "werkzeug", "non-web-test")
+    saved = {}
+    for name in names:
+        logger = logging.getLogger(name)
+        saved[name] = (list(logger.handlers), logger.level, logger.parent, logger.propagate, logger.disabled)
+    yield
+    logging._defaultFormatter = default_formatter
+    for name, (handlers, level, parent, propagate, disabled) in saved.items():
+        logger = logging.getLogger(name)
+        logger.handlers = handlers
+        logger.setLevel(level)
+        logger.parent = parent
+        logger.propagate = propagate
+        logger.disabled = disabled
+
+
+@pytest.fixture
+def fresh_json_logging():
+    undo_imports_from_package("json_logging")
+    yield
+    undo_imports_from_package("json_logging")
+
+
+@pytest.mark.parametrize("enable_json", [True, False])
+def test_get_correlation_id_after_init_non_web_returns_empty_value(fresh_json_logging, enable_json):
+    import json_logging
+    json_logging.init_non_web(enable_json=enable_json)
+
+    assert json_logging.get_correlation_id() == json_logging.EMPTY_VALUE
+    assert json_logging.get_correlation_id() == json_logging.EMPTY_VALUE  # no ID is generated or cached
+
+
+def test_get_correlation_id_before_any_init_returns_empty_value(fresh_json_logging):
+    import json_logging
+    assert json_logging.get_correlation_id() == json_logging.EMPTY_VALUE
+
+
+def test_non_web_json_logging_output_is_unchanged(fresh_json_logging):
+    import json_logging
+    json_logging.init_non_web(enable_json=True)
+
+    logger = logging.getLogger("non-web-test")
+    logger.setLevel(logging.INFO)
+    logger.propagate = False
+    handler = FormattedMessageCollectorHandler()
+    handler.setFormatter(json_logging.JSONLogFormatter())
+    logger.addHandler(handler)
+    try:
+        logger.info("hello %s", "world")
+    finally:
+        logger.removeHandler(handler)
+
+    record = json.loads(handler.messages[0])
+    assert record["type"] == "log"
+    assert record["msg"] == "hello world"
+    assert record["logger"] == "non-web-test"
+    assert record["level"] == "INFO"
+    assert "correlation_id" not in record  # non-web records never carry a correlation ID
+
+
+def test_get_correlation_id_with_explicit_request_still_works_in_web_mode(fresh_json_logging):
+    """Web mode keeps its behaviour: an explicitly supplied request is still honoured."""
+    import flask
+    import json_logging
+
+    app = flask.Flask(__name__)
+    json_logging.init_flask(enable_json=True)
+    json_logging.init_request_instrument(app)
+    with app.test_request_context("/", headers={"X-Correlation-ID": "web-1"}):
+        assert json_logging.get_correlation_id() == "web-1"
+        assert json_logging.get_correlation_id(request=flask.request) == "web-1"