Feature: Update consumer logging to include task ID for log correlation (#12510)

src/paperless/logging.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+import logging
+from contextvars import ContextVar
+
+consume_task_id: ContextVar[str] = ContextVar("consume_task_id", default="")
+
+
+class ConsumeTaskFormatter(logging.Formatter):
+    """
+    Logging formatter that prepends a short task correlation ID to messages
+    emitted during document consumption.
+
+    The ID is the first 8 characters of the Celery task UUID, set via the
+    ``consume_task_id`` ContextVar at the entry of ``consume_file``.  When
+    the ContextVar is empty (any log outside a consume task) no prefix is
+    added and the output is identical to the standard verbose format.
+    """
+
+    def __init__(self) -> None:
+        super().__init__(
+            fmt="[{asctime}] [{levelname}] [{name}] {task_prefix}{message}",
+            style="{",
+            validate=False,  # {task_prefix} is not a standard LogRecord attribute, so Python's
+            # init-time format-string validation would raise ValueError without
+            # this. Runtime safety comes from format() always setting
+            # record.task_prefix before calling super().format().
+        )
+
+    def format(self, record: logging.LogRecord) -> str:
+        task_id = consume_task_id.get()
+        record.task_prefix = f"[{task_id}] " if task_id else ""
+        return super().format(record)