Log to a file and make it visible via the API

src/openflexure_microscope_server/logging.py

@@ -0,0 +1,38 @@
+import logging
+from logging.handlers import RotatingFileHandler
+import os
+
+from fastapi.responses import FileResponse, PlainTextResponse
+
+OFM_LOG_FOLDER =  "/var/openflexure/log/"
+OFM_LOG_FILE = os.path.join(OFM_LOG_FOLDER, "openflexure-microscope-server.log")
+
+def configure_logging():
+    root_logger = logging.getLogger()
+    root_logger.setLevel(logging.INFO)
+    try:
+        if not os.path.exists(OFM_LOG_FOLDER):
+            os.makedirs(OFM_LOG_FOLDER)
+        handler = RotatingFileHandler(
+            filename = OFM_LOG_FILE,
+            mode = "a",
+            maxBytes = 1000000,
+            backupCount = 10,
+        )
+        handler.setFormatter(
+            logging.Formatter(
+                "[%(asctime)s] [%(levelname)s] %(message)s"
+            )
+        )
+        root_logger.addHandler(handler)
+    except PermissionError as e:
+        logging.warning(f"Cannot create log file at {OFM_LOG_FILE}: {e}")
+    logging.info("")
+    logging.info("****************************************************")
+    logging.info("OFM server root logger has been set up at INFO level")
+    logging.info("****************************************************")
+
+
+def retrieve_log() -> PlainTextResponse:
+    """The most recent 1Mb of logs from the server"""
+    return FileResponse(OFM_LOG_FILE, media_type=PlainTextResponse.media_type)