analyze performance upgrade

django_project/analyzer/logutil.py

@@ -0,0 +1,78 @@
+"""Logging helpers: per-run log files and consistent formatting."""
+
+from __future__ import annotations
+
+import contextlib
+import logging
+import threading
+from typing import Iterator, Optional
+
+LOG_FORMAT = "%(asctime)s %(levelname)-7s [%(name)s] %(message)s"
+DATE_FORMAT = "%Y-%m-%d %H:%M:%S"
+
+# Loggers that describe a capture analysis end to end.
+ANALYSIS_LOGGERS = ("analyzer", "IoTAnalyzer.analyze")
+
+
+class _ThreadFilter(logging.Filter):
+    """Only pass records emitted by the thread that opened the run log."""
+
+    def __init__(self, thread_id: int):
+        super().__init__()
+        self.thread_id = thread_id
+
+    def filter(self, record: logging.LogRecord) -> bool:
+        return record.thread == self.thread_id
+
+
+@contextlib.contextmanager
+def run_log(path: Optional[str], level: int = logging.DEBUG) -> Iterator[Optional[logging.Handler]]:
+    """Write everything this thread logs about the analysis to ``path``.
+
+    Concurrent analyses in other threads do not leak into the file.
+    """
+    if not path:
+        yield None
+        return
+    handler: Optional[logging.FileHandler] = None
+    try:
+        handler = logging.FileHandler(path, mode="w", encoding="utf-8")
+    except OSError as exc:
+        logging.getLogger("analyzer").warning("Run log %s could not be opened: %s", path, exc)
+        yield None
+        return
+    handler.setLevel(level)
+    handler.setFormatter(logging.Formatter(LOG_FORMAT, DATE_FORMAT))
+    handler.addFilter(_ThreadFilter(threading.get_ident()))
+    loggers = [logging.getLogger(n) for n in ANALYSIS_LOGGERS]
+    previous = [(lg, lg.level) for lg in loggers]
+    for lg in loggers:
+        lg.addHandler(handler)
+        if lg.level == logging.NOTSET or lg.level > level:
+            lg.setLevel(level)
+    try:
+        yield handler
+    finally:
+        for lg, lvl in previous:
+            lg.removeHandler(handler)
+            lg.setLevel(lvl)
+        handler.close()
+
+
+def configure_console(level: str = "INFO") -> None:
+    """Console logging for CLI use."""
+    logging.basicConfig(level=getattr(logging, level.upper(), logging.INFO),
+                        format=LOG_FORMAT, datefmt=DATE_FORMAT)
+
+
+def tail(path: str, lines: int = 400, max_bytes: int = 256 * 1024) -> str:
+    """Return the last ``lines`` lines of a text file."""
+    try:
+        with open(path, "rb") as fh:
+            fh.seek(0, 2)
+            size = fh.tell()
+            fh.seek(max(0, size - max_bytes))
+            data = fh.read().decode("utf-8", "replace")
+    except OSError:
+        return ""
+    return "\n".join(data.splitlines()[-lines:])