Ugh. Fix a bug in the new refactor of the env var config stuff.

[python_utils.git] / lockfile.py

diff --git a/lockfile.py b/lockfile.py
index f64a2c3aeba2eec62ea09246db2af44409a67d69..7d187ea1c5c2c47b71b46ef01a5919a68012e0c9 100644 (file)
--- a/lockfile.py
+++ b/lockfile.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python3
 
+# © Copyright 2021-2022, Scott Gasch
+
 """File-based locking helper."""
 
 from __future__ import annotations
@@ -40,20 +42,24 @@ class LockFileContents:
     """The contents we'll write to each lock file."""
 
     pid: int
+    """The pid of the process that holds the lock"""
+
     commandline: str
+    """The commandline of the process that holds the lock"""
+
     expiration_timestamp: Optional[float]
+    """When this lock will expire as seconds since Epoch"""
 
 
 class LockFile(contextlib.AbstractContextManager):
     """A file locking mechanism that has context-manager support so you
-    can use it in a with statement.  e.g.
-
-    with LockFile('./foo.lock'):
-        # do a bunch of stuff... if the process dies we have a signal
-        # handler to do cleanup.  Other code (in this process or another)
-        # that tries to take the same lockfile will block.  There is also
-        # some logic for detecting stale locks.
+    can use it in a with statement.  e.g.::
 
+        with LockFile('./foo.lock'):
+            # do a bunch of stuff... if the process dies we have a signal
+            # handler to do cleanup.  Other code (in this process or another)
+            # that tries to take the same lockfile will block.  There is also
+            # some logic for detecting stale locks.
     """
 
     def __init__(
@@ -64,6 +70,18 @@ class LockFile(contextlib.AbstractContextManager):
         expiration_timestamp: Optional[float] = None,
         override_command: Optional[str] = None,
     ) -> None:
+        """C'tor.
+
+        Args:
+            lockfile_path: path of the lockfile to acquire
+            do_signal_cleanup: handle SIGINT and SIGTERM events by
+                releasing the lock before exiting
+            expiration_timestamp: when our lease on the lock should
+                expire (as seconds since the Epoch).  None means the
+                lock will not expire until we explicltly release it.
+            override_command: don't use argv to determine our commandline
+                rather use this instead if provided.
+        """
         self.is_locked: bool = False
         self.lockfile: str = lockfile_path
         self.locktime: Optional[int] = None
@@ -74,12 +92,19 @@ class LockFile(contextlib.AbstractContextManager):
         self.expiration_timestamp = expiration_timestamp
 
     def locked(self):
+        """Is it locked currently?"""
         return self.is_locked
 
     def available(self):
+        """Is it available currently?"""
         return not os.path.exists(self.lockfile)
 
     def try_acquire_lock_once(self) -> bool:
+        """Attempt to acquire the lock with no blocking.
+
+        Returns:
+            True if the lock was acquired and False otherwise.
+        """
         logger.debug("Trying to acquire %s.", self.lockfile)
         try:
             # Attempt to create the lockfile.  These flags cause
@@ -105,6 +130,20 @@ class LockFile(contextlib.AbstractContextManager):
         backoff_factor: float = 2.0,
         max_attempts=5,
     ) -> bool:
+        """Attempt to acquire the lock repeatedly with retries and backoffs.
+
+        Args:
+            initial_delay: how long to wait before retrying the first time
+            backoff_factor: a float >= 1.0 the multiples the current retry
+                delay each subsequent time we attempt to acquire and fail
+                to do so.
+            max_attempts: maximum number of times to try before giving up
+                and failing.
+
+        Returns:
+            True if the lock was acquired and False otherwise.
+        """
+
         @decorator_utils.retry_if_false(
             tries=max_attempts, delay_sec=initial_delay, backoff=backoff_factor
         )
@@ -119,6 +158,7 @@ class LockFile(contextlib.AbstractContextManager):
         return _try_acquire_lock_with_retries()
 
     def release(self):
+        """Release the lock"""
         try:
             os.unlink(self.lockfile)
         except Exception as e: