From 5833b7e63bb751a1d5da16ffadc4ed0be50d8ab3 Mon Sep 17 00:00:00 2001
From: Balazs Lecz <leczb@google.com>
Date: Fri, 9 Apr 2010 15:02:13 +0100
Subject: [PATCH] Add ExecuteWithUnusedUid() to uidpool.py
Signed-off-by: Balazs Lecz <leczb@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
---
lib/uidpool.py | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/lib/uidpool.py b/lib/uidpool.py
index d216ec5cd..21c911369 100644
--- a/lib/uidpool.py
+++ b/lib/uidpool.py
@@ -328,3 +328,31 @@ def ReleaseUid(uid):
except OSError, err:
raise errors.LockError("Failed to remove user-id lockfile"
" for user-id %s: %s" % (uid, err))
+
+
+def ExecWithUnusedUid(fn, all_uids, *args, **kwargs):
+ """Execute a callable and provide an unused user-id in its kwargs.
+
+ This wrapper function provides a simple way to handle the requesting,
+ unlocking and releasing a user-id.
+ "fn" is called by passing a "uid" keyword argument that
+ contains an unused user-id (as a string) selected from the set of user-ids
+ passed in all_uids.
+ If there is an error while executing "fn", the user-id is returned
+ to the pool.
+
+ @param fn: a callable
+ @param all_uids: a set containing all user-ids in the user-id pool
+
+ """
+ uid = RequestUnusedUid(all_uids)
+ kwargs["uid"] = str(uid)
+ try:
+ return_value = fn(*args, **kwargs)
+ except:
+ # The failure of "callabe" means that starting a process with the uid
+ # failed, so let's put the uid back into the pool.
+ ReleaseUid(uid)
+ raise
+ uid.Unlock()
+ return return_value
--
GitLab