From da595427ff01e3dedccef22db839895150ed1270 Mon Sep 17 00:00:00 2001 From: Nikolaus Schulz Date: Sat, 16 Jan 2010 00:58:35 +0100 Subject: Fail as gracefully as possible if writing out the new mailboxes fails In particular: * If writing the archived messages to the final archive fails, try to restore the archive and abort (by not handling the exception). This is possible since we first save the archive, and only then the modified mailbox, so we don't corrupt the original mbox in this case. * If writing a modified mbox file fails, save the temporary copy. --- archivemail.py | 40 +++++++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-) diff --git a/archivemail.py b/archivemail.py index fbbbc28..bdc26f5 100755 --- a/archivemail.py +++ b/archivemail.py @@ -67,6 +67,7 @@ import tempfile import time import urlparse import errno +import socket # From_ mangling regex. from_re = re.compile(r'^From ', re.MULTILINE) @@ -393,7 +394,6 @@ class Mbox(mailbox.UnixMailbox): def _dotlock_lock(self): """Create a dotlock file for the 'mbox' mailbox""" - import socket hostname = socket.gethostname() pid = os.getpid() box_dir, prelock_prefix = os.path.split(self.mbox_file_name) @@ -460,7 +460,14 @@ class ArchiveMbox: def append(self, filename): """Append the content of the given file to the mbox.""" fin = open(filename, "r") - shutil.copyfileobj(fin, self.mbox_file) + oldsize = os.fstat(self.mbox_file.fileno()).st_size + try: + shutil.copyfileobj(fin, self.mbox_file) + except: + # We can safely abort here without data loss, because + # we have not yet changed the original mailbox + self.mbox_file.truncate(oldsize) + raise fin.close() def close(self): @@ -529,6 +536,12 @@ class TempMbox: vprint("closing file '%s'" % self.mbox_file_name) self.mbox_file.close() + def saveas(self, filename): + """Rename this temporary mbox file to the given name, making it + permanent. Emergency use only.""" + os.rename(self.mbox_file_name, filename) + _stale.temp_mboxes.remove(retain.mbox_file_name) + def remove(self): """Delete the temporary mbox file.""" os.remove(self.mbox_file_name) @@ -1126,14 +1139,29 @@ def _archive_mbox(mailbox_name, final_archive_name): if original.starting_size != original.get_size(): unexpected_error("the mailbox '%s' changed size during reading!" % \ mailbox_name) + # Write the new archive before modifying the mailbox, to prevent + # losing data if something goes wrong commit_archive(archive, final_archive_name) if retain: pending_changes = original.mbox_file.tell() != retain.mbox_file.tell() retain.close() if pending_changes: - vprint("overwriting mbox '%s' with temporary mbox '%s'" % \ - (original.mbox_file_name, retain.mbox_file_name)) - original.overwrite_with(retain.mbox_file_name) + vprint("writing back changed mailbox '%s'..." % \ + original.mbox_file_name) + # Prepare for recovery on error. + # FIXME: tempfile.tempdir is our nested dir. + saved_name = "%s/%s.%s.%s-%s-%s" % \ + (tempfile.tempdir, options.script_name, + os.path.basename(original.mbox_file_name), + socket.gethostname(), os.getuid(), + os.getpid()) + try: + original.overwrite_with(retain.mbox_file_name) + except: + retain.saveas(saved_name) + print "Error writing back changed mailbox; saved good copy to " \ + "%s" % saved_name + raise else: vprint("no changes to mbox '%s'" % original.mbox_file_name) retain.remove() @@ -1185,6 +1213,8 @@ def _archive_dir(mailbox_name, final_archive_name, type): else: vprint("decision: retain message") vprint("finished reading messages") + # Write the new archive before modifying the mailbox, to prevent + # losing data if something goes wrong commit_archive(archive, final_archive_name) for file_name in delete_queue: vprint("removing original message: '%s'" % file_name) -- cgit v1.2.3