Add incpozo, the incremental repozo restorer

zodbtools/incpozo.py

+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (C) 2002-2017 Zope Foundation + Nexedi + Contributors
+# See LICENSE-ZPL.txt for full licensing terms.
+
+# Based on ZODB's repozo do_recover and main functions.
+
+"""
+Incremental repozo restore.
+
+Locates the first incremental to start restoring based on output file size.
+Checks the previous chunk to detect mismatched backup & destinations.
+Restores increments from that point on, following repozo arguments.
+"""
+import os
+import shutil
+import sys
+from ZODB.scripts.repozo import NoFiles, checksum, find_files, parseargs, log, concat, RECOVER
+
+def do_inc_recover(options):
+    repofiles = find_files(options)
+    if not repofiles:
+        if options.date:
+            raise NoFiles('No files in repository before %s', options.date)
+        else:
+            raise NoFiles('No files in repository')
+    datfile = os.path.splitext(repofiles[0])[0] + '.dat'
+    log('Recovering file to %s', options.output)
+    with open(datfile) as fp, open(options.output, 'r+b') as outfp:
+        outfp.seek(0, 2)
+        initial_length = outfp.tell()
+        previous_chunk = None
+        for line in fp:
+            fn, startpos, endpos, _ = chunk = line.split()
+            startpos = int(startpos)
+            endpos = int(endpos)
+            if endpos > initial_length:
+                break
+            previous_chunk = chunk
+        else:
+            # XXX: log + return so exit status is zero ?
+            raise NoFiles('Target file is longer than or as large at latest backup, doing nothing')
+        if previous_chunk is None:
+            # XXX: trigger a normal restore ?
+            raise NoFiles('Target file shorter than full backup, doing nothing')
+        check_start = int(previous_chunk[1])
+        check_end = int(previous_chunk[2])
+        outfp.seek(check_start, 0)
+        if previous_chunk[3] != checksum(outfp, check_end - check_start):
+            raise NoFiles('Last whole common chunk checksum did not match with backup, doing nothing')
+        assert outfp.tell() == startpos, (outfp.tell(), startpos)
+        if startpos < initial_length:
+            log('Truncating target file %i bytes before its end', initial_length - startpos)
+        filename = os.path.join(options.repository,
+                                os.path.basename(fn))
+        first_file_to_restore = repofiles.index(filename)
+        assert first_file_to_restore > 0, (first_file_to_restore, options.repository, fn, filename, repofiles)
+        reposz, reposum = concat(repofiles[first_file_to_restore:], outfp)
+    log('Recovered %s bytes, md5: %s', reposz, reposum)
+
+    if options.output is not None:
+        last_base = os.path.splitext(repofiles[-1])[0]
+        source_index = '%s.index' % last_base
+        target_index = '%s.index' % options.output
+        if os.path.exists(source_index):
+            log('Restoring index file %s to %s', source_index, target_index)
+            shutil.copyfile(source_index, target_index)
+        else:
+            log('No index file to restore: %s', source_index)
+
+def main(argv=None):
+    if argv is None:
+        argv = sys.argv[1:]
+    options = parseargs(argv)
+    assert options.mode == RECOVER, 'This tool only supports "recover" (-R|--recover) mode'
+    assert options.output is not None, 'This tool cannot recover to stdout'
+    try:
+        do_inc_recover(options)
+    except NoFiles as e:
+        sys.exit(str(e))
+
+if __name__ == '__main__':
+    main()