zodbcommit: Don't forget to call tpc_abort on an error

Two-phase commit protocol assumes that after tpc_begin, it will be
either successful tpc_vote + tpc_finish, or tpc_abort. We were not
calling tpc_abort on an error, potentially leaving storage in "commit is
in progress" state on an error.

zodbtools/zodbcommit.py

-# Copyright (C) 2018-2020  Nexedi SA and Contributors.
+# Copyright (C) 2018-2021  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -58,49 +58,56 @@ def zodbcommit(stor, at, txn):
     before = p64(u64(at)+1)
 
     stor.tpc_begin(txn)
-    for obj in txn.objv:
-        data = None # data do be committed - setup vvv
-        if isinstance(obj, zodbdump.ObjectCopy):
-            # NEO does not support restore, and even if stor supports restore,
-            # going that way requires to already know tid for transaction we are
-            # committing. -> we just imitate copy by actually copying data and
-            # letting the storage deduplicate it.
-            data, _, _ = stor.loadBefore(obj.oid, p64(u64(obj.copy_from)+1))
 
-        elif isinstance(obj, zodbdump.ObjectDelete):
-            data = None
+    def _():
+        for obj in txn.objv:
+            data = None # data do be committed - setup vvv
+            if isinstance(obj, zodbdump.ObjectCopy):
+                # NEO does not support restore, and even if stor supports restore,
+                # going that way requires to already know tid for transaction we are
+                # committing. -> we just imitate copy by actually copying data and
+                # letting the storage deduplicate it.
+                data, _, _ = stor.loadBefore(obj.oid, p64(u64(obj.copy_from)+1))
 
-        elif isinstance(obj, zodbdump.ObjectData):
+            elif isinstance(obj, zodbdump.ObjectDelete):
+                data = None
 
-            if isinstance(obj.data, zodbdump.HashOnly):
-                raise ValueError('cannot commit transaction with hashonly object')
+            elif isinstance(obj, zodbdump.ObjectData):
 
-            data = obj.data
+                if isinstance(obj.data, zodbdump.HashOnly):
+                    raise ValueError('cannot commit transaction with hashonly object')
 
-        else:
-            panic('invalid object record: %r' % (obj,))
+                data = obj.data
+
+            else:
+                panic('invalid object record: %r' % (obj,))
 
 
-        # now we have the data.
-        # find out what is oid's serial as of <before state
-        try:
-            xdata = stor.loadBefore(obj.oid, before)
-        except POSKeyError:
-            serial_prev = z64
-        else:
-            if xdata is None:
+            # now we have the data.
+            # find out what is oid's serial as of <before state
+            try:
+                xdata = stor.loadBefore(obj.oid, before)
+            except POSKeyError:
                 serial_prev = z64
             else:
-                _, serial_prev, _ = xdata
-
-        # store the object.
-        # if it will be ConflictError - we just fail and let the caller retry.
-        if data is None:
-            stor.deleteObject(obj.oid, serial_prev, txn)
-        else:
-            stor.store(obj.oid, serial_prev, data, '', txn)
+                if xdata is None:
+                    serial_prev = z64
+                else:
+                    _, serial_prev, _ = xdata
+
+            # store the object.
+            # if it will be ConflictError - we just fail and let the caller retry.
+            if data is None:
+                stor.deleteObject(obj.oid, serial_prev, txn)
+            else:
+                stor.store(obj.oid, serial_prev, data, '', txn)
 
-    stor.tpc_vote(txn)
+    try:
+        _()
+        stor.tpc_vote(txn)
+    except:
+        stor.tpc_abort(txn)
+        raise
 
     # in ZODB >= 5 tpc_finish returns tid directly, but on ZODB 4 it
     # does not do so. Since we still need to support ZODB 4, utilize tpc_finish