Between NEO/go and NEO/py there are various incompatibilities.
This branch aims to transparently communicate those incompatibilities.
We can also specify a SR in SlapOS which uses this branch in case
someone aims to use WC2.

Here we start from the old-proto (e.g. pre-messagepack) branch, because
in NEO/go msgpack support isn't fully implemented yet. This isn't
considered as an incompatibility but simply as a remaining TODO on
NEO/go side.

(cherry picked from commit ba0bc779)

(cherry picked from commit fa581be5)

======================================================================
FAIL: check_tid_ordering_w_commit (neo.tests.zodb.testBasic.BasicTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "ZODB/tests/BasicStorage.py", line 397, in check_tid_ordering_w_commit
    self.assertEqual(results.pop('lastTransaction'), tids[1])
  File "neo/tests/__init__.py", line 301, in assertEqual
    return super(NeoTestBase, self).assertEqual(first, second, msg=msg)
failureException: '\x03\xd8\x85H\xbffp\xbb' != '\x03\xd8\x85H\xbfs\x0b\xdd'

(cherry picked from commit f4cb59d2)

This requires ZODB >= 5.6.0

(cherry picked from commit a7d101ec)

(cherry picked from commit 43029be2)

This fixes the following assertion:

  Traceback (most recent call last):
    File "neo/master/app.py", line 172, in run
      self._run()
    File "neo/master/app.py", line 182, in _run
      self.playPrimaryRole()
    File "neo/master/app.py", line 302, in playPrimaryRole
      self.backup_app.provideService())
    File "neo/master/backup_app.py", line 114, in provideService
      node, conn = bootstrap.getPrimaryConnection()
    File "neo/lib/bootstrap.py", line 74, in getPrimaryConnection
      poll(1)
    File "neo/lib/event.py", line 160, in poll
      to_process.process()
    File "neo/lib/connection.py", line 504, in process
      self._handlers.handle(self, self._queue.pop(0))
    File "neo/lib/connection.py", line 92, in handle
      self._handle(connection, packet)
    File "neo/lib/connection.py", line 107, in _handle
      pending[0][1].packetReceived(connection, packet)
    File "neo/lib/handler.py", line 125, in packetReceived
      self.dispatch(*args)
    File "neo/lib/handler.py", line 75, in dispatch
      method(conn, *args, **kw)
    File "neo/lib/handler.py", line 159, in notPrimaryMaster
      assert primary != self.app.server
  AttributeError: 'BackupApplication' object has no attribute 'server'

(cherry picked from commit dba07e72)

The following 2 operations can be onerous and they should not be
directly usable without some kind of confirmation by the user:
- Dropping a node now requires to first stop it.
- Tweaking does not exclude anymore automatically DOWN nodes,
  because a node could go DOWN between the moment the user sends
  the command to tweak and the actual tweak by the master.

Initially, I wanted to do the simulation inside neoctl but it has no knowledge
of the topology (the master don't send devpath values of storage nodes).
Therefore, the work is delegated to the master node, which implies a change
of the protocol.

This stops abusing ProtocolError, which disconnects the admin node needlessly.

The many 'if ... raise RuntimeError' in neo/neoctl/neoctl.py
could be turned into assertions.

neoctl gets a new command to change the number of replicas.

The number of replicas becomes a new partition table attribute and
like the PT id, it is stored in the config table. On the other side,
the configuration value for the number of partitions is dropped,
since it can be computed from the partition table, which is
always stored in full.

The -p/-r master options now only apply at database creation.

Some implementation notes:

- The protocol is slightly optimized in that the master now sends
  automatically the whole partition tables to the admin & client
  nodes upon connection, like for storage nodes.
  This makes the protocol more consistent, and the master is the
  only remaining node requesting partition tables, during recovery.

- Some parts become tricky because app.pt can be None in more cases.
  For example, the extra condition in NodeManager.update
  (before app.pt.dropNode) was added for this is the reason.
  Or the 'loadPartitionTable' method (storage) that is not inlined
  because of unit tests.
  Overall, this commit simplifies more than it complicates.

- In the master handlers, we stop hijacking the 'connectionCompleted'
  method for tasks to be performed (often send the full partition
  table) on handler switches.

- The admin's 'bootstrapped' flag could have been removed earlier:
  race conditions can't happen since the AskNodeInformation packet
  was removed (commit d048a52d).

It is often faster to set up replicas by stopping a node (and any
underlying database server like MariaDB) and do a raw copy of the
database (e.g. with rsync). So far, it required to stop the whole
cluster and use tools like 'mysql' or sqlite3' to edit:
- the 'pt' table in databases,
- the 'config.nid' values of the new nodes.

With this new option, if you already have 1 replica, you can set up
new replicas with such fast raw copy, and without interruption of
service. Obviously, this implies less redundancy during the operation.

--kill-mysqld should be combined with something like -f .3 -r .1
to give storage nodes enough time to recover.
And also -D 0 to focus testing on the storage backend rather than NEO.

This also reverts commit 442bb43a.

This fixes up commit be839e92.

This is not used currently.

This breaks compatibily but it was mentionned from the beginning
that these options are only there for testing purpose.

TODO: rename all remaining occurrences of UUID into NID in the code

If the source DB is lost during the import and then restored from a backup,
all new transactions have to written back again on resume. It is the most
common case for which the writeback hits the maximum number of transactions
per partition to process at each iteration; the previous code was buggy in
that it could skip transactions.