慎重挪捕！慎重烧栋！照這個(gè)方法刪除cell后并鸵，會(huì)導(dǎo)致已存在的虛擬機(jī)無法獲取詳情！

此文后續(xù) http://www.reibang.com/p/48e1451cf7dc

自從為了配置高可用集群捌蚊，給OpenStack裝了雙控制節(jié)點(diǎn)后集畅，就遇到了一個(gè)奇怪的現(xiàn)象：

cell0.png

所有計(jì)算節(jié)點(diǎn)都出現(xiàn)了兩次！

當(dāng)時(shí)想排查錯(cuò)誤缅糟，但一來沒頭緒挺智，二來任務(wù)緊急，淺淺嘗試一下就放棄排查了窗宦。好在也不影響使用赦颇，就這么用了下去，直到有一天赴涵！

直到有一天媒怯，我運(yùn)行了如下命令：

nova-manage cell_v2 discover_hosts --verbose

看到如下輸出時(shí)，突然產(chǎn)生疑惑：

cell1.png

為什么出現(xiàn)了兩次cell髓窜？

好像隱隱預(yù)感到了什么扇苞！

連忙輸入如下命令查看一下：

nova-manage cell_v2 list_cells

見下圖：

cell2.png

果然，有一個(gè)兄弟跟 “正統(tǒng)”的cell1 長(zhǎng)得很像!

它應(yīng)該就是罪魁禍?zhǔn)琢耍?/p>

那么這個(gè)Name是None的兄弟寄纵，是怎么混進(jìn)來的鳖敷？

我一看就明白了，原來它曾經(jīng)也是一個(gè)正統(tǒng)的cell1程拭，畢竟它的數(shù)據(jù)庫配置中還@了曾經(jīng)的controller定踱，可是改朝換代后，原來的單控制節(jié)點(diǎn) controller 由虛擬IP對(duì)應(yīng)的hostname controllerv 代替恃鞋。在配置第二個(gè)控制節(jié)點(diǎn)時(shí)屋吨，我又創(chuàng)了一個(gè)cell1，導(dǎo)致原來的cell1變成了無名無姓的None山宾。

既然你沒有用了至扰，就把你刪掉吧，于是我：

nova-manage cell_v2 delete_cell --cell_uuid 88d1334b-8794-4481-9207-aa12dae132ad

可是：

cell3.png

意思是你根深蒂固资锰，我除不了你了唄敢课？

不行，我又：

nova-manage cell_v2 delete_cell --force --cell_uuid 88d1334b-8794-4481-9207-aa12dae132ad

結(jié)果還是：

cell4.png

好了绷杜，原來這個(gè)force是假的 https://bugs.launchpad.net/nova/+bug/1721179

不行直秆，我要把你連根拔起：

nova-manage cell_v2 delete_host --cell_uuid 88d1334b-8794-4481-9207-aa12dae132ad --host compute1

結(jié)果：

cell5.png

好了好了，惹不起鞭盟！只能祭出終極武器了圾结，改一下源碼。

來到 /usr/lib/python2.7/dist-packages/nova/cmd/manage.py

找到 delete_cell 方法：

@args('--force', action='store_true', default=False,
          help=_('Delete hosts that belong to the cell as well.'))
    @args('--cell_uuid', metavar='<cell_uuid>', dest='cell_uuid',
          required=True, help=_('The uuid of the cell to delete.'))
    def delete_cell(self, cell_uuid, force=False):
        """Delete an empty cell by the given uuid.
        This command will return a non-zero exit code in the following cases.
        * The cell is not found by uuid.
        * It has hosts and force is False.
        * It has instance mappings.
        If force is True and the cell has host, hosts are deleted as well.
        Returns 0 in the following cases.
        * The empty cell is found and deleted successfully.
        * The cell has hosts and force is True and the cell and the hosts are
          deleted successfully.
        """
        ctxt = context.get_admin_context()
        # Find the CellMapping given the uuid.
        try:
            cell_mapping = objects.CellMapping.get_by_uuid(ctxt, cell_uuid)
        except exception.CellMappingNotFound:
            print(_('Cell with uuid %s was not found.') % cell_uuid)
            return 1

        # Check to see if there are any HostMappings for this cell.
        host_mappings = objects.HostMappingList.get_by_cell_id(
            ctxt, cell_mapping.id)
        nodes = []
        if host_mappings:
            if not force:
                print(_('There are existing hosts mapped to cell with uuid '
                        '%s.') % cell_uuid)
                return 2
            # We query for the compute nodes in the cell,
            # so that they can be unmapped.
            with context.target_cell(ctxt, cell_mapping) as cctxt:
                nodes = objects.ComputeNodeList.get_all(cctxt)

        # Check to see if there are any InstanceMappings for this cell.
        instance_mappings = objects.InstanceMappingList.get_by_cell_id(
            ctxt, cell_mapping.id)
        if instance_mappings:
            print(_('There are existing instances mapped to cell with '
                    'uuid %s.') % cell_uuid)
            return 3

        # Unmap the compute nodes so that they can be discovered
        # again in future, if needed.
        for node in nodes:
            node.mapped = 0
            node.save()

        # Delete hosts mapped to the cell.
        for host_mapping in host_mappings:
            host_mapping.destroy()

        # There are no hosts or instances mapped to the cell so delete it.
        cell_mapping.destroy()
        return 0

把 return 2 和 return 3 的部分注釋掉齿诉！

直奔主題筝野，即最后一句cell_mapping.destroy() 晌姚！

好了，再刪一下：

root@controller:~# nova-manage cell_v2 delete_cell --force --cell_uuid 88d1334b-8794-4481-9207-aa12dae132ad
An error has occurred:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/nova/cmd/manage.py", line 1868, in main
    ret = fn(*fn_args, **fn_kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/cmd/manage.py", line 1713, in delete_cell
    cell_mapping.destroy()
  File "/usr/lib/python2.7/dist-packages/oslo_versionedobjects/base.py", line 226, in wrapper
    return fn(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/objects/cell_mapping.py", line 114, in destroy
    self._destroy_in_db(self._context, self.uuid)
  File "/usr/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 979, in wrapper
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/objects/cell_mapping.py", line 108, in _destroy_in_db
    uuid=uuid).delete()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/query.py", line 3212, in delete
    delete_op.exec_()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/persistence.py", line 1179, in exec_
    self._do_exec()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/persistence.py", line 1363, in _do_exec
    mapper=self.mapper)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1107, in execute
    bind, close_with_result=True).execute(clause, params or {})
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 945, in execute
    return meth(self, multiparams, params)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/elements.py", line 263, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1053, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1189, in _execute_context
    context)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1398, in _handle_dbapi_exception
    util.raise_from_cause(newraise, exc_info)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1182, in _execute_context
    context)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 470, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/lib/python2.7/dist-packages/pymysql/cursors.py", line 166, in execute
    result = self._query(query)
  File "/usr/lib/python2.7/dist-packages/pymysql/cursors.py", line 322, in _query
    conn.query(q)
  File "/usr/lib/python2.7/dist-packages/pymysql/connections.py", line 856, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "/usr/lib/python2.7/dist-packages/pymysql/connections.py", line 1057, in _read_query_result
    result.read()
  File "/usr/lib/python2.7/dist-packages/pymysql/connections.py", line 1340, in read
    first_packet = self.connection._read_packet()
  File "/usr/lib/python2.7/dist-packages/pymysql/connections.py", line 1014, in _read_packet
    packet.check_error()
  File "/usr/lib/python2.7/dist-packages/pymysql/connections.py", line 393, in check_error
    err.raise_mysql_exception(self._data)
  File "/usr/lib/python2.7/dist-packages/pymysql/err.py", line 107, in raise_mysql_exception
    raise errorclass(errno, errval)
DBReferenceError: (pymysql.err.IntegrityError) (1451, u'Cannot delete or update a parent row: a foreign key constraint fails (`nova_api`.`instance_mappings`, CONSTRAINT `instance_mappings_ibfk_1` FOREIGN KEY (`cell_id`) REFERENCES `cell_mappings` (`id`))') [SQL: u'DELETE FROM cell_mappings WHERE cell_mappings.uuid = %(uuid_1)s'] [parameters: {u'uuid_1': u'88d1334b-8794-4481-9207-aa12dae132ad'}]

雖然出錯(cuò)了歇竟！但看到最后一段挥唠，我知道故事已經(jīng)要走到結(jié)局了。

破局的關(guān)鍵就在于這張圖：

cell6.png

簡(jiǎn)單的說焕议，就是我想在 nova_api 數(shù)據(jù)庫的 cell_mappings 表中刪除 uuid 為 88d1334b-8794-4481-9207-aa12dae132ad 的這位仁兄宝磨。

但這位仁兄在cell_mappings 表中的 id 和 instance_mappings 表中的 cell_id 有“裙帶關(guān)系” ！刪不掉盅安！

哦原來是上頭有人唤锉，那就簡(jiǎn)單了！

mysql -uroot -p
use nova_api;

找一下這位仁兄：

select * from cell_mappings where cell_mappings.uuid = '88d1334b-8794-4481-9207-aa12dae132ad';

cell7.png

找到了别瞭，id 是 2 腌紧！

然后，刪畜隶！

delete from instance_mappings where cell_id = '2';

cell8.png

再刪！

delete from cell_mappings where cell_mappings.uuid = '88d1334b-8794-4481-9207-aa12dae132ad';

cell9.png

好了号胚，趕緊看一下：

nova-manage cell_v2 list_cells

cell10.png

同步下數(shù)據(jù)庫籽慢，重啟下nova服務(wù)：

nova-manage api_db sync
service nova-api restart
service nova-consoleauth restart
service nova-scheduler restart
service nova-conductor restart
service nova-novncproxy restart

又回到最初的起點(diǎn)：

openstack compute service list

cell11.png

干凈了！

雖然好像并沒什么用猫胁，但也是時(shí)候?qū)W習(xí)一下nova中關(guān)于cell的知識(shí)了……