Cassandra管理之備份與恢復

Cassandra的備份就是對現有的數據作一個快照，恢復則是把快照進行還原。不只能夠對全庫作快照，也能夠針對表、keyspace單獨作備份。另外它也支持增量備份。

一、全量備份

[root@db03 ~]# nodetool snapshot
Requested creating snapshot(s) for [all keyspaces] with snapshot name [1570691336948] and options {skipFlush=false}
Snapshot directory: 1570691336948

操做完成後，能夠經過listsnapshots驗證，以下圖所示：

備份完成後，系統會在每一個表所在的目錄下生成一個1570691336948文件夾，裏面存放了每一個表的備份數據。這裏用rhnchecksum表進行說明，以下圖所示：

二、增量備份

默認狀況下，它的增量備份是禁用的，能夠經過如下命令進行驗證：

[root@db03 ~]# nodetool statusbackup
not running

啓用增量備份，命令以下：

[root@db03 ~]# nodetool enablebackup 
[root@db03 ~]# nodetool statusbackup 
running

執行下備份以下：

[root@db03 spacewalk]# nodetool snapshot
Requested creating snapshot(s) for [all keyspaces] with snapshot name [1570695931097] and options {skipFlush=false}
Snapshot directory: 1570695931097

三、恢復數據

cassandra的恢復過程以下:

• 清空表

cqlsh:spacewalk> select count(*) from rhnchecksum;           

 count
---------
 8404215

(1 rows)

Warnings :
Aggregation query used without partition key

cqlsh:spacewalk> truncate rhnchecksum;
cqlsh:spacewalk> select count(*) from rhnchecksum;

 count
-------
     0

(1 rows)

• 還原snapshot目錄的數據
  這裏將snapshot目錄的數據拷貝到數據目錄，而後執行refresh，以下：

  [root@db03 rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc]# pwd
  /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc
  [root@db03 rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc]# cp -ra snapshots/1570695931097/* .
  --若是有索引數據也要進行拷貝操做
  [root@db03 rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc]# cp -ra snapshots/1570695931097/.rhnchecksum_idx/* .rhnchecksum_idx/

  當把快照文件複製到對應表的目錄下後，運行refresh命令加載新的SSTables 不須要重啓機器節點。

[root@db03 ~]# nodetool refresh spacewalk rhnchecksum
--完成後，cassandra的日誌會出現下面的提示:
[root@db03 ~]# tail -f /var/log/cassandra/system.log 
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,513 ColumnFamilyStore.java:734 - Loading new SSTables for spacewalk/rhnchecksum...
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,517 ColumnFamilyStore.java:782 - Renaming new SSTable /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-47-big to /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-50-big
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,548 ColumnFamilyStore.java:782 - Renaming new SSTable /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-49-big to /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-51-big
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,567 ColumnFamilyStore.java:782 - Renaming new SSTable /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-48-big to /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-52-big
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,589 ColumnFamilyStore.java:782 - Renaming new SSTable /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-46-big to /var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-53-big
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,610 ColumnFamilyStore.java:817 - Loading new SSTables and building secondary indexes for spacewalk/rhnchecksum: [BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-52-big-Data.db'), BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-51-big-Data.db'), BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-53-big-Data.db'), BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-50-big-Data.db')]
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:41:22,614 SecondaryIndexManager.java:366 - Submitting index build of rhnchecksum_idx for data in BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-52-big-Data.db'),BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-51-big-Data.db'),BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-53-big-Data.db'),BigTableReader(path='/var/lib/cassandra/data/spacewalk/rhnchecksum-dbbb8330dde111e99dfb45c418aaa2bc/md-50-big-Data.db')
INFO  [Service Thread] 2019-10-10 16:41:34,134 GCInspector.java:284 - ConcurrentMarkSweep GC in 467ms.  CMS Old Gen: 1227906720 -> 508200320; Code Cache: 35251328 -> 35276800; Metaspace: 45251080 -> 45251832; Par Eden Space: 6575264 -> 139631912; Par Survivor Space: 41943040 -> 14759936
INFO  [Service Thread] 2019-10-10 16:41:43,679 GCInspector.java:284 - ParNew GC in 236ms.  CMS Old Gen: 844136912 -> 967814552; Par Eden Space: 335544320 -> 0; Par Survivor Space: 35314704 -> 41943040
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:47:00,987 SecondaryIndexManager.java:386 - Index build of rhnchecksum_idx complete
INFO  [RMI TCP Connection(68)-127.0.0.1] 2019-10-10 16:47:00,987 ColumnFamilyStore.java:825 - Done loading load new SSTables for spacewalk/rhnchecksum

恢復完成後，驗證數據以下圖所示：

nodetool命令的選項中文解釋參考：Cassandra nodetool經常使用操做