扩缩容
Contents
扩缩容#
扩容#
随着业务的发展, 当前集群的拓扑不能满足要求就需要动态的扩容。扩容就是把一部分分片从现有tablet节点迁移到新的tablet节点上从而减小内存占用
1 启动一个新的tablet节点#
启动后查看新增节点是否加入集群。如果执行showtablet命令列出了新节点endpoint说明已经加入到集群中
$ ./bin/openmldb --zk_cluster=172.27.128.31:8090,172.27.128.32:8090,172.27.128.33:8090 --zk_root_path=/openmldb_cluster --role=ns_client
> showtablet
endpoint state age
-------------------------------------------
172.27.128.31:8541 kTabletHealthy 15d
172.27.128.32:8541 kTabletHealthy 15d
172.27.128.33:8541 kTabletHealthy 15d
172.27.128.37:8541 kTabletHealthy 1min
2 迁移副本#
副本迁移用到的命令是migrate。命令格式: migrate src_endpoint table_name partition des_endpoint
一旦表创建好了，不能新增和减少分片，只能迁移分片。迁移的时候只能迁移从分片, 不能迁移主分片
$ ./bin/openmldb --zk_cluster=172.27.128.31:8090,172.27.128.32:8090,172.27.128.33:8090 --zk_root_path=/openmldb_cluster --role=ns_client
> use demo_db
> showtable
name tid pid endpoint role ttl is_alive compress_type offset record_cnt memused
----------------------------------------------------------------------------------------------------------------------
flow 4 0 172.27.128.32:8541 leader 0min yes kNoCompress 0 0 0.000
flow 4 0 172.27.128.33:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 0 172.27.128.31:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.33:8541 leader 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.31:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.32:8541 follower 0min yes kNoCompress 0 0 0.000
> migrate 172.27.128.33:8541 flow 0 172.27.128.37:8541
> showopstatus flow
op_id op_type name pid status start_time execute_time end_time cur_task
------------------------------------------------------------------------------------------------
51 kMigrateOP flow 0 kDone 20180824163316 12s 20180824163328 -
> showtable
name tid pid endpoint role ttl is_alive compress_type offset record_cnt memused
----------------------------------------------------------------------------------------------------------------------
flow 4 0 172.27.128.32:8541 leader 0min yes kNoCompress 0 0 0.000
flow 4 0 172.27.128.37:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 0 172.27.128.31:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.33:8541 leader 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.31:8541 follower 0min yes kNoCompress 0 0 0.000
flow 4 1 172.27.128.32:8541 follower 0min yes kNoCompress 0 0 0.000
说明: 迁移副本还可以用删除副本然后新增副本的方式来操作。
缩容#
缩容就是减小现有集群的节点数。
1 选定需要下线的节点#
2 将需要下线节点上的分片迁移到其他节点上#
执行showtable命令查看表分片分布
执行migrage命令将副本迁移到其他节点。如果要下线的节点上有leader，需要执行changeleader命令将leader切换到其他节点上才能执行migrate
3 下线节点#
执行停止命令
sh bin/start.sh stop tablet
如果该节点部署有nameserver也需要把nameserver停掉
sh bin/start.sh stop nameserver
注：保持高可用至少需要两个nameserver节点