如何缩小板条簇簇

Question

用于测试，我想缩小3个节点群集到2个节点，以便为我的5个节点簇做同样的事情。

但是，在遵循缩小集群的最佳实践之后：

1. 备份所有表
2. 对于所有表：alter table xyz set (number_of_replicas=2)如果在
之前小于2
3. SET GLOBAL PERSISTENT discovery.zen.minimum_master_nodes = <half of the cluster + 1>;
   3 a。如果数据检查始终是绿色的，请将Min_available设置为"完整"： https://crate.io/docs/reference/configuration.html#graceful-stop
4. 在一个节点上启动优雅停止
5. 等待数据检查转动绿色
6. 重复3。
7. 完成后，将 crate.yml中的节点配置持续。 gateway.recover_after_nodes: n discovery.zen.minimum_master_nodes:[![enter image description here][1]][1] (n/2) +1 gateway.expected_nodes: n

我的群集再也没有回到"绿色"，而且我也有关键的节点检查失败。

这里出了什么问题？

crate.yml：

  ... 
  ################################## Discovery ##################################
  # Discovery infrastructure ensures nodes can be found within a cluster
  # and master node is elected. Multicast discovery is the default.
  # Set to ensure a node sees M other master eligible nodes to be considered
  # operational within the cluster. Its recommended to set it to a higher value
  # than 1 when running more than 2 nodes in the cluster.
  #
  # We highly recommend to set the minimum master nodes as follows:
  #   minimum_master_nodes: (N / 2) + 1 where N is the cluster size
  # That will ensure a full recovery of the cluster state.
  #
  discovery.zen.minimum_master_nodes: 2
  # Set the time to wait for ping responses from other nodes when discovering.
  # Set this option to a higher value on a slow or congested network
  # to minimize discovery failures:
  #
  # discovery.zen.ping.timeout: 3s
  #
  # Time a node is waiting for responses from other nodes to a published
  # cluster state.
  #
  # discovery.zen.publish_timeout: 30s
  # Unicast discovery allows to explicitly control which nodes will be used
  # to discover the cluster. It can be used when multicast is not present,
  # or to restrict the cluster communication-wise.
  # For example, Amazon Web Services doesn't support multicast discovery.
  # Therefore, you need to specify the instances you want to connect to a
  # cluster as described in the following steps:
  #
  # 1. Disable multicast discovery (enabled by default):
  #
  discovery.zen.ping.multicast.enabled: false
  #
  # 2. Configure an initial list of master nodes in the cluster
  #    to perform discovery when new nodes (master or data) are started:
  #
  # If you want to debug the discovery process, you can set a logger in
  # 'config/logging.yml' to help you doing so.
  #
  ################################### Gateway ###################################
  # The gateway persists cluster meta data on disk every time the meta data
  # changes. This data is stored persistently across full cluster restarts
  # and recovered after nodes are started again.
  # Defines the number of nodes that need to be started before any cluster
  # state recovery will start.
  #
  gateway.recover_after_nodes: 3
  # Defines the time to wait before starting the recovery once the number
  # of nodes defined in gateway.recover_after_nodes are started.
  #
  #gateway.recover_after_time: 5m
  # Defines how many nodes should be waited for until the cluster state is
  # recovered immediately. The value should be equal to the number of nodes
  # in the cluster.
  #
  gateway.expected_nodes: 3

Answer 1

，所以有两件事很重要：

• 复制品的数量本质上是您可以在典型设置中失去的节点的数量（建议使用2个节点，以便您可以在过程中缩放和松开节点，但仍然可以）
）
• 建议将过程用于簇> 2个节点;）

cratedb将以无复制和主共享节点的方式自动在群集上分布碎片。如果是不可能的（如果您有2个节点和1个带有2个副本的主题，则数据检查将永远不会返回"绿色"。因此，在您的情况下，将复制品数设置为1集群回到绿色（alter table mytable set (number_of_replicas = 1)）。

关键节点检查是由于群集尚未收到更新的板条。由于CRATEDB仅在启动时加载Expection_nodes（这不是运行时设置），因此需要重新启动整个群集以结论缩小。可以通过滚动重新启动来完成，但是请确保正确设置SET GLOBAL PERSISTENT discovery.zen.minimum_master_nodes = <half of the cluster + 1>;，否则共识将无法正常工作...

另外，建议逐一缩小一对一的规模，以避免将集群重载与重新平衡并意外丢失数据。