Observe的流程 4. MDS使用election模块的功能进行选主 4.1 Curve中MDS的选举过程 4.2 图示说明选举流程 4.2.1 正常流程 4.2.2 异常情况1：MDS1退出，可以正常处理 4.2.3 异常情况2：Etcd集群的leader发生重新选举，MDS1未受影响，可以正常处理 4.2.4 异常情况3：Etcd的leader发生重新选举，MDS1受到影响退出，不一定可以正常处理。 2 GetTimeout < ElectionTime 4.2.4.3 MDS1、MDS2、MDS3的租约全部过期 4.2.4.4 总结 4.2.5 异常情况四: Etcd集群与MDS1(当前leader)出现网络分区 4.2.5.1 事件一先发生 4.2.5.2 事件二先发生 4.2.6 异常情况4：Etcd集群的follower节点异常 4.2.7 各情况汇总 1. 需求 mds是元 考虑当前系统中mds有两个外部依赖模块，一是mysql， 用于存储集群拓扑的相关信息；二是etcd，用于存储文件的元数据信息。而etcd可以用于实现mds高可用，没必要引入其他组件。 使用etcd实现元数据节点的leader主要依赖于它的两个核心机制: TTL和CAS。TTL(time to live)指的是给一个key设置一个有效期，到期后key会被自动删掉。这在很多分布式锁的实现上都会用到，可以保证锁的实时性和有效性。CAS(Atomic

implementation of Raft protocol in etcd [https://coreos.com/etcd/]. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers major types of peer; there are two other roles a peer can adopt: Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes responsibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

ordering service based on an implementation of Raft protocol in etcd. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers types of peer; there are two other roles a peer can adopt: • Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes respon- sibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

implementation of Raft protocol in etcd [https://coreos.com/etcd/]. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers major types of peer; there are two other roles a peer can adopt: Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes responsibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

ordering service based on an implementation of Raft protocol in etcd. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers types of peer; there are two other roles a peer can adopt: • Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes respon- sibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

ordering service based on an implementation of Raft protocol in etcd. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers types of peer; there are two other roles a peer can adopt: • Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes respon- sibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

implementation of Raft protocol in etcd [https://coreos.com/etcd/]. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers major types of peer; there are two other roles a peer can adopt: Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes responsibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

implementation of Raft protocol in etcd [https://coreos.com/etcd/]. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers major types of peer; there are two other roles a peer can adopt: Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes responsibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

ordering service based on an implementation of Raft protocol in etcd. Raft follows a “leader and follower” model, where a leader node is elected (per channel) and its decisions are replicated to the followers types of peer; there are two other roles a peer can adopt: • Leader peer. When an organization has multiple peers in a channel, a leader peer is a node which takes respon- sibility for distributing transactions have static leader selection, and those with dynamic leader selection. For the static set, zero or more peers can be configured as leaders. For the dynamic set, one peer will be elected leader by the set

you wish to inspect its contents. Configuring Leader Election Note This section is included as a general reference for understanding the leader election settings when adding organizations to a network network after the initial channel configuration has completed. This sample defaults to dynamic leader election, which is set for all peers in the network in peer-base.yaml. Newly joining peers are bootstrapped that they receive blocks from the ordering service: 1. To utilize static leader mode, configure the peer to be an organization leader: CORE_PEER_GOSSIP_USELEADERELECTION=false CORE_PEER_GOSSIP_ORGLEADER=true