// 以下为官方介绍，说白了就是进行系统的集群节点管理

Serf uses an efficient gossip protocol to solve three major problems:

Membership: Serf maintains cluster membership lists and is able to execute custom handler scripts when that membership changes. For example, Serf can maintain the list of web servers for a load balancer and notify that load balancer whenever a node comes online or goes offline.

Failure detection and recovery: Serf automatically detects failed nodes within seconds, notifies the rest of the cluster, and executes handler scripts allowing you to handle these events. Serf will attempt to recover failed nodes by reconnecting to them periodically.

Custom event propagation: Serf can broadcast custom events and queries to the cluster. These can be used to trigger deploys, propagate configuration, etc. Events are simply fire-and-forget broadcast, and Serf makes a best effort to deliver messages in the face of offline nodes or network partitions. Queries provide a simple realtime request/response mechanism.

// 测试的是连个节点的模式

a. download

https://www.serf.io/downloads.html

b. start up

serf agent 实际使用为  serf agent -node=node-name -bind=bindaddress

c. join cluster

serf join nodebindaddress

d. members

serf members

e. leave cluster

stop the serf agent

// event handler

foo.sh - The script "foo.sh" will be invoked for any/every event.

member-join=foo.sh - The script "foo.sh" will only be invoked for the "member-join" event.

member-join,member-leave=foo.sh - The script "foo.sh" will be invoked for either member-join or member-leave events. Any combination of events may be specified in this way.

user=foo.sh - The script "foo.sh" will be invoked for all user events.

user:deploy=foo.sh - The script "foo.sh" will be invoked only for "deploy" user events.

query=foo.sh - The script "foo.sh" will be invoked for all queries.

query:load=uptime - The uptime command will be invoked only for "load" queries.

// web-site loadbalance

https://github.com/hashicorp/serf/tree/master/demo/web-load-balancer