consistentHash

consistentHash provides a consistent hashing implementation using murmur3 with a 64bit ring space. Virtual nodes are used to provide a good distribution.

This package has an almost identical API to StatHat's consistent package at https://github.com/stathat/consistent , that packages uses a crc32 hash and a smaller number of vnodes by default.

See:
http://en.wikipedia.org/wiki/Consistent_hashing
http://en.wikipedia.org/wiki/MurmurHash

The only time an error will be returned from a Get(), Get2(), or GetN() call is if there are not enough members added.

Basic Example:

  ch := consistentHash.New()  
  ch.Add("server1")  
  ch.Add("server2")  
  ch.Add("server3")
  for _,key := range []string{"A","B","C","D","E","F","G"} {
	   server,_ := ch.Get([]byte(key)
	   fmt.Println("key=%s server=%s\n",key,server)
  }

Outputs:
key=A server=server3
key=B server=server3
key=C server=server1
key=D server=server3
key=E server=server2
key=F server=server2
key=G server=server1

Example with 3 servers and then removing a member:

    ch := consistentHash.New()
	ch.Add("server1")
	ch.Add("server2")
	ch.Add("server3")
	keys := []string{"A", "B", "C", "D", "E", "F", "G"}
	fmt.Println("3 servers")
	for _, key := range keys {
		server, _ := ch.Get([]byte(key))
		fmt.Printf("key=%s server=%s\n", key, server)
	}
	fmt.Println("Removing server3")
	ch.Remove("server3")
	for _, key := range keys {
		server, _ := ch.Get([]byte(key))
		fmt.Printf("key=%s server=%s\n", key, server)
	}

Output:
3 servers
key=A server=server3
key=B server=server3
key=C server=server1
key=D server=server3
key=E server=server2
key=F server=server2
key=G server=server1
Removing server3
key=A server=server1  // remapped from 3->1
key=B server=server2  // remapped from 3->2
key=C server=server1  // stayed in same location
key=D server=server1  // remapped from 3->1
key=E server=server2  // stayed in same location
key=F server=server2  // stayed in same location
key=G server=server1  // stayed in same location