1 // Copyright 2019 The etcd Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package tracker 16 17 // StateType is the state of a tracked follower. 18 type StateType uint64 19 20 const ( 21 // StateProbe indicates a follower whose last index isn't known. Such a 22 // follower is "probed" (i.e. an append sent periodically) to narrow down 23 // its last index. In the ideal (and common) case, only one round of probing 24 // is necessary as the follower will react with a hint. Followers that are 25 // probed over extended periods of time are often offline. 26 StateProbe StateType = iota 27 // StateReplicate is the state steady in which a follower eagerly receives 28 // log entries to append to its log. 29 StateReplicate 30 // StateSnapshot indicates a follower that needs log entries not available 31 // from the leader's Raft log. Such a follower needs a full snapshot to 32 // return to StateReplicate. 33 StateSnapshot 34 ) 35 36 var prstmap = [...]string{ 37 "StateProbe", 38 "StateReplicate", 39 "StateSnapshot", 40 } 41 42 func (st StateType) String() string { return prstmap[uint64(st)] } 43