6台服务器，3主master，3从slave
当把一台master的进程kill掉之后，slave那台机器就自动变成master
但是当你把原来kill掉的那台机器重启之后，会发现它还是slave，不会从slave变成master
172.31.4.164:6379> cluster nodes
bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 172.31.4.169:6379 master - 0 1544081422840 6 connected 0-5460
c9b9010f6e9bf750537e751bc7b9dae024eef0eb 172.31.4.165:6379 slave 9d10a69cae541def6f133c3024ab872c47213a88 0 1544081421835 5 connected
9d10a69cae541def6f133c3024ab872c47213a88 172.31.4.168:6379 master - 0 1544081420832 5 connected 5461-10922
4cf2944587cbd0d4ab0dff6b8d0cd090bb59b2a5 172.31.4.166:6379 slave bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 0 1544081419829 6 connected
20365b7b0e299dc1503a2463d113b5ba87ab2a61 172.31.4.167:6379 master - 1544081413213 1544081411811 4 disconnected 10923-16383
a1f586b5e5fa2eed20565207ea81862e9742efae 172.31.4.164:6379 myself,slave 20365b7b0e299dc1503a2463d113b5ba87ab2a61 0 0 1 connected
停掉了master后，
172.31.4.164:6379>
172.31.4.164:6379> cluster nodes
bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 172.31.4.169:6379 master - 0 1544081428861 6 connected 0-5460
c9b9010f6e9bf750537e751bc7b9dae024eef0eb 172.31.4.165:6379 slave 9d10a69cae541def6f133c3024ab872c47213a88 0 1544081426855 5 connected
9d10a69cae541def6f133c3024ab872c47213a88 172.31.4.168:6379 master - 0 1544081430866 5 connected 5461-10922
4cf2944587cbd0d4ab0dff6b8d0cd090bb59b2a5 172.31.4.166:6379 slave bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 0 1544081429863 6 connected
20365b7b0e299dc1503a2463d113b5ba87ab2a61 172.31.4.167:6379 master,fail - 1544081413213 1544081411811 4 disconnected
a1f586b5e5fa2eed20565207ea81862e9742efae 172.31.4.164:6379 myself,master - 0 0 7 connected 10923-16383
172.31.4.164:6379>
再讲167启起来之后
172.31.4.164:6379> cluster nodes
bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 172.31.4.169:6379 master - 0 1544081519025 6 connected 0-5460
c9b9010f6e9bf750537e751bc7b9dae024eef0eb 172.31.4.165:6379 slave 9d10a69cae541def6f133c3024ab872c47213a88 0 1544081518024 5 connected
9d10a69cae541def6f133c3024ab872c47213a88 172.31.4.168:6379 master - 0 1544081516020 5 connected 5461-10922
4cf2944587cbd0d4ab0dff6b8d0cd090bb59b2a5 172.31.4.166:6379 slave bcb7da7b9a451cb9eb218e14f9a5407098eb4bfc 0 1544081517023 6 connected
20365b7b0e299dc1503a2463d113b5ba87ab2a61 172.31.4.167:6379 slave a1f586b5e5fa2eed20565207ea81862e9742efae 0 1544081517523 7 connected
a1f586b5e5fa2eed20565207ea81862e9742efae 172.31.4.164:6379 myself,master - 0 0 7 connected 10923-16383