Re: [GENERAL] the master has two sync slave, which slave can promoteto master and the other slave as the new master's slave?

Hi,

    everyone. I am puzzled about the question: the master A has two slave slave_1 , slave_2 , the version of postgres is 9.3. I want to promote one slave to master, and the other slave as the new master's slave, but which slave should can promote ?

get the master-slave information from old master:

postgres=# select * from pg_stat_replication;

-[ RECORD 1 ]----+------------------------------

pid              | 15377

usesysid         | 10

usename          | postgres

application_name | slave_1

client_addr      | 10.20.16.201

client_hostname  | 

client_port      | 46086

backend_start    | 2017-03-19 12:42:02.026278+08

state            | streaming

sent_location    | 1/34FB0000

write_location   | 1/34EB0000

flush_location   | 1/34DB0000

replay_location  | 1/34C4FFD8

sync_priority    | 0

sync_state       | async

-[ RECORD 2 ]----+------------------------------

pid              | 15411

usesysid         | 10

usename          | postgres

application_name | slave_2

client_addr      | 10.20.16.200

client_hostname  | 

client_port      | 51102

backend_start    | 2017-03-19 12:42:12.477886+08

state            | streaming

sent_location    | 1/414FD320

write_location   | 1/414FD320

flush_location   | 1/414FD320

replay_location  | 1/3DD91468

sync_priority    | 0

sync_state       | async

1. which one can promote to master ,slave_1 or slave_2 ?

:: I think it is slave_2, because write_location  slave_2 1/414FD320  >  slave_1 (1/34FB0000), it is right?

2. If the slave_1 is sync state, which one can promote to master?  I am puzzled.