Pgpool II : unable to read message length between two network interfaces Start log file:

2015-03-06 01:57:56: pid 2760: LOG:  Setting up socket for 0.0.0.0:9999
2015-03-06 01:57:56: pid 2760: LOG:  Setting up socket for :::9999
2015-03-06 01:57:56: pid 2760: LOG:  pgpool-II successfully started. version 3.4.
0 (tataraboshi)
2015-03-06 01:57:56: pid 2760: LOG:  find_primary_node: checking backend no 0
2015-03-06 01:57:56: pid 2760: LOG:  find_primary_node: primary node id is 0
2015-03-06 01:58:02: pid 2792: ERROR:  unable to read message length
2015-03-06 01:58:02: pid 2792: DETAIL:  message length (8) in slot 1 does not mat
ch with slot 0(12)


Debug log file:

2015-03-06 01:55:07: pid 2680: LOG:  find_primary_node: primary node id is 0
2015-03-06 01:55:42: pid 2712: DEBUG:  I am 2712 accept fd 6
2015-03-06 01:55:42: pid 2712: DEBUG:  reading startup packet
2015-03-06 01:55:42: pid 2712: DETAIL:  Protocol Major: 1234 Minor: 5679 database
:  user: 
2015-03-06 01:55:42: pid 2712: DEBUG:  selecting backend connection
2015-03-06 01:55:42: pid 2712: DETAIL:  SSLRequest from client
2015-03-06 01:55:42: pid 2712: DEBUG:  reading startup packet
2015-03-06 01:55:42: pid 2712: DETAIL:  application_name: psql
2015-03-06 01:55:42: pid 2712: DEBUG:  reading startup packet
2015-03-06 01:55:42: pid 2712: DETAIL:  Protocol Major: 3 Minor: 0 database: post
gres user: enterprisedb
2015-03-06 01:55:42: pid 2712: DEBUG:  creating new connection to backend
2015-03-06 01:55:42: pid 2712: DETAIL:  connecting 0 backend
2015-03-06 01:55:42: pid 2712: DEBUG:  creating new connection to backend
2015-03-06 01:55:42: pid 2712: DETAIL:  connecting 1 backend
2015-03-06 01:55:42: pid 2712: DEBUG:  reading message length
2015-03-06 01:55:42: pid 2712: DETAIL:  slot: 0 length: 12
2015-03-06 01:55:42: pid 2712: DEBUG:  reading message length
2015-03-06 01:55:42: pid 2712: DETAIL:  slot: 1 length: 8
2015-03-06 01:55:42: pid 2712: ERROR:  unable to read message length
2015-03-06 01:55:42: pid 2712: DETAIL:  message length (8) in slot 1 does not mat
ch with slot 0(12)


psql command:

[enterprisedb@testing_ppas93]$ psql -h localhost -p 9999 -d postgres
psql: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request


I use pgpool II to control failover event between two servers (master on google cloud, slave on my local, centos x64, database: Postgres Plus Advanced Server 9.3). When I try to connect my database via port 9999 (example: psql -h localhost -p 9999 -d postgres) , pgpool raises the error 


  ERROR: Unable to read message length
About errors above, because of the connection between pgpool and slave server, if I change slave's pg_hba.conf for pgpool host from md5 to trust, it work fine. 

Two ways to fix:


ssh config among: pgpool, slave, master . 
set up trust method in pg_hba.conf for pgpool .