question regarding connection failover URL postgresql 9.6 (master/slave)

Hello

question regarding connection failover URL postgresql 9.6 (master/slave),
when a node( SLAVE per se) does down connections failover MASTER as
expected but ONE WAY ONLY!!, if we restart SLQVE service connections never
recover back.

*stack:* postgresql 9.6 (master/slave) + jdbc driver 9.4-1211 + tomcat7 +
jdk7 + built-in ConnectionPool

*ref: * https://jdbc.postgresql.org/documentation/head/connect.html
(bottom section)

*Issue*: upon having MASTER + SLAVE services running , we segregate via
two DataSources to point to 1st: MASTER and 2nd:

url="
*jdbc:postgresql://MASTER:5432,SLAVE:5432/XXDB?targetServerType=preferSlave*
"

when stopping SLAVE service connections failover MASTER as expected, but it
seems to be *a one way failover,* if I restart SLAVE service it never fails
back to SLAVE (unless we restart Tomcat service)

I played around with other parameters hostRecheckSeconds and
loadBalanceHosts as well as changing order
*url="SLAVE,MASTER?targetServerType=preferSlave"* as well but same thing.

Your helps is extremely appreciated!! thanks in advance.......

Sincerely,
Martin <http://www.linkedin.com/in/martinzoldano>