Log Shipping

It is my understanding that if PostgeSQL has log shipping enabled, if for
whatever reason it cannot ship the file the master server will hold it. But
for how long?

Secondly, I have 2 servers I ship log files to using the following script:

#!/usr/local/bin/bash

# Slave 1
rsync -a $1 pgi(at)192(dot)168(dot)1(dot)105:archive/$2 < /dev/null;

# Slave 2
rsync -a $1 pg(at)192(dot)168(dot)1(dot)93:archive/$2 < /dev/null;

In this case if Slave 1 is up but Slave 2 is down. It will ship the log
file to Slave 1 but not Slave 2 and move one. Thereby Slave 2 will now be
out of sync, correct?

To allow both slaves to remain in sync when one is restarted I would need
to modify my script to return an error or false to PostgreSQL, this way it
will hold the WAL files until both Slaves are online. Correct?

Thanks,
-Joseph