replica question

Hi,

I have the following situation


Machine - A equiped with
    -  a database
    - Internet application that receives records and stores them into a
table on this machine

Machine - B equiped with
    -  the same database
    -  the same internet application but it only receives records when
machine A is down


What I would like to achieve is that the tables in both databases are
kept consistent.

How to do this with postgres ?

Do a write a C-program for that that is started by a trigger ?


Thanks,


Feite Brekeveld