PostgreSQL dbConnect to shiny app in ec2 instance - r

Question

I have an ec2 instance set up with my shiny app and my postgresql database, I want to get the shiny-app to read from the database
If I type psql and \conninfo while ssh-ed into my instance I get
You are connected to database "ubuntu" as user "ubuntu" via socket in "/var/run/postgresql" at port "5432".
When I use R in the ec2 command line and type the following, I can read from my database no problem!
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "ubuntu", host = "/var/run/postgresql", port = 5432, user = "ubuntu", password = pw)
However, when I put these same lines in my shiny app.R file I get
Error in postgresqlNewConnection(drv, ...) :
RS-DBI driver: (could not connect ubuntu#/var/run/postgresql:5432 on dbname "ubuntu": FATAL: Peer authentication failed for user "ubuntu")
I've tried so many different values for host like
host = "localhost"
host = "my ec2 public ip address"
host = "127.0.0.1"
for example and nothing has been working.
my security group for this ec2 instance has an inboud connection to port 5432.
could this be it: why is one file green and the other pink? the green one is the one that works (local) and the pink one is on my instance

Answer 1

Finally figured it out.. this is the same problem as Getting error: Peer authentication failed for user "postgres", when trying to get pgsql working with rails
except that I was getting a different error for the same underlying problem.
the answer that worked for me is the second one:
1.
nano /etc/postgresql/9.x/main/pg_hba.conf
change peer in this line
local all postgres peer
to
local all postgres trust
Restart the server
sudo service postgresql restart
Login into psql and set your password
psql -U postgres
ALTER USER postgres with password 'your-pass';
Finally change the pg_hba.conf from
local all postgres trust
to
local all postgres md5
and that finally worked