R Shiny breaks PostgreSQL authentication with .pgpass

I have my password to database stored in pgpass.conf file. I am connecting to database from R with RPostgres, without specifying password so it is read from pgpass.conf, like this:

con <- dbConnect(RPostgres::Postgres(), 
                 dbname = "dbname",
                 user = "username",
                 host = "localhost",
                 port = "5432")

It usually works perfectly, however when I try to connect to database from shiny app it doesn't work. Connection definition is exactly the same as above and placed in server.R script. When I run Shiny app with default arguments I get an error:

FATAL:  password authentication failed for user "username"
password retrieved from file "C:\Users\...\AppData\Roaming/postgresql/pgpass.conf"

When password is explicitly given in connection definition:

con <- dbConnect(RPostgres::Postgres(), 
                 dbname = "dbname",
                 user = "username",
                 host = "localhost",
                 password = "mypass",
                 port = "5432")

everything works.

To make things stranger, when port for shiny is set to some value, for example: shiny::runApp(port = 4000), connection is established without specifying password, but ONLY for the first time - that means when app is closed and reopened in the same R session, the error occurs again.

I've tested package 'RPostgreSQL' - it doesn't work neither, only error message is different:

Error in postgresqlNewConnection(drv, ...) : 
  RS-DBI driver: (could not connect postgres@localhost on dbname "dbname")

I use 32-bit R but I've tested it on 64-bit and it was the same. Shiny app was run both in browser (Chrome) and in Rstudio Viewer.

Here my session info:

R version 3.2.2 (2015-08-14)
Platform: i386-w64-mingw32/i386 (32-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=Polish_Poland.1250  LC_CTYPE=Polish_Poland.1250        LC_MONETARY=Polish_Poland.1250
[4] LC_NUMERIC=C                   LC_TIME=Polish_Poland.1250    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] RPostgres_0.1  DBI_0.3.1.9008 shiny_0.12.2  

loaded via a namespace (and not attached):
[1] R6_2.1.1         htmltools_0.2.6  tools_3.2.2      rstudioapi_0.3.1     Rcpp_0.12.1.3    jsonlite_0.9.17  digest_0.6.8    
[8] xtable_1.7-4     httpuv_1.3.3     mime_0.4         RPostgreSQL_0.4

Solution

There's likely something different about the environment in which the command is run between Shiny and your system R GUI. I get around this by storing my credentials in an Renviron file:

readRenviron("~/.Renviron")
con <- dbConnect(RPostgres::Postgres(), 
                 dbname = Sys.getenv('pg_db'),
                 user = Sys.getenv('api_user'),
                 ...)

The thing about that is you could maintain separate Renvirons for staging and production environments. This allows your script to take a commandArgs() to specify which DB credentials it should use:

#!/usr/bin/env Rscript
environ_path <- switch(commandArgs(),
                  'staging' = {"~/staging.Renviron"},
                  'production' = {"~/production/Renviron"})

readRenviron(environ_path)

Then from BASH:

Rscript analysis.R staging