R SSH tunnel to MySQL database via Shiny App Access Denied or Can't connect to MySQL server on '127.0.0.1'

Question

I've looked through other posts without success, so here we are. The following code snippet runs as expected on a Windows 10 laptop in RStudio.

library(RMySQL)
library(ssh)
library(callr)

rs <- r_session$new(wait = TRUE, wait_timeout = 3500)

rs$call(function(){
  session <- ssh::ssh_connect('<ssh-user>@<remote-ip-address>', keyfile = "<path-to-.pem-file>", verbose = FALSE)
  
  ssh::ssh_tunnel(session, port=3306, target = "127.0.0.1:3306")
})

# Connect to TRAQ DB.
Sys.sleep(1)

db-connection <- dbConnect(MySQL(), user = '<remote-user-name>', password = '<remote-password>', dbname = '<remote-database>', port=3306, host='127.0.0.1')

The snippet runs runs successfully too when dbConnect() has host='localhost'

---

I am attempting to run the snippet on a virtual machine running Ubuntu 22 within an R shiny app. I receive the following messages while trying to load the app

Using localhost:

ERROR 1044 (42000): Access denied for user '<remote-user-name>'@'localhost'

Using 127.0.0.1:

ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1' (111)

I have received the (115) error code too.

---

If run directly from the R terminal, the snippet must be modified as follows for success.

ssh::ssh_tunnel(session, port=3306, target = "127.0.0.1:3306")

to

ssh::ssh_tunnel(session, port=3307, target = "127.0.0.1:3306")

AND

db-connection <- dbConnect(MySQL(), user = '<remote-user-name>', password = '<remote-password>', dbname = '<remote-database>', port=3306, host='127.0.0.1')

to

db-connection <- dbConnect(MySQL(), user = '<remote-user-name>', password = '<remote-password>', dbname = '<remote-database>', port=3307, host='127.0.0.1')

If the host is set to 'localhost' or ports are left at 3306, an Access denied message is displayed.

---

Unclear if this is due to a MySQL discrepancy or an operating system discrepancy. I don't believe it to be an issue on the remote server being SSH'd into since it works on the Windows laptop.

Answer 1

select user,host from mysql.user; Check your legal username and host and replace it. In addition, there is a difference between 127.0.0.1 and localhost. You should pay attention to whether the /etc/hosts file is mapped.