connect to host mysql database from inside rstudio docker

Question

I have set up Rstudio as a container on a server using a Rocker image. My MySQL instance is not in a docker and is running on the host machine. The db is a production database - so to dockerise the db as well isn't an option.

Can I connect to the host MySQL from inside the docker container running RStudio? The RStudio container runs perfectly, its just when I try and connect to the 'outside' MySQL to write data to db that I get a problem.

Currently trying with R just hanging in the end:

library(RMySQL)
library(DBI)
  db_user <- Sys.getenv("server_user")
  db_password <- Sys.getenv("server_pass")
  db_host <- '172.17.0.1' # docker ip
  db_dbname <- "test"

  mydb <-
    dbConnect(
      MySQL(),
      user = db_user,
      password = db_password,
      dbname = db_dbname,
      host = db_host, 
      port = 3306
    )
Error in .local(drv, ...) : 
  Failed to connect to database: Error: Can't connect to MySQL server on '172.17.0.1' (107)

UPDATE, hack solution:

Wanting to keep the container running with all the port mapping I ended up adding a rule to the iptables and connecting to the database as if I was connecting to it from another server:

sudo iptables -I INPUT 5 -p tcp -s 172.17.0.2 --dport 3306 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT -m comment --comment "docker DB access"

I also created a special docker user in MySQL that can access database:

CREATE USER 'docker'@'172.17.0.2' IDENTIFIED BY 'XXX';
GRANT SELECT, INSERT, CREATE ON *.* 'docker'@'172.17.0.2' IDENTIFIED BY 'XXX';

Although its a bit of a hack, I avoid all the problems that come with --net='host'

Answer 1

Yes. You can run your image as host mode.

docker run --net="host" ...

If you use host mode, mean you can't listen the same port in your container, because that will cause port already bind error .

When you run your container as host mode, you can visit your Host's server. Here is MySQL with 127.0.0.1 instead of 172.17.0.1 .