main.tf

provider "docker" {
  host = "unix:///var/run/docker.sock"
}

resource "docker_image" "mysql_outer" {
  name = "mysql:5.7"
}

resource "docker_container" "mysql_outer" {
  name = "mysql_outer"
  image = "${docker_image.mysql_outer.latest}"

  ports {
    internal = 3306
  }
}

module "mysql_inner" {
  source = "./modules/mysql"
}

modules_mysql_main.tf

resource "docker_image" "mysql_inner" {
  name = "mysql:5.7"
}

resource "docker_container" "mysql_inner" {
  name = "mysql_inner"
  image = "${docker_image.mysql_inner.latest}"

  ports {
    internal = 3306
    external = 13306
  }
}

modules_mysql_outputs.tf

output "host" {
  value = "${docker_container.mysql_inner.ip_address}"
}

output "port" {
  value = "${docker_container.mysql_inner.ports.0.external}"
}

output "address" {
  value = "${docker_container.mysql_inner.ip_address}:${docker_container.mysql_inner.ports.0.external}"
}

outputs.tf

output "mysql_outer_host" {
  value = "${docker_container.mysql_outer.ip_address}"
}

output "mysql_outer_port" {
  value = "${docker_container.mysql_outer.ports.0.external}"
}

output "mysql_outer_address" {
  value = "${docker_container.mysql_outer.ip_address}:${docker_container.mysql_outer.ports.0.external}"
}

output "mysql_inner_host" {
  value = "${module.mysql_inner.host}"
}

output "mysql_inner_port" {
  value = "${module.mysql_inner.port}"
}

output "mysql_inner_address" {
  value = "${module.mysql_inner.address}"
}

terraform apply result

docker_image.mysql_outer: Creating...
  latest: "" => "<computed>"
  name:   "" => "mysql:5.7"
module.mysql_inner.docker_image.mysql_inner: Creating...
  latest: "" => "<computed>"
  name:   "" => "mysql:5.7"
module.mysql_inner.docker_image.mysql_inner: Creation complete
docker_image.mysql_outer: Creation complete
module.mysql_inner.docker_container.mysql_inner: Creating...
  bridge:                   "" => "<computed>"
  gateway:                  "" => "<computed>"
  image:                    "" => "sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b"
  ip_address:               "" => "<computed>"
  ip_prefix_length:         "" => "<computed>"
  log_driver:               "" => "json-file"
  must_run:                 "" => "1"
  name:                     "" => "mysql_inner"
  ports.#:                  "" => "1"
  ports.382260533.external: "" => "13306"
  ports.382260533.internal: "" => "3306"
  ports.382260533.ip:       "" => ""
  ports.382260533.protocol: "" => "tcp"
  restart:                  "" => "no"
docker_container.mysql_outer: Creating...
  bridge:                   "" => "<computed>"
  gateway:                  "" => "<computed>"
  image:                    "" => "sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b"
  ip_address:               "" => "<computed>"
  ip_prefix_length:         "" => "<computed>"
  log_driver:               "" => "json-file"
  must_run:                 "" => "1"
  name:                     "" => "mysql_outer"
  ports.#:                  "" => "1"
  ports.275610719.external: "" => ""
  ports.275610719.internal: "" => "3306"
  ports.275610719.ip:       "" => ""
  ports.275610719.protocol: "" => "tcp"
  restart:                  "" => "no"
docker_container.mysql_outer: Creation complete
module.mysql_inner.docker_container.mysql_inner: Creation complete

Apply complete! Resources: 4 added, 0 changed, 0 destroyed.

The state of your infrastructure has been saved to the path
below. This state is required to modify and destroy your
infrastructure, so keep it safe. To inspect the complete state
use the `terraform show` command.

State path: terraform.tfstate

Outputs:

  mysql_inner_host = 172.17.0.4
  mysql_outer_host = 172.17.0.3

terraform plan result

Refreshing Terraform state prior to plan...


The Terraform execution plan has been generated and is shown below.
Resources are shown in alphabetical order for quick scanning. Green resources
will be created (or destroyed and then created if an existing resource
exists), yellow resources are being changed in-place, and red resources
will be destroyed.

Note: You didn't specify an "-out" parameter to save this plan, so when
"apply" is called, Terraform can't guarantee this is what will execute.

+ docker_container.mysql_outer
    bridge:                   "" => "<computed>"
    gateway:                  "" => "<computed>"
    image:                    "" => "${docker_image.mysql_outer.latest}"
    ip_address:               "" => "<computed>"
    ip_prefix_length:         "" => "<computed>"
    log_driver:               "" => "json-file"
    must_run:                 "" => "1"
    name:                     "" => "mysql_outer"
    ports.#:                  "" => "1"
    ports.275610719.external: "" => ""
    ports.275610719.internal: "" => "3306"
    ports.275610719.ip:       "" => ""
    ports.275610719.protocol: "" => "tcp"
    restart:                  "" => "no"

+ docker_image.mysql_outer
    latest: "" => "<computed>"
    name:   "" => "mysql:5.7"

+ module.mysql_inner.docker_container.mysql_inner
    bridge:                   "" => "<computed>"
    gateway:                  "" => "<computed>"
    image:                    "" => "${docker_image.mysql_inner.latest}"
    ip_address:               "" => "<computed>"
    ip_prefix_length:         "" => "<computed>"
    log_driver:               "" => "json-file"
    must_run:                 "" => "1"
    name:                     "" => "mysql_inner"
    ports.#:                  "" => "1"
    ports.382260533.external: "" => "13306"
    ports.382260533.internal: "" => "3306"
    ports.382260533.ip:       "" => ""
    ports.382260533.protocol: "" => "tcp"
    restart:                  "" => "no"

+ module.mysql_inner.docker_image.mysql_inner
    latest: "" => "<computed>"
    name:   "" => "mysql:5.7"


Plan: 4 to add, 0 to change, 0 to destroy.

terraform show result

docker_container.mysql_outer:
  id = f263ccc241e99807ba1d15dcf8281d2f16d017db54740510f2c43febc8908f2c
  bridge = 
  gateway = 172.17.0.1
  image = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b
  ip_address = 172.17.0.3
  ip_prefix_length = 16
  log_driver = json-file
  must_run = true
  name = mysql_outer
  ports.# = 1
  ports.275610719.external = 0
  ports.275610719.internal = 3306
  ports.275610719.ip = 
  ports.275610719.protocol = tcp
  restart = no
docker_image.mysql_outer:
  id = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217bmysql:5.7
  latest = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b
  name = mysql:5.7

module.mysql_inner.docker_container.mysql_inner:
  id = 9ba8b352b474a34a467abf7359ba7686c7f4f83033f174d7b9efaf52302e3f7c
  bridge = 
  gateway = 172.17.0.1
  image = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b
  ip_address = 172.17.0.4
  ip_prefix_length = 16
  log_driver = json-file
  must_run = true
  name = mysql_inner
  ports.# = 1
  ports.382260533.external = 13306
  ports.382260533.internal = 3306
  ports.382260533.ip = 
  ports.382260533.protocol = tcp
  restart = no
module.mysql_inner.docker_image.mysql_inner:
  id = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217bmysql:5.7
  latest = sha256:e13b20a4f248755275fa7db87769cb3c2d25d5d242e1b9946e1e75a2f419217b
  name = mysql:5.7


Outputs:

mysql_inner_host = 172.17.0.4
mysql_outer_host = 172.17.0.3