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Advanced Terraform: managing Docker containers

Overview

This advanced tutorial will guide you through setting up a Terraform project with Docker.

Goals

Understand how to use registry.terraform.io

Understand practical terraform advanced language concepts by orchestrating Docker containers

Understand how to install software and provision multiple VMs

Understand how Terraform is used to orchestrate VMs together

Undertand how Terraform is used to create a multi-node JupyterHub

Things we won't cover

Basic management of Kubernetes clusters (that is a different lesson)

All of Terraform's features

Using registry.terraform.io

Terraform maintains an active registry site located at https://registry.terraform.io.

This is the Terraform's defacto catalog for

  • providers
  • modules
  • policies (enforcement rules via Terraform Cloud)
  • runtasks (integrations with other services via Terraform Cloud)

Examples of providers:

Prerequisites in doing Terraform exercises

Outcomes

By the end of this tutorial, you will

have used Terraform to manage Docker containers while learning advanced Terraform concepts

Using a Terraform to simply manage Docker

We will use VMs with Docker installed and learn how to launch containers in a declarative way, rather than using the docker command. Once you gain access to your VM, perform the following steps

  1. ssh into your VM (alternatively, you can declare use the Docker Terraform provider using ssh access)
  2. git clone https://gitlab.com/stack0/terraform-docker-helloworld.git
  3. cd terraform-docker-helloworld

  4. Review input.tf, main.tf, and terraform.tfvars.example to get a sense of how to manage a Docker container using Terraform

    1. Review the concept of a Terraform resource
    2. How many resources are created?
    3. What is the relationship between the resources?
    4. Is there any question that comes to mind about the port property of docker_container resource

  5. cp terraform.tfvars.example terraform.tfvars

  6. edit terraform.tfvars

    1. feel free to edit the image or container_name with a container you prefer, but if you do, please select a container with a port that you can access
    2. if you are using local docker access, use the default value; if you are accessing the docker host remotely, use the string "ssh://myuser@1.2.3.4", where myuser is replaced with your vm username and 1.2.3.4 is replaced with your vm's ip address

  7. terraform apply -auto-approve

    Expected Response 
    Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following
symbols:
+ create

Terraform will perform the following actions:

# docker_container.mycontainer will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "edwins-container"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60
    }

# docker_image.mydocker will be created
+ resource "docker_image" "mydocker" {
    + id          = (known after apply)
    + image_id    = (known after apply)
    + name        = "nginx:latest"
    + repo_digest = (known after apply)
    }

Plan: 2 to add, 0 to change, 0 to destroy.
docker_image.mydocker: Creating...
docker_image.mydocker: Creation complete after 3s [id=sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287nginx:latest]
docker_container.mycontainer: Creating...
docker_container.mycontainer: Creation complete after 1s [id=54f9987cde7fe5b474348ca3e89955c24eb076d6d4ea49aee7e44928f3f8e711]

Apply complete! Resources: 2 added, 0 changed, 0 destroyed.

  8. terraform destroy -auto-approve

Increasing the number of containers using count

We will next update Terraform to create multiple containers of the same image.

  1. Modify the input.tf with a new variable 

    variable "num_containers" {
    type = number
    description = "number, number of containers to launch"
    default = 1
}

  2. Modify the main.tf with the following changes (highlighted lines): 

    resource "docker_container" "mycontainer" {
    count = var.num_containers
    image = docker_image.mydocker.image_id
    name = "${format("%s%02d", var.container_name, count.index)}"
    ports {
        internal = 80
        external = "${8080 + count.index}" # illustrates using count.index to indicate which port to use
    }
}
output "docker_containers" {
    value = keys({
        for index, d in docker_container.mycontainer.* : "${format("%s,%s,%s", index, d.name,d.id)}" => d
    })
}

  3. Edit your terraform.tfvars to include a new num_containers input variable with a value 5

  4. terraform apply -auto-approve

    Expected Response 
    $ terraform apply -auto-approve

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
+ create

Terraform will perform the following actions:

# docker_container.mycontainer[0] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer00"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8080
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_container.mycontainer[1] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer01"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8081
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_container.mycontainer[2] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer02"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8082
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_container.mycontainer[3] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer03"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8083
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_container.mycontainer[4] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = (known after apply)
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer04"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8084
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_image.mydocker will be created
+ resource "docker_image" "mydocker" {
    + id          = (known after apply)
    + image_id    = (known after apply)
    + name        = "nginx:latest"
    + repo_digest = (known after apply)
    }

Plan: 6 to add, 0 to change, 0 to destroy.

Changes to Outputs:
+ docker_containers = (known after apply)
docker_image.mydocker: Creating...
docker_image.mydocker: Creation complete after 3s [id=sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287nginx:latest]
docker_container.mycontainer[1]: Creating...
docker_container.mycontainer[4]: Creating...
docker_container.mycontainer[2]: Creating...
docker_container.mycontainer[0]: Creating...
docker_container.mycontainer[3]: Creating...
docker_container.mycontainer[1]: Creation complete after 1s [id=8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8]
docker_container.mycontainer[3]: Creation complete after 1s [id=c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06]
docker_container.mycontainer[0]: Creation complete after 1s [id=4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064]
docker_container.mycontainer[2]: Creation complete after 1s [id=36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99]
docker_container.mycontainer[4]: Creation complete after 1s [id=46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501]

Apply complete! Resources: 6 added, 0 changed, 0 destroyed.

Outputs:

docker_containers = [
"0,mycontainer00,4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064",
"1,mycontainer01,8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8",
"2,mycontainer02,36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99",
"3,mycontainer03,c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06",
"4,mycontainer04,46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501",
]

  5. Notice some pieces of the codes that were introduced

    1. What is the count.index?
    2. What is the format function and why use it?
    3. What will index start at?
    4. Terraform supports math operations
    5. An example of using the keys() method and ad hoc dictionary construction

  6. terraform destroy -auto-approve

When resources change outside of Terraform

In this exercise we'll discover how to use Terraform to handle change.

  1. Use docker stop and docker rm to stop and delete docker containers 2 and 3.

    Expected Response 
    $ docker stop 36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99 c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06
36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99
c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06
$ docker rm 36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99 c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06
36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99
c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06

  2. Execute a terraform show and count the number of instances in the state

  3. Execute a terraform refresh

    Expected Response 
    $ terraform refresh
docker_image.mydocker: Refreshing state... [id=sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287nginx:latest]
docker_container.mycontainer[3]: Refreshing state... [id=c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06]
docker_container.mycontainer[2]: Refreshing state... [id=36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99]
docker_container.mycontainer[1]: Refreshing state... [id=8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8]
docker_container.mycontainer[4]: Refreshing state... [id=46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501]
docker_container.mycontainer[0]: Refreshing state... [id=4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064]

Outputs:

docker_containers = [
"0,mycontainer00,4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064",
"1,mycontainer01,8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8",
"2,mycontainer02,36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99",
"3,mycontainer03,c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06",
"4,mycontainer04,46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501",
]

  4. Execute a terraform show again and recount the instance in the state. Why doesn't the output variable change?

  5. Execute a terraform apply (without the -auto-approve) and review what will be updated. Once you are satisfied with the changes that will happen, enter yes at the prompt.

    Expected Response 
    $ terraform apply 
docker_image.mydocker: Refreshing state... [id=sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287nginx:latest]
docker_container.mycontainer[0]: Refreshing state... [id=4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064]
docker_container.mycontainer[1]: Refreshing state... [id=8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8]
docker_container.mycontainer[4]: Refreshing state... [id=46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
+ create

Terraform will perform the following actions:

# docker_container.mycontainer[2] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = "sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287"
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer02"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8082
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

# docker_container.mycontainer[3] will be created
+ resource "docker_container" "mycontainer" {
    + attach                                      = false
    + bridge                                      = (known after apply)
    + command                                     = (known after apply)
    + container_logs                              = (known after apply)
    + container_read_refresh_timeout_milliseconds = 15000
    + entrypoint                                  = (known after apply)
    + env                                         = (known after apply)
    + exit_code                                   = (known after apply)
    + hostname                                    = (known after apply)
    + id                                          = (known after apply)
    + image                                       = "sha256:89da1fb6dcb964dd35c3f41b7b93ffc35eaf20bc61f2e1335fea710a18424287"
    + init                                        = (known after apply)
    + ipc_mode                                    = (known after apply)
    + log_driver                                  = (known after apply)
    + logs                                        = false
    + must_run                                    = true
    + name                                        = "mycontainer03"
    + network_data                                = (known after apply)
    + read_only                                   = false
    + remove_volumes                              = true
    + restart                                     = "no"
    + rm                                          = false
    + runtime                                     = (known after apply)
    + security_opts                               = (known after apply)
    + shm_size                                    = (known after apply)
    + start                                       = true
    + stdin_open                                  = false
    + stop_signal                                 = (known after apply)
    + stop_timeout                                = (known after apply)
    + tty                                         = false
    + wait                                        = false
    + wait_timeout                                = 60

    + ports {
        + external = 8083
        + internal = 80
        + ip       = "0.0.0.0"
        + protocol = "tcp"
        }
    }

Plan: 2 to add, 0 to change, 0 to destroy.

Changes to Outputs:
~ docker_containers = [
    - "0,mycontainer00,4ce1d4e0617994ba225701e5e0ef243daa8762968c8d7202be2612ecaeaca064",
    - "1,mycontainer01,8c80b558394f62fe004ff156fa1fee06ce723f2b0721cfdfd0f4e64fb6fb28f8",
    - "2,mycontainer02,36cf1496a418395408a9d5630c8e1cf8b12fa948ab73fe95a3b1a3d8ce767e99",
    - "3,mycontainer03,c0bc456f847a4e403ee4bcd133f79a21f22b4ec8f94db8793160b28807789e06",
    - "4,mycontainer04,46ab03a8cd2616f20d34058d20b298df8ecc84bf5e8cfaf8013086f21ba1f501",
    ] -> (known after apply)

Do you want to perform these actions?
Terraform will perform the actions described above.
Only 'yes' will be accepted to approve.

Enter a value:

  6. terraform destroy -auto-approve

Validating your input data

Next we will show how to add validation to your inputs

  1. In your input.tf, add the following variable

    variable "port_assignment_list" {
  type = list(number)
  description = "list of port assignments, size should = num_containers"
  default = []
  validation {
    condition     = length(var.port_assignment_list) > 0
    error_message = "Port assignment not > 0"
  }
}

  2. In your main.tf, replace your docker_container resource to the following:

    resource "docker_container" "mycontainer" {
  count = var.num_containers
  image = docker_image.mydocker.image_id
  name = "${format("%s%02d", var.container_name, count.index)}"
  ports {
    internal = 80
    external = var.port_assignment_list[count.index] # illustrates using count.index to indicate which port to use
  }
}

  3. Add/update the following variables in your terraform.tfvars

    num_containers=5
port_assignment_list=[]

  4. terraform apply -auto-approve

  5. What do you expect?
    • Try updating the condition such that length must equal num_containers

Now, let's figure out how to make our validation slightly more useful

  1. If necessary, restore your input.tf to include the original validation block

    variable "port_assignment_list" {
  type = list(number)
  description = "list of port assignments, size should = num_containers"
  default = []
  validation {
    condition     = length(var.port_assignment_list) > 0
    error_message = "Port assignment not > 0"
  }
}

  2. Update your main.tf to include a validation block like the following:

    resource "docker_container" "mycontainer" {
  count = var.num_containers
  image = docker_image.mydocker.image_id
  name = "${format("%s%02d", var.container_name, count.index)}"
  ports {
    internal = 80
    external = var.port_assignment_list[count.index] # illustrates using count.index to indicate which port to use
  }

  lifecycle {
    precondition {
      condition = length(var.port_assignment_list) == num_containers
      error_message = "length != num_containers"
    }
  }
}

  3. Update your terraform.tfvars with the following settings

    num_containers=5
port_assignment_list=[4040,5050,6060,7070]

  4. terraform apply -auto-approve

  5. What do you expect?

    • Try adding another port (or remove a port) so that num_containers and the length of the list is equal

  6. terraform destroy -auto-approve

Increasing the number of containers using for_each

Next we will create multiple docker containers, but using a different method, for_each.

  1. copy input.tf, main.tf from 01c-multiple-containers (overwrite your existing files)

    1. review the differences in input.tf
    2. review the differences in main.tf

  2. remove the num_containers from your terraform.tfvars and add a new variable called containers_map, something like

    containers_map={
    cat = 8080,
    dog = 8090,
    bird = 9090,
    cow = 9080,
    horse = 9070
}

  3. terraform apply -auto-approve

  4. Notice some pieces of the codes that were introduced

    1. Notice the declaration of a map, the default value, and how to set it in terraform.tfvars
    2. Map keys do not need quoting. What about values?
    3. How would you compare the how ports are configured in between the use of count and for_each
    4. Why might you use count and for_each

  5. terraform destroy -auto-approve

Using dynamic blocks create repeatable nestable blocks in resources

Next we will see an example of resource properties that can be repeated

  1. Copy input.tf, main.tf from 02a-using-ports (overwrite your existing files)

    1. Review the differences in main.tf

  2. Edit input.tf with a new variable

    variable "container_ports" {
    type = list(object({
      internal=string,
      external=string
    }))
    description = "map(object), port object as defined by https://registry.terraform.io/providers/kreuzwerker/docker/latest/docs/resources/container#nestedblock--ports"
    default = []
}

  3. edit the main.tf with the following docker_container resource definition

    resource "docker_container" "mycontainer" {
  image = docker_image.mydocker.image_id
  name  = var.container_name

  dynamic "ports" {
    for_each = var.container_ports
    content {
      internal = ports.value.internal
      external = ports.value.external
    }
  }
}

  4. Add the following variable in your terraform.tfvars

    ports = [
    {internal="80", external="8080"},
    {internal="90", external="9090"}
]

  5. terraform apply -auto-approve

  6. Verify the ports were added when you use docker ps
  7. terraform destroy -auto-approve

Adapted from CyVerse Container Camp (last source update 2023-08-17), CC BY 4.0. Spotted a problem? Open an issue.