visar · March 7, 2019 23:43 · Nov 16, 2018 · Nov 16, 2018 · Mar 29, 2018 · Mar 29, 2018
diff --git a/0.12.tf b/0.12.tf
@@ -0,0 +1,227 @@
+# first class expresssion
+variable "ami" {}
+resource "aws_instance" "example" {
+  ami           = var.ami
+}
+
+###
+
+# list & map
+resource "aws_instance" "example" {
+  vpc_security_group_ids = var.security_group_id != "" ? [var.security_group_id] : []
+}
+
+###
+
+# In 0.12, HCL resolves this by making an explicit distinction between attributes and blocks. Attributes are single-assigned values using the assignment operator =. Blocks are repeated maps of key/value configuration pairs
+resource "aws_security_group" "example" {
+
+  # "ingress" is parsed as a block because there is no equals sign
+  ingress {
+    # ..
+  }
+
+  # "value" is parsed as a attribute as it has equal sign
+  value = {
+    # ..
+  }
+}
+
+###
+
+# For Expressions for List and Map Transformations
+variable "subnet_numbers" {
+  description = "List of 8-bit numbers of subnets of base_cidr_block that should be granted access."
+  default = [1, 2, 3]
+}
+
+resource "aws_security_group" "example" {
+    # For each number in subnet_numbers, extend the CIDR prefix of the
+    # requested VPC to produce a subnet CIDR prefix.
+    # For the default value of subnet_numbers above and a VPC CIDR prefix
+    # of 10.1.0.0/16, this would produce:
+    #   ["10.1.1.0/24", "10.1.2.0/24", "10.1.3.0/24"]
+    cidr_blocks = [
+      for num in var.subnet_numbers:
+      cidrsubnet(data.aws_vpc.example.cidr_block, 8, num)
+    ]
+  }
+}
+
+###
+
+# how to produce a map
+output "instance_private_ip_addresses" {
+  # Result is a map from instance id to private IP address, such as:
+  #  {"i-1234" = "192.168.1.2", "i-5678" = "192.168.1.5"}
+  value = {
+    for instance in aws_instance.example:
+    instance.id => instance.private_ip
+    # if statement
+    if instance.associate_public_ip_address
+  }
+}
+
+output "instances_by_availability_zone" {
+  # Result is a map from availability zone to instance ids, such as:
+  #  {"us-east-1a": ["i-1234", "i-5678"]}
+  value = {
+    for instance in aws_instance.example:
+    # mind the ...
+    instance.availability_zone => instance.id...
+  }
+}
+
+###
+
+# Dynamic Nested Blocks
+variable "subnets" {
+  default = [
+    {
+      name   = "a"
+      number = 1
+    },
+    {
+      name   = "b"
+      number = 2
+    },
+    {
+      name   = "c"
+      number = 3
+    },
+  ]
+}
+
+locals {
+  base_cidr_block = "10.0.0.0/16"
+}
+
+resource "azurerm_virtual_network" "example" {
+  name                = "example-network"
+  resource_group_name = azurerm_resource_group.test.name
+  address_space       = [local.base_cidr_block]
+  location            = "West US"
+
+  dynamic "subnet" {
+    # [{"name": "a", "prefix": "10.1.0.0/24"}, 
+    # {"name": "b", "prefix": "10.2.0.0/24"}, 
+    # {"name": "c", "prefix": "10.3.0.0/24"}]
+    for_each = [for s in subnets: {
+      name   = s.name
+      prefix = cidrsubnet(local.base_cidr_block, 4, s.number)
+    }]
+
+    content {
+      name           = subnet.name
+      address_prefix = subnet.prefix
+    }
+  }
+}
+
+###
+
+# splat operator
+# before only work with resource with "count", now work for any list value
+output "instance_ip_addrs" {
+  value = google_compute_instance.example.network_interface.*.address
+}
+
+###
+
+# full splat operator
+# instead of network_interface.*.
+output "instance_net_ip_addrs" {
+  value = google_compute_instance.example.network_interface[*].access_config[0].assigned_nat_ip
+}
+
+###
+
+# Conditional Operator Improvements
+locals {
+  first_id = length(azurerm_virtual_machine.example) > 0 ? azurerm_virtual_machine.example[0].id : ""
+
+  buckets = (var.env == "dev" ? [var.build_bucket, var.qa_bucket] : [var.prod_bucket])
+}
+
+###
+
+# Conditionally Omitted Arguments
+variable "override_private_ip" {
+  type    = string
+  default = null
+}
+
+resource "aws_instance" "example" {
+  # By using the new null value, the aws_instance resource can dynamically assign a private IP address when no override is provided, 
+  # but set an explicit IP address if the calling module provides a value for override_private_ip.
+  private_ip = var.override_private_ip
+}
+
+###
+
+# Complex Values
+# complex objects can now be passed to child modules as inputs, and returned to parent modules as outputs
+# access with `for network in var.networks`
+module "subnets" {
+  source = "./subnets"
+
+  parent_vpc_id = "vpc-abcd1234"
+  networks = {
+    production_a = {
+      network_number    = 1
+      availability_zone = "us-east-1a"
+    }
+    production_b = {
+      network_number    = 2
+      availability_zone = "us-east-1b"
+    }
+    staging_a = {
+      network_number    = 1
+      availability_zone = "us-east-1a"
+    }
+  }
+}
+
+###
+
+# Rich types
+variable "networks" {
+  # custom type
+  # no quote
+  type = map(object({
+    network_number    = number
+    availability_zone = string
+    tags              = map(string)
+  }))
+}
+
+###
+
+# Resources and Modules as Values
+# return the whole object
+output "vpc" {
+  value = aws_vpc.example
+}
+
+###
+
+# New Template syntax
+locals {
+  lb_config = <<EOT
+%{ for instance in opc_compute_instance.example ~}
+server ${instance.label} ${instance.ip_address}:8080
+%{ endfor }
+EOT
+}
+
+###
+
+# JSON comment
+{
+  "variable": {
+    "example": {
+      "#": "This property is ignored",
+      "default": "foo"
+    }
+  }
+}
diff --git a/provider.md b/provider.md
@@ -18,11 +18,11 @@ import (
 )
 
 func Provider() *schema.Provider {
-    return &schema.Provider{
-        ResourcesMap: map[string]*schema.Resource{
-          "example_server": resourceServer(),
-        },
-    }
+  return &schema.Provider{
+    ResourcesMap: map[string]*schema.Resource{
+      "example_server": resourceServer(),
+    },
+  }
 }
 ```
 
@@ -37,11 +37,11 @@ import (
 )
 
 func main() {
-    plugin.Serve(&plugin.ServeOpts{
-        ProviderFunc: func() terraform.ResourceProvider {
-            return Provider()
-        },
-    })
+  plugin.Serve(&plugin.ServeOpts{
+    ProviderFunc: func() terraform.ResourceProvider {
+      return Provider()
+    },
+  })
 }
 ```
 
@@ -58,17 +58,17 @@ import (
 
 func resourceServer() *schema.Resource {
   return &schema.Resource{
-      Create: resourceServerCreate,
-      Read:   resourceServerRead,
-      Update: resourceServerUpdate,
-      Delete: resourceServerDelete,
-
-      Schema: map[string]*schema.Schema{
-          "address": &schema.Schema{
-              Type:     schema.TypeString,
-              Required: true,
-          },
+    Create: resourceServerCreate,
+    Read:   resourceServerRead,
+    Update: resourceServerUpdate,
+    Delete: resourceServerDelete,
+
+    Schema: map[string]*schema.Schema{
+      "address": &schema.Schema{
+        Type:     schema.TypeString,
+        Required: true,
       },
+    },
   }
 }
 

diff --git a/provider.md b/provider.md
@@ -57,19 +57,19 @@ import (
 )
 
 func resourceServer() *schema.Resource {
-    return &schema.Resource{
-        Create: resourceServerCreate,
-        Read:   resourceServerRead,
-        Update: resourceServerUpdate,
-        Delete: resourceServerDelete,
-
-        Schema: map[string]*schema.Schema{
-            "address": &schema.Schema{
-                Type:     schema.TypeString,
-                Required: true,
-            },
-        },
-    }
+  return &schema.Resource{
+      Create: resourceServerCreate,
+      Read:   resourceServerRead,
+      Update: resourceServerUpdate,
+      Delete: resourceServerDelete,
+
+      Schema: map[string]*schema.Schema{
+          "address": &schema.Schema{
+              Type:     schema.TypeString,
+              Required: true,
+          },
+      },
+  }
 }
 
 func resourceServerCreate(d *schema.ResourceData, m interface{}) error {

diff --git a/provider.md b/provider.md
@@ -73,9 +73,9 @@ func resourceServer() *schema.Resource {
 }
 
 func resourceServerCreate(d *schema.ResourceData, m interface{}) error {
-    address := d.Get("address").(string)
-    d.SetId(address)
-    return nil
+  address := d.Get("address").(string)
+  d.SetId(address)
+  return nil
 }
 
 func resourceServerRead(d *schema.ResourceData, m interface{}) error {

diff --git a/provider.md b/provider.md
@@ -73,6 +73,8 @@ func resourceServer() *schema.Resource {
 }
 
 func resourceServerCreate(d *schema.ResourceData, m interface{}) error {
+    address := d.Get("address").(string)
+    d.SetId(address)
     return nil
 }
 

diff --git a/provider.md b/provider.md
@@ -1,5 +1,7 @@
 # Terraform provider
 
+[Source](https://www.terraform.io/guides/writing-custom-terraform-providers.html)
+
 ```bash
 ├── main.go
 ├── provider.go

diff --git a/provider.md b/provider.md
@@ -86,3 +86,10 @@ func resourceServerDelete(d *schema.ResourceData, m interface{}) error {
     return nil
 }
 ```
+
+main.tf
+
+```hcl
+resource "example_server" "my-server" {
+  address = "1.2.3.4"
+}
diff --git a/provider.md b/provider.md
@@ -1 +1,88 @@
-touch
+# Terraform provider
+
+```bash
+├── main.go
+├── provider.go
+├── resource_server.go
+```
+
+provider.go
+
+```go
+package main
+
+import (
+    "github.com/hashicorp/terraform/helper/schema"
+)
+
+func Provider() *schema.Provider {
+    return &schema.Provider{
+        ResourcesMap: map[string]*schema.Resource{
+          "example_server": resourceServer(),
+        },
+    }
+}
+```
+
+main.go
+
+```go
+package main
+
+import (
+    "github.com/hashicorp/terraform/plugin"
+    "github.com/hashicorp/terraform/terraform"
+)
+
+func main() {
+    plugin.Serve(&plugin.ServeOpts{
+        ProviderFunc: func() terraform.ResourceProvider {
+            return Provider()
+        },
+    })
+}
+```
+
+> As a general convention, Terraform providers put each resource in their own file, named after the resource, prefixed with resource_
+
+resource_server.go
+
+```go
+package main
+
+import (
+    "github.com/hashicorp/terraform/helper/schema"
+)
+
+func resourceServer() *schema.Resource {
+    return &schema.Resource{
+        Create: resourceServerCreate,
+        Read:   resourceServerRead,
+        Update: resourceServerUpdate,
+        Delete: resourceServerDelete,
+
+        Schema: map[string]*schema.Schema{
+            "address": &schema.Schema{
+                Type:     schema.TypeString,
+                Required: true,
+            },
+        },
+    }
+}
+
+func resourceServerCreate(d *schema.ResourceData, m interface{}) error {
+    return nil
+}
+
+func resourceServerRead(d *schema.ResourceData, m interface{}) error {
+    return nil
+}
+
+func resourceServerUpdate(d *schema.ResourceData, m interface{}) error {
+    return nil
+}
+
+func resourceServerDelete(d *schema.ResourceData, m interface{}) error {
+    return nil
+}
+```
diff --git a/terraform.md b/terraform.md
@@ -1,22 +1,27 @@
+# Cheatsheet
+
 ## Map Loop
 
 For e.g, we have the following values:
+
 ```hcl
 vpc_peering_list = {
   k8s-production = "vpc-111111"
   k8s-service = "vpc-222222"
-  k8s-zdata = "vpc-333333" 
+  k8s-zdata = "vpc-333333"
 }
 ```
+
 **IMPORTANT** Map follows alphanumeric sequence.
 
 We can loop through this map with:
+
 ```hcl
 resource "aws_vpc_peering_connection" "vpc_peering" {
   count = "${length(keys(var.vpc_peering_list))}"
   vpc_id = "${element(values(var.vpc_peering_list), count.index)}"
   peer_vpc_id   = "${aws_vpc.vpc.id}"
- 
+
   tags {
     Name = "${element(keys(var.vpc_peering_list), count.index)}-vpc-peering-${var.service_name}"
   }
@@ -38,16 +43,19 @@ resource "aws_route53_record" "www" {
 ```
 
 ## Default values for external module output
+
 https://github.com/hashicorp/terraform/issues/11566#issuecomment-289417805
 
 https://github.com/coreos/tectonic-installer/blob/master/modules/aws/vpc/vpc.tf#L24
 
 External module should return output as a `list`
+
 ```hcl
 id = "${var.external_vpc_id == "" ? join(" ", aws_vpc.new_vpc.*.id) : var.external_vpc_id }"
 ```
 
 Default value when using conditional check. See [this](https://github.com/hashicorp/terraform/issues/2831#issuecomment-298751019)
+
 ```hcl
 resource "example" "conditional" {
   count = "${var.enabled ? 1 : 0}"
@@ -56,4 +64,4 @@ resource "example" "conditional" {
 resource "example" "dependent" {
   argument = "${join("", example.conditional.*.attribute)}"
 }
-```
+```
diff --git a/provider.md b/provider.md
@@ -0,0 +1 @@
+touch
diff --git a/terraform.md b/terraform.md
@@ -45,4 +45,15 @@ https://github.com/coreos/tectonic-installer/blob/master/modules/aws/vpc/vpc.tf#
 External module should return output as a `list`
 ```hcl
 id = "${var.external_vpc_id == "" ? join(" ", aws_vpc.new_vpc.*.id) : var.external_vpc_id }"
+```
+
+Default value when using conditional check. See [this](https://github.com/hashicorp/terraform/issues/2831#issuecomment-298751019)
+```hcl
+resource "example" "conditional" {
+  count = "${var.enabled ? 1 : 0}"
+}
+
+resource "example" "dependent" {
+  argument = "${join("", example.conditional.*.attribute)}"
+}
 ```
diff --git a/terraform.md b/terraform.md
@@ -39,6 +39,7 @@ resource "aws_route53_record" "www" {
 
 ## Default values for external module output
 https://github.com/hashicorp/terraform/issues/11566#issuecomment-289417805
+
 https://github.com/coreos/tectonic-installer/blob/master/modules/aws/vpc/vpc.tf#L24
 
 External module should return output as a `list`

diff --git a/terraform.md b/terraform.md
@@ -35,4 +35,13 @@ variable "bucket_name" {
 resource "aws_route53_record" "www" {
   count = "${length(var.bucket_name)}"
   name  = "${var.bucket_name[count.index]}"
+```
+
+## Default values for external module output
+https://github.com/hashicorp/terraform/issues/11566#issuecomment-289417805
+https://github.com/coreos/tectonic-installer/blob/master/modules/aws/vpc/vpc.tf#L24
+
+External module should return output as a `list`
+```hcl
+id = "${var.external_vpc_id == "" ? join(" ", aws_vpc.new_vpc.*.id) : var.external_vpc_id }"
 ```
diff --git a/terraform.md b/terraform.md
@@ -21,4 +21,18 @@ resource "aws_vpc_peering_connection" "vpc_peering" {
     Name = "${element(keys(var.vpc_peering_list), count.index)}-vpc-peering-${var.service_name}"
   }
 }
+```
+
+## List Loop
+
+```hcl
+variable "bucket_name" {
+  description = "Bucket Name"
+  type        = "list"
+  default     = ["develop", "staging", "prod"]
+}
+
+resource "aws_route53_record" "www" {
+  count = "${length(var.bucket_name)}"
+  name  = "${var.bucket_name[count.index]}"
 ```
diff --git a/terraform.md b/terraform.md
@@ -0,0 +1,24 @@
+## Map Loop
+
+For e.g, we have the following values:
+```hcl
+vpc_peering_list = {
+  k8s-production = "vpc-111111"
+  k8s-service = "vpc-222222"
+  k8s-zdata = "vpc-333333" 
+}
+```
+**IMPORTANT** Map follows alphanumeric sequence.
+
+We can loop through this map with:
+```hcl
+resource "aws_vpc_peering_connection" "vpc_peering" {
+  count = "${length(keys(var.vpc_peering_list))}"
+  vpc_id = "${element(values(var.vpc_peering_list), count.index)}"
+  peer_vpc_id   = "${aws_vpc.vpc.id}"
+ 
+  tags {
+    Name = "${element(keys(var.vpc_peering_list), count.index)}-vpc-peering-${var.service_name}"
+  }
+}
+```