terraform-generator

terraform-generator

Use Node.js to generate Terraform plan.

You do not need to have Terraform installed to use this module.

The end result of using this module is Terraform plan in plain text, you will need to write the text into a file and execute it yourself.

Currently support generating plan for Terraform version 0.11 and 0.12.

Disclamer

This module is still in development and testing phase, it might not work fully correctly. Feel free to report issues/bugs, make requests or give suggesstions in GitHub page.

Benefit

Make use of all Javascript programming features (some of which is not available in Terraform), e.g. functions, array, loops, if-else, map, etc. to generate a plain Terraform plan.

You can easily maintain your infra in Javascript/Typescript.

You don't need to use Terraform variables, you can use your own Javascript/JSON variables or use dot env.

You don't need to use Terraform modules for reusable resource creations, you can make use of Javascript functions.

Limitation

The generated plan is unformatted and its validity is not verified, use terraform fmt and terraform plan to format it and check its validity yourself.

Install via NPM

npm install terraform-generator

Usage

Import

import TerraformGenerator, { Resource, map, fn } from 'terraform-generator';

Initiate TerraformGenerator

const tfg = new TerraformGenerator({ version: '0.12' }, {
  required_version: '>= 0.12'
});

Blocks

Block's arguments are not typed, please refer to official Terraform documentation on what arguments can be supplied.

tfg.addProvider('aws', {
  region: 'ap-southeast-1',
  profile: 'example'
});

const vpc = tfg.addResource('aws_vpc', 'vpc', {
  cidr_block: '172.88.0.0/16'
});

Convert resource to data source and filter by resource's tags

import { vpc } from 'other-terraform-project';

tfg.addBlock(vpc.toDataSourceByTags());

Arguments

{
  string: 'str',
  number: 123,
  boolean: true,
  stringList: ['str1', 'str2', 'str3'],
  numberList: [111, 222, 333],
  booleanList: [true, false, true],
  tuple: ['str', 123, true],
  object: {
    arg1: 'str',
    arg2: 123,
    arg3: true
  },
  objectList: [
    {
      arg1: 'str'
    },
    {
      arg1: 'str'
    }
  ],
  map: map({
    arg1: 'str',
    arg2: 123,
    arg3: true
  }),
  block: block,
  blockAttribute: block.attr('attrName'),
  heredoc: heredoc(`line1
                        line2
                        line3`),
  function1: fn('max', 5, 12, 19),
  function2: fn('sort', 'a', block.attr('attrName'), 'c'),
  custom1: arg('max(5, 12, 9)'),
  custom2: arg('as is', true) // it will be printed as is, without extra symbol, quotes and whatnot, regardless of Terraform version
}

Attributes

block.attr('id')                 // block id, string
block.attr('subnets')            // subnet objects, object list
block.attr('subnets.*.id')       // subnet ids, string list
block.attr('subnets.*.id[0]')    // first subnet id, string

Generate Terraform plan

// Generate Terraform plan as string
tfg.generate();

// Write Terraform plan to a file
// Default filename is terraform.tf
// Default format is false, if format is true, Terraform needs to be installed
tfg.write('outputDir', { filename: 'output.tf', format: true });

Example

import TerraformGenerator, { Map, map } from 'terraform-generator';
import path from 'path';

// Constants
const project = 'example';

// Environment variables
const configs = {
  env: 'dev',
  tiers: [
    {
      name: 'web',
      cidr: '172.88.100.0/22',
      subnetCidrs: ['172.88.100.0/24', '172.88.101.0/24', '172.88.102.0/24']
    },
    {
      name: 'app',
      cidr: '172.88.104.0/22',
      subnetCidrs: ['172.88.104.0/24', '172.88.105.0/24', '172.88.106.0/24']
    },
    {
      name: 'db',
      cidr: '172.88.108.0/22',
      subnetCidrs: ['172.88.108.0/24', '172.88.109.0/24', '172.88.110.0/24']
    }
  ]
};

// Utility functions
const getAvailabilityZone = (i: number): string => {
  if (i === 0) {
    return 'ap-southeast-1a';
  } else if (i === 1) {
    return 'ap-southeast-1b';
  } else {
    return 'ap-southeast-1c';
  }
};

const getTagName = (type: string, name?: string): string =>
  `${type}-${project}-${configs.env}${name ? `-${name}` : ''}`;

const getTags = (type: string, name?: string): Map => new Map({
  Name: getTagName(type, name),
  Project: project,
  Env: configs.env
});

// Start writing Terraform plan
const tfg = new TerraformGenerator({ version: '0.12' });

// Configure provider
tfg.addProvider('aws', {
  region: 'ap-southeast-1',
  profile: 'example'
});

// Find VPC by name
const vpc = tfg.addDataSource('aws_vpc', 'vpc', {
  filter: [{
    name: 'tag:Name',
    values: [getTagName('vpc')]
  }]
});

const subnets = {
  web: [],
  app: [],
  db: []
};

// Create 3-tiers, each tier has 3 subnets spread across availabilty zones
configs.tiers.forEach(tier => {
  tier.subnetCidrs.forEach((cidr, i) => {
    const name = `${tier.name}${i}`;
    const subnet = tfg.addResource('aws_subnet', `subnet_${name}`, {
      vpc_id: vpc.attr('id'),
      cidr_block: cidr,
      availability_zone: getAvailabilityZone(i),
      tags: getTags('subnet', name)
    });
    subnets[tier.name].push(subnet);
  });
});

// Output all subnet ids
tfg.addOutput('subnets', {
  value: map({
    webSubnets: subnets.web.map(subnet => subnet.attr('id')),
    appSubnets: subnets.app.map(subnet => subnet.attr('id')),
    dbSubnets: subnets.db.map(subnet => subnet.attr('id'))
  })
});

// Write the plan into a terraform.tf file
const outputDir = path.join('output', configs.env, 'subnets');
tfg.write(outputDir, { format: true });