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terraform-generator

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Readme

terraform-generator

Use Node.js to generate Terraform configurations.

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

The end result of using this module is Terraform configurations in plain text, you will need to write the text into a file (terraform-generator does provide an utility function to write the file for you) and execute it yourself.

Currently support generating configurations for Terraform version 0.11 and 0.12.

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 configurations.

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 configurations are 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';

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

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

Convert resource to data source

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

const vpc = tfg.dataFromResource(vpcDS, null, ['cidr_block', ['tags', 'tag']]);

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 configuration

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

// Write Terraform configuration to a file
// Default dir is .
// Default filename is terraform.tf
// Default format is false, if format is true, Terraform needs to be installed
tfg.write({ dir: '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 configuration
const tfg = new TerraformGenerator({ version: '0.12' });

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

// Find VPC by name
const vpc = tfg.data('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.resource('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.output('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 configuration into a terraform.tf file
const outputDir = path.join('output', configs.env, 'subnets');
tfg.write({ dir: outputDir, format: true });