Derrick Bryant 7a553c569f Add option for real time Terraform output

2017-03-31 11:54:26 -07:00

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Introduction

python-terraform is a python module provide a wrapper of terraform command line tool. terraform is a tool made by Hashicorp, please refer to https://terraform.io/

Status

Installation

pip install python-terraform

Usage

####For any terraform command

from python_terraform import Terraform
t = Terraform()
return_code, stdout, stderr = t.<cmd_name>(*arguments, **options)

####For any argument simply pass the string to arguments of the method, for example,

terraform apply target_dir 
    --> <instance>.apply('target_dir')
terraform import aws_instance.foo i-abcd1234 
    --> <instance>.import('aws_instance.foo', 'i-abcd1234')

####For any options

dash to underscore

remove first dash, and then use underscore to replace dash symbol as option name
```
  ex. -no-color --> no_color
```

for a simple flag option

use IsFlagged/None as value for raising/not raising flag, for example,

  terraform taint -allow-missing 
     --> <instance>.taint(allow＿missing=IsFlagged)
  terraform taint 
     --> <instance>.taint(allow＿missing=None) or <instance>.taint()
  terraform apply -no-color
     --> <instance>.apply(no_color=IsFlagged)

for a boolean value option

assign True or False, for example,

  terraform apply -refresh=true --> <instance>.apply(refresh=True)

if a flag could be used multiple times, assign a list to it's value

  terraform apply -target=aws_instance.foo[1] -target=aws_instance.foo[2]
  ---> 
  <instance>.apply(target=['aws_instance.foo[1]', 'aws_instance.foo[2]'])

for the "var" flag, assign dictionary to it

  terraform apply -var='a=b' -var='c=d'
  --> tf.apply(var={'a':'b', 'c':'d'})

if an option with None as value, it won't be used

Examples

Have a test.tf file under folder "/home/test"

1. apply with variables a=b, c=d, refresh=false, no color in the output

In shell:

cd /home/test
terraform apply -var='a=b' -var='c=d' -refresh=false -no-color

In python-terraform:

from python_terraform import Terraform
tf = Terraform(working_dir='/home/test')
tf.apply(no_color=IsFlagged, refresh=False, var={'a':'b', 'c':'d'})

from python_terraform import Terraform
tf = Terraform()
tf.apply('/home/test', no_color=IsFlagged, refresh=False, var={'a':'b', 'c':'d'})

from python_terraform import Terraform
tf = Terraform(working_dir='/home/test', variables={'a':'b', 'c':'d'})
tf.apply(no_color=IsFlagged, refresh=False)

2. fmt command, diff=true

In shell:

cd /home/test
terraform fmt -diff=true

In python-terraform:

from python_terraform import Terraform
tf = terraform(working_dir='/home/test')
tf.fmt(diff=True)

Terraform Output

By default, stdout and stderr are captured and returned. This causes the application to appear to hang. To print terraform output in real time, provide the capture_output option with any value other than None. This will cause the output of terraform to be printed to the terminal in real time. The value of stdout and stderr below will be None.

from python_terraform import Terraform
t = Terraform()
return_code, stdout, stderr = t.<cmd_name>(capture_output=False)

default values

for apply/plan/destroy command, assign with following default value to make caller easier in python

input=False, in this case process won't hang because you missing a variable
no_color=IsFlagged, in this case, stdout of result is easier for parsing

Implementation

IMHO, how terraform design boolean options is confusing. Take input=True and -no-color option of apply command for example, they're all boolean value but with different option type. This make api caller don't have a general rule to follow but to do a exhaustive method implementation which I don't prefer to. Therefore I end-up with using IsFlagged or IsNotFlagged as value of option like -no-color and True/False value reserved for option like refresh=true

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