TuxLabs

All things DevOps

Category: Python

How To: Create An AWS Lambda Function To Backup/Snapshot Your EBS Volumes

Published September 23, 2017 / by tuxninja / Leave a Comment

AWS Lambda functions are a great way to run some code on a trigger/schedule without needing a whole server dedicated to it. They can be cost effective, but be careful depending on how long they run, and the number of executions per hour, they can be quite costly as well.

For my use case, I wanted to create snapshot backups of EBS volumes for a Mongo Database every day. I originally implemented this using only CloudWatch, which is a monitoring service, but because it’s focused on scheduling, AWS also uses it for other things that require scheduling/cron like features. Unfortunately, the CloudWatch implementation of snapshot backups was very limited. I could not ‘tag’ the backups, which was certainly something I needed for easy finding and cleanups later (past a retention period).

Anyway, there were a couple pitfalls I ran into when creating this function.

Pitfalls

  1. Make sure you security group allows you to communicate to the Internet for any AWS API’s you need to talk to.
  2. Make sure your time-out is set to 1 minute or greater depending on your use case. The default is seconds, and is likely not high enough.
  3. “The Lambda function execution role must have permissions to create, describe and delete ENIs. AWS Lambda provides a permissions policy, AWSLambdaVPCAccessExecutionRole, with permissions for the necessary EC2 actions (ec2:CreateNetworkInterface, ec2:DescribeNetworkInterfaces, and ec2:DeleteNetworkInterface) that you can use when creating a role”
    1. Personally, I did inline permissions and included the specific actions.
  4. Upload your zip file and make sure your handler section is configured with the exact file_name.method_in_your_code_for_the_handler
  5. Also this one is more of an FYI, Lambda Function have a maximum TTL of 5 minutes ( 300 seconds).

I think that was it, after that everything worked fine. To finish this short article off, screenshots and the code!

Screenshots

 

 

And finally the code…

Function Code

And here is an additional function to add for cleanup

The end, happy server-lessing (ha !)

 

Posted In AWS | Cloud | How To's | Programming | Python | Systems Administration
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How to use Boto to Audit your AWS EC2 instance security groups

Published June 06, 2016 / by tuxninja / Leave a Comment

Boto is a Software Development Kit for accessing the AWS API’s using Python.

https://github.com/boto/boto3

Recently, I needed to determine how many of my EC2 instances were spawned in a public subnet, that also had security groups with wide open access on any port via any protocol to the instances. Because I have an IGW (Internet Gateway) in my VPC’s and properly setup routing tables, instances launched in the public subnets with wide open security groups (allowing ingress traffic from any source) is a really bad thing 🙂

Here is the code I wrote to identify these naughty instances. It will require slight modifications in your own environment, to match your public subnet IP Ranges, EC2 Tags, and Account names.

To run this you also need to setup your .aws/config and .aws/credentials file.

http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files

Email me tuxninja [at] tuxlabs.com if you have any issues.
Boto is awesome 🙂 Note so is the AWS CLI, but requires some shell scripting as opposed to Python to do cool stuff.

The github for this code here https://github.com/jasonriedel/AWS/blob/master/sg-audit.py

Enjoy !

Posted In AWS | Cloud | Programming | Python | Security | Systems Administration
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Fun with Python, Tabular & AWS IP ranges

Published March 09, 2016 / by tuxninja / Leave a Comment

I have been spending a lot of time designing a Hybrid Cloud that consists of Openstack and public cloud platforms. In particular I have been spending a lot of time designing the AWS portion of the Hybrid Cloud Platform. Today I found myself continually needing to look up AWS public address space and then parsing out regions & services. Then I remembered something a mentor of mine told me…

if you are going to do something more than once, there is probably value in automating it.

I love writing command line tools and thus a short Python script was born. Since I rarely share Python code, even though I didn’t spend a lot time on this, and I certainly didn’t optimize it for DRY etc. I am sharing it anyway for others to use, enjoy and hack on,

but mainly to learn, which is…The entire purpose of the Tuxlabs site

I should mention I have strong views about when to use Python vs. Go a language I find myself writing in more and more and this tool falls under my rules for things that I should write in Go. So later as a follow up I will likely re-code this in Go and post the code for review & learning. For now here’s the Python code, enjoy !

Listing all IP Ranges

Filtering

The code

Posted In AWS | Cloud | Programming | Python
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Object-Oriented Programming With Python : Inheritance (2/3)

Published August 25, 2015 / by tuxninja / Leave a Comment

Continuing on our Object-Oriented Programming with Python series, this is article 2 of 3 on the 2nd pillar, Inheritance. You can find the first article about Encapsulation in this series here.

Inheritance – The Second Pillar

Inheritance in OOP is the ability to have one class inherit the attributes of another class.

Inheritance is simple to implement, but arguably the most powerful pillar in OOP, providing the most value to a programmer. It is the pillar that allows for effective re-use of code organized in classes reducing the amount of lines a programmer has to write to do something useful in their program.

In case you don’t remember from the previous article in this series on encapsulation, a class is a blueprint or template that contains methods, objects and attributes. Once defined a class can be inherited by another class. At which point the child class (aka derived class or subclass) contains all the goodness that the parent class ( aka super class or base class) provides.

Here is an example of inheritance :

The code above downloads the webpage ‘tuxlabs.com’ and outputs it’s contents to STDOUT using the ‘requests’ module.

<rant>If you are a Python developer who is not already familiar with the requests module you should be ashamed of yourself 🙂 It is the most fantastically simple implementation of Python HTTP client functions available.</end rant>

In this example we have defined two classes, one called ‘Tuxlabs’ and one called ‘Crawl’. Tuxlabs inherits a base class ‘object’ and the ‘Crawl’ class inherits ‘Tuxlabs’. If you’re wondering why Tuxlabs inherits from object see here.  Our ‘Tuxlabs’ class has two methods a setter() & a getter() you will remember from the previous article on encapsulation. Now let’s focus on the real point in this example, the ‘Crawl’ class.

The ‘Crawl’ class as previously mention inherits the Tuxlabs class when it is defined or implemented ‘class Crawl(Tuxlabs):’. This means when an instance of Crawl initialized it will inherit all the attributes from the Tuxlabs class in addition to it’s own methods defined in the ‘Crawl’ class. The ‘Crawl’ class has only one method defined ‘download’ that takes a single argument, website.

Inside the download method in the crawl class we see ‘self.setter(website)’, but this is interesting, because we are using ‘self’ to call ‘setter()’, but self is actually referring to the ‘Crawl’ class and the ‘Crawl’ class  only has download defined. So shouldn’t an error be thrown when we try to access ‘self.setter(website)’ inside the ‘Crawl’ class, when setter() lives in ‘Tuxlabs’ ?

No, and the answer is because self, which refers to our ‘Crawl’ class, which is actually inheriting from our ‘Tuxlabs’ class. So this actually works ! Now from within ‘Crawl’ we can access all methods and attributes in Tuxlabs or Crawl, nifty, handy and powerful are the words that come to mind. Before moving on to some even cooler features, let’s show the abbreviated output of this script (I can’t show the entire webpage output, yuck!).

Nothing magical there, but I did want to show you that this code works !

Now then, we should talk about __init__ & super().

__init__() if you don’t already know is the initial method called in a class. It is what other languages might refer to as a constructor. When you create an instance object of a class the __init__() method within that class is called and whatever code is in it is executed. Init can be good for setting up default/static values used within the scope of the class and other methods. A typical example of an init class might look like this.

Here we are defining a class ‘Foundation’ and an init constructor that accepts a dictionary as an argument containing SQL Credentials. Then within the init constructor we define several attributes who’s values are populated from that dictionary. We also made ‘port’ an optional argument with a default port of ‘3306’ the MySQL default port. This is a very useful start to a class, and it is my actual code from a project. From here we would build on top of this class many other methods like SQL queries we frequently used and other data processing techniques we frequently need like parsing JSON or XML.

Now let’s assume for a moment, this is a larger scale project. One that requires many classes. Classes that are inheriting from each other. Because the ‘Foundation’ class above is so generic, it can be used over and over again in other classes. However, those other classes will have slightly different purposes. In the case of databases, perhaps each class represents a different database. This makes sense, but we would still want to make use of the lovely constructor code inside of ‘Foundation’, thanks to it’s well written generic-ness. Here is an example of how we would do that, using something called super().

We have our original class ‘Foundation’, and a new child class ‘Cloud’ that inherits ‘Foundation’. In addition ‘Cloud’ is defining it’s own __init__ constructor and accepting a dictionary for SQL credentials ‘sqlCredsCloud’. Finally, we call super() and pass our ‘Cloud’ class to the inherited class ‘Foundation’  (in this case self) and pass our SQL Creds to the ‘Foundation’ class constructor.

Whew.. I think I did an ok job explaining that, but you may need to read it back a couple of times and re-visit after trying to use this concept. Let’s take a look at how we would use these classes.

First we modify our Python path to locate the foundation module and import it. Then we create a subroutine for setting up our connection to the database and creating our instance object of our Cloud class. Notice we are passing sqlCredsCloud to the Cloud class and remember internally this is passing sqlCreds to the Foundation class constructor.  Finally, in the main routine of the program, after we setup the credentials and after we setup our database connection, we call ‘TruncateTable’, which is a method within the Cloud class that I have not shown in our code above, but you get the idea. Well I think that is about all I can muster, you now know what I know about inheritance.

For more information on super() click here

See ya next time !
Jason Riedel

Posted In How To's | Programming | Python
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Introducing Vault

Published August 25, 2015 / by tuxninja / Leave a Comment

Vault

Vault is a command line utility for encrypting & decrypting things. Those things are stored on disk in hidden files, meaning in *nix they simply have a ‘.’ in front and don’t show up unless you type ls -la 😉 But anyway, who cares if someone can locate the files ! They are AES encrypted !

I wrote Vault for a couple of reasons.

  1. To learn how to use encryption in Python
  2. To store passwords for stuff
  3. To turn Vault into methods in my Utilities class that I use for my daily programming activities. First write a command line utility, then write a class 🙂

Vault Usage

I literally wrote vault earlier today and even though it is super simple, I still find it cool & useful so I had to share. Here’s a demo on it’s simple usage !

Keys

AES / Vault supports 16, 24, or 32 byte encryption keys. A byte is one character. Your key should be something ambiguous that you can remember and you should not use the ‘0123…’ example below. What would really be paranoid is to encrypt your keys in a separate vault somewhere 🙂 Note, you will need to use the same key to encrypt as decrypt for a given stored piece of encrypted data.

Encrypting

Can You Read The File Contents ?

Decrypting

Alternatively, you can hide the key from the command line, by not specifying it. 

Clone Vault on github

Enjoy !
Jason Riedel

Posted In Encryption | Programming | Python | Security
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