Unleashing Chaos: How Chaos Monkey Can Help Bulletproof Your Shopify Store

As an online retailer, there‘s nothing more frustrating or potentially costly than unexpected downtime or system failures. With consumers demanding a seamless digital experience, even a few minutes of an unresponsive website or failed checkout process can lead to lost sales and damaged customer trust.

While it may seem counterintuitive, intentionally causing failures in your production environment can actually be one of the best ways to prevent damaging outages and improve your system‘s resilience. This is the core idea behind chaos engineering – a practice pioneered by Netflix with their infamous Chaos Monkey tool.

In this post, we‘ll dive into what Chaos Monkey is, how it works, and why Shopify store owners should consider putting this powerful primate to work in their own infrastructure. We‘ll cover the steps to get started with chaos testing, look at some real-world examples, and discuss best practices for making the most of this valuable resilience-building tool. Let‘s monkey around!

Chaos Engineering 101

Before we get into the specifics of Chaos Monkey, it‘s important to understand the broader concept of chaos engineering. To quote Netflix, chaos engineering is "the discipline of experimenting on a distributed system in order to build confidence in the system‘s capability to withstand turbulent conditions in production."

In simpler terms, it means intentionally causing harm to your live production systems in a planned and controlled way to identify weaknesses before they turn into real customer-impacting outages. By proactively breaking things on purpose, you can test how your system responds, find hidden bugs, and build automated recovery mechanisms to minimize damage during a real crisis.

Chaos engineering emerged from Netflix‘s own challenges in scaling their massive global streaming platform. As Werner Vogels, CTO of Amazon, famously said "Everything fails, all the time." Netflix took this to heart and realized that rather than aiming for perfect 100% uptime (an impossible goal), they needed to architect their systems to be resilient to inevitable failures.

Meet the Monkey

One of the primary tools Netflix developed to facilitate their chaos engineering practice is Chaos Monkey. Originally unleashed in 2011, Chaos Monkey is a service that randomly terminates virtual machine instances and containers in Netflix production environment. By randomly killing servers, Chaos Monkey acts as a forcing function to design services to be resilient to single-node failures.

Here‘s how it works: Chaos Monkey runs on a defined schedule (say, every weekday at 9am) and selects a random set of instances to terminate. It uses predefined rules, such as only targeting idle instances or limiting the "blast radius" to a certain percentage of instances to contain the potential impact.

When Chaos Monkey kills an instance, it forces the surrounding services to deal with the failure in real-time. This could mean rerouting traffic to healthy nodes, spinning up new instances to maintain capacity, or gracefully handling the loss of any stateful data. If all goes well, end users should be blissfully unaware that anything went wrong behind the scenes.

The beauty of Chaos Monkey is that it shifts failure testing left – rather than waiting for things to break in production and scrambling to recover, teams get used to proactively breaking their own systems in safe and controlled ways on a regular basis. It also provides a feedback loop to identify and fix reliability bugs during the normal development process vs. as costly post-incident remediation.

Since its inception, Chaos Monkey has inspired an entire menagerie of "Simian Army" failure testing tools, from Latency Monkey for injecting network delays to Chaos Gorilla for simulating an outage of an entire Amazon availability zone. The practice has also gained broader adoption, with companies like Microsoft, Google, Amazon, and Capital One implementing their own versions of chaos engineering.

Monkeying Around Your Shopify Store

So how is Chaos Monkey relevant for Shopify store owners and developers? After all, Shopify is a fully hosted platform, so you don‘t have direct access to the underlying cloud infrastructure to terminate instances. However, the principles of chaos engineering and proactive failure testing still very much apply to building resilient Shopify stores.

Think about all the potential points of failure in a typical Shopify e-commerce flow: a buggy theme update, a misbehaving third-party app, an API integration timeout, a sudden traffic spike from a flash sale, an expired SSL certificate, or an inadvertent change by a team member. Any one of these issues could lead to frustrated customers, abandoned carts, and lost revenue.

Injecting Chaos Monkey-style failures into your Shopify environments can help you proactively find and fix these weak points. Some examples of potential experiments:

• Intentionally break integrations with payment gateways, shipping providers, or ERP systems to see how your store responds
• Simulate a traffic surge to stress test your theme and identify performance bottlenecks
• Force API timeouts or rate limiting to harden your custom apps
• Randomly disable apps or scripts to measure the impact on user experience
• Take down your CDN to validate caching and failover behaviors

The key is to prioritize testing the most critical components that could bring your store down, and are tricky to fully test in a staging environment. By causing controlled failures in production, you can experience how your store behaves under realistic conditions and have confidence it will degrade gracefully during a real incident.

Of course, you‘ll want to carefully plan and communicate your chaos experiments, ideally running them during low-traffic periods and monitoring key metrics like conversions and bounce rates to know when to abort if things go sideways. It‘s also a good idea to inform customer support teams ahead of time so they can adequately respond to any inbound inquiries.

Chaos Toolkit for Shopify

While Chaos Monkey itself is geared towards cloud infrastructure, there are a number of tools in the broader Chaos Toolkit ecosystem that can be used to inject failure into Shopify stores. The Chaos Toolkit is an open source project that provides a way to describe and automate chaos experiments using a simple JSON or YAML configuration file.

To get started with the Chaos Toolkit, you‘ll first need to install it using pip:

pip install chaostoolkit

Next, create a new experiment file to describe the failure scenario you want to test. Here‘s a simple example that simulates a failure in the Shopify Admin API:

{
  "version": "1.0.0",
  "title": "Shopify Admin API failure",
  "description": "Simulate a failure in the Shopify Admin API",
  "tags": ["shopify", "api"],
  "steady-state-hypothesis": {
    "title": "Shopify API is responsive",
    "probes": [
      {
        "name": "api-responsive",
        "type": "probe",
        "provider": {
          "type": "python",
          "module": "shopify_probes",
          "func": "api_responsive",
          "arguments": {
            "url": "https://${shopify_store}.myshopify.com/admin/api/2021-07/products.json",
            "access_token": "${shopify_access_token}"
          }
        }
      }
    ]
  },
  "method": [
    {
      "type": "action",
      "name": "simulate-api-failure",
      "provider": {
        "type": "python",
        "module": "shopify_actions",
        "func": "simulate_api_failure",
        "arguments": {
          "url": "https://${shopify_store}.myshopify.com/admin/api/2021-07/products.json",
          "access_token": "${shopify_access_token}"        
        }
      }
    }
  ]
}

This experiment does a few things:

1. Defines a steady-state hypothesis that the Shopify Admin API should be responsive, using a custom probe to make a request to the Products endpoint.
2. Injects a failure into that same API endpoint using a custom action.

The shopify_probes and shopify_actions modules referenced here would contain custom Python code to implement these steps, using the Shopify API library to make requests.

With the experiment defined, you can run it using the chaos run command:

chaos run experiment.json

The Chaos Toolkit will run the experiment and output the results, including whether the steady-state hypothesis was validated before and after the failure was injected.

There are a number of other experiments you could create using a similar approach to test different failure scenarios in Shopify, such as:

• Simulating downtime of a critical app
• Injecting latency into API requests
• Mocking error responses from payment or shipping providers
• Overloading your store with a surge of traffic

The possibilities are endless – the key is to prioritize the failures that pose the highest risk to your business and customer experience.

Real-World Learnings

Chaos engineering has been successfully adopted by a number of high-profile companies beyond Netflix. For example:

• Amazon runs a "game day" every year where they purposely cause failures in their production systems to test their resilience and train engineers to respond effectively. In one exercise, they simulated an outage of an entire geographic region to validate their failover processes.
• Uber has a dedicated Chaos Engineering team that runs over 100 experiments per week to inject failure into every layer of their stack, from infrastructure to APIs to user interfaces. One experiment uncovered a bug that could have left riders stranded due to app crashes.
• Stripe created a custom failure injection service called Vautour to test their payments infrastructure. They‘ve open-sourced a number of their chaos testing tools, including a proxy for manipulating API requests and responses.

While these examples come from large enterprises with dedicated engineering teams, the lessons learned are valuable for any organization looking to improve their resilience:

1. Start small and prioritize high-impact experiments. Focus on the failures that could cause the most damage to your customer experience or revenue first.
2. Use experiments to not only find bugs, but also train your team. Chaos engineering isn‘t just about breaking things, it‘s about improving your people and processes to better prevent and respond to real incidents.
3. Automate experiments and run them continuously. Just like a vaccine, the "immunity" from chaos experiments fades over time as your systems and teams change. Regularly injecting failure keeps your resilience strong.
4. Share your findings and fixes. Be transparent about what you‘ve learned from experiments and use them to drive prioritized fixes and architectural improvements.

Getting Started With Chaos

As the old saying goes, "the best defense is a good offense." With the complexity and pace of change in today‘s e-commerce landscape, waiting until things break to fix them is a recipe for costly outages and frustrated customers.

Chaos Monkey and related chaos engineering tools offer a way to proactively validate your store‘s resilience by intentionally breaking things in a safe and controlled way. By causing "fun" failures on a regular basis, you can continuously improve your ability to prevent and quickly recover from real incidents when they happen.

Whether you‘re a solo shop owner or part of a larger team, there are a few simple ways to get started with chaos engineering in your Shopify environments:

1. Make a list of your most business-critical dependencies and user flows. These should be the focus areas for your first chaos experiments.
2. Choose one simple experiment to start, such as injecting latency into a specific API call or third-party app. Create a rollback plan and communicate with your team before running it.
3. Run the experiment during a low-risk time, closely monitoring key metrics for any impact. Be prepared to abort if things start to go wrong.
4. Document the results and learnings, including any surprises or unintended consequences. Share with your team and prioritize any necessary fixes.
5. Automate the experiment if possible, and gradually increase the scope and frequency as you build confidence.

Remember, the goal of chaos engineering isn‘t to cause gratuitous damage or create unnecessary work. It‘s about proactively surfacing weaknesses and hidden risks so you can fix them before they turn into costly outages. By embracing a bit of controlled chaos, you can build a more resilient store that delights customers even when the unexpected happens.

With the right approach and tools, even the smallest Shopify store can harness the power of Chaos Monkey to build world-class reliability and uptime. So go ahead and unleash the monkey – your future self (and your customers) will thank you!

Further Reading:

• Principles of Chaos Engineering
• Awesome Chaos Engineering
• Chaos Engineering: Crash Test Your Applications
• Shopify APIs and SDKs