Shopify wanted a cache format that would not blow up when we shipped code changes. Part two of Caching Without Marshal describes the MessagePack format, and how we migrated to MessagePack.
Overview
This article discusses the transition from Ruby's Marshal serialization to MessagePack for caching in Rails applications. It highlights the advantages of MessagePack, such as better performance, support for multiple programming languages, and the ability to define custom extension types, ultimately leading to a safer and more efficient caching mechanism.
What You'll Learn
1
How to replace Ruby's Marshal with MessagePack for serialization
2
Why MessagePack is more efficient than Marshal for caching
3
How to define custom extension types in MessagePack
4
When to handle cache misses effectively during deployments
Prerequisites & Requirements
- Understanding of caching concepts and serialization formats
- Familiarity with Ruby and Rails development environment
Key Questions Answered
What are the advantages of using MessagePack over Marshal?
MessagePack offers a more efficient binary serialization format compared to Marshal, which is Ruby-specific. It supports multiple programming languages, reduces payload size, and allows for custom extension types, making it a more robust choice for caching in Rails applications.
How does MessagePack handle unsupported object types?
MessagePack raises a NoMethodError for objects without a defined type, allowing developers to catch and log these exceptions. This feature helps prevent caching objects that could break on deployment due to class changes, thus maintaining cache integrity.
What is the process of migrating from Marshal to MessagePack?
The migration involves running both serialization methods side-by-side, defining a MessagePack factory with extension types, and logging any failures to encode objects. If an object fails to encode, it falls back to using Marshal, allowing for a gradual transition.
How does the ActiveRecordCoder improve caching efficiency?
ActiveRecordCoder caches both the attributes and the loaded associations of ActiveRecord objects. This approach avoids additional database queries, making the caching process more efficient and reducing the payload size significantly compared to Marshal.
Key Statistics & Figures
Cache payload size reduction
13 times more space efficient than Marshal
This statistic highlights the significant efficiency improvements achieved by using ActiveRecordCoder with MessagePack compared to the previous Marshal implementation.
Total cache usage drop
over 25 percent
After switching to MessagePack, the overall cache usage decreased, indicating better space management and efficiency.
Technologies & Tools
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Serialization
Messagepack
Used as the new serialization format for caching in Rails applications.
Programming Language
Ruby
The primary language used for implementing the caching mechanism.
Orm
Activerecord
Used for managing database records and their associations in the Rails application.
Key Actionable Insights
1Transitioning to MessagePack can significantly reduce cache payload sizes, leading to improved performance.By implementing MessagePack, the article notes a reduction in cache usage by over 25%, which is crucial for maintaining system efficiency, especially in large applications.
2Defining custom extension types in MessagePack can enhance serialization capabilities for complex objects.This flexibility allows developers to tailor the serialization process to their specific needs, ensuring that all necessary object types can be effectively cached.
3Implementing a robust error handling strategy during the migration can prevent issues related to class changes.By catching exceptions raised during serialization, developers can log and address potential problems before they affect production, ensuring a smoother transition.
Common Pitfalls
1
Failing to define extension types for custom objects can lead to serialization errors.
Without proper extension types, MessagePack may not know how to handle certain objects, resulting in NoMethodError exceptions that can disrupt caching processes.
2
Assuming that MessagePack handles subclasses of core types like Hash automatically.
This misconception can lead to unexpected behavior, as MessagePack does not automatically serialize subclasses unless explicitly defined, which can cause issues during cache retrieval.
Related Concepts
Serialization Formats
Caching Strategies
Activerecord Associations
Error Handling In Ruby