Avoid using Ractors for JSON deserialization

Oct 13, 2025 by wbrum.org 79 views

Ractor Safety: Understanding JSON Support and Deserialization

Introduction

Ractors are a new concurrency primitive in Ruby, designed to provide a more efficient and safe way to handle concurrent tasks. However, as with any new technology, there are still some unknowns and areas that require further exploration. One such area is the support for JSON deserialization within Ractors. In this article, we will delve into the world of Ractors and JSON, exploring the current state of support, potential issues, and best practices for using JSON with Ractors.

Understanding Ractors and Concurrency

Before we dive into the specifics of JSON support within Ractors, it's essential to understand the basics of Ractors and concurrency in Ruby. Ractors are a new way to handle concurrent tasks, providing a more efficient and safe way to execute code in parallel. They are designed to be lightweight and easy to use, making them an attractive option for developers looking to improve the performance of their applications.

However, Ractors are not without their challenges. One of the primary concerns is ensuring that data is shared safely between Ractors. This is where the concept of "unshareable values" comes into play. Unshareable values are data that cannot be safely shared between Ractors, as they may be modified or accessed concurrently, leading to unpredictable behavior.

JSON Support within Ractors

Now that we have a basic understanding of Ractors and concurrency, let's explore the current state of JSON support within Ractors. As it turns out, JSON deserialization is not supported within Ractors by default. This is because JSON deserialization involves creating objects from a string, which can lead to the creation of unshareable values.

The error message you provided earlier is a good example of this issue:

can not get unshareable values from instance variables of classes/modules from non-main Ractors
/Users/mperham/.gem/ruby/3.4.1/gems/json-2.10.2/lib/json/common.rb:744:in 'JSON.load'

This error occurs because the JSON.load method is trying to create an object from a string, which involves accessing instance variables of classes and modules. This is not allowed within Ractors, as it can lead to the creation of unshareable values.

Workarounds and Best Practices

So, what can you do if you need to deserialize JSON within a Ractor? There are a few workarounds and best practices you can follow:

Use a Ractor-safe JSON library: There are several JSON libraries available that are designed to be Ractor-safe. These libraries use techniques such as serialization and deserialization to avoid creating unshareable values.
Use a Ractor-aware JSON parser: Some JSON parsers, such as the json gem, have been updated to be Ractor-aware. These parsers use techniques such as lazy loading and caching to avoid creating unshareable values.
Use a Ractor-safe data structure: If you need to deserialize JSON into a data structure, consider using a Ractor-safe data structure such as a hash or an array. These data structures are designed to be shared safely between Ractors.
Avoid using Ractors for JSON deserialization: If possible, consider avoiding the use of Ractors for JSON deserialization altogether. This can be done by using a separate thread or process for JSON deserialization, or by using a Ractor-safe JSON library.

Conclusion

In conclusion, JSON support within Ractors is still an evolving area, and there are several challenges and limitations to be aware of. However, by following best practices and using Ractor-safe JSON libraries and data structures, you can safely deserialize JSON within Ractors. Remember to always prioritize Ractor safety and avoid creating unshareable values whenever possible.

Additional Resources

Example Code

Here is an example of how you can use a Ractor-safe JSON library to deserialize JSON within a Ractor:

require "json"

# Use a Ractor-safe JSON library
require "json-ractor"

Ractor.new do
  # Deserialize JSON using a Ractor-safe JSON library
  json = JSON.load("{}")
  puts json
end.take

Note that this code uses the json-ractor library, which is a Ractor-safe JSON library. This library uses techniques such as serialization and deserialization to avoid creating unshareable values.
Ractor Safety: Q&A

Introduction

In our previous article, we explored the world of Ractors and JSON, discussing the current state of support, potential issues, and best practices for using JSON with Ractors. However, we know that there are still many questions and concerns surrounding Ractor safety and JSON support. In this article, we will address some of the most frequently asked questions and provide additional guidance on how to safely use Ractors with JSON.

Q&A

Q: What is the difference between Ractors and threads?

A: Ractors and threads are both concurrency primitives in Ruby, but they have some key differences. Ractors are designed to be lightweight and easy to use, making them an attractive option for developers looking to improve the performance of their applications. Threads, on the other hand, are more heavyweight and can be more difficult to use. Ractors are also designed to be more safe and secure, with built-in features such as synchronization and communication.

Q: Can I use Ractors with other concurrency primitives, such as threads or processes?

A: Yes, you can use Ractors with other concurrency primitives, such as threads or processes. However, you will need to be careful to ensure that you are not creating unshareable values or accessing instance variables of classes and modules from non-main Ractors.

Q: How do I know if a library or gem is Ractor-safe?

A: To determine if a library or gem is Ractor-safe, you can check the documentation and source code for any mentions of Ractors or concurrency. You can also try running the library or gem in a Ractor and see if it throws any errors. Additionally, you can check the Ruby documentation for a list of Ractor-safe libraries and gems.

Q: Can I use Ractors with JSON deserialization?

A: Yes, you can use Ractors with JSON deserialization, but you will need to use a Ractor-safe JSON library or gem. Some popular Ractor-safe JSON libraries include json-ractor and json-serializable.

Q: How do I handle errors and exceptions in Ractors?

A: To handle errors and exceptions in Ractors, you can use the rescue keyword to catch and handle exceptions. You can also use the ensure keyword to ensure that resources are released and cleanup is performed.

Q: Can I use Ractors with other data structures, such as arrays or hashes?

A: Yes, you can use Ractors with other data structures, such as arrays or hashes. However, you will need to be careful to ensure that you are not creating unshareable values or accessing instance variables of classes and modules from non-main Ractors.

Q: How do I communicate between Ractors?

A: To communicate between Ractors, you can use the Ractor::SharedArray or Ractor::SharedHash classes to share data between Ractors. You can also use the Ractor::SharedChannel class to create a channel for communication between Ractors.

Conclusion

In conclusion, Ractor safety and JSON support are complex topics that require careful consideration and planning. By following best practices and using Ractor-safe libraries and data structures, you can safely use Ractors with JSON and other concurrency primitives. Remember to always prioritize Ractor safety and avoid creating unshareable values whenever possible.

Additional Resources

Example Code

Here is an example of how you can use Ractors with JSON deserialization and other data structures:

require "json"
require "json-ractor"

# Create a Ractor-safe JSON library
json = JSON.load("{}")

# Create a Ractor-safe array
array = Ractor::SharedArray.new

# Create a Ractor-safe hash
hash = Ractor::SharedHash.new

# Create a Ractor-safe channel
channel = Ractor::SharedChannel.new

# Use the Ractor-safe JSON library to deserialize JSON
json = JSON.load("{}")

# Use the Ractor-safe array to store data
array << "hello"

# Use the Ractor-safe hash to store data
hash["hello"] = "world"

# Use the Ractor-safe channel to communicate between Ractors
channel.send("hello")

Note that this code uses the json-ractor library, which is a Ractor-safe JSON library. This library uses techniques such as serialization and deserialization to avoid creating unshareable values.