Ruby on Rails 8: Simplifying Sharding with New Methods

Ruby on Rails 8 brings helpful updates for working with sharded databases. The new methods .shard_keys, .sharded?, and .connected_to_all_shards make it easier to manage multiple shards. If you handle sharded data, these tools can streamline your workflow.

How to Use the New Sharding Methods

Set Up Your Sharded Base Class

Begin by defining an abstract class that connects to your shards:

class ShardedBase < ActiveRecord::Base
  self.abstract_class = true

  connects_to shards: {
    shard_one: { writing: :shard_one },
    shard_two: { writing: :shard_two }
  }
end

Here, ShardedBase connects to two shards: :shard_one and :shard_two.

Create a Sharded Model

Inherit from ShardedBase to create models that use these shards:

class ShardedModel < ShardedBase
end

Use the New Methods

• Get Shard Keys

Retrieve the list of shard keys:

  ShardedModel.shard_keys
  # => [:shard_one, :shard_two]

• Check if a Model is Sharded

Determine if your model uses sharding:

  ShardedModel.sharded?
  # => true

• Connect to All Shards

Run code across all shards:

  ShardedBase.connected_to_all_shards do
    ShardedModel.current_shard
    # Perform actions on all shards
  end

Practical Use Cases

1. Running Migrations on All Shards

Apply migrations or updates across every shard without manual switching:

   ShardedBase.connected_to_all_shards do
     ActiveRecord::Migrator.migrate("db/migrate/")
   end

2. Data Aggregation Across Shards

Collect and combine data from all shards:

   total_users = 0

   ShardedBase.connected_to_all_shards do
     total_users += ShardedModel.count
   end

   puts "Total users across all shards: #{total_users}"

3. Conditional Logic Based on Sharding

Adjust your code if the model is sharded or not:

   if ShardedModel.sharded?
     # Logic for sharded environment
   else
     # Logic for single database
   end

4. Listing All Shards for Monitoring

Generate a list of shards for health checks or monitoring:

   ShardedModel.shard_keys.each do |shard|
     puts "Checking status of #{shard}"
     # Add monitoring logic here
   end

5. Parallel Processing on Shards

Improve performance by processing shards in parallel:

   threads = []

   ShardedModel.shard_keys.each do |shard|
     threads << Thread.new do
       ShardedBase.connected_to(shard: shard) do
         # Perform time-consuming task
       end
     end
   end

   threads.each(&:join)

Why This Matters

Managing multiple database shards can be challenging. These new Rails methods reduce complexity:

• .shard_keys gives you quick access to all shard identifiers.
• .sharded? lets you write code that adapts if sharding is in use.
• .connected_to_all_shards allows batch operations across all shards effortlessly.

By using these tools, you save time and write cleaner code. Your applications become more scalable and maintainable.

Give these new methods a try to enhance how you work with sharded databases in Rails!