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!