schema_cache_race.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", github: "rails/rails", branch: "main"
  gem "pg"
end

require "active_record"
require "minitest/autorun"
require "logger"


THREADS = 15  # number of parallel threads to execute


ActiveRecord::Base.establish_connection(
  adapter:  "postgresql",
  database: "schema_cache_race",
  pool:     THREADS+5,
  host:     "localhost",
  # username: "...",
  # password: "...",
)
ActiveRecord::Base.logger = Logger.new(STDOUT)


## override query() to add a delay to simulate network latency
# module ActiveRecord
#   module ConnectionAdapters
#     module PostgreSQL
#       module DatabaseStatements
#
#         def query(sql, name = nil) # :nodoc:
#           mark_transaction_written_if_write(sql)
#
#           log(sql, name) do
#             with_raw_connection do |conn|
#               sleep rand(0..0.1)
#               conn.async_exec(sql).map_types!(@type_map_for_results).values
#             end
#           end
#         end
#
#       end
#     end
#   end
# end


ActiveRecord::Schema.define do
  THREADS.times do |idx|
    create_table "table#{idx}s", force: true
  end
end

TABLES = THREADS.times.map do |idx|
  eval <<-TABLE
    class Table#{idx} < ActiveRecord::Base
    end
  TABLE
  "Table#{idx}".constantize
end


class BugTest < Minitest::Test
  def test_schema_cache_access
    sc = TABLES.first.connection_pool.schema_cache
    TABLES.map.with_index do |klass, idx|
      Thread.new do
        1000.times do
          # printf (idx+97).chr  # view progress
          klass.attribute_types
          klass.send(:reload_schema_from_cache, false)
          sc.clear_data_source_cache!(klass.table_name)
          assert true  # count completions
        end
      end
    end.each(&:join)
  end
end