the-spectator · March 2, 2025 17:48 · Feb 26, 2025 · Feb 26, 2025 · Feb 26, 2025 · Feb 26, 2025
diff --git a/rails_7_print_pool.rb b/rails_7_print_pool.rb
@@ -22,8 +22,8 @@ def internal_poll(timeout)
     puts "\nThread list:"
     Thread.list.each_with_index do |t, i|
       connection_mark = connection_owners.include?(t) ? "[HAS CONNECTION]" : "[NO CONNECTION]"
-      connection_mark = "[CURRENT]" if t == Thread.current
-      connection_mark = "[MAIN]" if t == Thread.main
+      connection_mark += "[CURRENT]" if t == Thread.current
+      connection_mark += "[MAIN]" if t == Thread.main
       puts "---- #{connection_mark} : Thread #{i}, status: #{t.status.inspect}, thread_info: #{t.inspect.split(' ', 2)[1].chop}"
     end
 

diff --git a/rails_7_print_pool.rb b/rails_7_print_pool.rb
@@ -23,6 +23,7 @@ def internal_poll(timeout)
     Thread.list.each_with_index do |t, i|
       connection_mark = connection_owners.include?(t) ? "[HAS CONNECTION]" : "[NO CONNECTION]"
       connection_mark = "[CURRENT]" if t == Thread.current
+      connection_mark = "[MAIN]" if t == Thread.main
       puts "---- #{connection_mark} : Thread #{i}, status: #{t.status.inspect}, thread_info: #{t.inspect.split(' ', 2)[1].chop}"
     end
 

diff --git a/rails_7_print_pool.rb b/rails_7_print_pool.rb
@@ -35,7 +35,7 @@ def internal_poll(timeout)
 # Configure a very small connection pool
 ActiveRecord::Base.establish_connection(
 adapter: "postgresql",
-database: "playground",
+database: "playground", # create a database named "playground" in your local PostgreSQL
 pool: 2,
 checkout_timeout: 2
 )

diff --git a/rails_7_print_pool.rb b/rails_7_print_pool.rb
@@ -22,6 +22,7 @@ def internal_poll(timeout)
     puts "\nThread list:"
     Thread.list.each_with_index do |t, i|
       connection_mark = connection_owners.include?(t) ? "[HAS CONNECTION]" : "[NO CONNECTION]"
+      connection_mark = "[CURRENT]" if t == Thread.current
       puts "---- #{connection_mark} : Thread #{i}, status: #{t.status.inspect}, thread_info: #{t.inspect.split(' ', 2)[1].chop}"
     end
 

diff --git a/rails_7_print_pool.rb b/rails_7_print_pool.rb
@@ -0,0 +1,76 @@
+require "bundler/inline"
+gemfile(true) do
+  source "https://rubygems.org"
+  gem "rails", "~> 7.2"
+  gem "pg"
+end
+
+require "active_record"
+require "logger"
+
+class ActiveRecord::ConnectionAdapters::ConnectionPool::ConnectionLeasingQueue
+  private
+  def internal_poll(timeout)
+    result = super
+    result
+  rescue ActiveRecord::ConnectionTimeoutError => e
+    puts "\n=== Connection Pool Timeout ==="
+    puts "\nPool size: #{ActiveRecord::Base.connection_pool.size}"
+    puts "Checked out connections: #{ActiveRecord::Base.connection_pool.connections.count}"
+
+    connection_owners = ActiveRecord::Base.connection_pool.connections.map(&:owner)
+    puts "\nThread list:"
+    Thread.list.each_with_index do |t, i|
+      connection_mark = connection_owners.include?(t) ? "[HAS CONNECTION]" : "[NO CONNECTION]"
+      puts "---- #{connection_mark} : Thread #{i}, status: #{t.status.inspect}, thread_info: #{t.inspect.split(' ', 2)[1].chop}"
+    end
+
+    puts "\nCurrent thread: #{Thread.current.inspect}"
+    puts "\n=== End Debug Info ===\n"
+    raise e
+  end
+end
+
+# Configure a very small connection pool
+ActiveRecord::Base.establish_connection(
+adapter: "postgresql",
+database: "playground",
+pool: 2,
+checkout_timeout: 2
+)
+ActiveRecord::Base.logger = Logger.new(STDOUT)
+
+# Create a simple table
+ActiveRecord::Schema.define do
+  create_table :shipments, force: true do |t|
+    t.string :status
+  end
+end
+
+class Shipment < ActiveRecord::Base
+end
+
+def dangerous_threads
+  threads = []
+  # We duplicate code to report different lines in the stack trace
+  threads << Thread.new do
+    puts "Thread 1 starting..."
+    ActiveRecord::Base.connection.execute("select pg_sleep(5)")
+  end
+
+  threads << Thread.new do
+    puts "Thread 2 starting..."
+    ActiveRecord::Base.connection.execute("select pg_sleep(5)")
+  end
+
+  threads << Thread.new do
+    puts "Thread 2 starting..."
+    ActiveRecord::Base.connection.execute("select pg_sleep(5)")
+  end
+
+  threads.each(&:join)
+end
+
+puts "Connection pool size: #{ActiveRecord::Base.connection_pool.size}"
+puts "Starting threads..."
+dangerous_threads
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