Odtnhj

I am running rails 5.2.1 app in the ec2 server of instance type t3.small. But server got hang after a few days run. In the puma_access.log there is following error log

Listen loop error: #<ThreadError: can't create Thread: Resource temporarily unavailable>
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:87:in `initialize'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:87:in `new'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:87:in `spawn_thread'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:162:in `block in <<'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:154:in `synchronize'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/thread_pool.rb:154:in `<<'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/server.rb:398:in `block in handle_servers'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/server.rb:385:in `each'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/server.rb:385:in `handle_servers'
/var/www/rails/rails-api/shared/bundle/ruby/2.5.0/gems/puma-3.12.0/lib/puma/server.rb:358:in `block in run'

In the server we are connecting to two RDS instance, second by using the class

class SecondDbBase < ActiveRecord::Base
 establish_connection "#Rails.env_sec".to_sym
 self.abstract_class = true

 def readonly?
 true
 end

 def write_attribute(name, value)
 raise NotImplementedError, 'read only table'
 end

end

and in the corresponding model I have extended the class

class Student < SecondDbBase

puma.rb file

workers 1
# Min and Max threads per worker
threads 1, 6

app_dir = File.expand_path("../..", __FILE__)
shared_dir = "#app_dir/shared"
tmp_dir = "#app_dir/tmp"

# Default to production
rails_env = ENV['RAILS_ENV'] || "production"
environment rails_env

# Set up socket location
bind "unix://#tmp_dir/sockets/puma.sock"

# Logging
stdout_redirect "#tmp_dir/log/puma.stdout.log", "#tmp_dir/log/puma.stderr.log", true

# Set master PID and state locations
pidfile "#tmp_dir/pids/puma.pid"
state_path "#tmp_dir/pids/puma.state"
preload_app!
activate_control_app

on_worker_boot do
 require "active_record"
 ActiveRecord::Base.connection.disconnect! rescue ActiveRecord::ConnectionNotEstablished
 ActiveRecord::Base.establish_connection(YAML.load_file("#app_dir/config/database.yml")[rails_env])
end

Is the issue related to any database connection pool? How can I solve it?