class ConnectionPool

Generic connection pool class for e.g. sharing a limited number of network connections among many threads. Note: Connections are lazily created.

Example usage with block (faster):

@pool = ConnectionPool.new { Redis.new }

@pool.with do |redis|
  redis.lpop('my-list') if redis.llen('my-list') > 0
end

Using optional timeout override (for that single invocation)

@pool.with(:timeout => 2.0) do |redis|
  redis.lpop('my-list') if redis.llen('my-list') > 0
end

Example usage replacing an existing connection (slower):

$redis = ConnectionPool.wrap { Redis.new }

def do_work
  $redis.lpop('my-list') if $redis.llen('my-list') > 0
end

Accepts the following options:

:size - number of connections to pool, defaults to 5
:timeout - amount of time to wait for a connection if none currently available, defaults to 5 seconds

Constants

DEFAULTS
VERSION

Public Class Methods

new(options = {}, &block) click to toggle source

# File lib/connection_pool.rb, line 44
def initialize(options = {}, &block)
  raise ArgumentError, 'Connection pool requires a block' unless block

  options = DEFAULTS.merge(options)

  @size = options.fetch(:size)
  @timeout = options.fetch(:timeout)

  @available = TimedStack.new(@size, &block)
  @key = :"current-#{@available.object_id}"
end

wrap(options, &block) click to toggle source

# File lib/connection_pool.rb, line 40
def self.wrap(options, &block)
  Wrapper.new(options, &block)
end

Public Instance Methods

checkin() click to toggle source

# File lib/connection_pool.rb, line 98
def checkin
  conn = pop_connection # mutates stack, must be on its own line
  @available.push(conn) if stack.empty?

  nil
end

checkout(options = {}) click to toggle source

# File lib/connection_pool.rb, line 86
def checkout(options = {})
  conn = if stack.empty?
    timeout = options[:timeout] || @timeout
    @available.pop(timeout: timeout)
  else
    stack.last
  end

  stack.push conn
  conn
end

shutdown(&block) click to toggle source

# File lib/connection_pool.rb, line 105
def shutdown(&block)
  @available.shutdown(&block)
end

with(options = {}) { |conn| ... } click to toggle source

MRI

# File lib/connection_pool.rb, line 59
def with(options = {})
  Thread.handle_interrupt(Exception => :never) do
    conn = checkout(options)
    begin
      Thread.handle_interrupt(Exception => :immediate) do
        yield conn
      end
    ensure
      checkin
    end
  end
end

Private Instance Methods

pop_connection() click to toggle source

# File lib/connection_pool.rb, line 111
def pop_connection
  if stack.empty?
    raise ConnectionPool::Error, 'no connections are checked out'
  else
    stack.pop
  end
end

stack() click to toggle source

# File lib/connection_pool.rb, line 119
def stack
  ::Thread.current[@key] ||= []
end