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

GLOBAL_MONOTONIC_CLOCK

Clock that cannot be set and represents monotonic time since some unspecified starting point.

@!visibility private

VERSION

Public Class Methods

monotonic_time() click to toggle source

Returns the current time a tracked by the application monotonic clock.

@return [Float] The current monotonic time when `since` not given else

the elapsed monotonic time between `since` and the current time

# File lib/connection_pool/monotonic_time.rb, line 62
def monotonic_time
  GLOBAL_MONOTONIC_CLOCK.get_time
end

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}"
  @key_count = :"current-#{@available.object_id}-count"
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

available() click to toggle source

Number of pool entries available for checkout at this instant.

# File lib/connection_pool.rb, line 122
def available
  @available.length
end

checkin() click to toggle source

# File lib/connection_pool.rb, line 97
def checkin
  if ::Thread.current[@key]
    if ::Thread.current[@key_count] == 1
      @available.push(::Thread.current[@key])
      ::Thread.current[@key]= nil
    else
      ::Thread.current[@key_count]-= 1
    end
  else
    raise ConnectionPool::Error, 'no connections are checked out'
  end

  nil
end

checkout(options = {}) click to toggle source

# File lib/connection_pool.rb, line 87
def checkout(options = {})
  if ::Thread.current[@key]
    ::Thread.current[@key_count]+= 1
    ::Thread.current[@key]
  else
    ::Thread.current[@key_count]= 1
    ::Thread.current[@key]= @available.pop(options[:timeout] || @timeout)
  end
end

get_time() click to toggle source

@!visibility private

# File lib/connection_pool/monotonic_time.rb, line 15
def get_time
  Process.clock_gettime(Process::CLOCK_MONOTONIC)
end

shutdown(&block) click to toggle source

# File lib/connection_pool.rb, line 112
def shutdown(&block)
  @available.shutdown(&block)
end

size() click to toggle source

Size of this connection pool

# File lib/connection_pool.rb, line 117
def size
  @size
end

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

MRI

# File lib/connection_pool.rb, line 60
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