Fix max_idle_pool_size race condition (#186)

* Add Fiber.yield to dummy driver to mimic real drivers IO

* Add manual load test file

* Fix race condition

* Drop unused code

* Less state, less bugs

* Update spec/manual/load_test.cr

Co-authored-by: Beta Ziliani <beta@manas.tech>

---------

Co-authored-by: Beta Ziliani <beta@manas.tech>
This commit is contained in:
Brian J. Cardiff 2023-07-31 11:04:18 -03:00 committed by GitHub
parent ce95cd2257
commit 9471b33ffe
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 63 additions and 21 deletions

View file

@ -19,6 +19,7 @@ class DummyDriver < DB::Driver
class DummyConnection < DB::Connection
def initialize(options : DB::Connection::Options)
super(options)
Fiber.yield
@connected = true
@@connections ||= [] of DummyConnection
@@connections.not_nil! << self
@ -113,6 +114,7 @@ class DummyDriver < DB::Driver
end
protected def perform_query(args : Enumerable) : DB::ResultSet
Fiber.yield
@connection.as(DummyConnection).check
set_params args
DummyResultSet.new self, command
@ -161,6 +163,8 @@ class DummyDriver < DB::Driver
def initialize(statement, command)
super(statement)
Fiber.yield
@top_values = command.split.map { |r| r.split(',') }.to_a
@column_count = @top_values.size > 0 ? @top_values[0].size : 2

54
spec/manual/load_test.cr Normal file
View file

@ -0,0 +1,54 @@
# This file is to be executed as:
#
# % crystal ./spec/manual/load_test.cr
#
# It generates a number of producers and consumers. If the process hangs
# it means that the connection pool is not working properly. Likely a race condition.
#
require "../dummy_driver"
require "../../src/db"
require "json"
CONNECTION = "dummy://host?initial_pool_size=5&max_pool_size=5&max_idle_pool_size=5"
alias TChannel = Channel(Int32)
alias TDone = Channel(Bool)
COUNT = 200
def start_consumer(channel : TChannel, done : TDone)
spawn do
indeces = Set(Int32).new
loop do
indeces << channel.receive
puts "Received size=#{indeces.size}"
break if indeces.size == COUNT
end
done.send true
end
end
def start_producers(channel : TChannel)
db = DB.open CONNECTION do |db|
sql = "1,title,description,2023 " * 100_000
COUNT.times do |index|
spawn(name: "prod #{index}") do
puts "Sending #{index}"
_films = db.query_all(sql, as: {Int32, String, String, Int32})
rescue ex
puts "Error: #{ex.message}"
ensure
channel.send index
end
end
end
end
channel = TChannel.new
done = TDone.new
start_consumer(channel, done)
start_producers(channel)
done.receive

View file

@ -57,8 +57,6 @@ module DB
# communicate that a connection is available for checkout
@availability_channel : Channel(Nil)
# signal how many existing connections are waited for
@waiting_resource : Int32
# global pool mutex
@mutex : Mutex
@ -82,7 +80,6 @@ module DB
@retry_delay = pool_options.retry_delay
@availability_channel = Channel(Nil).new
@waiting_resource = 0
@inflight = 0
@mutex = Mutex.new
@ -200,8 +197,11 @@ module DB
end
end
if idle_pushed && are_waiting_for_resource?
@availability_channel.send nil
if idle_pushed
select
when @availability_channel.send(nil)
else
end
end
end
@ -281,29 +281,13 @@ module DB
end
private def wait_for_available
sync_inc_waiting_resource
select
when @availability_channel.receive
sync_dec_waiting_resource
when timeout(@checkout_timeout.seconds)
sync_dec_waiting_resource
raise DB::PoolTimeout.new("Could not check out a connection in #{@checkout_timeout} seconds")
end
end
private def sync_inc_waiting_resource
sync { @waiting_resource += 1 }
end
private def sync_dec_waiting_resource
sync { @waiting_resource -= 1 }
end
private def are_waiting_for_resource?
@waiting_resource > 0
end
private def sync
@mutex.lock
begin