Application freezes when trying to connect to Mongodb

[StephanieSunshine]

Trying to setup a connection to a Mongo database, an application just hangs. If I take the connection line in question into irb or pry it works as expected. Strace points to something within io_uring.

Strace output:

clone3({flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, child_tid=0x7ff2fa55c990, parent_tid=0x7ff2fa55c990, exit_signal=0, stack=0x7ff2fa35c000, stack_size=0x1fff80, tls=0x7ff2fa55c6c0} => {parent_tid=[47625]}, 88) = 47625
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 2, 0, 0, NULL, 8)     = 2
io_uring_enter(5, 0, 1, IORING_ENTER_GETEVENTS, NULL, 8) = 0
getpid()                                = 47614
futex(0x5596d2b2ce68, FUTEX_WAIT_BITSET_PRIVATE, 0, {tv_sec=97766, tv_nsec=523406835}, FUTEX_BITSET_MATCH_ANY) = 0
futex(0x5596d2b2cfd8, FUTEX_WAIT_PRIVATE, 2, NULL) = 0
futex(0x7ff2f4003ee8, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5596d2b2cfd8, FUTEX_WAKE_PRIVATE, 1) = 0
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 1, 0, 0, NULL, 8)     = 1
io_uring_enter(5, 0, 1, IORING_ENTER_GETEVENTS, NULL, 8

server.rb

require 'logger'
require 'mongo'
require 'tipi'

opts = {
  reuse_addr:  true,
  dont_linger: true
}

L = Logger.new(STDOUT)

L.info 'Connecting to database'

# Offending line that hangs if uncommented 
#M = Mongo::Client.new(['node1.cloud:27017', 'node2.cloud:27017', 'node3.cloud:27017'], database: 'xxxxx', max_pool_size: 200, max_connecting: 10, read: { mode: :secondary_preferred })

L.info "pid: #{Process.pid}"
L.info 'Listening on port 12345...'

server = Tipi.route do |r|
  r.on 'get' do
    L.info 'route /get called'
    r.respond 'get'
  end

spin do
  Tipi.serve('0.0.0.0', 12345, opts, &server)

[StephanieSunshine]

Just to add to this, reducing the server.rb app to just the most basic test, the Mongo connect line does work.

bare.rb

require 'logger'
require 'mongo'
require 'pry'

L = Logger.new(STDOUT)
L.info 'Connecting to database'
M = Mongo::Client.new(['node1.cloud:27017', 'node2.cloud:27017', 'node3.cloud:27017'], database: 'xxxxx', max_pool_size: 200, max_connecting: 10, read: { mode: :secondary_preferred })
binding.pry