Redis LUA script. Reserve instance from queue/list with TTL.

reserveWithTtl.lua

local list = KEYS[1]
local user = KEYS[2]
local instance = redis.call('RPOPLPUSH', list, list)
if nil == instance then return nil end
local first = instance

while true do 
  local id = string.sub(tostring(instance), string.len('instance.') + 1)
  local reserved = 'reserved.' .. id
  local confirmed = redis.call('SET', reserved, user, 'EX', 2400, 'NX')
  if type(confirmed) == "table" then 
    if confirmed['ok'] == 'OK' then return instance end
  end
  
  instance = redis.call('RPOPLPUSH', list, list)
  if first == instance then break end
end

return nil

Usage:

const Redis = require('ioredis')
const REDIS_URL = '{your instance name}.amazonaws.com'
const QUEUE_AVAILABLE = 'genymotion-queue'
const REDIS_SET_TIMEOUT_SECONDS = 40 * 60

    const redis = new Redis(6379, REDIS_URL)
        redis.defineCommand('reserveWithTtl', {
          numberOfKeys: 2,
          lua: `
local list = KEYS[1]
local user = KEYS[2]
local instance = redis.call('RPOPLPUSH', list, list)
if nil == instance then return instance end
local first = instance

while true do 
  local id = string.sub(tostring(instance), string.len('instance.') + 1)
  local reserved = 'reserved.' .. id
  local confirmed = redis.call('SET', reserved, user, 'EX', ${REDIS_SET_TIMEOUT_SECONDS}, 'NX')
  if type(confirmed) == "table" then 
    if confirmed['ok'] == 'OK' then return instance end
  end
  
  instance = redis.call('RPOPLPUSH', list, list)
  if first == instance then break end
end

return nil
`,
        })
        instance = await redis.reserveWithTtl(QUEUE_AVAILABLE, user)