MySQL IDO prematurely logs "Finished reconnecting"

[Al2Klimov]

Describe the bug

At least IdoMysqlConnection#Reconnect():

1. calls UpdateAllObjects()
   • UpdateAllObjects() puts lots of stuff in m_QueryQueue
2. puts a callback in m_QueryQueue
   • that callback logs "Finished reconnecting"

So at least the MySQL IDO fires all initial queries and then logs "Finished reconnecting" – right? Wrong!

The MySQL IDO indeed TRIES to fire those queries before logging "Finished reconnecting". But if any of them yet misses an ID of a parent object (which is to be inserted by a query not fired yet), it lands again in m_QueryQueue AFTER logging "Finished reconnecting".

To Reproduce

• Kick off a full dump (empty DB) of a bunch of hosts + services + notifications, etc.
• Watch number of pending queries and "Finished reconnecting"

Expected behavior

Either – or:

• (Simple solution) IdoMysqlConnection#Reconnect() puts a callback in m_QueryQueue which puts a callback in m_QueryQueue which logs "Finished reconnecting"
• (Less simple solution) "Finished reconnecting" callback checks whether all items from DbConnection#UpdateAllObjects() are done (atomic counter needed), otherwise it re-enqueues itself
• (Least simple solution) Putting a callback in m_QueryQueue which logs "Finished reconnecting" happens not directly in IdoMysqlConnection#Reconnect(), but in a Shared<Defer> – all m_QueryQueue items from DbConnection#UpdateAllObjects() hold pointers to that Defer

Your Environment

• Version used (icinga2 --version): fe85bf1
• Operating System and version: any
• Enabled features (icinga2 feature list): ido-mysql

Additional context

One shouldn't need the above insider knowledge to know when the IDO actually "Finished reconnecting".