Issue on MySQL 5.7 and PHP 7.0

Question

Hi, I have been facing terrible issue since I upgraded my database to MYSQL 5.7. Q2A is doing a lot of connections to Database and I'm getting the following message in Apache log:

PHP Warning:  mysqli::__construct(): (HY000/1040): Too many connections in /var/www/html/qa/qa-include/qa-db.php on line 83

For MYSQL I see a lot of threads and most of them sleeping. I do not have persistent connections enabled and have set 30s for timeout. Still what could be the problem ?

 7267 | qauser | localhost:43418 | qa1  | Sleep   |    4 |          | NULL             |
| 7268 | qauser | localhost:43420 | qa1  | Sleep   |    4 |          | NULL             |
| 7269 | qauser | localhost:43426 | qa1  | Sleep   |    4 |          | NULL             |
| 7270 | qauser | localhost:43428 | qa1  | Sleep   |    4 |          | NULL             |
| 7271 | qauser | localhost:43432 | qa1  | Sleep   |    4 |          | NULL             |
| 7273 | qauser | localhost:43440 | qa1  | Sleep   |    4 |          | NULL             |
| 7275 | qauser | localhost:43448 | qa1  | Sleep   |    4 |          | NULL             |
| 7277 | qauser | localhost:43458 | qa1  | Sleep   |    4 |          | NULL             |
| 7280 | qauser | localhost:43464 | qa1  | Sleep   |    4 |          | NULL             |
| 7281 | qauser | localhost:43470 | qa1  | Sleep   |    4 |          | NULL

Comments

I just glanced at the plugin's code and couldn't find any database query.  I don't think it would generate additional database connections. Maybe there was a peek on the users, exceeded your connection and just circumstantially they dropped when you removed the plugin. I would retest this.

In Github's issue #17 you mention a memory leak. That has nothing to do with the issue in this question. You also mentioned server crashes and you haven't provided any log about the crash. That would considerably help to identify the issue.

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Thank you pupi. I suppose the memory leak caused mysql to ran out of memory and subsequently the DB connections started failing. There was nothing interesting in the log -- I'll re-test it if possible.

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Did you confirm MySQL settings below?
1. max_connections (Normally, default is 151)
2. max_user_connections (Normally, default is 0 [unlimited])

Investigation query for phpMyAdmin:
SHOW GLOBAL VARIABLES like 'max_%connections';

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Yes, I believe I tried many settings -- this happened about a year ago and only option was to remove the plugin. I later on added the plugin back and commented out the problem part -- which was creating an image.