Fix 2 errors: write to closed socket and unblock opportunity for blocked clients

[svagner]

There are 2 bugs:

1. When router tries to write to the closed socket, it gets signal SIGPIPE. The program will be terminated by default in this case (watch man 7 signal). To represent a bug at GNU Linux OS:

• run mysqlrouter with routing at some port (ex. 7001)
• run telnet to the port and terminate it without any inputs with Ctrl+C

2. We don't cleanup a map with blocks notation (MySQLRouting::auth_error_counters_ (private)). If we have some problems at client side (or may be we check port without normal termination of socket or etc.) we block this client for perpetuity (client will be unblocked only if mysqlproxy restarts). But with the production system it is imposible. To represent a bug:

• set max_connect_errors to 1
• run mysqlrouter with routing at some port (ex. 7001)
• run telnet to mysqlrouter port and exit from telnet normally
• run telnet again...

I've added option max_connect_errors_timeout to the routing plugin. This option doesn't affect to current behavior when it is set to 0 (we don't need to unblock clients).

[mysql-oca-bot]

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Thanks

[svagner]

Thanks! I've sent it.

[mysql-oca-bot]

Hi, thank you for your contribution. Please confirm this code is submitted under the terms of the OCA (Oracle's Contribution Agreement) you have previously signed by cutting and pasting the following text as a comment:
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Thanks

[svagner]

I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.

[mysql-oca-bot]

Hi, thank you for your contribution. Your code has been assigned to an internal queue. Please follow
bug http://bugs.mysql.com/bug.php?id=81548 for updates.
Thanks

[emkookmer]

I have the same problem as described here, what is the merge status ?

[emkookmer]

@geertjanvdk @bkandasa @amitab @mysql-oca-bot Can this be merged ?