Problem with MySQL connection through load balancer

[Winfield, Alister]

If no other sane options exist then enabling more aggressive TCP-keepalive
probes can often help here.


On 23/07/2014 23:59, "Dean Goldhill" <dgoldhill at netutils.com> wrote:

>Thanks very much.
>That does clear up where I should be looking.
>
>I will update if I find a solution.
>
>Sent from my iPhone
>
>> On 23 Jul 2014, at 17:39, "Phil Mayers" <p.mayers at imperial.ac.uk> wrote:
>>
>>> On 23/07/14 17:10, Dean Goldhill wrote:
>>>
>>> I have tried to use the Œlifetime = 120¹ option in the sql.conf
>>>
>>> Under normal operation, this will cause radius to close and
>>>re-establish
>>> the SQL connection every 120 seconds, so I hoped that when in this
>>>stuck
>>> state, it would do the same and re-establish the connection. But does
>>>not.
>>
>> The problem is, FreeRADIUS will be blocked inside the mysql libraries.
>>So "lifetime" probably won't help.
>>
>>>
>>> Is there anything someone can suggest?
>>>
>>> I don¹t have the ability to sync the session table between the 2 load
>>> balancers.
>>
>> The problem isn't FreeRADIUS - it's the mysql libraries. They're not
>>detecting the dead connections.
>>
>> Does the load balancer have the ability to return a TCP RST or ICMP
>>error when it receives a packet for an unknown session? If so, this will
>>probably trigger the mysql libraries to drop the connection, and
>>FreeRADIUS to reconnect.
>>
>> Otherwise, you'll need to investigate if MySQL has any form of dead
>>connection detection, and how you can persuade your mysql libraries to
>>do it.
>>
>> TCP keepalives probably won't help - they're usually too slow for this
>>kind of thing.
>>
>> Alternatively, something like:
>>
>> http://dev.mysql.com/downloads/mysql-proxy/
>>
>> ...could be run locally. We use pgbouncer on postgres for this - it can
>>check the connection is alive before sending a query and reconnect as
>>needed.
>> -
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