3.0.2: rlm_sql_null duplicating its statements

[Phil Mayers]

On 11/04/14 12:24, Alan DeKok wrote:
> Stefan Winter wrote:
>> Whoa. Why would that be a configuration error?
>
>    Because we can't guarantee that the writes occur properly.
>
>> I have multiple instances
>> of rlm_sql_null, all writing different SQL statements, and all writing
>> into the same file for forwarding to the SQL server by radsqlrelay.
>
>    Which doesn't work with POSIX locks, as you pointed out.  It might
> work accidentally, but different threads writing to the same file will
> cause problems.  One thread closing a file descriptor will cause another
> thread to magically lose its lock.

I think it's important to note this *will* be working for 2.2.x on Linux 
because the locking #ifdef will end up using flock() which has saner, 
per-fd semantics.

That said: I don't see why your changes would cause semantic problems 
here. Since all rlm_sql instances use the logging api, surely they'll 
all interact just fine with >1 instance writing to the same name?

I am rather concerned about the locking overhead of the new approach 
though; my gut feeling tells me a double mutex acquire/release will 
likely be more expensive than the open()/close() calls, but hopefully 
I'm wrong.