rlm_python failing

Arran Cudbard-Bell a.cudbardb at freeradius.org
Tue Sep 22 20:26:26 CEST 2015

> On 22 Sep 2015, at 01:46, Alan DeKok <aland at deployingradius.com> wrote:
> On Sep 21, 2015, at 7:06 PM, Andrew Parisio <parisioa at gmail.com> wrote:
>> Like I said in my original email we are aware of the problems caused by the
>> lack of a timeout and are actively working to fix that, so you don't need
>> to be condescending and rude about the lack of a timeout.
> His message was neither condescending nor rude.  It simply points out that you're blaming FreeRADIUS, when the real blame lies elsewhere.  I suggest learning how to take feedback without getting offended.

Right, I was pointing out the issue with the mental model OP constructed to explain what was occurring.

I then explained the technical limitation that prevents FreeRADIUS from intervening, control is never returned to rlm_python during blocking calls.

For that you'd need a python/C coroutine implementation, which probably doesn't exist, or a python interpreter on the end of a socket, which would allow you to implement an asynchronous interface.  Even there, there'd still be issues with blocking, but at least it'd allow FreeRADIUS to control the timeout.

>> My question was that even after dynamo recovered FreeRADIUS continued to
>> fail to call python, and I wanted to make sure that even after we fix the
>> timeout issue that there isn't another problem that could be triggered.
>> Are you suggesting the only possible explanation for what we saw was that
>> all of the worker threads were still waiting for a response from dynamo 2
>> days later, and that there is no point in debugging why FreeRADIUS was
>> unable to execute rlm_python?
> That is what Arran said.
> FreeRADIUS calls Python, which calls your software.  If your software doesn't return execution to FreeRADIUS for 2 days, it's the fault of *your software*.  Go fix it.

They're blocked with an infinite timeout.  What could cause them to unblock? Probably nothing.  Fix the blindingly obvious issue first, before going hunting for other issues you're not sure exist.

>> I suppose that's possible but it seems
>> unlikely that that many sockets were hung open for that long.  Is there any
>> way to see what the worker threads were doing?
> Do python / C debuggers exist?  If so, use them.  Use "strace".  These are all tools which are available to you as an administrator.  There is nothing FreeRADIUS-specific about debugging a program.

I think in this case it'd be more python debugger.  Given the weird way Python deals with I/O strace probably won't show a blocking system call, but it may allow examination of the sequence of calls.


Arran Cudbard-Bell <a.cudbardb at freeradius.org>
FreeRADIUS development team

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