[c++]: logging levels (was Re: C++ broker - some newbie questions)

[Gordon Sim <gs...@redhat.com>]

Robert Greig wrote:
> 1) the broker's default output logging level is nothing. If you start
> it up, it gives no indication that it is doing anything at all. Is
> this deliberate? I think it should really be INFO level, or at least
> some level that enables the user to see that it is listening on a port
> without running netstat.

I agree that it would be nice to get a bit more information on startup.

The current default log level is set to error+ as info and warning were 
felt to be too verbose. To date the approach to adding log statements 
has been rather ad-hoc and really needs to be codified into a more 
explicit and useful system.

At present for example a warning is logged for every published message 
that cannot be routed; every 'local' message dropped due to a 'no-local' 
directive results in an info level log message etc. As these are 
per-message events they could result in lots of log entries.

We could alter those events to be logged only at the debug level, but 
they then become hard to see without further filtering as the output at 
debug level is extremely verbose. The logging system does allow control 
of levels by components but as it stands this does require a fair bit of 
knowledge of the codebase.

I don't have any clear answers yet but I do think we need to start 
thinking about more user friendly logging. Anyone else have any thoughts 
here?

Re: [c++]: logging levels (was Re: C++ broker - some newbie questions)

[Gordon Sim <gs...@redhat.com>]

Robert Greig wrote:
> 2009/1/2 Gordon Sim <gs...@redhat.com>:
> 
>> At present for example a warning is logged for every published message that
>> cannot be routed; every 'local' message dropped due to a 'no-local'
>> directive results in an info level log message etc. As these are per-message
>> events they could result in lots of log entries.
> 
> Yes, I can see this will be an issue.
> 
> Does your logging infrastructure have the concept of categories (like
> log4j)? It may be useful to have a *small* set of categories (not like
> log4j common usage which tends to map onto package namespaces) such as
> "general", "message-delivery", "connection" etc. and these can have
> levels controlled independently. The default for "general" would be
> INFO (say) but for "message-delivery" it could be "error+".
> 
> I think having a small set of categories is a good idea and one that
> would be nice to see in the Java world since the log level is hard to
> tweak without detailed knowledge of the code structure (effectively).

Yes, I agree. Our log statements can be filtered by a substring match on 
the file in which they occur. That is a bit tricky for those who don't 
know the code and also does not take into account the frequency of the 
event (per message, per connection or general etc).

One simple (though not very elegant) option would be to create separate 
classes for logging message level events (and perhaps session- and 
connection- level events also) with a name chosen to make it easy and 
intuitive to turn on and off.

There is some overlap between diagnostic messages of this sort and 
management events. So perhaps another approach is to treat them as 
management events and have a separate 'dimension' of configuration for 
determining how various management events are treated (E.g. log all info 
events for exchange A, but only log warnings for exchange B etc).

Thats perhaps overly complex for now. Maybe a good first step would be 
something in between these two, e.g. have the management object do the 
logging for per-message events making the component to turn on/off in 
filtering more consistent. (E.g. it would not be the particular exchange 
subclass that logged a warning about inability to route a message but 
the exchanges management object).

Re: [c++]: logging levels (was Re: C++ broker - some newbie questions)

[Carl Trieloff <cc...@redhat.com>]

Robert Greig wrote:
> 2009/1/2 Gordon Sim <gs...@redhat.com>:
>
>   
>> At present for example a warning is logged for every published message that
>> cannot be routed; every 'local' message dropped due to a 'no-local'
>> directive results in an info level log message etc. As these are per-message
>> events they could result in lots of log entries.
>>     
>
> Yes, I can see this will be an issue.
>
> Does your logging infrastructure have the concept of categories (like
> log4j)? It may be useful to have a *small* set of categories (not like
> log4j common usage which tends to map onto package namespaces) such as
> "general", "message-delivery", "connection" etc. and these can have
> levels controlled independently. The default for "general" would be
> INFO (say) but for "message-delivery" it could be "error+".
>
> I think having a small set of categories is a good idea and one that
> would be nice to see in the Java world since the log level is hard to
> tweak without detailed knowledge of the code structure (effectively).
>
>   

You can do stuff like this (only enable debug+ for cluster for example)

--log-enable=debug+:cluster

regards
Carl.



> RG
>   

Re: [c++]: logging levels (was Re: C++ broker - some newbie questions)

[Robert Greig <ro...@gmail.com>]

2009/1/2 Gordon Sim <gs...@redhat.com>:

> At present for example a warning is logged for every published message that
> cannot be routed; every 'local' message dropped due to a 'no-local'
> directive results in an info level log message etc. As these are per-message
> events they could result in lots of log entries.

Yes, I can see this will be an issue.

Does your logging infrastructure have the concept of categories (like
log4j)? It may be useful to have a *small* set of categories (not like
log4j common usage which tends to map onto package namespaces) such as
"general", "message-delivery", "connection" etc. and these can have
levels controlled independently. The default for "general" would be
INFO (say) but for "message-delivery" it could be "error+".

I think having a small set of categories is a good idea and one that
would be nice to see in the Java world since the log level is hard to
tweak without detailed knowledge of the code structure (effectively).

RG