RFR: 8142366: Add develop_debug and develop_trace levels to Unified Logging

Thu Nov 12 08:34:18 UTC 2015

Hi Rachel and Coleen,

Thanks for providing more background on this.

Would it be possible to use tags to give users the control you want to 
give them?

Let's say you introduce a "verbose" tag. Then you could do something like:

log_develop(vtables)("Main logging for vtables");
log_develop(vtables, verbose)("Very detailed logging for vtables");

Thanks,
Bengt

On 2015-11-11 21:32, Coleen Phillimore wrote:
>
> I agree with what Rachel has written.   Many of the runtime 
> debug/tracing flags are not appropriate for product level logging. 
> Should they not be converted?    If we can't have multiple Develop 
> levels for TraceItables and PrintVtables, we can't convert them to 
> UL.    It would have been nice to remove all of these command line 
> flags and use UL tags though.
>
> Coleen
>
> On 11/11/15 3:05 PM, Rachel Protacio wrote:
>> Hi,
>>
>> Thanks for the feedback. I appreciate the justification behind 
>> wanting a single develop level, but our desire for multiple levels I 
>> think comes again from letting the user have fine control over the 
>> amount of output. In particular, I am working on TraceItables and 
>> PrintVtables, which contain code that (before the change) has regular 
>> and verbose output. This would translate to "debug" and "trace" 
>> levels in the product mode, but I don't think anyone will argue that 
>> the hundreds of lines that print out about itables and vtables need 
>> to be in the product. So if we move all the code to a single develop 
>> level, the user loses the ability to distinguish between some extra 
>> information and tons of extra information. I think it would be wrong 
>> to rob them of this amount of control, when the existing non-product 
>> implementation allows them to have it. I don't think, though, that 
>> the non-product levels should be in a separate system; I think it is 
>> right for them to aggregate below the product levels. As you and 
>> Marcus pointed out, it would be confusing to have non-product and 
>> product logging appear together as if it were the same level. The 
>> develop logging is more detailed, so it should still be below. I just 
>> think we need to have multiple levels below - ones that do not need 
>> to take up space in the product release but should still allow users 
>> to control their verbosity.
>>
>> Does that make sense?
>>
>> Thanks,
>> Rachel
>>
>> On 11/11/2015 2:25 PM, Bengt Rutisson wrote:
>>>
>>> Hi all,
>>>
>>> I agree with Marcus here. Adding more levels below the Trace level 
>>> seems odd.
>>>
>>> I interpret Marcus' suggestion 2) as that there would be for example 
>>> a log_develop_trace() macro that does nothing in product builds and 
>>> that calls log_trace() in debug builds. Similarly for info and debug.
>>>
>>> To me that seems like a reasonable approach. But I do see the 
>>> problem that Marcus mentions. That it will be hard to distinguish 
>>> develop logging from normal logging in the output.
>>>
>>> So far it's been enough for me with the single Develop level. Can 
>>> you give an example of a use case where the different develop levels 
>>> are needed?
>>>
>>> Thanks,
>>> Bengt
>>>
>>> On 2015-11-11 15:01, Marcus Larsson wrote:
>>>> Hi,
>>>>
>>>> I don't think this is the right approach for this problem.
>>>>
>>>> These new develop levels are introduced as even finer levels than 
>>>> the trace, but have names that somewhat say otherwise.
>>>> For example, develop_info is finer than trace, but it isn't 
>>>> unreasonable to expect that develop_info actually shares verbosity 
>>>> with the regular info level.
>>>>
>>>>
>>>> I see two ways to look at this:
>>>>
>>>> 1) develop is a level, which is so verbose/expensive that it is not 
>>>> possible to include it in the product (current implementation).
>>>> The following levels are used: error, warning, info, debug, trace 
>>>> and develop. There is no concept of levels for the develop only 
>>>> logging (it IS the level).
>>>> Selecting/distinguishing different logging on develop level is done 
>>>> by using tags.
>>>>
>>>> 2) There is no concept of a develop level, either the logging is 
>>>> included in product or it isn't (compare to using #ifdefs around 
>>>> the logging calls).
>>>> Development-only logging is orthogonal to the regular log levels, 
>>>> i.e. some log_info calls should only be made in non-product builds 
>>>> (log_develop_info),
>>>> but should still follow the regular log level system (as all other 
>>>> logging does) and use the info level.
>>>> The following levels are used: error, warning, info, debug, trace, 
>>>> and convenience macros are used to strip develop-logging from 
>>>> non-product builds.
>>>>
>>>> The downside of this approach is that it becomes harder to 
>>>> distinguish what is logged only in non-product builds and what is 
>>>> always logged.
>>>> Depending on if the build is non-product or not one can get 
>>>> different output for "-Xlog".
>>>>
>>>>
>>>> The current proposal mixes these two approaches and adds develop 
>>>> "levels" that are all finer than trace, which is confusing.
>>>>
>>>> In my opinion, there should be no reason to require multiple levels 
>>>> for non-product logging. I would assume all develop level logging 
>>>> to be very specific, i.e. have a very specific tagset,
>>>> and require no support for selection/separation using log levels. 
>>>> If it does, then I would argue for that the logging is missing some 
>>>> classifying log tag that could be used instead of a level.
>>>> The logging has already been classified as verbose/expensive, why 
>>>> classify it further on a level scale?
>>>>
>>>> Thanks,
>>>> Marcus
>>>>
>>>>
>>>> On 2015-11-11 00:13, Coleen Phillimore wrote:
>>>>>
>>>>> I think this looks good.   I added serviceability-dev to the 
>>>>> mailing list.
>>>>>
>>>>> Coleen
>>>>>
>>>>> On 11/10/15 2:18 PM, Rachel Protacio wrote:
>>>>>> Good point. I have changed Develop to DevelopInfo. I think it's 
>>>>>> better to maintain the same levels of levels on the develop side 
>>>>>> so that the logging can just shift laterally to non-product, as 
>>>>>> it were.
>>>>>>
>>>>>> And yes, they are specified as -Xlog:<tag>=develop_debug
>>>>>>
>>>>>> Updated webrev: http://cr.openjdk.java.net/~rprotacio/8142366.01/
>>>>>> I re-tested with logging jtreg tests and ExecuteInternalVMTests 
>>>>>> test, and for anyone who was curious (namely Max who had the good 
>>>>>> idea for me to check), the debug levels do correctly "nest" with 
>>>>>> more verbose ones printing out the less verbose and product mode 
>>>>>> logging as well.
>>>>>>
>>>>>> Thanks,
>>>>>> Rachel
>>>>>>
>>>>>> On 11/9/2015 6:05 PM, Coleen Phillimore wrote:
>>>>>>>
>>>>>>> Hi Rachel,
>>>>>>>
>>>>>>> I sort of thought DevelopDebug would replace plain Develop, and 
>>>>>>> DevelopTrace would be additional lower level.   Maybe plain 
>>>>>>> Develop should be DevelopInfo then?
>>>>>>>
>>>>>>> Another question - how do you specify these levels? Is it 
>>>>>>> -Xlog:itables=develop_debug ?
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Coleen
>>>>>>>
>>>>>>> On 11/9/15 5:55 PM, Rachel Protacio wrote:
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> Please see my small changeset to add two develop levels to UL.
>>>>>>>>
>>>>>>>> Summary: This adds develop (that is, non-product) logging 
>>>>>>>> levels to the Unified Logging framework in order to support 
>>>>>>>> performance, footprint, and usefulness-of-output considerations 
>>>>>>>> while maintaining the ability for the user to specify levels of 
>>>>>>>> verbosity, i.e. default, "debug," and "trace" levels.
>>>>>>>> Open webrev: http://cr.openjdk.java.net/~rprotacio/8142366/
>>>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8142366
>>>>>>>>
>>>>>>>> I tested the added levels locally with sample log messages to 
>>>>>>>> ensure proper functioning. When I convert future tags to 
>>>>>>>> logging with these levels, those tags will have their own tests 
>>>>>>>> and inherently exercise the added levels.
>>>>>>>>
>>>>>>>> Thank you,
>>>>>>>> Rachel
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>