[wildfly-dev] Design Proposal: Log Viewer

[Scott Marlow]

On 06/11/2014 11:43 AM, Stuart Douglas wrote:
> I don't think we should be worrying about that. Management operations
> happen under a global lock, and it is already possible to perform
> operations that return a lot of content (e.g. reading the whole resource
> tree).

If we already have a single mutually exclusive, global lock in use for 
operations like "viewing logs", I'm less worried.

>
> There would need to be a *lot* of admins and a very under powered server
> to make this a problem, and even then the solution is 'don't do that'.

I've seen this "lot of admins" situation before with log viewing, which 
is why I brought it up.

>
> Stuart
>
> Scott Marlow wrote:
>> On 06/11/2014 11:01 AM, James R. Perkins wrote:
>>> On 06/10/2014 06:53 PM, Scott Marlow wrote:
>>>> Any concern about the number of users viewing the server logs at the
>>>> same time and the impact that could have on a system under load?  For
>>>> example, if a bunch of users arrive at work around the same time and
>>>> they are all curious about how things went last night.  They all could
>>>> make a request to show the last 1000 lines of the server.log file
>>>> (which
>>>> could peg the CPU).  You might ask why a large number of users have
>>>> access to view the logs but the problem is still worth considering.
>>> Actually it's not something I've thought of. Though I suppose this could
>>> be an issue with any operation that returns large results.
>>
>> Would be good to have feedback on how many users are likely to
>> concurrently view logs.  I suspect the count will be higher than we
>> might expect (depending on which users have access for a particular
>> deployment).
>>
>> One possible solution could be a
>> http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Semaphore.html
>>
>> that is configured for the maximum number of users allowed to view logs
>> concurrently.  For example, if the number of Semaphore permits is
>> configured for five and eighty users are trying to view logs at the same
>> time, logs will be returned for five users at a time (until all users
>> have received their logs or a timeout occurs).
>>
>> There are probably other ways to deal with this as well.
>>
>>>>
>>>> On 06/10/2014 07:33 PM, James R. Perkins wrote:
>>>>> While there wasn't a huge talk about this at the Brno meeting I know
>>>>> Heiko brought it up as part of the extended metrics. It's on some
>>>>> future
>>>>> product road maps as well too. I figured I might as well bring it up
>>>>> here and get opinions on it.
>>>>>
>>>>> This design proposal covers how capturing log messages. The "viewer"
>>>>> will likely be an operation that returns an object list of log record
>>>>> details. The design of how a GUI view would look/work is beyond the
>>>>> scope of this proposal.
>>>>>
>>>>> There is currently an operation to view a log file. This has several
>>>>> limitations. The file must be defined as a known file handler.
>>>>> There is
>>>>> also no way to filter results, e.g. errors only. If per-deployment
>>>>> logging is used, those log messages are not viewable as the files are
>>>>> not accessible.
>>>>>
>>>>> For the list of requirements I'm going to be lazy and just give the
>>>>> link
>>>>> the wiki page https://community.jboss.org/wiki/LogViewerDesign.
>>>>>
>>>>> Implementation:
>>>>>
>>>>> 1) There will be a new resource on the logging subsystem resource that
>>>>> can be enabled or disabled, currently called log-collector. Probably
>>>>> some attributes, but I'm not sure what will need to be configurable at
>>>>> this point. This will likely act like a handler and be assignable only
>>>>> to loggers and not the async-handler.
>>>>>
>>>>> 2) If a deployment uses per-deployment logging then a separate
>>>>> log-collector will need to be added to the deployments log context
>>>>>
>>>>> 3) Logging profiles will also have their own log-collector.
>>>>>
>>>>> 4) The messages should be written asynchronously and to a file in some
>>>>> kind of formatted structure. The structure will likely be JSON.
>>>>>
>>>>> 5) An operation to query the messages will need to be create. This
>>>>> operation should allow the results to be filtered on various fields as
>>>>> well as limit the data set returned and allow for a starting position.
>>>>>
>>>>> 6) All operations associated with view the log should use RBAC to
>>>>> control the access.
>>>>>
>>>>> 7) Audit logs will eventually need to be viewable and queryable. This
>>>>> might be separate from the logging subsystem as it is now, but it will
>>>>> need to be done.
>>>>>
>>>>>
>>>>> There are things like how long or how many records should we keep that
>>>>> needs to be determined. This could possibly be configurable via
>>>>> attributes on the resource.
>>>>>
>>>>> This is about all I've got at this point. I'd appreciate any feedback.
>>>>>
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