[Hawkular-dev] Metric id and url restrictions

[Matt Wringe]

On 18/09/15 11:32 AM, John Mazzitelli wrote:
> Metric IDs from our Wildfly Agent contain "/" because those are characters that are valid for Wildfly resources and we use the Wildfly resource names as part of the metric ID to uniquely identify them.

Yeah, and the cAdvisor metrics from Heapster also contain slashes, which 
is where I am seeing the problem right now with OpenShift proxies.  
Outside of the proxy, then everything works fine with having encoded 
slashes in the URL, which is why I don't see the issue with my own 
testing. But it looks like for the UI they may need to use the proxy.

Its not just the OpenShift proxies that have this problem, its a common 
issue with some types proxies and servers as well.

>
> So for IDs of metrics coming from things like "/deployment=the-app.war/subsystem=ejb3" will have "/" in them. The only alternative would be for us to replace "/" with a character that is valid for URLs but invalid for Wildfly resource names. Say "$deployment=the-app.war$subsystem=ejb3" or something like that.

I don't know if it really matter here how wildfly does things. Your 
client should be able to encode the metricid in one format when going 
into hawkular and then decode when they get things back from hawkular.


I don't know what should be the right solution there:

1) we could enforce what is allowed in a metric id field. This means we 
break backwards compatibility with what we currently have, but it also 
means that we can open up the door to things like restricting some 
metrics to some internal only things (see 
https://issues.jboss.org/browse/HWKMETRICS-208).

2) we keep our current endpoint as is, but add a new endpoint which can 
do queries via a post (essentially this is just an escape route to get 
around the issue when dealing with systems like this).

So to do the equivalence of:

GET 
http://localhost:8080/hawkular/metrics/gauges/foo%2fbar/data?start=10&end=110&buckets=2

You could do also do something like:
POST http://localhost:8080/hawkular/metrics/gauges/data
{
   "metric-id": foo/bar,
   "start": 10,
   "end": 110,
   "buckets":2
}

3) Band-aid solution to fix the immediate problem: update the heapster 
sink to encode metric ids in a format which does not include the '/' 
anywhere in it. This doesn't really solve the problem, but it would at 
least get us past the problem until we come up with a better, more 
permanent solution.

Any thoughts?

>
>
> ----- Original Message -----
>> Currently we are storing metric id as any string. There are no
>> restrictions on how we name the metrics, and when you access a single
>> metric via a url you just need to make sure its url encoded properly here.
>>
>> This works fine when dealing with a client and the Hawkular Metrics
>> directly, but can cause problems when dealing with proxies or other
>> intermediary servers which are not exactly url compliant.
>>
>> The big issue is with slashes in the metric id. Even when properly
>> encoded this can cause problems with things like proxies not accepting
>> them (and even certain web container don't like them).
>>
>> Since we need to be able to integrate over networks with these types of
>> servers, we need to find a solution to resolve this in hawkular.
>>
>> Possible solutions
>>
>> - enforce naming of anything which can show up in a the URL to make sure
>> it cannot include a '/' . This would include things like metric Id. This
>> should probably be enabled by default, but we could have an option to
>> disable this if a user needs it.
>>
>> - create a new endpoint which can be used to perform a POST instead of
>> doing a GET on the metric endpoint. This would mean sending things like
>> the metric id and query string as part of the message body in the POST
>> instead of in the URL.
>>
>> Any thoughts?
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