Hello,

let me start with terminology explanation:

Span is one unit of work. It can be a method/REST endpoint invocation or just any unit of work.

List of spans form a trace which is currently tree like structure(every span has its parent, except root span).

Span captures its start and end, therefore it is possible to calculate a duration.

By default all spans reported to the server are persisted in elasticsearch.

I think there are two different things in this email:

1. OpenTracing standard "kpi" tag. Tags are key-value pairs, so I guess value would be a metric name (e.g. "user-registration": duration of user registration which consist of multiple service calls). I think that any duration is considered as KPI. Typically when users want to show durations for a particular service they can use filtering by tags(custom/standard). Is there really need for KPI tag?

2. integration with h-metrics. What are the benefits for users? Integration with grafana? Cannot be grafana directly connected to elastic APM is using? All durations (span, trace) are stored in our backend and published to JMS so an integration with other systems should be possible.

Regards,

On Sat, Jan 7, 2017 at 5:09 PM, John Sanda <jsanda@redhat.com> wrote:

I want to make sure I understand the difference between trace and span. A trace captures the call between two services whether those are REST endpoints, EJBs, etc. Let’s say we want a trace of A calling B. Within that A calls C which in turn calls D, etc. and then finally B is called. Would a span measure the duration of the call between C and D?

Are all spans captured/recorded by default?

Would this be optional functionality? I am wondering because it obviously requires having Hawkular Metrics running which also means Cassandra.

Under what tenant would you store these metrics?

> On Jan 7, 2017, at 7:36 AM, Gary Brown <gbrown@redhat.com> wrote:
>
> Hi
>
> Wanted to discuss a proposal for recording some metric data captured from Hawkular APM in Hawkular Metrics.
>
> For those not familiar with Hawkular APM, it captures the end to end trace instance (think of it as a distributed call stack), for each invocation of an application. This trace can include information about the communications between services, but can also include details about internal components used within the services (e.g. EJBs, database calls, etc).
>
> First point is that if we were to record duration metrics for each 'span' captured (i.e. scope within which a task is performed), for each invocation of an application, then it would result in a large amount of data that may be of no interest. So we need to find a way for end users/developers to express which key points within an application they do want recorded as metrics.
>
> The proposal is to allow the application/services to define a tag/property on the spans of interest, e.g. 'kpi', that would indicate to the server that the duration value for the span should be stored in H-Metrics. The value for the tag should define the name/description of the KPI.
>
> If considered a suitable solution, then we can also propose it as a standard tag in the OpenTracing standard.
>
> There are a couple of metrics that we could record by default, first being the trace instance completion time, and the second possibly being the individual service response times (although this could potentially also be governed by the 'kpi' tag).
>
> Thoughts?
>
> Regards
> Gary
>
>
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