2:03 a.m.
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(a)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(a)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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