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From "Wei-Che Wei (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7935) Metrics with user supplied scope variables
Date Thu, 04 Jan 2018 02:17:03 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7935?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16310618#comment-16310618

Wei-Che Wei commented on FLINK-7935:

Hi [~elevy]
What you described is almost correct. The FLINK-7692 provides users to expose their own variables
to {{MetricGroup}}, but how to map the metric name and metric's variables to the third party
metric system is the reporter's responsibility.
You can use {{MetricGroup#getAllVariables()}} to get {{type:messageType}} and other system
scope variables. These can map to tags in DataDog reporter.
{{AbstractMetricGroup#getLogicalScope(CharacterFilter)}} can get {{<parent.logical.scope>.messages.type}}
back, so use this function to expose metric name, which will be {{<parent.logical.scope>.messages.type.counts}}.
For example, Prometheus reporter use it to expose metric name. [[1|https://github.com/apache/flink/blob/beb11976fe63c20a5dc9f22ea713c05b4d5e9585/flink-metrics/flink-metrics-prometheus/src/main/java/org/apache/flink/metrics/prometheus/PrometheusReporter.java#L217]]
However, {{MetricGroup#getMetricIdentifier(String)}} will still return {{<parent.identifier>.messages.type.<messageType>}}.
It seems that DataDog reporter used this function to get metric name. [[2|https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-datadog/src/main/java/org/apache/flink/metrics/datadog/DatadogHttpReporter.java#L63]]
I think that is the limitation in DataDog reporter, maybe we can make {{AbstractMetricGroup#getLogicalScope(CharacterFilter)}}
as a public API, and update DataDog reporter.

cc [~Zentol]
Do you have any suggestions and comments? If I make any mistake on my comment, please correct
me. Thank you.

> Metrics with user supplied scope variables
> ------------------------------------------
>                 Key: FLINK-7935
>                 URL: https://issues.apache.org/jira/browse/FLINK-7935
>             Project: Flink
>          Issue Type: Improvement
>          Components: Metrics
>    Affects Versions: 1.3.2
>            Reporter: Elias Levy
> We use DataDog for metrics.  DD and Flink differ somewhat in how they track metrics.
> Flink names and scopes metrics together, at least by default. E.g. by default  the System
scope for operator metrics is {{<host>.taskmanager.<tm_id>.<job_name>.<operator_name>.<subtask_index>}}.
 The scope variables become part of the metric's full name.
> In DD the metric would be named something generic, e.g. {{taskmanager.job.operator}},
and they would be distinguished by their tag values, e.g. {{tm_id=foo}}, {{job_name=var}},
> Flink allows you to configure the format string for system scopes, so it is possible
to set the operator scope format to {{taskmanager.job.operator}}.  We do this for all scopes:
> {code}
> metrics.scope.jm: jobmanager
> metrics.scope.jm.job: jobmanager.job
> metrics.scope.tm: taskmanager
> metrics.scope.tm.job: taskmanager.job
> metrics.scope.task: taskmanager.job.task
> metrics.scope.operator: taskmanager.job.operator
> {code}
> This seems to work.  The DataDog Flink metric's plugin submits all scope variables as
tags, even if they are not used within the scope format.  And it appears internally this does
not lead to metrics conflicting with each other.
> We would like to extend this to user defined metrics, but you can define variables/scopes
when adding a metric group or metric with the user API, so that in DD we have a single metric
with a tag with many different values, rather than hundreds of metrics to just the one value
we want to measure across different event types.

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