[
https://issues.apache.org/jira/browse/FLINK-13418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16909034#comment-16909034
]
Yun Tang commented on FLINK-13418:
----------------------------------
[~Zentol], the comparison of these two different concepts is listed below and
summarized from [influxdb official
doc|https://docs.influxdata.com/influxdb/v1.7/concepts/key_concepts/#field-set]：
||concept||whether required||whether indexed||whether count for series||
|field|required|not indexed|no|
|tag|optional|indexed|yes|
Take our {{numBytesInRemotePerSecond}} of input channel metrics as example, it
is a task scope metrics with default naming
{{<host>.taskmanager.<tm_id>.<job_name>.<task_name>.<subtask_index>}}. If we
want to know the change of bytes input throughput of specific tasks, we need
query with specific {{task_name}} and {{subtask_index}}. Just like
[doc|https://docs.influxdata.com/influxdb/v1.7/concepts/key_concepts/#tag-set]
said, if {{task_name}} and {{subtask_index}} were filed instead of tag, InfuxDB
have to scan every value of {{task_name}} and {{subtask_index}}. On the other
side, these could be set as tags to optimize the performance as tag is indexed
in influxDB. The value of {{numBytesInRemotePerSecond}} is appropriate to act
as field as we would not query on condign of values in most cases.
However, in InfluxDB, a {{series}} is the collection of data that share a
retention policy, measurement, and tag set. In other words, more tags, more
series could be counted. Since series number would impact the overall index
performance especially the default in-memory index version for InfluxDB, and
the default limit for series per data-base is only one million. If we include
the {{task_attempt_id}} and other unnecessary tags in influxDB, the total
series number would increase dramatically especially {{task_attempt_id}} set
would be a high dimension set. That's why [~TheoD] come across the huge memory
usage of InfluxDB.
> Avoid InfluxdbReporter to report unnecessary tags
> -------------------------------------------------
>
> Key: FLINK-13418
> URL: https://issues.apache.org/jira/browse/FLINK-13418
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Metrics
> Reporter: Yun Tang
> Priority: Major
> Fix For: 1.10.0
>
>
> Currently, when building measurement info within {{InfluxdbReporter}}, it
> would involve all variables as tags (please see code
> [here|https://github.com/apache/flink/blob/d57741cef9d4773cc487418baa961254d0d47524/flink-metrics/flink-metrics-influxdb/src/main/java/org/apache/flink/metrics/influxdb/MeasurementInfoProvider.java#L54]).
> However, user could adjust their own scope format to abort unnecessary
> scope, while {{InfluxdbReporter}} could report all the scopes as tags to
> InfluxDB.
> This is due to current {{MetricGroup}} lacks of any method to get necessary
> scopes but only {{#getScopeComponents()}} or {{#getAllVariables()}}. In other
> words, InfluxDB need tag-key and tag-value to compose as its tags while we
> could only get all variables (without any filter acording to scope format) or
> only scopeComponents (could be treated as tag-value). I think that's why
> previous implementation have to report all tags.
> From our experience on InfluxDB, as the size of tags contribute to the
> overall series in InfluxDB, it would never be a good idea to contain too many
> tags, not to mention the [default value of series per
> database|https://docs.influxdata.com/influxdb/v1.7/troubleshooting/errors/#error-max-series-per-database-exceeded]
> is only one million.
--
This message was sent by Atlassian JIRA
(v7.6.14#76016)
