Recording http metrics at host level

[iamgr0ot]

Host name level opencensus metrics are insanely useful while troubleshooting production issues and we would like to give it back to the community.

• Recording opencensus client http metrics at hostname level based on configuration.
• Introducing HttpClientMetricGranularity to define, at what level, one would like to collect metrics.
• The change is backward compatible and metrics will be collected at http method level by default.

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[bogdandrutu]

Can you please sign the CLA?

[bogdandrutu]

Not sure why do you need this? What you can do is to always add the HOST tag, but don't change the default views. So you can define your own custom views that include the host :)

[iamgr0ot]

what if some applications have a high cardinality hostname space, for example web crawlers? Metric backends may run into cardinality issues in that case. What do you think?

[bogdandrutu]

If the defined views do not include the HOST we just ignore the tag so no cardinality issue.

[iamgr0ot]

I don't quite get your comment on custom views.

[iamgr0ot]

I signed it!

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[iamgr0ot]

@bogdandrutu - You are right. There is no need to change default views. I could define my own view with the exposed measure. Now, I am just tagging host name and not changing any default views.

[songy23]

LGTM

OC-Specs also specified that default HTTP views don't have the host key. Though it definitely should be in the context that measurements are recorded against.

[iamgr0ot]

@songy23 - I would love to get this change with a release. Could you please help me with that?

[songy23]

@iamgr0ot We can do a new release after finishing the remaining HTTP work - @rghetia do you have an estimate on it?

EDIT: sorry for mentioning the wrong username

[rghetia]

I have two PRs pending. I will post them today. we can release later today or tomorrow.