metrics with same metric name cannot use binary arithmetic operators to calculate.

[cauwulixuan]

Proposal

Use case. Why is this important?

Nice to have' is not a good use case :)

Bug Report

What did you do?
I have defined a metric name "hadoop_namenode_fsname_system_capacity_bytes" with different labels.
And metrics can be scraped like:

# HELP hadoop_namenode_fsname_system_capacity_bytes Current DataNodes capacity in each mode in bytes
# TYPE hadoop_namenode_fsname_system_capacity_bytes gauge
hadoop_namenode_fsname_system_capacity_bytes{mode="UsedNonDFS"} 203908392012.0
hadoop_namenode_fsname_system_capacity_bytes{mode="Total"} 422567952384.0
hadoop_namenode_fsname_system_capacity_bytes{mode="Used"} 156852491239.0
hadoop_namenode_fsname_system_capacity_bytes{mode="Remaining"} 144899711054.0

Now I want to calculate capacity_used_ratio using:

hadoop_namenode_fsname_system_capacity_bytes{mode="Used"} / hadoop_namenode_fsname_system_capacity_bytes{mode="Total"}

What did you expect to see?
The result of the calculation.

What did you see instead? Under which circumstances?
no data

Environment

• System information:

  insert output of uname -srm here

• Prometheus version:

  insert output of prometheus --version here

• Alertmanager version:

  insert output of alertmanager --version here (if relevant to the issue)

• Prometheus configuration file:

insert configuration here

• Alertmanager configuration file:

insert configuration here (if relevant to the issue)

• Logs:

insert Prometheus and Alertmanager logs relevant to the issue here

[cauwulixuan]

Any ideas? Many thanks.

[krasi-georgiev]

Thanks for your report. It looks as if this is actually a question about usage and not development.

no crash, no panic = support question 😉

To make support question, and all replies, easier to find, I suggest you move this to our user mailing list.

If you haven't looked already you might find your answer in the official docs and examples or by searching in the users or devs groups.
The #prometheus IRC channel is also a great place to mix up with the community and ask questions (don't be afraid to answers few while waiting).

If you think this is not purely a support question, feel free to comment in here or in the dev mailing list.

Once your questions have been answered, please add a link to the solution to help other Prometheans in trouble reaching this from a search 👍

[cauwulixuan]

It works by ignore "mode" label, because by default Prometheus wants to match all labels on both sides:

hadoop_namenode_fsname_system_capacity_bytes{mode="Used"} / ignoring(mode) hadoop_namenode_fsname_system_capacity_bytes{mode="Total"}

Wish could help others.

[krasi-georgiev]

Thanks!

[lock]

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