Binary Operators not working as expected in Prometheus 2.0

[pslobo]

I've got the following simple query that is working in older versions of Prometheus:

node_load1{instance=~"$instance.*"} / count by(job, instance)(count by(job, instance, cpu)(node_cpu{instance=~"$instance.*"}))

For some odd reason, this isn't working. When I test it out in Prometheus dashboard, it returns no_data. However, when I try each individual section of the query, it works just fine.

Example:

• node_load1{instance=~"db_server.*"} => 0.54
• count by(job, instance)(count by(job, instance, cpu)(node_cpu{instance=~"db_server.*"})) => 2

If I try any of these queries:

0.54 / count by(job, instance)(count by(job, instance, cpu)(node_cpu{instance=~"db_server.*"})) or node_load1{instance=~"db_server.*"} / 2 I get the expected results, but join the two and I get no_data

Environment
CentOS 7 server
Linux 3.10.0-693.11.1.el7.x86_64 x86_64
Prometheus, Grafana, Alertmanager all running on Docker

docker version
Client:
Version: 17.12.0-ce
API version: 1.35
Go version: go1.9.2
Git commit: c97c6d6
Built: Wed Dec 27 20:10:14 2017
OS/Arch: linux/amd64

Server:
Engine:
Version: 17.12.0-ce
API version: 1.35 (minimum version 1.12)
Go version: go1.9.2
Git commit: c97c6d6
Built: Wed Dec 27 20:12:46 2017
OS/Arch: linux/amd64
Experimental: false

[pslobo]

Ok, so got this working. Changing the equation and surrounding the second part of the equation with scalar() did the trick. Odd that this wasn't needed in v1. Something change in that regard?

[gouthamve]

@brian-brazil Did we break anything here?

[brian-brazil]

Looks like a typical misunderstanding of binary operator vector matching.

[pslobo]

@brian-brazil totally possible given I'm rather new to all this. What puzzles me though is that the same query (without scalar() seems to be working in others instances of Prometheus (v1) and this was in fact taken from published Grafana Dashboards with the obvious tweaks for grafana templating (this one for instance: https://grafana.com/dashboards/893).

[brian-brazil]

I see no indications of a bug in PromQL here.

[lock]

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