hwmon and so node_exporter very slow with a lot of DS18b20 sensors (taking ~22 seconds to complete)

[JsBergbau]

Host operating system: output of uname -a

Linux hostname 5.10.17-v7+ #1414 SMP Fri Apr 30 13:18:35 BST 2021 armv7l GNU/Linux

node_exporter version: output of node_exporter --version

node_exporter, version 1.3.1 (branch: HEAD, revision: a2321e7b940ddcff26873612bccdf7cd4c42b6b6) build user: root@2efabfa20624 build date: 20211205-11:09:40 go version: go1.17.3 platform: linux/arm

node_exporter command line flags

./node-exporter with no flags

Are you running node_exporter in Docker?

No

What did you do that produced an error?

attached 23 DS18b20 1-Wire sensors to RasbperryPI

What did you expect to see?

node-exporter reporting the metrics very fast

What did you see instead?

It takes about 22 seconds until request to http://<IP>:9100/metrics is completed.

When running node-exporter with ./node_exporter --no-collector.hwmon then request is done in less than one second, as it should. You can query the DS180b20 sensors in parallel, so query time is about one second. I use this in a python script via asyncio and works very well. Also I'd like the idea to disable querying the DS18b20 for hwmon collector, if that is somehow possible.

[discordianfish]

Adding a flag to include/exclude sensors makes sense.

Not sure if parallelizing this is worth it, but given we already do it for mount point it's probably fine.

[PSSGCSim]

Ability to disable certain chips or sensors would be great as some sensors are inherently broken and report nonsensical values. Currently we use silences as a workaround.