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docs: add observableGauge to the prometheus experimental example #4267

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Lp-Francois
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@Lp-Francois Lp-Francois commented Nov 8, 2023

Which problem is this PR solving?

Lack of documentation for async functions and gauge observable regarding the prometheus experimental example.

Short description of the changes

  • Add an example with a promise returning a value and the createObservableGauge() function.
  • Add an image for the prometheus graph for the gauge metrics.

Type of change

improve documentation

How Has This Been Tested?

  • Ran locally the project with the changes, then went to http://localhost:9464 on chrome, and noticed the value changed for observable_gauge_requests at every reload.
Screenshot 2023-11-08 at 20 14 22

Checklist:

  • Followed the style guidelines of this project
  • Unit tests have been added
  • Documentation has been updated

@Lp-Francois Lp-Francois requested a review from a team November 8, 2023 19:26
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codecov bot commented Nov 9, 2023

Codecov Report

Merging #4267 (2a980f9) into main (df63272) will decrease coverage by 0.43%.
The diff coverage is n/a.

Additional details and impacted files
@@            Coverage Diff             @@
##             main    #4267      +/-   ##
==========================================
- Coverage   92.22%   91.79%   -0.43%     
==========================================
  Files         336      214     -122     
  Lines        9521     6547    -2974     
  Branches     2017     1465     -552     
==========================================
- Hits         8781     6010    -2771     
+ Misses        740      537     -203     

see 125 files with indirect coverage changes

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@pichlermarc pichlermarc left a comment

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Thank you for opening this PR.

I'm wondering if it wouldn't be better to just link to the documentation on metrics instrumentation from the readme. The observable gauge is not really prometheus specific and its behvaior does not vary depending on which exporter is used. 🤔

experimental/examples/prometheus/index.js Outdated Show resolved Hide resolved
@Lp-Francois
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Thank you for opening this PR.

I'm wondering if it wouldn't be better to just link to the documentation on metrics instrumentation from the readme. The observable gauge is not really prometheus specific and its behvaior does not vary depending on which exporter is used. 🤔

I did the PR in the first place because I was trying to move away from https://github.com/siimon/prom-client, so going directly to this repo was helpful to find an easy example on how opentelemtry js works for prometheus.
As gauge example was missing, I added it :)

@Lp-Francois
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@pichlermarc any update? 👀

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I see. I guess it wouldn't hurt to have the example here. 🙂
I think we can make it sync though for simplicity.

Comment on lines +54 to +57
observableGauge.addCallback(async observableResult => {
const value = await randomMetricPromise();
observableResult.observe(value, attributes);
});
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hmm, why not observe the value synchronously here? 🤔

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hmm, why not observe the value synchronously here? 🤔

Often, when I had to observe a value at querying time, it was from an async process, so I just replicated what I often deal with :)

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I agree that the ability to collect gauge asynchronously can be a good point to present in the example.

Comment on lines +54 to +57
observableGauge.addCallback(async observableResult => {
const value = await randomMetricPromise();
observableResult.observe(value, attributes);
});
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I agree that the ability to collect gauge asynchronously can be a good point to present in the example.

@Lp-Francois
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Lp-Francois commented Jan 16, 2024

Hey @pichlermarc , should we merge the PR now it is approved? :)

@pichlermarc pichlermarc merged commit 5afbcdb into open-telemetry:main Jan 25, 2024
17 checks passed
Zirak pushed a commit to Zirak/opentelemetry-js that referenced this pull request Sep 14, 2024
…n-telemetry#4267)

* docs: add observableGauge to the prometheus experimental example

Signed-off-by: Francois LP <[email protected]>

* docs: add gauge image to README

Signed-off-by: Francois LP <[email protected]>

* refactor: change comment wording

from @pichlermarc

Co-authored-by: Marc Pichler <[email protected]>

---------

Signed-off-by: Francois LP <[email protected]>
Co-authored-by: Marc Pichler <[email protected]>
Co-authored-by: Daniel Dyla <[email protected]>
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4 participants