[processor/groupbytrace] Add num_workers doc to README

[bryan-aguilar]

Description: In PR #2902 the groupbytrace processor added a configuration option for multiple workers. This change was not reflected in the README. This PR updates the readme example and explanation.

Link to tracking Issue: n/a

Testing: n/a

Documentation: README update.

[bryan-aguilar]

Can this get a skipchangelog label? It's a minor doc update.

[runforesight]

Foresight Summary

    
Major Impacts

TestScraper ❌ failed 1 times in 3 runs (33% fail rate).

TestScraper/metrics_golden ❌ failed 1 times in 3 runs (33% fail rate).

TestScraper/metrics_golden_sftp ❌ failed 1 times in 3 runs (33% fail rate).

build-and-test-windows duration(4 seconds) has decreased 40 minutes 26 seconds compared to main branch avg(40 minutes 30 seconds).

View More Details

✅  telemetrygen workflow has finished in 55 seconds (1 minute 29 seconds less than main branch avg.) and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
build-dev	-     🔗	N/A	See Details
publish-latest	-     🔗	N/A	See Details
publish-stable	-     🔗	N/A	See Details

---

✅  tracegen workflow has finished in 1 minute (1 minute 25 seconds less than main branch avg.) and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
build-dev	-     🔗	N/A	See Details
publish-latest	-     🔗	N/A	See Details
publish-stable	-     🔗	N/A	See Details

---

✅  check-links workflow has finished in 1 minute 22 seconds and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
changed files	-     🔗	N/A	See Details
check-links	-     🔗	N/A	See Details

---

✅  prometheus-compliance-tests workflow has finished in 3 minutes 55 seconds (3 minutes 38 seconds less than main branch avg.) and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
prometheus-compliance-tests	-     🔗	✅ 21  ❌ 0  ⏭ 0    🔗	See Details

---

✅  load-tests workflow has finished in 8 minutes 6 seconds (6 minutes 3 seconds less than main branch avg.) and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
loadtest (TestIdleMode)	-     🔗	✅ 1  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetric10kDPS|TestMetricsFromFile)	-     🔗	✅ 6  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetricResourceProcessor|TestTrace10kSPS)	-     🔗	✅ 12  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceNoBackend10kSPS|TestTrace1kSPSWithAttrs)	-     🔗	✅ 8  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceAttributesProcessor)	-     🔗	✅ 3  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceBallast1kSPSWithAttrs|TestTraceBallast1kSPSAddAttrs)	-     🔗	✅ 10  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestBallastMemory|TestLog10kDPS)	-     🔗	✅ 19  ❌ 0  ⏭ 0    🔗	See Details
setup-environment	-     🔗	N/A	See Details

---

✅  build-and-test workflow has finished in 33 minutes 36 seconds (18 minutes 26 seconds less than main branch avg.) and finished at 26th Jan, 2023.

---

Job	Failed Steps	Tests
unittest-matrix (1.18, exporter)	-     🔗	✅ 2416  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.18, receiver-1)	-     🔗	✅ 1944  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, receiver-1)	-     🔗	✅ 1944  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, exporter)	-     🔗	✅ 2416  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, other)	-     🔗	✅ 4659  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.18, other)	-     🔗	✅ 4659  ❌ 0  ⏭ 0    🔗	See Details
unittest (1.19)	-     🔗	N/A	See Details
unittest (1.18)	-     🔗	N/A	See Details
cross-compile (darwin, amd64)	-     🔗	N/A	See Details
cross-compile (darwin, arm64)	-     🔗	N/A	See Details
cross-compile (linux, 386)	-     🔗	N/A	See Details
cross-compile (linux, amd64)	-     🔗	N/A	See Details
cross-compile (linux, arm)	-     🔗	N/A	See Details
cross-compile (linux, arm64)	-     🔗	N/A	See Details
cross-compile (linux, ppc64le)	-     🔗	N/A	See Details
cross-compile (windows, 386)	-     🔗	N/A	See Details
cross-compile (windows, amd64)	-     🔗	N/A	See Details
build-package (deb)	-     🔗	N/A	See Details
build-package (rpm)	-     🔗	N/A	See Details
windows-msi	-     🔗	N/A	See Details
publish-check	-     🔗	N/A	See Details
publish-dev	-     🔗	N/A	See Details
publish-stable	-     🔗	N/A	See Details

---

⭕  build-and-test-windows workflow has finished in 4 seconds (40 minutes 26 seconds less than main branch avg.) and finished at 27th Jan, 2023.

---

Job	Failed Steps	Tests
windows-unittest-matrix	-     🔗	N/A	See Details
windows-unittest	-     🔗	N/A	See Details

---

⭕  changelog workflow has finished in 4 seconds (2 minutes less than main branch avg.) and finished at 27th Jan, 2023.

---

Job	Failed Steps	Tests
changelog	-     🔗	N/A	See Details

---

🔎 See details on Foresight

^{*You can configure Foresight comments in your organization settings page.}

[bryan-aguilar]

Thanks for all the input so far. I have added default values for each of the configuration options to the README. I have also pruned away the recommendation for num_workers to match physical processors. Based on the conversation above it seems like end users should be encouraged to tune this configuration value based on their environment. Since this could vary wildly I have opted to make no recommendation at all.

Do we believe any deeper verbiage is required?

[andrzej-stencel]

This is good enough for me.

[bryan-aguilar]

@pkositsyn @jpkrohling @Aneurysm9 I have updated the README to suggest that a user could use GOMAXPROCS as a starting point for optimization.

[pkositsyn]

LGTM
My approve doesn't count though. We need @jpkrohling

[jpkrohling]

My approve doesn't count though

I'm happy to see you here again, @pkositsyn. Hopefully you'll stay around and become an approver soon :-)