increase size of buffer in InitMsgBuilder

[missirol]

PR description:

This PR fixes a problem reported by @fwyzard when running the full HLT GRun menu using GlobalEvFOutputModule as cms.OutputModule (which is how the HLT produces output files online).

The issue occurs in the beginRun stage, when serializing the content of the "INI" streamer files: the size of the buffer given by InitMsgBuilder to EventMsgBuilder can be too small if the number of L1 and HL triggers is above certain values.

The current size of 256 is insufficient, for example, in the presence of 500 L1T seeds and 500 HLT paths.

The issue leads to a crash, and it can be reproduced with this minimal update of the relevant DAQ unit test.

diff --git a/EventFilter/Utilities/test/startFU.py b/EventFilter/Utilities/test/startFU.py
index c00d612aae8..9133a1196aa 100644
--- a/EventFilter/Utilities/test/startFU.py
+++ b/EventFilter/Utilities/test/startFU.py
@@ -128,6 +128,9 @@ process.tcdsRawToDigi.InputLabel = cms.InputTag("rawDataCollector")
 process.p1 = cms.Path(process.a*process.tcdsRawToDigi*process.filter1)
 process.p2 = cms.Path(process.b*process.filter2)
 
+for pidx in range(3,1000):
+  setattr(process, f'p{pidx}', cms.Path(process.b))
+
 process.streamA = cms.OutputModule("EvFOutputModule",
     SelectEvents = cms.untracked.PSet(SelectEvents = cms.vstring( 'p1' ))
 )

./EventFilter/Utilities/test/LocalRunBUFU.sh

To my knowledge, this problem affects both GlobalEvFOutputModule and EvFOutputModule.

Given the deadline for 12_4_0_pre4 (and possible need for a patch release in 12_3_X), this PR applies a minimal fix increasing the buffer size.

A buffer size of 640 should be sufficient for 512 L1T seeds and 2000 HLT paths (the current HLT menu for pp collisions has approx. 800 paths).

In the near future, the algorithm could be improved to find an optimal buffer size based on the number of L1 and HL triggers in the configuration.

This PR will need to be backported at least to 12_3_X.

Debugged with @fwyzard.

PR validation:

Manual tests. This fix solves the original issue found when testing the full GRun menu.

If this PR is a backport, please specify the original PR and why you need to backport that PR:

N/A

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-37937/29988

• This PR adds an extra 12KB to repository

[cmsbuild]

A new Pull Request was created by @missirol (Marino Missiroli) for master.

It involves the following packages:

• IOPool/Streamer (core)

@cmsbuild, @smuzaffar, @Dr15Jones, @makortel can you please review it and eventually sign? Thanks.
@makortel, @wddgit this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

[missirol]

Attn: @smorovic

[fwyzard]

@missirol thanks for debugging the problem!

[missirol]

urgent

Targets 12_4_0_pre4.

[missirol]

type bugfix

[missirol]

thanks for debugging the problem!

(much) help from @fwyzard is acknowledged :)

[missirol]

please test

[smorovic]

+1

[smorovic]

Thanks for debugging and fixing it. Are you also planning to create a backport for 12_3_X?

[smorovic]

Also, it looks like 'core' needs to sign-off Streamer directory, I don't have the rights.

[missirol]

Are you also planning to create a backport for 12_3_X?

Yes, definitely. I can prepare this tomorrow.

[Dr15Jones]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs after it passes the integration tests. This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4cb6ea/24690/summary.html
COMMIT: 79ef5e2
CMSSW: CMSSW_12_4_X_2022-05-12-1100/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/37937/24690/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 49
• DQMHistoTests: Total histograms compared: 3697209
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3697185
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 48 files compared)
• Checked 206 log files, 45 edm output root files, 49 DQM output files
• TriggerResults: no differences found

[qliphy]

+1