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GeezerVison is showing github.com — Thread-safe `HttpKnownHeaderNames` initialization by iSazonov · Pull Request #15519 · PowerShell/PowerShell

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@iSazonov

@iSazonov Ilya (iSazonov) commented Jun 4, 2021 •
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PR Summary

Fix #15513

Move HttpKnownHeaderNames initialization to static constructor.

PR Context

See #15513.

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      • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode
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@iSazonov
Thread-safe HttpKnownHeaderNames initialization
b4856dd
@iSazonov Ilya (iSazonov) added the CL-General Indicates that a PR should be marked as a general cmdlet change in the Change Log label Jun 4, 2021
@iSazonov
Ilya (iSazonov) requested review from Paul Higinbotham (PaulHigin), Dongbo Wang (daxian-dbw) and Rain Sallow (/u/ta11ow) (vexx32) June 4, 2021 04:54
@iSazonov Ilya (iSazonov) self-assigned this Jun 4, 2021
@vexx32

Rain Sallow (/u/ta11ow) (vexx32) commented Jun 4, 2021

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Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it? We should probably add a test using the code samples in the issue to verify that this is sufficient to resolve it. Since the user reporting it mentioned that it was a bit intermittent, we should repeat their test a few times in our own tests.
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@iSazonov

Ilya (iSazonov) commented Jun 4, 2021

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Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it?

A root of the issue was that second thread read the HashSet while first thread still initializes the HashSet.
The HashSet is used only in one place for reading so no need to concern more about race conditions.

We should probably add a test

It's not worth it. We will not be able to make such tests stable and defensible. Please use compiled artifact to check locally.
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@dperez83

dperez83 commented Jun 4, 2021 •
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Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it?

A root of the issue was that second thread read the HashSet while first thread still initializes the HashSet.
The HashSet is used only in one place for reading so no need to concern more about race conditions.

We should probably add a test

It's not worth it. We will not be able to make such tests stable and defensible. Please use compiled artifact to check locally.

If the only writes are the ones when the object is generated :
s_contentHeaderSet.Add(HttpKnownHeaderNames.Allow);
s_contentHeaderSet.Add(HttpKnownHeaderNames.LastModified);
...

I think the write race condition is eliminated with this change.

I am a C# dev, but I have zero knowledge on the Powershell source code. Hope I could help you somehow.
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@iSazonov

Ilya (iSazonov) commented Jun 4, 2021 •
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I am a C# dev, but I have zero knowledge on the Powershell source code. Help I could help you somehow.

dperez83 PowerShell is great project to improve skills. It's too big to learn it well in a short time but you can pick an area you like best and work there with some workgroup https://devblogs.microsoft.com/powershell/powershell-working-groups/
After monitoring issues and PRs for about a month you will be able to make good contributions.

PowerShell Team
PowerShell Working Groups | PowerShell Team
Since we open sourced PowerShell in 2016, PowerShell has been an immensely popular project on GitHub. Every year, 700-1000 PRs and 1300-1500 issues are submitted to the PowerShell repo, with roughly half of the PRs and 90% of the issues filed from the community.
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PaulHigin
Paul Higinbotham (PaulHigin) approved these changes Jun 4, 2021
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LGTM

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vexx32
Rain Sallow (/u/ta11ow) (vexx32) approved these changes Jun 4, 2021
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@ghost ghost added the Review - Needed The PR is being reviewed label Jun 12, 2021
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Deleted user (ghost) commented Jun 12, 2021

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This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author
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@iSazonov

Ilya (iSazonov) commented Jun 12, 2021

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Dongbo Wang (@daxian-dbw) Could you please review?
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@ghost ghost removed the Review - Needed The PR is being reviewed label Jun 12, 2021
@iSazonov

Ilya (iSazonov) commented Jun 18, 2021

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Steve Lee (@SteveL-MSFT) Could you please approve? It is impossible to merge without green flag :-)
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@ghost ghost added the Review - Needed The PR is being reviewed label Jun 25, 2021
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Deleted user (ghost) commented Jun 25, 2021

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This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author
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@dperez83

dperez83 commented Aug 4, 2021

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I see that there's a pending review from Dongbo Wang (@daxian-dbw)
Is there anything else you need from me?

Thank you
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@iSazonov
Ilya (iSazonov) requested a review from Travis Plunk (TravisEz13) August 4, 2021 08:28
@iSazonov

Ilya (iSazonov) commented Aug 4, 2021

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Travis Plunk (@TravisEz13) Please review/approve.
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@ghost ghost removed the Review - Needed The PR is being reviewed label Aug 4, 2021
TravisEz13
Travis Plunk (TravisEz13) reviewed Aug 4, 2021
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Comment thread ...osoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/HttpKnownHeaderNames.cs
if (s_contentHeaderSet == null)
{
s_contentHeaderSet = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
// Thread-safe initialization.

@TravisEz13 Travis Plunk (TravisEz13) Aug 4, 2021

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Suggested change
// Thread-safe initialization.
// Thread-safe initialization because the constructor is only called once per AppDomain.

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TravisEz13
Travis Plunk (TravisEz13) approved these changes Aug 4, 2021
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@TravisEz13 Travis Plunk (TravisEz13) assigned Travis Plunk (TravisEz13) and unassigned Ilya (iSazonov) Aug 4, 2021
@TravisEz13 Travis Plunk (TravisEz13) changed the title Thread-safe HttpKnownHeaderNames initialization Thread-safe HttpKnownHeaderNames initialization Aug 4, 2021
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Travis Plunk (TravisEz13) merged commit aaaa0f2 into PowerShell:master Aug 4, 2021
@iSazonov
Ilya (iSazonov) deleted the racecondition-in-httpknownheadernames branch August 5, 2021 02:52
@iSazonov Ilya (iSazonov) added this to the 7.2.0-preview.9 milestone Aug 5, 2021
@ghost

Deleted user (ghost) commented Aug 23, 2021

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🎉v7.2.0-preview.9 has been released which incorporates this pull request.:tada:

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  • Release Notes
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@ghost ghost mentioned this pull request Aug 23, 2021
Invoke-RestMethod parallel problem #15513
Closed
@ghost

Deleted user (ghost) commented Sep 28, 2021

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🎉v7.2.0-preview.10 has been released which incorporates this pull request.:tada:

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Thatgfsj (Thatgfsj) pushed a commit to Thatgfsj-contribs/PowerShell that referenced this pull request Aug 6, 2026
@iSazonov
Thread-safe HttpKnownHeaderNames initialization (PowerShell#15519)
73c4337
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Reviewers

@TravisEz13 Travis Plunk (TravisEz13) TravisEz13 approved these changes
@daxian-dbw Dongbo Wang (daxian-dbw) Awaiting requested review from daxian-dbw
+2 more reviewers
@PaulHigin Paul Higinbotham (PaulHigin) PaulHigin approved these changes
@vexx32 Rain Sallow (/u/ta11ow) (vexx32) vexx32 approved these changes
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@TravisEz13 Travis Plunk (TravisEz13)

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5 participants

@iSazonov @vexx32 @dperez83 @TravisEz13 @PaulHigin
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