SymLinksMayExistIndependentlyOfTarget failure

[danmoseley]

Frequency:

Day	Run	Notes

4/1-7/22 7/12 | Official run | Win10 7/6 | PR #71263 | Win10 6/3 | PR #69885 | Win10

let failedTests = (methodName : string, includePR : bool, messageSubstr: string, includePassedOnRerun : bool) {
cluster('engsrvprod.kusto.windows.net').database('engineeringdata').AzureDevOpsTests
    //| where TestName startswith "System.Net" 
    | where TestName contains methodName
    | where includePassedOnRerun or (Outcome == 'Failed')
    | extend startOfTestName = indexof_regex(TestName, @"[^.]+$")
    | extend Method = substring(TestName, startOfTestName)
    | extend Type = substring(TestName, 0, startOfTestName - 1)
    | project-away startOfTestName
    | where Method == methodName
    | where Message contains messageSubstr
    | distinct JobId, WorkItemId, Message, StackTrace, Method, Type, Arguments, Outcome
    | join kind=inner (cluster('engsrvprod.kusto.windows.net').database('engineeringdata').Jobs
        | where ((Branch == 'refs/heads/main') or (Branch == 'refs/heads/master') or (includePR and (Source startswith "pr/")))
        | where Type startswith "test/functional/cli/"
            and not(Properties contains "runtime-staging")
        | summarize arg_max(Finished, Properties, Type, Branch, Source, Started, QueueName) by JobId
        | project-rename JobType = Type) on JobId
    | extend PropertiesJson = parse_json(Properties)
    | extend OS = replace_regex(tostring(PropertiesJson.operatingSystem), @'\((.*)\).*|([^\(].*)', @'\1\2')
    | extend Runtime = iif(PropertiesJson.runtimeFlavor == "mono", "Mono", iif(PropertiesJson.DefinitionName contains "coreclr", "CoreCLR", ""))
    | extend TargetBranch = extractjson("$.['System.PullRequest.TargetBranch']", Properties)
    | extend Architecture = PropertiesJson.architecture
    | extend Scenario = iif(isempty(PropertiesJson.scenario), "--", PropertiesJson.scenario)
    //| extend DefinitionName = PropertiesJson.DefinitionName
    | project-away PropertiesJson
};
failedTests('SymLinksMayExistIndependentlyOfTarget', true, '', true);

Runfo query for last 60 days (incl. PRs) with less hits than Kusto (from unknown reason)

ystem.IO.Tests.File_Exists.SymLinksMayExistIndependentlyOfTarget [FAIL]
      linkPath should no longer exist
      Expected: False
      Actual:   True
      Stack Trace:
        /_/src/libraries/System.IO.FileSystem/tests/File/Exists.cs(138,0): at System.IO.Tests.File_Exists.SymLinksMayExistIndependentlyOfTarget()

'System.IO.FileSystem.Tests' from job 3683fd05-6451-4dba-848b-64f9d459eac3 workitem 46af4fdd-dcb6-4ead-9081-44d83202df31 (windows.10.amd64.open.rt) executed on machine a009Z5S

hit in #64677

[ghost]

Tagging subscribers to this area: @dotnet/area-system-io See info in area-owners.md if you want to be subscribed.

Issue Details

---

``` ystem.IO.Tests.File_Exists.SymLinksMayExistIndependentlyOfTarget [FAIL] linkPath should no longer exist Expected: False Actual: True Stack Trace: /_/src/libraries/System.IO.FileSystem/tests/File/Exists.cs(138,0): at System.IO.Tests.File_Exists.SymLinksMayExistIndependentlyOfTarget() ``` 'System.IO.FileSystem.Tests' from job 3683fd05-6451-4dba-848b-64f9d459eac3 workitem 46af4fdd-dcb6-4ead-9081-44d83202df31 (windows.10.amd64.open.rt) executed on machine a009Z5S hit in #64677

Author:	danmoseley
Assignees:	-
Labels:	`area-System.IO`
Milestone:	-

[danmoseley]

            // Now delete the symlink.
            File.Delete(linkPath);
            Assert.False(File.Exists(linkPath), "linkPath should no longer exist");

odd

[jozkee]

I was thinking on name collision but that can't be the case for this test, this is how path and linkPath look like:

  path: C:\Users\david\AppData\Local\Temp\File_Exists_rvyyngfh.y1s\SymLinksMayExistIndependentlyOfTarget_121_9d65b352
  linkPath: C:\Users\david\AppData\Local\Temp\File_Exists_rvyyngfh.y1s\GetRandomLinkName_84_57004724.link

  path: C:\Users\david\AppData\Local\Temp\PathFile_Exists_vlbp50lx.sjy\SymLinksMayExistIndependentlyOfTarget_121_fe1a95b8
  linkPath: C:\Users\david\AppData\Local\Temp\PathFile_Exists_vlbp50lx.sjy\GetRandomLinkName_84_6cbea16a.link

Even though GetRandomLinkName_84 persist, we also use GetType() + Path.GetRandomFileName() and that should avoid the collision.

[danmoseley]

The way Windows handles file deletes has been a bit unintuitive to me in the past, and I believe changed at one point. @JeremyKuhne may have thoughts.

[danmoseley]

Another possibility perhaps is that the delete failed for some reason and we ate the error somehow

[jozkee]

FWIW the only error we eat on Delete is File Not Found. https://github.com/dotnet/runtime/blob/ccd67b0c449e11cb6fbfea75507b6d01c2182b2d/src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs#L99-L106

[JeremyKuhne]

The way Windows handles file deletes has been a bit unintuitive to me in the past, and I believe changed at one point

For NTFS the name would not be freed for use until all file handles were closed. It changed in 1903- we have tests that check this behavior:

https://github.com/dotnet/runtime/blob/57bfe474518ab5b7cfe6bf7424a79ce3af9d6657/src/libraries/System.IO.FileSystem/tests/FileStream/ctor_str_fm_fa_fs.delete.cs#L115-L119

[danmoseley]

Maybe this is pre-1903 and it was a virus checker or something.

[jozkee]

For NTFS the name would not be freed for use until all file handles were closed.

@JeremyKuhne does this imply that File.Exists(path) will return true if not all handles to that file are yet closed? Cause that's what is happening here, File.Exists() is returning true right after the file was deleted.

@danmoseley CI says windows.10.amd64.open.rt, matching that to the list in https://helix.dot.net/ (ctrl+f) shows:

Operating System Windows Server 2016-Datacenter Architecture AMD64

I don't know how to check if that is pre-1903 cc @dotnet/area-infrastructure-libraries

[JeremyKuhne]

will return true if not all handles to that file are yet closed?

I believe so. And 2016 is way before 1903 (2019 March).

[jozkee]

@JeremyKuhne, thanks. Will close this issue as it is non actionable for us IMO.

[danmoseley]

@MattGal does anything like a virus checker run on these Server 2016 machines? Something that could grab random handles and potentially defeat deleting things.

[MattGal]

@MattGal does anything like a virus checker run on these Server 2016 machines? Something that could grab random handles and potentially defeat deleting things.

Any SKU that's effectively Windows 8 or newer has anti-virus stuff that you can't defeat even if it's a throwaway machine only used for testing. More recently, we've started allowing (because we absolutely must and it's unfortunately not up for debate... would that it were) Azure Security Pack and Geneva Monitoring onto the machines. These are services that can try to reconfigure antivirus as well as perform their own scans on the machine. When you combine this with enough executions, the behavior you're suspecting is pretty darn likely to be the case. See https://github.com/dotnet/core-eng/issues/15161 for more details.

One thing to note though, is that people who would run this test locally are also likely to have some form of antivirus turned on, and hardening the tests to both understand and tolerate this is likely the only long term solution that keeps us off automatic-scanning radar.

[danmoseley]

Thanks that makes it clear. OK if this happens again I'll put some retry around it. Right now there's zero evidence that this line is more likely to need a retry than any of the other places.

[jtschuster]

Hit again in rolling build 1873896 on net7.0-windows-Release-x86-CoreCLR_checked-Windows.10.Amd64.Open Log

[danmoseley]

@Jozkee what do you recommend here? this is blocking-clean-ci so we either need to fix, workaround or disable.

[jozkee]

A retry should be the best. This kind of failure is not exclusive to this unit test. The same happens on this other one that exercises the same assert:

https://dataexplorer.azure.com/clusters/engsrvprod/databases/engineeringdata?query=H4sIAAAAAAAAA22PsU7DYAyE9zzFqUth6guQraoUBAtUYv6JT4lJaqPfLgWJhydqJMTAZN3d9w0+MvKJcZ4z0HzjzdUwqUmrZqx48Tp1yVPA7Td08h96769XarmdLPtlZCUOahojBXctzC83t81uV0zwyIgyEL1bFrXAhh+0hKgsXML7/lxRAvx8Z5+UTbNqObr8sfacmWrD89fpQW3aO8PyWvJY6sBcvfVFtC22h6Lz9gfcOQWS9wAAAA==

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19906508	974759625		de30fe19-f93c-4d00-9023-25a9e2979c01	0070981a-3424-4773-b1c7-2675326f385c	System.IO.FileSystem.Tests	System.IO.Tests.DirectoryInfo_Delete	DeletingSymLinkDoesntDeleteTarget			Fail	0.077		linkPath should no longer exist Expected: False Actual: True	at System.IO.Tests.Directory_Deletestr.DeletingSymLinkDoesntDeleteTarget() in //src/libraries/System.IO.FileSystem/tests/Directory/Delete.cs:line 121 at System.RuntimeMethodHandle.InvokeMethod(Object target, Void* arguments, Signature sig, Boolean isConstructor) at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr args, BindingFlags invokeAttr) in /_/src/libraries/System.Private.CoreLib/src/System/Reflection/MethodInvoker.cs:line 81				48061842	171875	19906508	974759625	de30fe19-f93c-4d00-9023-25a9e2979c01	0070981a-3424-4773-b1c7-2675326f385c	System.IO.FileSystem.Tests	Pass	0	0	0	0	2022-06-02T23:24:30.597Z	2022-06-02T23:41:31.987Z	2022-06-02T23:44:00.819Z	0	https://helixre107v0xdeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-70180-merge-de30fe19f93c4d0090/System.IO.FileSystem.Tests/1/console.77514c80.log?helixlogtype=result	a0005EE	other		0	1	windows.10.amd64.open.rt	0	0	19906508	de30fe19-f93c-4d00-9023-25a9e2979c01	pr/public/dotnet/runtime/refs/pull/70180/merge	test/functional/cli/innerloop/		27		true		2022-06-02T23:24:30.488Z	2022-06-02T23:24:30.519Z	2022-06-02T23:49:23.744Z	96092	1	1259	278	0	0	0	0	0	277	278	https://helixde107v0xdeko0k025g8.blob.core.windows.net/helix-job-2efdb516-920f-4186-8036-0b6aeb199ff777aff45fee040748a/job-list-ed8ed7fa-1ef2-483f-9d39-55ac6b530110.json?helixlogtype=result	{"operatingSystem":"Windows.10.Amd64.Open","System.JobId":"215a953c-1e4b-5cc0-95e2-5484aabbe659","configuration":"Debug","runtimeFlavor":"coreclr","DefinitionId":"686","System.JobName":"__default","architecture":"x86","DefinitionName":"runtime","System.StageAttempt":"1","BuildNumber":"20220602.105","System.PullRequest.TargetBranch":"main","Reason":"PullRequest","BuildId":"1803799","System.PhaseAttempt":"1","AzurePipelinesTestRunId":"48061842","Project":"public","System.JobAttempt":"1","CollectionUri":"https://dev.azure.com/dnceng/","System.PhaseName":"libraries_test_run_checked_coreclr_windows_x86_Debug","System.StageName":"__default"}	windows.10.amd64.open.rt	0	0	0		0	windows.10.amd64.open		public	dotnet/runtime	refs/pull/70180/merge

[karelz]

Only 1 hit in last 60 days (as of 7/22). Only 3 hits since 4/1 in Kusto -- see frequency in top post. Removing blocking-clean-ci label.