Fetch Host JIT trace files from functions-release at build time by Francisco-Gamino · Pull Request #11719 · Azure/azure-functions-host

Francisco-Gamino · 2026-04-16T21:31:53Z

Issue describing the changes in this PR

The JIT trace files in PreJIT/ have been moved to functions-release (artifacts/Host/JitTrace/dev/).

Changes

Delete coldstart.jittrace and linux.coldstart.jittrace from src/WebJobs.Script.WebHost/PreJIT/
Add a step in run-coldstart.yml that downloads the latest files from functions-release via ADO REST API into PreJIT/ before dotnet publish
Extract repo path to jitTraceRepoPath variable in coldstart.yml
Add retry logic (MaximumRetryCount 3, RetryIntervalSec 5) and fail the pipeline on download failure

Testing

Nightly run (createJitTrace=false) completes successfully
Manual run with createJitTrace=true produces valid merged JIT trace artifacts

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

Backporting to the in-proc branch is not required
- Otherwise: Link to backporting PR
My changes do not require documentation changes
- Otherwise: Documentation issue linked to PR
My changes should not be added to the release notes for the next release
- Otherwise: I've added my notes to release_notes.md
My changes do not need to be backported to a previous version
- Otherwise: Backport tracked by issue/PR #issue_or_pr
My changes do not require diagnostic events changes
- Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

Copilot

Pull request overview

This PR updates the coldstart pipeline to source the host’s out-of-proc JIT trace files from the functions-release repo at build time (instead of keeping them in this repo), ensuring PreJIT/ is populated before dotnet publish.

Changes:

Added jitTraceRepoPath as a shared pipeline variable for the functions-release JIT trace location.
Added a pipeline step to download coldstart.jittrace and linux.coldstart.jittrace via ADO REST API into src/WebJobs.Script.WebHost/PreJIT/ with retries and failure-on-error behavior.
Added an explicit .NET 10 install step in the coldstart job.

Reviewed changes

Copilot reviewed 2 out of 4 changed files in this pull request and generated 4 comments.

File	Description
eng/ci/templates/variables/coldstart.yml	Introduces `jitTraceRepoPath` variable for the functions-release JIT trace location.
eng/ci/templates/official/jobs/run-coldstart.yml	Downloads JIT trace artifacts into `PreJIT/` before publishing; also adds an explicit .NET 10 install step.

Copilot · 2026-04-16T21:36:35Z

+  - task: UseDotNet@2
+    displayName: Install .NET 10
+    inputs:
+      packageType: sdk
+      version: 10.x
+


This installs .NET 10 again after /eng/ci/templates/install-dotnet.yml, which already installs the SDK pinned by global.json via useGlobalJson: true. The extra UseDotNet@2 version: 10.x step is redundant and can change which dotnet ends up on PATH (potentially diverging from the pinned SDK). Consider removing this step unless there’s a concrete need for a second .NET 10 install.

Suggested change

- task: UseDotNet@2

displayName: Install .NET 10

inputs:

packageType: sdk

version: 10.x

Copilot · 2026-04-16T21:36:36Z

+      $token = "$(System.AccessToken)"
+      $headers = @{
+        Authorization = "Basic " + [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(":$token"))
+      }


$(System.AccessToken) can be empty unless the job is configured to allow scripts to access the OAuth token. Consider failing fast when $token is null/empty with a clear error, and/or explicitly wiring the token into the step (e.g., via env:) so this doesn’t silently produce 401s depending on pipeline settings.

Copilot · 2026-04-16T21:36:36Z

+      }
+
+      $jitTracePath = "$(jitTraceRepoPath)"
+      $baseUrl = "https://dev.azure.com/azfunc/internal/_apis/git/repositories/functions-release/items"


The base URL is hardcoded to a specific org/project (dev.azure.com/azfunc/internal). If this pipeline is ever run in a different project or via forks, this will break. Prefer using built-in variables like $(System.CollectionUri) / $(System.TeamProject) and constructing the REST URL from those, keeping only the repository name/id as the hardcoded part if needed.

Suggested change

$baseUrl = "https://dev.azure.com/azfunc/internal/_apis/git/repositories/functions-release/items"

$collectionUri = "$(System.CollectionUri)".TrimEnd('/')

$teamProject = "$(System.TeamProject)"

$repositoryName = "functions-release"

$baseUrl = "$collectionUri/$teamProject/_apis/git/repositories/$repositoryName/items"

Copilot · 2026-04-16T21:36:36Z

+
+      foreach ($file in $files) {
+        $url = "${baseUrl}?path=${jitTracePath}/${file}&download=true&api-version=7.1"
+        $dest = Join-Path $targetDir $file
+        Write-Host "Downloading $file from functions-release (${jitTracePath})..."
+        try {
+          Invoke-RestMethod -Uri $url -Headers $headers -OutFile $dest -MaximumRetryCount 3 -RetryIntervalSec 5 -ErrorAction Stop
+          $lineCount = (Get-Content $dest | Measure-Object -Line).Lines
+          Write-Host "Downloaded $file ($lineCount lines) to $dest"


The download call has no explicit timeout, so a transient network stall can hang the job for a long time. Also, Get-Content reads the entire jittrace file to count lines, which can be very slow/memory-heavy. Consider adding a reasonable -TimeoutSec and logging/validating via file size (e.g., Get-Item) instead of reading the full content.

Suggested change

foreach ($file in $files) {

$url = "${baseUrl}?path=${jitTracePath}/${file}&download=true&api-version=7.1"

$dest = Join-Path $targetDir $file

Write-Host "Downloading $file from functions-release (${jitTracePath})..."

try {

Invoke-RestMethod -Uri $url -Headers $headers -OutFile $dest -MaximumRetryCount 3 -RetryIntervalSec 5 -ErrorAction Stop

$lineCount = (Get-Content $dest | Measure-Object -Line).Lines

Write-Host "Downloaded $file ($lineCount lines) to $dest"

$downloadTimeoutSec = 300

foreach ($file in $files) {

$url = "${baseUrl}?path=${jitTracePath}/${file}&download=true&api-version=7.1"

$dest = Join-Path $targetDir $file

Write-Host "Downloading $file from functions-release (${jitTracePath})..."

try {

Invoke-RestMethod -Uri $url -Headers $headers -OutFile $dest -MaximumRetryCount 3 -RetryIntervalSec 5 -TimeoutSec $downloadTimeoutSec -ErrorAction Stop

$downloadedFile = Get-Item -Path $dest -ErrorAction Stop

if ($downloadedFile.Length -le 0) {

throw "Downloaded file '$file' is empty."

}

Write-Host "Downloaded $file ($($downloadedFile.Length) bytes) to $dest"

jviau · 2026-04-16T21:39:56Z

+  # Download the latest out-of-proc JIT trace files from functions-release and place them
+  # in PreJIT/ so they are included in the host publish output. The files have been removed
+  # from the host repo; this step is the sole source of truth.
+  - pwsh: |


Azure pipelines has first-class support for fetching artifacts from another pipeline. Any reason we are not using that here?

The JIT trace files are committed files in the functions-release repository (dev), not pipeline artifacts. DownloadPipelineArtifact only works for artifacts published by pipeline runs.
To access these files, I will use a repository resource with a checkout of the other repo instead.

…ld time The JIT trace files in src/WebJobs.Script.WebHost/PreJIT/ were stale because the canonical source of truth moved to the functions-release repo (artifacts/Host/JitTrace/dev/). This change: - Deletes coldstart.jittrace and linux.coldstart.jittrace from PreJIT/ - Adds functions-release as an ADO repository resource in host.coldstart.yml - Adds checkout + copy steps in run-coldstart.yml to place the latest JIT trace files in PreJIT/ before dotnet publish - Extracts the repo path to jitTraceRepoPath variable in coldstart.yml - No changes to the .csproj glob (PreJIT\*.jittrace) or merge-jittrace.yml

Francisco-Gamino · 2026-04-17T01:51:51Z

This PR has been replaced by #11722.

Francisco-Gamino requested review from eliaslopezgt, pragnagopa and vrdmr as code owners April 16, 2026 21:31

Copilot AI review requested due to automatic review settings April 16, 2026 21:31

Francisco-Gamino requested a review from a team as a code owner April 16, 2026 21:31

Copilot started reviewing on behalf of Francisco-Gamino April 16, 2026 21:32 View session

Francisco-Gamino requested review from jviau and kshyju April 16, 2026 21:35

Copilot AI reviewed Apr 16, 2026

View reviewed changes

jviau reviewed Apr 16, 2026

View reviewed changes

Francisco-Gamino force-pushed the Francisco-Gamino/fetch-jittrace-from-functions-release branch from 931a9b3 to 3c3e594 Compare April 16, 2026 23:09

Remove accidental .NET 10 SDK install step

7044d74

Francisco-Gamino closed this Apr 17, 2026

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Fetch Host JIT trace files from functions-release at build time#11719

Fetch Host JIT trace files from functions-release at build time#11719
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Francisco-Gamino/fetch-jittrace-from-functions-release

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-      $baseUrl = "https://dev.azure.com/azfunc/internal/_apis/git/repositories/functions-release/items"
+      $collectionUri = "$(System.CollectionUri)".TrimEnd('/')
+      $teamProject = "$(System.TeamProject)"
+      $repositoryName = "functions-release"
+      $baseUrl = "$collectionUri/$teamProject/_apis/git/repositories/$repositoryName/items"

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Francisco-Gamino commented Apr 16, 2026

Issue describing the changes in this PR

Changes

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