Add missing mutex to tail.reader usage by dehaansa · Pull Request #4829 · grafana/alloy

dehaansa · 2025-11-13T05:31:44Z

PR Description

Race detected in tests.

WARNING: DATA RACE
Read at 0x00c0057833b0 by goroutine 1267:
  bufio.(*Reader).Buffered()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:339 +0x1b2
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).Tell()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:136 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).markPositionAndSize()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:354 +0x3ee
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).stop()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:370 +0x46
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:186 +0x3f3
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:120 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[github.com/grafana/alloy/internal/component/common/loki/positions.Entry]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:116 +0x4a
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:50 +0x37
  sync.(*WaitGroup).Go.func1()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:239 +0x5d

Previous write at 0x00c0057833b0 by goroutine 1271:
  bufio.(*Reader).reset()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:88 +0x2c5
  bufio.(*Reader).Reset()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:84 +0x234
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).seekTo()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:397 +0x16f
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).tailFileSync()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:294 +0x3b8
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.TailFile.gowrap1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:109 +0x33

Goroutine 1267 (running) created at:
  sync.(*WaitGroup).Go()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:237 +0x86
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:49 +0x304
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).scheduleSources-range1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:342 +0x128f
  github.com/grafana/alloy/internal/component/loki/source/file.(*staticResolver).Resolve.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/resolver.go:45 +0x166
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).scheduleSources()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:290 +0x229
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).Update()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:278 +0x424
  github.com/grafana/alloy/internal/component/loki/source/file.New()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:169 +0x546
  github.com/grafana/alloy/internal/component/loki/source/file.init.0.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:32 +0x177
  github.com/grafana/alloy/internal/runtime/componenttest.(*Controller).buildComponent()
      /home/runner/work/alloy/alloy/internal/runtime/componenttest/componenttest.go:192 +0x527
  github.com/grafana/alloy/internal/runtime/componenttest.(*Controller).Run()
      /home/runner/work/alloy/alloy/internal/runtime/componenttest/componenttest.go:130 +0x131
  github.com/grafana/alloy/internal/component/loki/source/file.TestLegacyConversion.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/legacy_file_test.go:61 +0x3c8

Goroutine 1271 (running) created at:
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.TailFile()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:109 +0x4e4
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).initRun()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:229 +0xa3d
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:156 +0x79
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:120 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[github.com/grafana/alloy/internal/component/common/loki/positions.Entry]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:116 +0x4a
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:50 +0x37
  sync.(*WaitGroup).Go.func1()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:239 +0x5d
==================
==================
WARNING: DATA RACE
Read at 0x00c0057833a8 by goroutine 1267:
  bufio.(*Reader).Buffered()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:339 +0x1d0
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).Tell()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:136 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).markPositionAndSize()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:354 +0x3ee
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).stop()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:370 +0x46
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:186 +0x3f3
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:120 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[github.com/grafana/alloy/internal/component/common/loki/positions.Entry]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:116 +0x4a
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:50 +0x37
  sync.(*WaitGroup).Go.func1()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:239 +0x5d

Previous write at 0x00c0057833a8 by goroutine 1271:
  bufio.(*Reader).reset()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:88 +0x2c5
  bufio.(*Reader).Reset()
      /opt/hostedtoolcache/go/1.25.1/x64/src/bufio/bufio.go:84 +0x234
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).seekTo()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:397 +0x16f
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.(*Tail).tailFileSync()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:294 +0x3b8
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.TailFile.gowrap1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:109 +0x33

Goroutine 1267 (running) created at:
  sync.(*WaitGroup).Go()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:237 +0x86
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:49 +0x304
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).scheduleSources-range1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:342 +0x128f
  github.com/grafana/alloy/internal/component/loki/source/file.(*staticResolver).Resolve.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/resolver.go:45 +0x166
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).scheduleSources()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:290 +0x229
  github.com/grafana/alloy/internal/component/loki/source/file.(*Component).Update()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:278 +0x424
  github.com/grafana/alloy/internal/component/loki/source/file.New()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:169 +0x546
  github.com/grafana/alloy/internal/component/loki/source/file.init.0.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/file.go:32 +0x177
  github.com/grafana/alloy/internal/runtime/componenttest.(*Controller).buildComponent()
      /home/runner/work/alloy/alloy/internal/runtime/componenttest/componenttest.go:192 +0x527
  github.com/grafana/alloy/internal/runtime/componenttest.(*Controller).Run()
      /home/runner/work/alloy/alloy/internal/runtime/componenttest/componenttest.go:130 +0x131
  github.com/grafana/alloy/internal/component/loki/source/file.TestLegacyConversion.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/legacy_file_test.go:61 +0x3c8

Goroutine 1271 (running) created at:
  github.com/grafana/alloy/internal/component/loki/source/file/internal/tail.TailFile()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/internal/tail/tail.go:109 +0x4e4
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).initRun()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:229 +0xa3d
  github.com/grafana/alloy/internal/component/loki/source/file.(*tailer).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/tailer.go:156 +0x79
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:120 +0x178
  github.com/grafana/alloy/internal/component/loki/source/file.(*SourceWithRetry[github.com/grafana/alloy/internal/component/common/loki/positions.Entry]).Run()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:116 +0x4a
  github.com/grafana/alloy/internal/component/loki/source/file.(*Scheduler[go.shape.struct { Path string "yaml:\"path\""; Labels string "yaml:\"labels\"" }]).ScheduleSource.func1()
      /home/runner/work/alloy/alloy/internal/component/loki/source/file/scheduler.go:50 +0x37
  sync.(*WaitGroup).Go.func1()
      /opt/hostedtoolcache/go/1.25.1/x64/src/sync/waitgroup.go:239 +0x5d

kalleep

Thanks, there are for sure more issues around locking in this package. I have done some improvements to it but we need to review the package as a whole.

Add mutex to missing tail.reader usage

9030132

dehaansa requested a review from a team as a code owner November 13, 2025 05:31

dehaansa changed the title ~~Add mutex to missing tail.reader usage~~ Add missing mutex to tail.reader usage Nov 13, 2025

dehaansa mentioned this pull request Nov 13, 2025

OTel v0.139.0 #4816

Merged

4 tasks

kalleep approved these changes Nov 13, 2025

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kalleep merged commit 65fda47 into main Nov 13, 2025
41 checks passed

kalleep deleted the tail-race branch November 13, 2025 08:32

dehaansa added a commit to madhub/alloy that referenced this pull request Dec 10, 2025

Add mutex to missing tail.reader usage (grafana#4829)

63ffd2b

github-actions Bot added the frozen-due-to-age label Dec 19, 2025

github-actions Bot locked as resolved and limited conversation to collaborators Dec 19, 2025

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Add missing mutex to tail.reader usage#4829

Add missing mutex to tail.reader usage#4829
kalleep merged 1 commit into
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dehaansa commented Nov 13, 2025

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dehaansa commented Nov 13, 2025

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