RUM-16501: Make file write atomic

[0xnm]

What does this PR do?

We may have a write failure, leading to the corrupted TLV block. This makes further read fail.

This PR makes file write atomic: we will try to rollback to the previous state if write failed.

The approach used is basically to record the original file size and truncate to that mark if write fails. It should work fine even if there is not enough space on the disk.

This change doesn't cover the situation when there is a process death, such case is harder to deal with. Maybe this change will be enough to get rid of majority read errors.

Performance impact

  ┌──────────────────────────┬────────────────────────┬───────────────────────────────────────────────────────────────────────────────────────────┬──────────────────────────────────────────────┐
  │        Operation         │         Before         │                                           After                                           │                      Δ                       │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ open()                   │ FileOutputStream       │ RandomAccessFile("rw")                                                                    │ same — both single syscalls, comparable cost │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ flock                    │ yes                    │ yes                                                                                       │ unchanged                                    │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ fstat for channel.size() │ —                      │ +1 syscall                                                                                │ ~1 µs                                        │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ ftruncate                │ —                      │ append=true: no-op (JDK short-circuits when new size ≥ current); append=false: +1 syscall │ 0 to ~2 µs                                   │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ lseek/position update    │ —                      │ in-memory field update, no syscall on Linux JDK                                           │ ~0                                           │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ write()                  │ one big buffered write │ same write() call, just looped for short-write safety                                     │ ~same                                        │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ buffer.flip()            │ —                      │ field update                                                                              │ ~0                                           │
  ├──────────────────────────┼────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────────────────┤
  │ close()                  │ yes                    │ yes                                                                                       │ unchanged                                    │
  └──────────────────────────┴────────────────────────┴───────────────────────────────────────────────────────────────────────────────────────────┴──────────────────────────────────────────────┘

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[aleksandr-gringauz]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

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[hamorillo]

🚀

[0xnm]

/ddci trigger

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-05-27 14:58:51 UTC ℹ️ Start processing command /ddci trigger

---

2026-05-27 14:59:08 UTC ℹ️ Devflow: /ddci trigger

Tasks sourcing running asynchronously in workflow devflow:c928ba52-e583-413b-99fa-e7f74ee950df_46:019e69f2-115c-7c12-a979-e65a20700554 under run id 019e69f2-4e13-702f-b7c2-b16156ad8d0b

[codecov-commenter]

Codecov Report

❌ Patch coverage is 71.42857% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.39%. Comparing base (a8fb3c6) to head (a35f4be).
⚠️ Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
...rsistence/file/batch/PlainBatchFileReaderWriter.kt	71.43%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3476      +/-   ##
===========================================
+ Coverage    72.28%   72.39%   +0.11%     
===========================================
  Files          964      964              
  Lines        35561    35576      +15     
  Branches      5922     5926       +4     
===========================================
+ Hits         25703    25753      +50     
+ Misses        8250     8234      -16     
+ Partials      1608     1589      -19     

Files with missing lines	Coverage Δ
...rsistence/file/batch/PlainBatchFileReaderWriter.kt	75.78% <71.43%> (+0.11%)	⬆️

... and 32 files with indirect coverage changes

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