in_tail: permission error handling

[kyo-ke]

Changer glob logic for tail input plugin.
Currently if path wildcard matches directories which have insufficient permission, entire tail plugin will fail.
By this PR just show warn and keep reading from file with sufficient permission and just show warning.

#10656

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• New Features

  • Added a configuration option to skip directories with permission errors during scanning, allowing continued processing of accessible directories.

• Bug Fixes

  • Enhanced error handling to avoid scan failures caused by permission issues when the new skip option is enabled.

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Walkthrough

A new boolean configuration option, skip_permission_errors, has been introduced to the in_tail plugin. This option allows the plugin to skip directories with permission errors during glob scanning, instead of failing entirely. Supporting logic was added to the configuration structure and the glob scanning function to implement this behavior.

Changes

Cohort / File(s)	Change Summary
Config Option Addition plugins/in_tail/tail.c, plugins/in_tail/tail_config.h	Introduced the skip_permission_errors boolean option in the config map and added an int skip_permission_errors field to the flb_tail_config struct.
Glob Scanning Logic plugins/in_tail/tail_scan_glob.c	Updated tail_scan_path to check the skip_permission_errors flag. On permission error (GLOB_ABORTED), logs a warning and retries glob scan (without GLOB_ERR) if skipping is enabled.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant TailPlugin
    participant FileSystem

    User->>TailPlugin: Start plugin with skip_permission_errors option
    TailPlugin->>FileSystem: Perform glob scan (with GLOB_ERR)
    FileSystem-->>TailPlugin: Permission error (GLOB_ABORTED)
    alt skip_permission_errors enabled
        TailPlugin->>TailPlugin: Log warning, retry glob scan (without GLOB_ERR)
        FileSystem-->>TailPlugin: Return accessible files/directories
        TailPlugin->>User: Continue processing
    else skip_permission_errors disabled
        TailPlugin->>User: Fail plugin initialization
    end

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related issues

• Tail plugin permission error handling for extracrting paths(glob error handling) #10656: Implements the same skip_permission_errors option and modifies glob scanning logic to handle permission errors, directly matching the changes in this PR.

Poem

A bunny hopped through files galore,
Skipping errors it found at the door.
"Permission denied?" it gave a shrug—
Retries the scan with a gentle tug.
Now logs are gathered, neat and bright,
Even when some doors are shut tight!
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between 3c8411f and 90999fb.

📒 Files selected for processing (3)

• plugins/in_tail/tail.c (1 hunks)
• plugins/in_tail/tail_config.h (1 hunks)
• plugins/in_tail/tail_scan_glob.c (1 hunks)

✅ Files skipped from review due to trivial changes (1)

• plugins/in_tail/tail.c

🚧 Files skipped from review as they are similar to previous changes (2)

• plugins/in_tail/tail_scan_glob.c
• plugins/in_tail/tail_config.h

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[sandy2008]

Thanks @kyo-ke 🙌 — solid work on the glob fallback logic!

The new skip_permission_errors option makes the tail input plugin far more resilient in real-world scenarios where permission inconsistencies are common (especially in multi-tenant environments or containerized workloads).

We've tested the changes with a mix of readable and unreadable directories, and the plugin now gracefully logs warnings and continues scanning valid paths as expected. No memory leaks observed via Valgrind, and everything looks clean on our end.