out_influxdb: documentation for tag prefix stripping

[ueli-g]

Documentation to go with fluent/fluent-bit#9427

This removes a defined prefix from measurement names which might otherwise be shared between many measurements in the same data bucket. Compatibility is not affected, default behavior (with documented default strip_prefix "") is to strip zero character from the front which identical to the existing mechanism.

When writing to a range of different buckets, routing to the corresponding out_influxdb instances happens on tag matches. This change allows to match on tag prefixes, but strip them from the measurement name. This avoids having identical prefixes for all measurement names in the same data bucket.

To achieve this, read from char tag[] with an offset when writing the measurement name, provided the prefix matches the tag completely and the overlap is at most tag_length - 1 characters.

Summary by CodeRabbit

Release Notes

• New Features
  • Added strip_prefix configuration parameter for InfluxDB output to remove exact prefixes from measurement names, simplifying event tag normalization.
  • Updated documentation with configuration examples and detailed usage guidance.

[patrick-stephens]

@fluent/chronosphere-tech-writers should we be ensuring we add YAML config as well now always?

[eschabell]

@esmerel can you review please, but leave open as code PR fluent/fluent-bit#9427 must merge first and is still open.

[eschabell]

@ueli-g can you resolve the conflicts and provide YAML config example (if you need help with that, happy to provide)? I also nudged you on the code PR fluent/fluent-bit#9427

[esmerel]

I fixed the merge conflicts and made review updates while I was fixing it since I was already in there.

[patrick-stephens]

Config example needs updating to latest standard.

[ueli-g]

@eschabell thank you for the review. I added a yaml config example as requested and added more information on the behaviour. please let me know if there is anything else I can do to move this forward.

[ueli-g]

Config example needs updating to latest standard.

@patrick-stephens can you please have another look and let me know if this is more appropriate?

[eschabell]

@ueli-g would you mind sorting out the conflicts now showing up for this PR?

[coderabbitai]

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ℹ️ Review info

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Reviewing files that changed from the base of the PR and between acf18a3 and 36a6fbb.

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• pipeline/outputs/influxdb.md

📝 Walkthrough

Walkthrough

Documentation for a new strip_prefix configuration parameter was added to the InfluxDB output plugin. This parameter removes exact prefixes from event tags when deriving InfluxDB measurement names, with constraints and example configurations included.

Changes

Cohort / File(s)	Summary
InfluxDB Output Documentation pipeline/outputs/influxdb.md	Added strip_prefix configuration parameter documentation, including a "Prefix stripping" section explaining the feature's behavior, constraints, and example configurations in YAML and fluent-bit.conf formats.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A prefix stripped away so clean,
InfluxDB tags now precise and keen,
With strip_prefix at your side,
Measurement names have room to glide!
~CodeRabbit

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and clearly describes the main change: adding documentation for the tag prefix stripping feature in the out_influxdb output plugin.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (1)

pipeline/outputs/influxdb.md (1)

154-164: Consider clarifying the input configuration in the example.

All four inputs use name: cpu even though the tags suggest different hardware types (gpu). While this is technically valid and simplifies the example to focus on routing and prefix stripping, it might be slightly confusing. Consider adding a brief comment explaining that the same input plugin is used with different tags for demonstration purposes, or acknowledging that in a real scenario, gpu tags might come from different sources.

💡 Optional clarification

You could add a comment above the inputs section like:

 ```yaml
 pipeline:
   inputs:
+    # Using cpu plugin with different tags to demonstrate routing and prefix stripping
     - name: cpu
       tag: cpu.one

Or in prose before the example:

-When collecting data from many inputs into many buckets, it can be helpful to remove a common prefix using `Strip_prefix`.
+When collecting data from many inputs into many buckets, it can be helpful to remove a common prefix using `Strip_prefix`. The following example uses the same input plugin with different tags to demonstrate how prefix stripping works with pattern-based routing.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@pipeline/outputs/influxdb.md` around lines 154 - 164, The example under
pipeline.inputs uses name: cpu for all four entries which can confuse readers
because tags include gpu; update the example to either (a) add a brief inline
comment above the inputs (referencing pipeline.inputs and the name: cpu entries)
explaining that the cpu plugin is intentionally reused with different tags for
demonstration of routing/prefix stripping, or (b) change the relevant entries to
use a more representative name (e.g., name: gpu) for gpu.* tags so tag names and
input plugin names align; ensure the comment or rename clearly references the
tag values (cpu.one, cpu.two, gpu.one, gpu.two) so readers understand the
intent.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@pipeline/outputs/influxdb.md`:
- Line 25: The documentation shows an inconsistency for the option strip_prefix:
the description says it defaults to an empty string but the Default column shows
"_none_"; update the Default column entry for strip_prefix to an explicit
empty-string representation (e.g., `""`) so it matches the textual description
and makes the default behavior clear; locate the table row referencing
strip_prefix and change the Default cell to `""` while leaving the description
and other cells unchanged.
- Around line 186-213: The fluent-bit.conf influxdb OUTPUT examples are missing
the Host and Port parameters shown in the YAML example; update both influxdb
OUTPUT blocks (the ones matching "cpu*" and "gpu*") to include Host and Port
entries (e.g., Host and Port keys alongside Name, Match, Bucket, and
Strip_prefix) so the two examples are consistent and clearly show the connection
endpoint settings.

---

Nitpick comments:
In `@pipeline/outputs/influxdb.md`:
- Around line 154-164: The example under pipeline.inputs uses name: cpu for all
four entries which can confuse readers because tags include gpu; update the
example to either (a) add a brief inline comment above the inputs (referencing
pipeline.inputs and the name: cpu entries) explaining that the cpu plugin is
intentionally reused with different tags for demonstration of routing/prefix
stripping, or (b) change the relevant entries to use a more representative name
(e.g., name: gpu) for gpu.* tags so tag names and input plugin names align;
ensure the comment or rename clearly references the tag values (cpu.one,
cpu.two, gpu.one, gpu.two) so readers understand the intent.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

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📒 Files selected for processing (1)

• pipeline/outputs/influxdb.md

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Inconsistency between Default column and description.

The Default column shows "none" but the description explicitly states "strip_prefix defaults to empty string, which does nothing." These should be consistent. Consider changing the Default column to "" (empty string) to match the described behavior.

📝 Proposed fix

-| `strip_prefix` | String prefix to be removed from the front of `tag` when writing InfluxDB measurement names. `strip_prefix` is removed only if it matches exactly at the beginning of and is strictly shorter than `tag` (`tag` length will not be reduced to zero if `strip_prefix` and `tag` are identical strings). `strip_prefix` defaults to empty string, which does nothing. | _none_ |
+| `strip_prefix` | String prefix to be removed from the front of `tag` when writing InfluxDB measurement names. `strip_prefix` is removed only if it matches exactly at the beginning of and is strictly shorter than `tag` (`tag` length will not be reduced to zero if `strip_prefix` and `tag` are identical strings). `strip_prefix` defaults to empty string, which does nothing. | `""` |

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	| `strip_prefix` | String prefix to be removed from the front of `tag` when writing InfluxDB measurement names. `strip_prefix` is removed only if it matches exactly at the beginning of and is strictly shorter than `tag` (`tag` length will not be reduced to zero if `strip_prefix` and `tag` are identical strings). `strip_prefix` defaults to empty string, which does nothing. | _none_ |
	| `strip_prefix` | String prefix to be removed from the front of `tag` when writing InfluxDB measurement names. `strip_prefix` is removed only if it matches exactly at the beginning of and is strictly shorter than `tag` (`tag` length will not be reduced to zero if `strip_prefix` and `tag` are identical strings). `strip_prefix` defaults to empty string, which does nothing. | `""` |

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@pipeline/outputs/influxdb.md` at line 25, The documentation shows an
inconsistency for the option strip_prefix: the description says it defaults to
an empty string but the Default column shows "_none_"; update the Default column
entry for strip_prefix to an explicit empty-string representation (e.g., `""`)
so it matches the textual description and makes the default behavior clear;
locate the table row referencing strip_prefix and change the Default cell to
`""` while leaving the description and other cells unchanged.

[ueli-g]

@edsiper thank you for your review, updated accordingly.

This has remained open for a while now, please let me know if there is anything that I can do or that I am missing to help move this and the corresponding feature in fluent-bit along.

[eschabell]

@ueli-g small fix here needed for vale check.

[eschabell]

@ueli-g please format all yaml and classic config example code with 2 spaced indents (currently using 4?).