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feat(cmp): add stdin support for Config Management Plugins#25917

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feat(cmp): add stdin support for Config Management Plugins#25917
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glennpratt:plugin-stdin

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@glennpratt glennpratt commented Jan 9, 2026 •
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This change introduces a new stdin field to the Application spec under source.plugin.stdin. The stdin value is interpolated with standard build environment variables and then passed via standard input to the CMP's generate, discover, and parameters commands.

This allows passing large payloads to plugins without hitting exceeding limits on things passed as argument to execve, including environment variables:

  • Linux MAX_ARG_STRLEN is 128 KB (a single argument, e.g. a single environment variable)
  • Linux MAX_ARG is generally 2 MB

Both of these appear as fork/exec $path: argument list too long errors.

Fixes #17914

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@glennpratt glennpratt mentioned this pull request Jan 9, 2026
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@glennpratt
feat(cmp): add stdin support for Config Management Plugins
2f5b4cd 
This change introduces a new `stdin` field to the Application spec under `source.plugin.stdin`.
The `stdin` value is interpolated with standard build environment variables and then passed
via standard input to the CMP's `generate`, `discover`, and `parameters` commands.

This allows passing large payloads to plugins without hitting exceeding limits
on environment variables passing through execve:
- Linux MAX_ARG_STRLEN is 128 KB
- Linux MAX_ARG is generally 2 MB

Both of these appear as `fork/exec PATH: argument list too long` errors.

Fixes argoproj#17914

Signed-off-by: Glenn Pratt <gpratt@akamai.com>
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taliesins commented Feb 24, 2026

We have run into this issue as well. If we could just write directly to a temp file and then refer to the temp file that would be great too.

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Successfully merging this pull request may close these issues.

Argument list too long. In an argoCD sidecar plugin.

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@glennpratt @taliesins