feat: add framework-level validation for conflicting env vars across …

[krishdef7]

What this PR does / why we need it

Adds framework-level validation to detect conflicts between environment variables managed by different runtime plugins (MPI, Torch), and between plugin-reserved envs and user-provided envs in a TrainJob.

Changes

• Add MPIRunReservedEnvNames constant for OpenMPI reserved env vars
• Add user-env conflict validation to MPI plugin (mirrors existing Torch pattern)
• Add EnvVarsReserverPlugin interface for plugins to expose reserved env var names
• Implement ReservedEnvVarNames() on MPI and Torch plugins
• Add cross-plugin env conflict detection in RunCustomValidationPlugins
• Add unit tests for MPI env validation

Which issue(s) this PR fixes

Closes #3147

[google-oss-prow]

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[Copilot]

Pull request overview

This PR adds framework-level validation to detect conflicts between environment variables managed by different runtime plugins (MPI, Torch) and between plugin-reserved envs and user-provided envs in a TrainJob.

Changes:

• Introduces EnvVarsReserverPlugin interface for plugins to expose reserved environment variable names
• Implements the interface on MPI and Torch plugins to return their respective reserved env var sets
• Adds cross-plugin env conflict detection in the framework's validation logic
• Adds user-env conflict validation to the MPI plugin (mirroring existing Torch pattern)
• Adds comprehensive test coverage for MPI env validation

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pkg/runtime/framework/interface.go	Defines new EnvVarsReserverPlugin interface for exposing reserved env var names
pkg/runtime/framework/core/framework.go	Implements cross-plugin env conflict detection in RunCustomValidationPlugins
pkg/runtime/framework/plugins/mpi/mpi.go	Implements EnvVarsReserverPlugin and adds user-env validation
pkg/runtime/framework/plugins/torch/torch.go	Implements EnvVarsReserverPlugin interface
pkg/constants/constants.go	Defines MPIRunReservedEnvNames set with OpenMPI reserved env vars
pkg/runtime/framework/plugins/mpi/mpi_test.go	Adds tests for MPI reserved env validation

[krishdef7]

Hi @jinchihe @kuizhiqing,

Adding a quick concrete example to clarify the validation:

If a user configures:

• MPI plugin (reserves OMPI_* envs)
• Torch plugin
• and manually sets OMPI_MCA_orte_default_hostfile in spec.trainer.env

This currently passes validation but can lead to runtime issues.

With this PR, validation fails early with a clear error indicating the conflicting env.

Happy to adjust the validation scope or placement if needed.