Add hook examples

[Luke-Roy-IBM]

PR Description

Add Fleet Worker Customization Examples to Documentation

This PR adds documentation for two experimental examples that demonstrate how to customize fleet workers using startup hooks.

Changes Made

Added new section to serverless-fleets/README.md:

• Title: "How to customize fleet workers"
• Location: Added in the HowTo section, between "How to access logs" and "Cleanup the Environment"

New Examples Documented

1. Running Ollama on Fleet Workers (run_hook_ollama)

   • Demonstrates running Ollama (local LLM runtime) on fleet workers
   • Includes automatic GPU detection and configuration
   • Shows how to preload AI models during worker startup
   • Example use case: Running inference workloads with pre-configured LLM models

2. Running Podman-in-Podman (run_hook_podman_in_podman)

   • Demonstrates nested containerization within fleet workers
   • Shows how to preload container images during startup
   • Includes configuration for privileged containers and host path mounts
   • Example use case: Running containerized workloads within fleet tasks

Key Features Documented

• Startup Hooks: Using __CE_INTERNAL_HOOK_AFTER_STARTUP to execute setup scripts before tasks run
• Hook Configuration: Retry limits and maximum execution time settings
• Advanced Options: Privileged container mode and host path mounting for specialized workloads

Important Note

The documentation includes a clear note that this is an experimental feature that may change or be deprecated in the future, setting appropriate expectations for users.

Files Modified

• serverless-fleets/README.md - Added new "How to customize fleet workers" section

Files Referenced

• serverless-fleets/run_hook_ollama - Ollama example script
• serverless-fleets/run_hook_podman_in_podman - Podman-in-Podman example script

[reggeenr]

Great stuff - And very very useful use cases.

[reggeenr]

LGTM

Soon we should add an example that demonstrates the BEFORE_SHUTDOWN, like mimic a worker registration and de-registration

PREHOOK=$(cat <<'EOF'
#!/bin/bash

echo "Registering fleet worker '${hostname}' ..."
// TODO implement your fleet worker registration logic

EOF
)

POSTHOOK=$(cat <<'EOF'
#!/bin/bash

echo "Deregistering fleet worker '${hostname}' ..."
// TODO implement your fleet worker deregistration logic

EOF
)

Furthermore, we should add a link to the automatically injected variables, once we merged the docs PR: https://github.ibm.com/cloud-docs/codeengine/pull/1100

[jeremiaswerner]

@Luke-Roy-IBM cool, thanks a lot! this is fantastic and will help users to experiment advanced use cases... looking forward to more examples like mounting remote HPC storage systems.

Just two small changes to remove the login logic.