Improve user id handling

[guarin]

What has changed and why?

How has it been tested?

• Unit tests

Did you update CHANGELOG.md?

• Yes
• Not needed (internal change)

Did you update the documentation?

• Yes
• Not needed (internal change without effects for user)

[guarin]

/review

[chatgpt-codex-connector]

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Reviewed commit: 23a8f36718

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[Copilot]

Pull request overview

This PR replaces the ephemeral per-process analytics identifier with a persistent user ID stored under the Lightly Train cache directory, and updates/extends unit tests to validate the new behavior.

Changes:

• Introduce _user_id and _load_user_id() to persist a UUID in userid.txt under Env.LIGHTLY_TRAIN_CACHE_DIR.
• Update event payload distinct_id to use the persisted _user_id rather than a session UUID.
• Expand tracker unit tests to cover file creation, reading an existing ID, and read/write error fallbacks.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/lightly_train/_events/tracker.py	Implements persistent user ID loading/creation and uses it as distinct_id for event tracking.
tests/_events/test_tracker.py	Updates existing assertions and adds tests for _load_user_id() file-based persistence and error fallbacks.

Comments suppressed due to low confidence (1)

src/lightly_train/_events/tracker.py:154

• track_event initializes _user_id (and may read/write userid.txt) before checking LIGHTLY_TRAIN_EVENTS_DISABLED / rate-limiting / queue-size early returns. This introduces a side effect (creating a persistent identifier file) even when analytics are disabled or the event is dropped. Consider moving the _user_id lazy-load to just before building event_data, after all early-return checks (at least after the events-disabled guard).

    global _last_flush, _user_id
    if _user_id is None:
        _user_id = _load_user_id()

    current_time = time.time()
    if Env.LIGHTLY_TRAIN_EVENTS_DISABLED.value or (
        current_time - _last_event_time.get(event_name, -100.0) < _RATE_LIMIT_SECONDS
    ):
        return

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: b527e02a18

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[guarin]

/review

[yutong-xiang-97]

Approved