Fix: Container Names Missing from Uploaded Profile Data

[artursarlo]

Fix: Container Names Missing from Uploaded Profile Data

Problem

When the --flamegraph flag is enabled, uploaded profiles were always reporting an empty containers list in the profile metadata, causing container attribution to be lost on the backend.

The root cause was a side effect in _make_profile_metadata (merge.py): every time it is called with a non-None container_names_client, it reads and then immediately clears the container name cache via container_names_client.reset_cache().

The pre-generation block in _snapshot — which creates a temporary merged result solely to generate the flamegraph_html — was passing the real self._profiler_state.container_names_client to both concatenate_profiles and merge_profiles. This caused reset_cache() to be called during the temporary merge, draining the cache before the actual merged_result (which is what gets uploaded) had a chance to consume it.

Fix

Pass container_names_client=None in both temporary merge calls (concatenate_profiles and merge_profiles) inside the flamegraph pre-generation block.

Container names are not needed by the temporary merge — its output is only used to extract stripped stack data for flamegraph rendering. Passing None skips the cache read entirely, preserving the container names for the real merge that follows.

Impact

• Before: metadata["containers"] was always [] in uploaded profiles when --flamegraph was enabled.
• After: metadata["containers"] is correctly populated, matching the behavior when --flamegraph is disabled.
• No change to flamegraph generation logic or output.