OTLP exporter fails silently on connection timeout

[Nancy-Chauhan]

Description\n\nWhen the Acme endpoint times out during an OTLP export, the exporter catches the exception and returns a success result with 0 exported spans. This is misleading because the caller thinks export succeeded.\n\n## Expected behavior\n\nThe ExportResult should indicate failure with an appropriate error message.\n\n## Steps to reproduce\n\n1. Configure client with a very short timeout (e.g., 0.001s)\n2. Export spans\n3. Observe that result.success is True but exported_count is 0\n\n## Environment\n- Python 3.11\n- acme-sdk 1.1.0\n- macOS 14.0

[Nancy-Chauhan]

I can reproduce this. The issue is in the _send method — when httpx.TimeoutException is raised, it gets caught by the retry logic but after retries are exhausted, the exception isn't propagated to the ExportResult.\n\nLooking at otlp.py line 68-75, the try/except only catches HTTPStatusError, not TimeoutException.

[Nancy-Chauhan]

Good catch. I think we need to handle httpx.TimeoutException separately in the OTLP exporter's export method, not just rely on the retry layer. The exporter should always surface transport errors in the ExportResult.\n\nI'll pick this up after the batch shutdown fix lands.