Fix no active span when trying to log tracing error on startup

[MadLittleMods]

Fix no active span when trying to log tracing error on startup.

Example error:

synapse.logging.opentracing - 427 - ERROR - wake_destinations_needing_catchup-0 - There was no active span when trying to log. Did you forget to start one or did a context slip?
Stack (most recent call last):
  File "/usr/lib/python3.13/threading.py", line 1014, in _bootstrap
    self._bootstrap_inner()
  File "/usr/lib/python3.13/threading.py", line 1043, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.13/threading.py", line 994, in run
    self._target(*self._args, **self._kwargs)
  File "python3.13/site-packages/twisted/_threads/_threadworker.py", line 75, in work
    task()
  File "python3.13/site-packages/twisted/_threads/_team.py", line 192, in doWork
    task()
  File "python3.13/site-packages/twisted/python/threadpool.py", line 269, in inContext
    result = inContext.theWork()  # type: ignore[attr-defined]
  File "python3.13/site-packages/twisted/python/threadpool.py", line 285, in <lambda>
    inContext.theWork = lambda: context.call(  # type: ignore[attr-defined]
  File "python3.13/site-packages/twisted/python/context.py", line 117, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "python3.13/site-packages/twisted/python/context.py", line 82, in callWithContext
    return func(*args, **kw)
  File "python3.13/site-packages/twisted/enterprise/adbapi.py", line 282, in _runWithConnection
    result = func(conn, *args, **kw)
  File "synapse/synapse/storage/database.py", line 1094, in inner_func
    return func(db_conn, *args, **kwargs)
  File "synapse/synapse/storage/database.py", line 822, in new_transaction
    opentracing.log_kv({"message": "commit"})
  File "synapse/synapse/logging/opentracing.py", line 427, in ensure_active_span_inner_2
    logger.error(

Why did this happen before?

This previously occurred because we called init_tracer(...) after the reactor started up in _base.start(). But we actually attempt some database transactions earlier than that which try to do some tracing because of that oidc = hs.get_oidc_handler() line.

Notice oidc = hs.get_oidc_handler() happened before _base.start(hs):

synapse/synapse/app/homeserver.py

Lines 397 to 408 in 5be7679

	async def start() -> None:
	# Load the OIDC provider metadatas, if OIDC is enabled.
	if hs.config.oidc.oidc_enabled:
	oidc = hs.get_oidc_handler()
	# Loading the provider metadata also ensures the provider config is valid.
	await oidc.load_metadata()
	await _base.start(hs)
	hs.get_datastores().main.db_pool.updates.start_doing_background_updates()
	register_start(hs, start)

With this PR, I've updated things to init_tracer(...) earlier on alongside where we setup_logging(...).

Dev notes

OpenTracing

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
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• Code style is correct (run the linters)

[MadLittleMods]

We setup tracing next to setup_logging which I think makes sense (early on)

[MadLittleMods]

Thanks for the review @reivilibre 🐀