Incorrect Parent Span Repro

event.json

{
  "event_id": "58cf30f61e064c59b3f6cb0e158db393",
  "project": 2301244,
  "release": null,
  "dist": null,
  "platform": "python",
  "message": "",
  "datetime": "2021-04-22T00:02:39.743010+00:00",
  "tags": [
    [
      "celery_task_id",
      "4b8ea86e-5d27-498f-a570-64d88c6bffea"
    ],
    [
      "environment",
      "production"
    ],
    [
      "level",
      "info"
    ],
    [
      "runtime",
      "CPython 3.8.2"
    ],
    [
      "runtime.name",
      "CPython"
    ],
    [
      "server_name",
      "Williams-MacBook-Pro.local"
    ],
    [
      "status",
      "ok"
    ],
    [
      "transaction",
      "main.add_together"
    ]
  ],
  "_metrics": {
    "bytes.ingested.event": 1079,
    "bytes.stored.event": 1632
  },
  "contexts": {
    "runtime": {
      "name": "CPython",
      "version": "3.8.2",
      "build": "3.8.2 (default, Oct  2 2020, 10:45:42) \n[Clang 12.0.0 (clang-1200.0.32.27)]",
      "type": "runtime"
    },
    "trace": {
      "trace_id": "81b0b4ababc34509beafa5d802f2d94f",
      "span_id": "bf51c619c015dd84",
      "parent_span_id": "88731de923d086b8",
      "op": "celery.task",
      "status": "ok",
      "type": "trace"
    }
  },
  "culprit": "main.add_together",
  "environment": "production",
  "extra": {
    "celery-job": {
      "args": [],
      "kwargs": {},
      "task_name": "main.add_together"
    },
    "sys.argv": [
      "/Users/wmak/.virtualenvs/celery-no-parent/bin/celery",
      "-A",
      "main.celery",
      "worker"
    ]
  },
  "grouping_config": {
    "enhancements": "eJybzDRxY3J-bm5-npWRgaGlroGxrpHxBABcYgcZ",
    "id": "newstyle:2019-10-29"
  },
  "key_id": "1059069",
  "level": "info",
  "location": "main.add_together",
  "logger": "",
  "metadata": {
    "location": "main.add_together",
    "title": "main.add_together"
  },
  "received": 1619049759.768175,
  "sdk": {
    "name": "sentry.python",
    "version": "1.0.0",
    "integrations": [
      "argv",
      "atexit",
      "celery",
      "dedupe",
      "excepthook",
      "flask",
      "logging",
      "modules",
      "stdlib",
      "threading"
    ],
    "packages": [
      {
        "name": "pypi:sentry-sdk",
        "version": "1.0.0"
      }
    ]
  },
  "spans": [],
  "start_timestamp": 1619049759.238811,
  "timestamp": 1619049759.74301,
  "title": "main.add_together",
  "transaction": "main.add_together",
  "type": "transaction",
  "version": "7"
}

main.py

import sentry_sdk
from sentry_sdk.integrations.flask import FlaskIntegration
from sentry_sdk.integrations.celery import CeleryIntegration

from flask import Flask
from celery import Celery


def make_celery(app):
    celery = Celery(
        app.import_name,
        backend=app.config['result_backend'],
        broker=app.config['broker_url']
    )
    celery.conf.update(
        beat_schedule={
            "time_scheduler": {
                "task": "main.add_together",
                "schedule": 5.0,  # every 5 seconds
            }
        }
    )
    celery.conf.update(app.config)

    class ContextTask(celery.Task):
        def __call__(self, *args, **kwargs):
            with app.app_context():
                return self.run(*args, **kwargs)

    celery.Task = ContextTask
    return celery

app = Flask(__name__)
app.config.update(
    broker_url='redis://localhost:6379',
    result_backend='redis://localhost:6379'
)
celery = make_celery(app)

sentry_sdk.init(
    dsn=YOUR_DSN_HERE,
    integrations=[
        CeleryIntegration(),
        FlaskIntegration(),
    ],

    # To set a uniform sample rate
    traces_sample_rate=1.0,
)

@app.route('/')
def hello_world():
    add_together.delay()
    return 'Hello, World!'

@celery.task()
def add_together():
    import time
    time.sleep(0.5)

requirements.txt

celery==4.4.7
flask==1.1.2
sentry-sdk==1.0.0
redis==3.5.3
blinker==1.4

to_reproduce.sh

# Run redis on 6379
celery -A main.celery worker  # start the celery worker
celery -A main.celery beat --loglevel=INFO --pidfile=''  # start the celerybeat
# After about 5s should see the task scheduled:
# __    -    ... __   -        _
# LocalTime -> 2021-04-21 20:02:29
# Configuration ->
#     . broker -> redis://localhost:6379//
#     . loader -> celery.loaders.app.AppLoader
#     . scheduler -> celery.beat.PersistentScheduler
#     . db -> celerybeat-schedule
#     . logfile -> [stderr]@%INFO
#     . maxinterval -> 5.00 minutes (300s)
# [2021-04-21 20:02:29,218: INFO/MainProcess] beat: Starting...
# [2021-04-21 20:02:34,258: INFO/MainProcess] Scheduler: Sending due task time_scheduler (main.add_together)