AttributeError: Unrecognized option 'task-runtime-metric-buckets' when accessing 'events' key in shelve db file

[krishnakumar18]

I'm running the flower app with persistent and db options to save the task statues to the file flower.db. When i try to open this shelve file and print the keys present in it, i only get one key events. When i try to access the value of db[events], i get the following error in Prometheus client, AttributeError: Unrecognized option 'task-runtime-metric-buckets'

How i start the flower app :-
celery -A project --broker=broker_url flower --port=5555 --persistent=True --db=flower_db.db

The code i used to read from the shelve file :-

import shelve
with shelve.open("flower_db.db", 'r') as db:
    keys = db.keys()
    # the for loop below prints `events`
    for key in keys:
        print(key)
    # this print statement errors out
    print(db['events'])

This is the full trace of the error :-

File ~/opt/anaconda3/lib/python3.10/site-packages/flower/events.py:72, in EventsState.__init__(self, *args, **kwargs)
     70 super(EventsState, self).__init__(*args, **kwargs)
     71 self.counter = collections.defaultdict(Counter)
---> 72 self.metrics = get_prometheus_metrics()

File ~/opt/anaconda3/lib/python3.10/site-packages/flower/events.py:31, in get_prometheus_metrics()
     29 global prometheus_metrics
     30 if prometheus_metrics is None:
---> 31     prometheus_metrics = PrometheusMetrics()
     33 return prometheus_metrics

File ~/opt/anaconda3/lib/python3.10/site-packages/flower/events.py:46, in PrometheusMetrics.__init__(self)
     39 self.events = PrometheusCounter('flower_events_total', "Number of events", ['worker', 'type', 'task'])
     42 self.runtime = Histogram(
     43     'flower_task_runtime_seconds',
     44     "Task runtime",
     45     ['worker', 'task'],
---> 46     buckets=options.task_runtime_metric_buckets
     47 )
     48 self.prefetch_time = Gauge(
     49     'flower_task_prefetch_time_seconds',
     50     "The time the task spent waiting at the celery worker to be executed.",
     51     ['worker', 'task']
     52 )
     53 self.number_of_prefetched_tasks = Gauge(
     54     'flower_worker_prefetched_tasks',
     55     'Number of tasks of given type prefetched at a worker',
     56     ['worker', 'task']
     57 )

File ~/opt/anaconda3/lib/python3.10/site-packages/tornado/options.py:158, in OptionParser.__getattr__(self, name)
    156 if isinstance(self._options.get(name), _Option):
    157     return self._options[name].value()
--> 158 raise AttributeError("Unrecognized option %r" % name)

AttributeError: Unrecognized option 'task-runtime-metric-buckets'

To Reproduce
Steps to reproduce the behavior:

1. Run flower app with persistent and db settings
2. Read the shelve file specified in db settings in python
3. Print the value of the key events

Expected behavior
db[events] should print the list of events that flower collected

System information

flower   -> flower:1.2.0 tornado:6.3.3 humanize:4.8.0
software -> celery:5.3.1 (emerald-rush) kombu:5.3.1 py:3.10.13
            billiard:4.1.0 py-amqp:5.1.1
platform -> system:Darwin arch:64bit
            kernel version:21.5.0 imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:amqp results:disabled

deprecated_settings: None

[krishnakumar18]

This could be related to this issue :- #1134
Tagging the relevant folks :- @mher @Tomasz-Kluczkowski. Please take a look at this issue.
Thanks!