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import json
import traceback
from contextvars import copy_context
import asyncio
from functools import partial
from _plotly_utils.utils import PlotlyJSONEncoder
from dash._callback_context import context_value
from dash._utils import AttributeDict
from dash.exceptions import PreventUpdate
from dash.background_callback._proxy_set_props import ProxySetProps
from dash.background_callback.managers import BaseBackgroundCallbackManager
class CeleryManager(BaseBackgroundCallbackManager):
"""Manage background execution of callbacks with a celery queue."""
def __init__(self, celery_app, cache_by=None, expire=None):
"""
Background callback manager that runs callback logic on a celery task queue,
and stores results using a celery result backend.
:param celery_app:
A celery.Celery application instance that must be configured with a
result backend. See the celery documentation for information on
configuration options.
:param cache_by:
A list of zero-argument functions. When provided, caching is enabled and
the return values of these functions are combined with the callback
function's input arguments, triggered inputs and source code to generate cache keys.
:param expire:
If provided, a cache entry will be removed when it has not been accessed
for ``expire`` seconds. If not provided, the lifetime of cache entries
is determined by the default behavior of the celery result backend.
"""
try:
import celery # type: ignore[reportMissingImports]; pylint: disable=import-outside-toplevel,import-error
from celery.backends.base import ( # type: ignore[reportMissingImports]; pylint: disable=import-outside-toplevel,import-error
DisabledBackend,
)
except ImportError as missing_imports:
raise ImportError(
"""\
CeleryManager requires extra dependencies which can be installed doing
$ pip install "dash[celery]"\n"""
) from missing_imports
if not isinstance(celery_app, celery.Celery):
raise ValueError("First argument must be a celery.Celery object")
if isinstance(celery_app.backend, DisabledBackend):
raise ValueError("Celery instance must be configured with a result backend")
self.handle = celery_app
self.expire = expire
super().__init__(cache_by)
def terminate_job(self, job):
if job is None:
return
self.handle.control.terminate(job)
def terminate_unhealthy_job(self, job):
task = self.get_task(job)
if task and task.status in ("FAILURE", "REVOKED"):
return self.terminate_job(job)
return False
def job_running(self, job):
future = self.get_task(job)
return future and future.status in (
"PENDING",
"RECEIVED",
"STARTED",
"RETRY",
"PROGRESS",
)
def make_job_fn(self, fn, progress, key=None):
return _make_job_fn(fn, self.handle, progress, key)
def get_task(self, job):
if job:
return self.handle.AsyncResult(job)
return None
def clear_cache_entry(self, key):
self.handle.backend.delete(key)
def call_job_fn(self, key, job_fn, args, context):
task = job_fn.delay(key, self._make_progress_key(key), args, context)
return task.task_id
def get_progress(self, key):
progress_key = self._make_progress_key(key)
progress_data = self.handle.backend.get(progress_key)
if progress_data:
self.handle.backend.delete(progress_key)
return json.loads(progress_data)
return None
def result_ready(self, key):
return self.handle.backend.get(key) is not None
def get_result(self, key, job):
# Get result value
result = self.handle.backend.get(key)
if result is None:
return self.UNDEFINED
result = json.loads(result)
# Clear result if not caching
if self.cache_by is None:
self.clear_cache_entry(key)
else:
if self.expire:
# Set/update expiration time
self.handle.backend.expire(key, self.expire)
self.clear_cache_entry(self._make_progress_key(key))
self.terminate_job(job)
return result
def get_updated_props(self, key):
updated_props = self.handle.backend.get(self._make_set_props_key(key))
if updated_props is None:
return {}
self.clear_cache_entry(key)
return json.loads(updated_props)
def _make_job_fn(fn, celery_app, progress, key): # pylint: disable=too-many-statements
cache = celery_app.backend
@celery_app.task(name=f"background_callback_{key}")
def job_fn(
result_key, progress_key, user_callback_args, context=None
): # pylint: disable=too-many-statements
def _set_progress(progress_value):
if not isinstance(progress_value, (list, tuple)):
progress_value = [progress_value]
cache.set(progress_key, json.dumps(progress_value, cls=PlotlyJSONEncoder))
maybe_progress = [_set_progress] if progress else []
def _set_props(_id, props):
cache.set(
f"{result_key}-set_props",
json.dumps({_id: props}, cls=PlotlyJSONEncoder),
)
ctx = copy_context()
def run():
c = AttributeDict(**context) # type: ignore[reportCallIssue]
c.ignore_register_page = False
c.updated_props = ProxySetProps(_set_props)
context_value.set(c)
errored = False
user_callback_output = None # to help type checking
try:
if isinstance(user_callback_args, dict):
user_callback_output = fn(*maybe_progress, **user_callback_args)
elif isinstance(user_callback_args, (list, tuple)):
user_callback_output = fn(*maybe_progress, *user_callback_args)
else:
user_callback_output = fn(*maybe_progress, user_callback_args)
except PreventUpdate:
# Put NoUpdate dict directly to avoid circular imports.
errored = True
cache.set(
result_key,
json.dumps(
{"_dash_no_update": "_dash_no_update"}, cls=PlotlyJSONEncoder
),
)
except Exception as err: # pylint: disable=broad-except
errored = True
cache.set(
result_key,
json.dumps(
{
"background_callback_error": {
"msg": str(err),
"tb": traceback.format_exc(),
}
},
),
)
if not errored:
cache.set(
result_key, json.dumps(user_callback_output, cls=PlotlyJSONEncoder)
)
async def async_run():
c = AttributeDict(**context)
c.ignore_register_page = False
c.updated_props = ProxySetProps(_set_props)
context_value.set(c)
errored = False
try:
if isinstance(user_callback_args, dict):
user_callback_output = await fn(
*maybe_progress, **user_callback_args
)
elif isinstance(user_callback_args, (list, tuple)):
user_callback_output = await fn(
*maybe_progress, *user_callback_args
)
else:
user_callback_output = await fn(*maybe_progress, user_callback_args)
except PreventUpdate:
# Put NoUpdate dict directly to avoid circular imports.
errored = True
cache.set(
result_key,
json.dumps(
{"_dash_no_update": "_dash_no_update"}, cls=PlotlyJSONEncoder
),
)
except Exception as err: # pylint: disable=broad-except
errored = True
cache.set(
result_key,
json.dumps(
{
"background_callback_error": {
"msg": str(err),
"tb": traceback.format_exc(),
}
},
),
)
if asyncio.iscoroutine(user_callback_output):
user_callback_output = await user_callback_output
if not errored:
cache.set(
result_key, json.dumps(user_callback_output, cls=PlotlyJSONEncoder)
)
if asyncio.iscoroutinefunction(fn):
func = partial(ctx.run, async_run)
asyncio.run(func())
else:
ctx.run(run)
return job_fn
class CeleryLongCallbackManager(CeleryManager):
"""Deprecated: use `from dash import CeleryManager` instead."""
|
