Replace long callback interval with request polling handled in renderer.

Author: T4rk1n

dash/_callback.py

@@ -1,12 +1,14 @@
 import collections
 from functools import wraps
 
+import flask
+
 from .dependencies import (
     handle_callback_args,
     handle_grouped_callback_args,
     Output,
 )
-from .exceptions import PreventUpdate
+from .exceptions import PreventUpdate, WildcardInLongCallback, DuplicateCallback
 
 from ._grouping import (
     flatten_grouping,
@@ -17,9 +19,11 @@
     create_callback_id,
     stringify_id,
     to_json,
+    coerce_to_list,
 )
 
 from . import _validate
+from .long_callback.managers import BaseLongCallbackManager
 
 
 class NoUpdate:
@@ -30,15 +34,28 @@ def to_plotly_json(self):  # pylint: disable=no-self-use
 
     @staticmethod
     def is_no_update(obj):
-        return obj == {"_dash_no_update": "_dash_no_update"}
+        return isinstance(obj, NoUpdate) or obj == {
+            "_dash_no_update": "_dash_no_update"
+        }
 
 
 GLOBAL_CALLBACK_LIST = []
 GLOBAL_CALLBACK_MAP = {}
 GLOBAL_INLINE_SCRIPTS = []
 
 
-def callback(*_args, **_kwargs):
+def callback(
+    *_args,
+    long=False,
+    long_interval=1000,
+    long_progress=None,
+    long_progress_default=None,
+    long_running=None,
+    long_cancel=None,
+    long_manager=None,
+    long_cache_args_to_ignore=None,
+    **_kwargs,
+):
     """
     Normally used as a decorator, `@dash.callback` provides a server-side
     callback relating the values of one or more `Output` items to one or
@@ -56,15 +73,79 @@ def callback(*_args, **_kwargs):
     not to fire when its outputs are first added to the page. Defaults to
     `False` and unlike `app.callback` is not configurable at the app level.
     """
+
+    long_spec = None
+
+    if long:
+        long_spec = {
+            "interval": long_interval,
+        }
+
+        if long_manager:
+            long_spec["manager"] = long_manager
+
+        if long_progress:
+            long_spec["progress"] = coerce_to_list(long_progress)
+            validate_long_inputs(long_spec["progress"])
+
+        if long_progress_default:
+            long_spec["progressDefault"] = coerce_to_list(long_progress_default)
+
+            if not len(long_spec["progress"]) == len(long_spec["progressDefault"]):
+                raise Exception(
+                    "Progress and progress default needs to be of same length"
+                )
+
+        if long_running:
+            long_spec["running"] = coerce_to_list(long_running)
+            validate_long_inputs(x[0] for x in long_spec["running"])
+
+        if long_cancel:
+            cancel_inputs = coerce_to_list(long_cancel)
+            validate_long_inputs(cancel_inputs)
+
+            cancels_output = [Output(c.component_id, "id") for c in cancel_inputs]
+
+            try:
+
+                @callback(cancels_output, cancel_inputs, prevent_initial_call=True)
+                def cancel_call(*_):
+                    job_ids = flask.request.args.getlist("cancelJob")
+                    manager = long_manager or flask.g.long_callback_manager
+                    if job_ids:
+                        for job_id in job_ids:
+                            manager.terminate_job(int(job_id))
+                    return NoUpdate()
+
+            except DuplicateCallback:
+                pass  # Already a callback to cancel, will get the proper jobs from the store.
+
+            long_spec["cancel"] = [c.to_dict() for c in cancel_inputs]
+
+        if long_cache_args_to_ignore:
+            long_spec["cache_args_to_ignore"] = long_cache_args_to_ignore
+
     return register_callback(
         GLOBAL_CALLBACK_LIST,
         GLOBAL_CALLBACK_MAP,
         False,
         *_args,
         **_kwargs,
+        long=long_spec,
     )
 
 
+def validate_long_inputs(deps):
+    for dep in deps:
+        if dep.has_wildcard():
+            raise WildcardInLongCallback(
+                f"""
+                long callbacks does not support dependencies with
+                pattern-matching ids
+                    Received: {repr(dep)}\n"""
+            )
+
+
 def clientside_callback(clientside_function, *args, **kwargs):
     return register_clientside_callback(
         GLOBAL_CALLBACK_LIST,
@@ -87,6 +168,7 @@ def insert_callback(
     state,
     inputs_state_indices,
     prevent_initial_call,
+    long=None,
 ):
     if prevent_initial_call is None:
         prevent_initial_call = config_prevent_initial_callbacks
@@ -98,19 +180,26 @@ def insert_callback(
         "state": [c.to_dict() for c in state],
         "clientside_function": None,
         "prevent_initial_call": prevent_initial_call,
+        "long": long
+        and {
+            "interval": long["interval"],
+        },
     }
+
     callback_map[callback_id] = {
         "inputs": callback_spec["inputs"],
         "state": callback_spec["state"],
         "outputs_indices": outputs_indices,
         "inputs_state_indices": inputs_state_indices,
+        "long": long,
     }
     callback_list.append(callback_spec)
 
     return callback_id
 
 
-def register_callback(
+# pylint: disable=R0912
+def register_callback(  # pylint: disable=R0914
     callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs
 ):
     (
@@ -129,6 +218,8 @@ def register_callback(
         insert_output = flatten_grouping(output)
         multi = True
 
+    long = _kwargs.get("long")
+
     output_indices = make_grouping_by_index(output, list(range(grouping_len(output))))
     callback_id = insert_callback(
         callback_list,
@@ -140,23 +231,118 @@ def register_callback(
         flat_state,
         inputs_state_indices,
         prevent_initial_call,
+        long=long,
     )
 
     # pylint: disable=too-many-locals
     def wrap_func(func):
+
+        if long is not None:
+            long_key = BaseLongCallbackManager.register_func(
+                func, long.get("progress") is not None
+            )
+
         @wraps(func)
         def add_context(*args, **kwargs):
             output_spec = kwargs.pop("outputs_list")
+            callback_manager = long.get(
+                "manager", kwargs.pop("long_callback_manager", None)
+            )
             _validate.validate_output_spec(insert_output, output_spec, Output)
 
             func_args, func_kwargs = _validate.validate_and_group_input_args(
                 args, inputs_state_indices
             )
 
-            # don't touch the comment on the next line - used by debugger
-            output_value = func(*func_args, **func_kwargs)  # %% callback invoked %%
+            response = {"multi": True}
+
+            if long is not None:
+                progress_outputs = long.get("progress")
+                cache_key = flask.request.args.get("cacheKey")
+                job_id = flask.request.args.get("job")
+
+                current_key = callback_manager.build_cache_key(
+                    func,
+                    # Inputs provided as dict is kwargs.
+                    func_args if func_args else func_kwargs,
+                    long.get("cache_args_to_ignore", []),
+                )
+
+                if not cache_key:
+                    cache_key = current_key
+
+                    job_fn = callback_manager.func_registry.get(long_key)
+
+                    job = callback_manager.call_job_fn(
+                        cache_key,
+                        job_fn,
+                        args,
+                    )
+
+                    data = {
+                        "cacheKey": cache_key,
+                        "job": job,
+                    }
+
+                    running = long.get("running")
+
+                    if running:
+                        data["running"] = {str(r[0]): r[1] for r in running}
+                        data["runningOff"] = {str(r[0]): r[2] for r in running}
+                    cancel = long.get("cancel")
+                    if cancel:
+                        data["cancel"] = cancel
+
+                    progress_default = long.get("progressDefault")
+                    if progress_default:
+                        data["progressDefault"] = {
+                            str(o): x
+                            for o, x in zip(progress_outputs, progress_default)
+                        }
+                    return to_json(data)
+                else:
+                    if progress_outputs:
+                        # Get the progress before the result as it would be erased after the results.
+                        progress = callback_manager.get_progress(cache_key)
+                        if progress:
+                            response["progress"] = {
+                                str(x): progress[i]
+                                for i, x in enumerate(progress_outputs)
+                            }
+
+                    output_value = callback_manager.get_result(cache_key, job_id)
+                    # Must get job_running after get_result since get_results terminates it.
+                    job_running = callback_manager.job_running(job_id)
+                    if not job_running and output_value is callback_manager.UNDEFINED:
+                        # Job canceled -> no output to close the loop.
+                        output_value = NoUpdate()
+
+                    elif (
+                        isinstance(output_value, dict)
+                        and "long_callback_error" in output_value
+                    ):
+                        error = output_value.get("long_callback_error")
+                        raise Exception(
+                            f"An error occurred inside a long callback: {error['msg']}\n{error['tb']}"
+                        )
+
+                    if job_running and output_value is not callback_manager.UNDEFINED:
+                        # cached results.
+                        callback_manager.terminate_job(job_id)
+
+                    if multi and isinstance(output_value, (list, tuple)):
+                        output_value = [
+                            NoUpdate() if NoUpdate.is_no_update(r) else r
+                            for r in output_value
+                        ]
+
+                    if output_value is callback_manager.UNDEFINED:
+                        return to_json(response)
+            else:
+                # don't touch the comment on the next line - used by debugger
+                output_value = func(*func_args, **func_kwargs)  # %% callback invoked %%
 
-            if isinstance(output_value, NoUpdate):
+            if NoUpdate.is_no_update(output_value):
                 raise PreventUpdate
 
             if not multi:
@@ -191,7 +377,7 @@ def add_context(*args, **kwargs):
             if not has_update:
                 raise PreventUpdate
 
-            response = {"response": component_ids, "multi": True}
+            response["response"] = component_ids
 
             try:
                 jsonResponse = to_json(response)

dash/_utils.py

@@ -217,3 +217,9 @@ def gen_salt(chars):
     return "".join(
         secrets.choice(string.ascii_letters + string.digits) for _ in range(chars)
     )
+
+
+def coerce_to_list(obj):
+    if not isinstance(obj, (list, tuple)):
+        return [obj]
+    return obj