rusackas commented on code in PR #44552:
URL: https://github.com/apache/superset/pull/44552#discussion_r4134612484


##########
superset/tasks/query_cancel.py:
##########
@@ -163,3 +172,150 @@ def cancel_chart_query(
             exc_info=True,
         )
         return False
+
+
+def _registry_key(user_id: int, client_id: str) -> str:
+    """Cache key for a user's in-flight, cancellable chart query.
+
+    The user id is part of the key rather than a field compared after lookup, 
so
+    a ``client_id`` is only ever resolvable within the namespace of the user 
who
+    registered it. A caller passing somebody else's ``client_id`` gets a miss —
+    it cannot read, cancel, or overwrite another user's entry.
+    """
+    return f"chart-query-cancel:{user_id}:{client_id}"
+
+
+def _registry_ttl() -> int:
+    """How long a cancel handle stays resolvable.
+
+    A synchronous chart query cannot outlive the web request running it, so the
+    webserver timeout is the natural upper bound. Entries are discarded as soon
+    as the query returns; this TTL only bounds the leak when a worker dies
+    mid-query.
+    """
+    return int(current_app.config.get("SUPERSET_WEBSERVER_TIMEOUT", 60))
+
+
+@contextmanager
+def cancellable_chart_query(
+    client_id: "str | None", database: "Database | None"
+) -> Iterator[None]:
+    """Let the requesting user cancel this synchronous chart query by 
``client_id``.
+
+    Captures the engine cancel id off the live cursor (for engines that expose
+    one before execution) and publishes it so a concurrent Stop request — which
+    lands on a different worker while this one is blocked on the query — can 
kill
+    the backend session. Engines without cancel support capture nothing and the
+    query stays non-cancellable, exactly as before.
+
+    A no-op without a ``client_id``, without a database (e.g. the annotation
+    datasource, which queries Superset's own metadata DB), or for an
+    unauthenticated request — an anonymous viewer of a public dashboard has no
+    user id to scope the handle to, and an unscoped handle would be cancellable
+    by any other anonymous visitor.
+    """
+    # Inline (also below, and in _publish_cancel_handle/_discard_cancel_handle/
+    # cancel_chart_query_for_user): the unit tests patch get_user_id and
+    # cache_manager at their defining modules (superset.utils.core,
+    # superset.extensions), not here. A module-level `from ... import X` binds
+    # X once at import time, before any test patch runs, so the patch would
+    # silently never take effect; re-importing on every call picks up the
+    # patched object instead.
+    from superset.utils.core import get_user_id
+
+    user_id = get_user_id()
+    if not client_id or database is None or user_id is None:
+        yield
+        return
+
+    # Rebound as non-optional locals: mypy does not carry the narrowing above
+    # into the nested function below.
+    owner_id: int = user_id
+    query_id: str = client_id
+    target: "Database" = database
+    database_id = target.id
+    captured = False
+
+    def _sink(cursor: Any) -> None:
+        # Republish for every cursor rather than only the first: one query
+        # object can execute several statements in turn (e.g. the grouping-sets
+        # fallback), each on whatever connection the pool hands out, and the
+        # handle must always name the session that is executing right now.
+        nonlocal captured
+        cancel_id = capture_cancel_query_id(target, cursor)
+        if cancel_id is None:
+            return
+        captured = True
+        _publish_cancel_handle(owner_id, query_id, database_id, cancel_id)
+
+    try:
+        with capture_cancel_id(_sink):
+            yield
+    finally:
+        if captured:
+            _discard_cancel_handle(owner_id, query_id)
+
+
+def _publish_cancel_handle(
+    user_id: int, client_id: str, database_id: int, cancel_query_id: str
+) -> None:
+    """Publish a cancel handle for the owning user. Best-effort."""
+    # Inline for test-patchability; see cancellable_chart_query's comment.
+    from superset.extensions import cache_manager
+
+    try:
+        cache_manager.cache.set(

Review Comment:
   Good catch. `cache_manager.cache` is the general `CACHE_CONFIG`, which 
defaults to `NullCache`. Split the registry onto its own 
`CHART_QUERY_CANCEL_CACHE_CONFIG`, required like `FILTER_STATE_CACHE_CONFIG`, 
so Stop actually persists a handle by default.



##########
superset/tasks/query_cancel.py:
##########
@@ -163,3 +172,150 @@ def cancel_chart_query(
             exc_info=True,
         )
         return False
+
+
+def _registry_key(user_id: int, client_id: str) -> str:
+    """Cache key for a user's in-flight, cancellable chart query.
+
+    The user id is part of the key rather than a field compared after lookup, 
so
+    a ``client_id`` is only ever resolvable within the namespace of the user 
who
+    registered it. A caller passing somebody else's ``client_id`` gets a miss —
+    it cannot read, cancel, or overwrite another user's entry.
+    """
+    return f"chart-query-cancel:{user_id}:{client_id}"
+
+
+def _registry_ttl() -> int:
+    """How long a cancel handle stays resolvable.
+
+    A synchronous chart query cannot outlive the web request running it, so the
+    webserver timeout is the natural upper bound. Entries are discarded as soon
+    as the query returns; this TTL only bounds the leak when a worker dies
+    mid-query.
+    """
+    return int(current_app.config.get("SUPERSET_WEBSERVER_TIMEOUT", 60))
+
+
+@contextmanager
+def cancellable_chart_query(
+    client_id: "str | None", database: "Database | None"
+) -> Iterator[None]:
+    """Let the requesting user cancel this synchronous chart query by 
``client_id``.
+
+    Captures the engine cancel id off the live cursor (for engines that expose
+    one before execution) and publishes it so a concurrent Stop request — which
+    lands on a different worker while this one is blocked on the query — can 
kill
+    the backend session. Engines without cancel support capture nothing and the
+    query stays non-cancellable, exactly as before.
+
+    A no-op without a ``client_id``, without a database (e.g. the annotation
+    datasource, which queries Superset's own metadata DB), or for an
+    unauthenticated request — an anonymous viewer of a public dashboard has no
+    user id to scope the handle to, and an unscoped handle would be cancellable
+    by any other anonymous visitor.
+    """
+    # Inline (also below, and in _publish_cancel_handle/_discard_cancel_handle/
+    # cancel_chart_query_for_user): the unit tests patch get_user_id and
+    # cache_manager at their defining modules (superset.utils.core,
+    # superset.extensions), not here. A module-level `from ... import X` binds
+    # X once at import time, before any test patch runs, so the patch would
+    # silently never take effect; re-importing on every call picks up the
+    # patched object instead.
+    from superset.utils.core import get_user_id
+
+    user_id = get_user_id()
+    if not client_id or database is None or user_id is None:
+        yield
+        return
+
+    # Rebound as non-optional locals: mypy does not carry the narrowing above
+    # into the nested function below.
+    owner_id: int = user_id
+    query_id: str = client_id
+    target: "Database" = database
+    database_id = target.id
+    captured = False
+
+    def _sink(cursor: Any) -> None:
+        # Republish for every cursor rather than only the first: one query
+        # object can execute several statements in turn (e.g. the grouping-sets
+        # fallback), each on whatever connection the pool hands out, and the
+        # handle must always name the session that is executing right now.
+        nonlocal captured
+        cancel_id = capture_cancel_query_id(target, cursor)
+        if cancel_id is None:
+            return
+        captured = True
+        _publish_cancel_handle(owner_id, query_id, database_id, cancel_id)
+
+    try:
+        with capture_cancel_id(_sink):
+            yield
+    finally:
+        if captured:
+            _discard_cancel_handle(owner_id, query_id)

Review Comment:
   Good catch, that gap's real for the grouping-sets fallback's sequential 
cursors, not just a client reusing its own id. Discard now only clears the 
entry if it still names the id that was actually cancelled, so a stale hit 
can't wipe a cursor that's already republished.



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