In the description of xSemaphoreGiveFromISR at http://www.freertos.org/a00124.html is written: "From FreeRTOS V7.3.0 pxHigherPriorityTaskWoken is an optional parameter and can be set to NULL."
The question is: If the parameter is NULL and there is higher priority task affected by the semaphore, will it automatically be switched after ISR - without portEND_SWITCHING_ISR( xHigherPriorityTaskWoken )?
If you set the parameter to NULL, the context switch will happen at the next tick (ticks happen each millisecond if you are using the default settings), not immediatlely after the end of the ISR. Depending on your use-case this may be acceptable or not.
No. The purpose of the pxHigherPriorityTaskWokenflag is only to indicate that a context switch is required. Then you need to call portEND_SWITCHING_ISR() or portYIELD_FROM_ISR() in your ISR code in order to request the context switch.
Related
I'm converting dart code to nnbd.
I have the following code.
var subscription = response.listen(
(newBytes) async {
/// if we don't pause we get overlapping calls from listen
/// which causes the [writeFrom] to fail as you can't
/// do overlapping io.
subscription.pause();
/// we have new data to save.
await raf.writeFrom(newBytes);
subscription.resume();
});
The problem is I get the following error:
The non-nullable local variable 'subscription' must be assigned before it can be used.
Try giving it an initializer expression, or ensure that it's assigned on every execution path.
I've had a similar problem solved here:
dart - correct coding pattern for subscription when using null saftey?
which was answered by #lrn
However the pattern solution pattern doesn't seem to work in this case.
raf.writeFrom is an async operation so I must use an 'async' method which means I can't use the 'forEach' solution as again I don't have access to the subscription object.
If you really want to use listen, I'd do it as:
var subscription = response.listen(null);
subscription.onData((newBytes) async {
subscription.pause();
await raf.writeFrom(newBytes);
subscription.resume();
});
or, without the async:
var subscription = response.listen(null);
subscription.onData((newBytes) {
subscription.pause(raf.writeFrom(newBytes));
});
which will pause the subscription until the future returned by raf.writeFrom completes (it shouldn't complete with an error, though).
If using listen is not a priority, I'd prefer to use an asynchronous for-in like:
await for (var newBytes in subscription) {
await raf.writeFrom(newBytes);
}
which automatically pauses the implicit subscription at the await and resumes it when you get back to the loop.
Both with stream.listen and the StreamController constructor, null safety has made it nicer to create them first without callbacks, and then add the callbacks later, if the callback needs to refer to the subscription/controller.
(That's basically the same nswer as in the linked question, only applied to onData instead of onDone. You have to pass a default onData argument to listen, but it can be null precisely to support this approach.)
I don't think your code, as written, was legal before null-safety either; you can't reference a variable (subscription) before it's declared, and the declaration isn't complete until after the expression you initialize it with (response.listen(...)) is evaluated. You will need to separate the declaration from the initialization to break the circular dependency:
StreamSubscription<List<int>> subscription;
subscription = response.listen(...);
Apache Beam has recently introduced state cells, through StateSpec and the #StateId annotation, with partial support in Apache Flink and Google Cloud Dataflow.
I cannot find any documentation on what happens when this is used with a GlobalWindow. In particular, is there a way to have a "state garbage collection" mechanism to get rid of states for keys that have not been seen for a while according to some configuration, while still maintaining a single all-time state for keys are that seen frequently enough?
Or, is the amount of state used in this case going to diverge, with no way to ever reclaim state corresponding to keys that have not been seen in a while?
I am also interested in whether a potential solution would be supported in either Apache Flink or Google Cloud Dataflow.
Flink and direct runners seem to have some code for "state GC" but I am not really sure what it does and whether it is relevant when using a global window.
State can be automatically garbage collected by a Beam runner at some point after a window expires - when the input watermark exceeds the end of the window by the allowed lateness, so all further input is droppable. The exact details depend on the runner.
As you correctly determined, the Global window may never expire. Then this automatic collection of state will not be invoked. For bounded data, including drain scenarios, it actually will expire, but for a perpetual unbounded data source it will not.
If you are doing stateful processing on such data in the Global window you can use user-defined timers (used through #TimerId, #OnTimer, and TimerSpec - I haven't blogged about these yet) to clear state after some timeout of your choosing. If the state represents an aggregation of some sort, then you'll want a timer anyhow to make sure your data is not stranded in state.
Here is a quick example of their use:
new DoFn<Foo, Baz>() {
private static final String MY_TIMER = "my-timer";
private static final String MY_STATE = "my-state";
#StateId(MY_STATE)
private final StateSpec<ValueState<Bizzle>> =
StateSpec.value(Bizzle.coder());
#TimerId(MY_TIMER)
private final TimerSpec myTimer =
TimerSpecs.timer(TimeDomain.EVENT_TIME);
#ProcessElement
public void process(
ProcessContext c,
#StateId(MY_STATE) ValueState<Bizzle> bizzleState,
#TimerId(MY_TIMER) Timer myTimer) {
bizzleState.write(...);
myTimer.setForNowPlus(...);
}
#OnTimer(MY_TIMER)
public void onMyTimer(
OnTimerContext context,
#StateId(MY_STATE) ValueState<Bizzle> bizzleState) {
context.output(... bizzleState.read() ...);
bizzleState.clear();
}
}
There is not automatic garbage collection of state if you use GlobalWindows. Only if you use some non-global window will state be garbage collected after the watermark passes the end of a window plus the allowed lateness.
What you can do if you must work with GlobalWindows is to manually keep as state the last update timestamp. Then you would periodically set a timer where you check this timestamp against the current time and delete state if necessary. You would set this timer when encountering a key for the first time (which you can see from the absence of your timestamp state) and then re-set it in the #OnTimer method.
For testing heartbeat, I think "the above 6th column" is actual heartbeat value. Is it right?
If true, what's the meaning of empty for rabbitmq-c client. Rabbitmq-c client always stay there and never die.
How to solve it?
Heartbeat interval can be suggested by the server, but the client might not take that value. I was looking the the source and you might be able to use this function:
AMQP_PUBLIC_FUNCTION
int
AMQP_CALL amqp_tune_connection(amqp_connection_state_t state,
int channel_max,
int frame_max,
int heartbeat);
i'm displaying a server calculated value to the enduser by using propertyChanged event.
i was using breeze 1.4.8 and i'm using the productivity stack (ms sql, web api, ef)
It was working fine.
Recently i've updated to 1.4.12 and i recognized that this event doesn't get fired anymore.
The property "A_ProvisionTotal" gets calculated serverside only.
<snip>
var token = vm.transaction.entityAspect.propertyChanged.subscribe(propertyChanged);
function propertyChanged(propertyChangedArgs) {
var propertyName = propertyChangedArgs.propertyName;
if (vm.transaction.tblEmployees.CalculationMethod == "A" && propertyName == "A_ProvisionTotal")
logSuccess('Provision neuberechnet' + '<br/>' + 'Aktuell: ' + $filter('number')(vm.transaction.Provision, 2), true);
</snip>
Let me know if this is a known regression and if you need more snippets.
A couple of thoughts for how you could accomplish your desired functionality.
The entity could remember the last calculated value in a private field. Then whenever the recalculation gets triggered, you can compare the new value to the last calculated value and if there is no change, ignore the new calculated value.
Alternatively, you could define the properties involved in your calculation as ES5 properties in the entity ctor function and then trigger the calculation in the setter of the relevant properties, when they get set with a new value. More information here: http://www.breezejs.com/documentation/extending-entities#es5-property. ES5 properties are convenient if you want to build behavior such as your calculation into setters.
Update 3
This is not a bug - see the response to this post that describes this as a documented and deliberate behavior.
Update 2 June 2014
I overlooked a key fact in your question ... one that only became clear to me after I looked at the code you included in your comments. Let me extract the key pieces for other readers:
Your test issues a query, then saves an unrelated change to the server (where the property-of-interest is updated server-side), then checks if that telltale property-of-interest raises propertyChanged when the save result is merged back into cache.
var query = EntityQuery.from("Orders").where('id', 'eq', 10248);
query.using(em).execute().then(querySucceeded).then(checkPropertyChanged).fin(start);
// querySucceed receives order 10248, updates an unrelated property (so you can save),
// wires up a propertyChanged listener and saves, returning the saveChanges promise
function checkPropertyChanged(saveResults) {
var saved = saveResults.entities[0];
// this passes because the server-side change to `Freight` was returned
ok(saved && saved.Freight() === 1200.00,
"freight got changed serverside");
// this fails because Breeze did not notify you that the `Freight` had changed
ok(notifications[0].propertyName === "Freight",
"notified serverside change of Freight Property");
}
Summarizing, you expected that a property change on the server would trigger a propertyChanged notification on the client when the entity data are re-retrieved from the server as a by-product of saveChanges.
Do I have that right?
Our documentation was not clear on whether the merge of query, save, and import entity results would raise propertyChanged.
I discussed internally and confirmed that these operations SHOULD raise propertyChanged. I also wrote another (somewhat simpler) test that reveals the bug you discovered: that merged save results may not raise propertyChanged.
We'll look into it and tell you when we've fixed it. Thanks for discovering it.
Original
We have regression tests that show that the Breeze EntityAspect.propertyChanged event is raised in v.1.4.12. For example, you can see it at work in the DocCode sample, "basicTodoTests.js"; scroll to: "Breeze propertyChanged raised when any property changes".
Can you confirm that it really is a Breeze failure? Perhaps the property you are changing is not actually an entity property? Sometimes you think you are changing an entity (e.g, your Transaction entity) but the thing whose property you changed isn't actually an entity. Then the problem is that the data you thought would be mapped to a Transaction was not ... and you can start looking for that quite different problem.
In any case, I suggest that you write a small test to confirm your suspicion ... most importantly for yourself ... and then for us. That will help us discover what is different about your scenario from our scenarios. We'll fix it if you can find it. Thanks.
Actually, I'm not sure that this is a bug. Property change events DO get fired during a save merge but the property name parameter is documented as being 'null' when fired as a result of a save.
http://www.breezejs.com/sites/all/apidocs/classes/EntityAspect.html#event_propertyChanged
From the API Docs for the 'propertyName' parameter returned by EntityAspect.propertyChanged:
The name of the property that changed. This value will be 'null' for operations that replace the entire entity. This includes queries, imports and saves that require a merge. The remaining parameters will not exist in this case either.
What may have happened between 1.4.8 and 1.4.13 is that we actually implemented our design spec more carefully and probably introduced your breaking behavior. ( which we should have documented as such but likely missed).
Update by Ward
I updated the DocCode test which first confirmed the behavior described in your question and then confirmed the documented behavior.
We do regret that we apparently neglected to implement the documented behavior earlier and that we didn't mention the breaking change in our release notes (since updated).
Here's that test:
asyncTest("propertyChanged raised when merged save result changes a property", 3, function () {
var em = newTodosEm();
var todo = em.createEntity('TodoItem', {Description: "Saved description" });
em.saveChanges().then(saveSucceeded).catch(handleFail).finally(start);
ok(todo.entityAspect.isBeingSaved, "new todo is in the act of being saved");
// This change should be overwritten with the server value when the save result is returned
// even though the entity is in an Added state and the MergeStrategy is PreserveChanges
// because save expects to merge server values into an entity it is saving
todo.Description("Changed on client before save returns");
var descriptionChanged = false;
todo.entityAspect.propertyChanged.subscribe(function (changeArgs) {
// Watch carefully! The subscription is called twice during merge
// 1) propertyName === "Id" (assigned with permanent ID)
// 2) propertyName === null (WAT?)
// and not called with propertyName === "Description" as you might have thought.
// Actually 'null' means "merged a lot of properties"
// Documented: http://www.breezejs.com/sites/all/apidocs/classes/EntityAspect.html#event_propertyChanged
// The reason for this: don't want to fire a ton of events on whole entity load
// especially when merging many entities at the same time.
if (changeArgs.propertyName === null || changeArgs.propertyName === 'Description') {
descriptionChanged = true;
}
});
function saveSucceeded(saveResult) {
var saved = saveResult.entities[0];
// passes
equal(saved && saved.Description(), "Saved description",
"the merge after save should have restored the saved description");
// fails
ok(descriptionChanged,
"should have raised propertyChanged after merge/update of 'Description' property");
}
});
Has the interface <none> in the gdbus-monitor output a special meaning?
What API call is required to create such a message using GDbus (g_dbus_connection_register_object does not allow to pass NULL as GDBusInterfaceInfo * and that seems to be the only to register a object to a path)
related: dbus - register object to remote on interface NULL
Looking into dbus-monitor's source code shows that it occures as soon as DBUS_EXPORT const char * dbus_message_get_interface ( DBusMessage * message ) returns NULL (which is valid!, but not according to the spec which requires minimum one . and two name chunks!! EDIT: A noteable exception are method calls which do not require the interface field of a message to be set http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-types).
g_dbus_message_new_method_call (...) allows interface_ to be null. But that still only solves half the problems (sender). The receiver method seems to not exist for interface_s being NULL.
Turns out it is a bug, I did a source code investigation and filed a bug (including fix) https://bugzilla.gnome.org/show_bug.cgi?id=706675
client needs to know the interface name while subscribing g_dbus_connection_signal_subscribe to any signal else it will listen to all interfaces hence inefficient.
Interface is required to bind methods and signals in single entity mentioned in server introspection xml file.