How to access the history of notification?

[longboy]

I am using notifer as event tigger but suffering the missing notifications. Do I have any way to access "all the history" of notifications instead of just the latest one like what we can do in "queue"?

BTW, I tried to figure out what is the difference between the following two functions: "wait on notification" and "wait on notification with history". It makes no difference to me especially with the existing parameter-"ignore previous" in both of these two functions.

Thank for your help.

[Phil_]

Queues and Notifiers are essentially the same, except queues have a buffer and notifiers do not.

If you are missing notifications, maybe use a queue instead of notifiers? 

[longboy]

yes thank you for your reply. However, queue doesn't notify actively, that's why I use notifier.

[MikeS81]

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@longboy wrote:
... However, queue doesn't notify actively, that's why I use notifier.

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Hi,

can you please explain this?

Mike

[longboy]

Dear Mike, hmmm... With queue, I have to query by myself instead of been notified when event occured. Regards, ChingLung

[crossrulz · Accepted solution]

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@longboy wrote:
Dear Mike, hmmm... With queue, I have to query by myself instead of been notified when event occured. Regards, ChingLung

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How is that?  A Dequeue Element will sleep while waiting for something to enter the queue.  I guess I don't know what you mean be "notified".

[Norbert_B]

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@Phil_ wrote:

Queues and Notifiers are essentially the same, except queues have a buffer and notifiers do not.

 [...]

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There is an additional difference:

Queues allow multiple writers but a single reader, the Notifier a Single writer and multiple reader.

You CAN use them differently, of course, but then you really need to know what you are doing (otherwise: welcome to the hell of debugging race conditions!)

Norbert

[longboy]

Dear Mike

oh, yes! I tried and it works well. Thank you for your patient and rescuing me from the two-day suffering.

Regard,  ChingLung

[longboy]

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Norbert_B 已寫：

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@Phil_ wrote:

Queues and Notifiers are essentially the same, except queues have a buffer and notifiers do not.

 [...]

---

There is an additional difference:

Queues allow multiple writers but a single reader, the Notifier a Single writer and multiple reader.

You CAN use them differently, of course, but then you really need to know what you are doing (otherwise: welcome to the hell of debugging race conditions!)

Norbert

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Dear Phil and Norbert, 

  Thanks for your explaination. It seems clear to me now. It works well now. Thanks again!!

Regards,    ChingLung

[Mark_Yedinak]

Notifier can be many to many. They are not restricted to a one to many relationship. The important part is that unlike a queue notifiers can have multiple listeners.