Command Mode : Two-level push

rajesh.palanisamy

I want to conform whether itemUpdate can be limited for client to receive only UPDATE and DELETE event, since in my case the items for in ADD has no Data other than item Key since our application has lot of Items to be ADDed we are finding ways to ignore it. can you please suggest is that an expected behavior or we can do some work around to limit the item updates using selector or something else..

NOTE:
I am using two adapters
1. INIT Adapter- To ADD/remove a record from External source say DB
2. DATA Adapter - To publish actual Data fields

Thanks
Rajesh

Giuseppe Corti

Hi Rajesh,

Please consider that ADD events for the Two-level push are of crucial importance and can not be prevented from being sent to the clients.
Indeed, the ADD event triggers in the client library the subscribe to the Item of the second level. If the client does not receive the ADD no second level data will be received.

They payload of an ADD event is very small, so it should not be a problem.
But maybe in your scenario you have a such big burst of ADD events which causes performance problems? In this case you have two options:

- give up the two-level push and fall back in the case of simple COMMAND.
Unfortunately with a two separate adapters it's a bit complicated, as you should coordinate the two to aggregate the add/remove information with the market data.

- give up the COMMAND mode at all. You could simply rely on MERGE Items. To handle a dynamic list of items the clients should subscribe you could use a symbolic group name as Item name.
So the list of Items to be pushed to the client can be determined by your Metadata Adapter via the getItems call.

Please let us know if you need any further clarifications.

Regards,
Giuseppe

rajesh.palanisamy

Thanks Giuseppe for quick turn around,

We are wondering is it possible to skip add events to the UI so we can populate the data and transmit only that to UI.

May i ask you to provide for any reference for the above two options. I am interested to explore more about it.

Awaiting for your response.

Thanks,
Rajesh

Giuseppe Corti

Hi Rajesh,

Did your application use one of our view widgets (Static Grid, Dyna Grid, Chart)?
In this case there is no way to prevent them from receiving and managing ADD events. Otherwise, if you rely on onItemUpdate of SubscriptionListener, you have complete freedom in sending to the UI only certain updates.

About the two options I proposed:

1) We have several demos showing the simple COMMAND mode (only one level), starting from the basic-portfolio-demo. But in your case, if I have understood correctly, the tricky part is to combine information from the DATA Adapter with the INIT Adapter.

2) In this case you should leverage the getItems method of Metadata Adapter interface. The client will subscribe a single Item in MERGE mode, but in getItems you will return the actual Item list.
This approach works fine when the composition of the list is static or changes very rarely; since for each change, you must warn the client that should repeat the subscription.

Regards,
Giuseppe

rajesh.palanisamy

Giuseppe,

I am not using those widgets , we are using angular and the data updates to ngRX store.

Let me go thru the options you provided and let me getback to you if any issues.

Thanks a lot.