Snapshot Processing

wwatts

In our system, we have the possibility of users subscribing to multiple types of items. With respect to snapshots we have the following questions. Sorry for the length of this post.

1. When a client initializes and receives the initial snapshot data, will the client always receive the Snapshot Complete event callback? If not what are the situations that could result in not receiving the Snapshot Complete event callback? Does this apply to initial subscriptions where the DataAdapter pushes the snapshot data with Snapshot set to true and for subsequent clients subscribing to an existing subscription?

2. Is the following scenario correct (assuming Command Mode). Client 1 subscribes to item1. The DataAdapter pushes 10 records of item1 with snapshot set to true. Client 1 receives Snapshot complete after receiving the 10th item1. Time passes and 5 more item1 are added. Client 2 subscribes to item1. Lightstreamer sends 15 item1 to Client 2 with snapshot set to true. After the 15th item1, Client 2 receives the snapshot complete. Is this correct?

3. Is there a way prior to subscribing to "look ahead" and determine the size of a snapshot? This would be for initialization purposes to provide feedback to the user for example that he has received 5 of 15 items.

4. With respect to monitoring of the Lightstreamer Server iteself, is it possible to examine what snapshots are contained in the server and how many users are subscribed to each snapshot? If so can you provide examples of how to do this type of monitoring?

Thanks in advance for your support.

Mone

1 may you please specify which subscription mode are you referring to?

2 this is correct assuming that after the DataProvider sent the 10th record a call to endOfSnapshot (or smartEndOfSnapshot in case of SmartDataProvider) is issued.

3 there is nothing ready for that; you may use a MERGE item that pushes the number of records in your command table at any given moment.

4 a snapshot is stored per each subscribed item; you can track the number of subscribed items in your DataProvider using subscribe and unsubscribe methods.
You can use your MeadataProvider to track new subscriptions for each single client and track them; take a look to wantsTablesNotification notifyNewTables and notifyTablesClose

HTH

david_cheong

Mone 1 may you please specify which subscription mode are you referring to?

2 this is correct assuming that after the DataProvider sent the 10th record a call to endOfSnapshot (or smartEndOfSnapshot in case of SmartDataProvider) is issued.

3 there is nothing ready for that; you may use a MERGE item that pushes the number of records in your command table at any given moment.

4 a snapshot is stored per each subscribed item; you can track the number of subscribed items in your DataProvider using subscribe and unsubscribe methods.
You can use your MeadataProvider to track new subscriptions for each single client and track them; take a look to wantsTablesNotification notifyNewTables and notifyTablesClose

HTH

I check on my LS snapshot, it only send the last action to my javascript client end which make the data inconsistency. I'm using the Command mode for my application, may i know why this happen?

My issue is i set the unique id for each item and the id is place in the Key parameter when publish the data, after few action done on the same data and refresh the browser to re-subscript the snapshot, i found that LS only send the last action for each unique key.

Can anyone help on this.

Giuseppe Corti

Hi David,

I suppose the question is the same of this post.