How to get only the latest sample per instance for later-join subscribers and keep reliability?
Assume that DataWriter and DataReader have Reliability QOS as RELIABLE_RELIABILITY_QOS, and History QOS as KEEP_LAST with depth=100. For a later-join DataReader, I would like to receive only the latest instance value, instead of the last 100. Is there a way to do it?
Thanks.
Hi Allen,
If you want to get the latest instance value instead of the last 100, you need to use KEEP_LAST with depth 1:
I want to highlight that HistoryQos is working in a per-instance basis. Having KEEP_LAST with depth 1 and 3 different instances will maintain 3 different samples.
Thanks,
Juan J. Martin
Professional Services Group
Juan,
Thank you for the answer. If I set depth 1 in the DataReader, the late-joiner would loss some reliability after start, where if my application pull the data slower from Connext DDS, the sample would be overwrite by late updates.
My purpose is to keep some kind of reliability, at the same time, the late-joiner should only get the latest data snapshot.