Hi Robert,
Don’t believe there are specific whitepapers/slides/video’s on the topic but the following can be stated: - There are no imposed limits on the number of keys in OpenSplice - Keys are basically limited to primitive types (see preprocessor user-manual chapter 1.5.1) - Keys define the ‘dimensions’ of your storage and unique-key-values represent instances, so typically the more keys you have, the more instances you likely have - As instances are basically database-entries (into a reader-cache or transient-cache), the more instances, the bigger the database, the more memory is used and the slower are queries/reads/takes (this is especially true if you don’t properly manage the lifecycle of keys/instances i.e. keep increasing key-values without ever ending the lifecycle of ‘old’ instances by unregistering them by key-value) - Typically when you exceed ‘tens of thousands’ (of instances), performance impact on todays’ platforms will become noticeable (both in reactivity as well as footprint) - W.r.t. topic-design/granularity: a good data-model is ‘key’ in DDS and granularity is typically driven by (a) the scope of a writer (i.e. the information available at that writer), (b) the ‘kind’ of data the publisher is writing (i.e. if its periodic measurements, you typically want that published in a volatile/best-effort topic, if its state-data, transient/reliable makes sense and if it’s a ‘setting’ then persistent/reliable makes sense). Note that since the data-model in DDS is relational (i.e. where shared key-attributes model relationships between topics), information from multiple related dataReaders can be reconstructed pretty easily at the subscriber side utilizing the relationships expressed by shared keys. We do have architecture workshops related to the topic though (including detailed information on the impact/overhead of any DDS-entity) .. Regards, Hans * * *Hans van 't Hag* OpenSplice DDS Product Manager PrismTech Netherlands Email: [email protected] Tel: +31742472572 Fax: +31742472571 Gsm: +31624654078 PrismTech is a global leader in standards-based, performance-critical middleware. Our products enable our OEM, Systems Integrator, and End User customers to build and optimize high-performance systems primarily for Mil/Aero, Communications, Industrial, and Financial Markets. ------------------------------ *From:* [email protected] [mailto: [email protected]] *On Behalf Of *Feider, Robert *Sent:* Wednesday, August 08, 2012 8:43 PM *To:* [email protected] *Subject:* [OSPL-Dev] Topic Construction Best Practices I am looking for resources (white paper, slides, videos etc.) that describe the best practices for creating DDS topics. In particular I am interested in discussions about Data Type Key construction and what the implications are (performance, scalability) of having a key that results in the creation of a large number of data instances. I have seen some anecdotal remarks that this should not be done, but I’d like to understand the issue a bit better as to what happens inside DDS and what the limits are. Thanks for your help, *Robert Feider* Lockheed Martin, IS&GS Defense 719-277-4069
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