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DDS durability service

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My statement was about not being able to support TRANSIENT/PERSISTENT data in your system once you remove all durability-services. It indeed doesn't impact TRANSIENT_LOCAL data-distribution.

So whereas using TRANSIENT_LOCAL data in your (current) applications is a 'local decision', not having any durability-services configured is more of a 'global decision' for the whole system.

I've also checked with the durability-exports on the cause of that warning and that's typically related to high network-latencies (i.e. like in a WIFI) network that's not anticipated by the durability-service's internal protocols do decide who is the 'master' to provide late-joining applications with TRANSIENT/PERSISTENT historical data.

We've introduced an alternative to that 'majority-voting' that can be easily enabled by adding the 'masterPriority="1"' attribute in the durability-configuration:

            <Policy alignee="Initial" aligner="true" durability="Durable" masterPriority="1" nameSpace="defaultNamespace"/>

Here's a complete ospl_sp_ddsi.xml that includes that setting


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Hi Jan-Marc,

If you only use TRANSIENT_LOCAL and VOLATILE (in other words, you don't use TRANSIENT or PERSISTENT), then you technically don't need to run a durability service. However, due to a bug in the product the function wait_for_historical_data only works when you have a durability service running: if that is not the case it will never unblock unless the specified timeout expires. Since some of the tools (e.g. Tester) invoke a wait_for_historical_data with unlimited timeout on all non-VOLATILE readers, the tool 'hangs' when no durability service is configured. I think that is what Hans was trying to explain.

For your information, the bug in question has been identified and is scheduled to be fixed in the upcoming commercial release.


Erik Hendriks.

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