Given FLINK 3311 & 3332, I am wondering it would be possible, without idempotent counters in Cassandra, to deliver on an exactly once sink into Cassandra. I do note that the verbiage/disc2 in 3332 does warn the user that this is not exactly "exactly once" sink. However my question has to do with whether having idempotent counters and a Data model that enables all other idempotent operations are a necessary prerequisite to exactly once semantics in flink. Asked a different way, what source and sink would enable a end-to-end exactly - once semantics, in the current state-of-the-art, with Flink in the middle. Thanks |
Hello Milind,
I'm not entirely sure i fully understood your question, but I'll try anyway :) There is now way to provide exactly-once semantics for Cassandra's counters. As such we (will) only provide exactly-once semantics for a subset of Cassandra operations; idempotent inserts/updates. There are several things that would allow exactly-once semantics:
Regards, Chesnay Schepler On 10.05.2016 07:48, milind parikh wrote:
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Hi Chesnay Sorry for asking the question in a confusing manner. Being new to flink, there are many questions swirling around in my head. Thanks for the details in your answers. Here's the facts , as I see them: (a) Cassandra Counters are not idempotent One could model the data model so as to make Flink work exceptionally well with Cassandra; except counter tables. There is no way in Cassandra currently to model an idempotent counter table that I know of. Therefore an event replay that affects a counter might end up double counting. When will the Cassandra sink be released? I am ready to test it out even now. Hello Milind,
I'm not entirely sure i fully understood your question, but I'll try anyway :) There is now way to provide exactly-once semantics for Cassandra's counters. As such we (will) only provide exactly-once semantics for a subset of Cassandra operations; idempotent inserts/updates. There are several things that would allow exactly-once semantics:
Regards, Chesnay Schepler On 10.05.2016 07:48, milind parikh wrote:
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On Tue, May 10, 2016 at 5:36 PM, milind parikh <[hidden email]> wrote:
> When will the Cassandra sink be released? I am ready to test it out even > now. You can work with Chesnay's branch here: https://github.com/apache/flink/pull/1771 Clone his repo via Git, check out the branch, and then build it from source (https://ci.apache.org/projects/flink/flink-docs-release-1.0/setup/building.html). |
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