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https://issues.apache.org/jira/browse/KAFKA-18191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17926636#comment-17926636
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A. Sophie Blee-Goldman commented on KAFKA-18191:
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ah, I see the problem. I didn't notice the StreamJoined#withName, so that's on
me. However what threw me off is, imo, a legitimate issue...maybe not a bug but
definitely a gap. For pretty much every operator that has a config class like
StreamJoined, the processor name can be specified via a static `ConfigClass#as`
method. When I saw that StreamJoined had an #as method I just assumed it worked
like everything else and set the processor name, but this is actually the store
name. So problem #1 is that the API is misleading
Problem 2 is that, AFAICT, there is no way to set just the processor name –
there's no static constructor like #as.
It's honestly not a huge problem and perhaps not even worth fixing now, but I
wish we had followed the established pattern for StreamJoined#as to specify the
processor name. We could add a static constructor for the processor name to
solve Problem #2 but imo Problem 1 is the bigger deal – it's not much to just
require users to specify the store name first in order to use #withName to set
the processor name, but I'm willing to bet there are users out there who (like
me) never realized that StreamJoined#as isn't setting the processor name and
could be in for a nasty surprise if they try to upgrade a topology
I guess that's where Sebastien's KIP comes in :)
Thoughts?
> StreamJoined name is not used for processor names
> -------------------------------------------------
>
> Key: KAFKA-18191
> URL: https://issues.apache.org/jira/browse/KAFKA-18191
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: A. Sophie Blee-Goldman
> Priority: Major
>
> The StreamJoined#as API allows you to set a name for a stream-stream join
> operator. The intention is to allow one to name the stores, and therefore
> changelogs, resulting in an upgradeable topology, but it is a bit strange
> that the name isn't also used for the processors themselves.
> Of course, the stream-stream join is a bit of an edge case compared to, say,
> a count or filter operator, where the operator is a 1:1 mapping to the
> processor node and the user can name the processor exactly, because the
> stream-stream join operator actually results in multiple processors which
> each need a unique name. However, we could at least use the specified
> StreamJoined name as the basis for the resulting processor names, to avoid
> getting stuck with names like "KSTREAM-JOINTHIS-0000000004" and
> "KSTREAM-WINDOWED-0000000003" which are difficult to interpret and make it
> hard to read a topology
> Note that there is some existing precedent for this: for example with
> cogroups, the individual processors inherit the base name of the cogroup's
> aggregate operator name. For example this code
>
> {code:java}
> grouped1
> .cogroup((k, v, a) -> a + v) // wrapped 1
> .cogroup(grouped2, (k, v, a) -> a + v) // wrapped 2
> .aggregate(() -> "", Named.as("myName"), Materialized.as("store")) {code}
>
> produces processors with these names: "myName-cogroup-agg-0",
> "myName-cogroup-agg-1", "myName-cogroup-merge"
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