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https://issues.apache.org/jira/browse/KAFKA-12286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17278673#comment-17278673
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Tom Bentley commented on KAFKA-12286:
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{quote}we will have options to deal with it if it does.{quote}
Just to note that one path to doing that is to decouple the serialized type
from the Java type in a versioned way. Concretely
[KIP-625|https://cwiki.apache.org/confluence/display/KAFKA/KIP-625%3A+Richer+encodings+for+integral-typed+protocol+fields#KIP625:Richerencodingsforintegraltypedprotocolfields-PublicInterfaces]
describes migrating fields from 32 to 64 bits, for example.
> Consider storage/cpu tradeoff in metadata record framing schema
> ---------------------------------------------------------------
>
> Key: KAFKA-12286
> URL: https://issues.apache.org/jira/browse/KAFKA-12286
> Project: Kafka
> Issue Type: Improvement
> Reporter: Jason Gustafson
> Priority: Major
>
> KIP-631 calls for unsigned varints in order to represent the api key and
> version. We are also adding a frame version, which will be unsigned varint.
> The use of the varint means we can save a byte from each of these fields
> compared to an int16. The downside is that it is that the serialization is a
> little more expensive. For varints, we typically require one call to compute
> the size of the field and a separate call to actually write it. If this
> becomes an issue, there are a couple options:
> 1. We can use the int16 and pay the extra 3 bytes.
> 2. We can let the generated classes compute the encoded api key and version
> as a byte and fail if we ever exceed the range of varint that can fit in a
> single byte. This would let us replace `writeUnsignedVarint` with `writeByte`.
> The second option seems reasonable to me. I think it's extremely unlikely
> we'll ever need more than a byte for either the api key or the version. At
> least it should be years before that happens and we will have options to deal
> with it if it does.
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