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From "Michal Borowiecki (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (KAFKA-4750) KeyValueIterator returns null values
Date Mon, 26 Jun 2017 08:34:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-4750?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062770#comment-16062770
] 

Michal Borowiecki edited comment on KAFKA-4750 at 6/26/17 8:33 AM:
-------------------------------------------------------------------

Deserialiser.deserialize javadoc says:
     * @param data serialized bytes; may be null; implementations are recommended to handle
null by +returning a value+ or null rather than throwing an exception.

If it's fair for deserializer to return a value when a null byte array is provided, by symmetry,
the serializer should be able to return null when such an object is provided and achieve correct
round-tripping.


was (Author: mihbor):
Deserialiser.deserialize javadoc says:
     * @param data serialized bytes; may be null; implementations are recommended to handle
null by +returning a value+ or null rather than throwing an exception.

If it's fair for deserializer to return a value when a null byte array is provided, by symmetry,
the serializer should be able to return null when such an object is provided.

> KeyValueIterator returns null values
> ------------------------------------
>
>                 Key: KAFKA-4750
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4750
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>    Affects Versions: 0.10.1.1, 0.11.0.0, 0.10.2.1
>            Reporter: Michal Borowiecki
>            Assignee: Evgeny Veretennikov
>              Labels: newbie
>         Attachments: DeleteTest.java
>
>
> The API for ReadOnlyKeyValueStore.range method promises the returned iterator will not
return null values. However, after upgrading from 0.10.0.0 to 0.10.1.1 we found null values
are returned causing NPEs on our side.
> I found this happens after removing entries from the store and I found resemblance to
SAMZA-94 defect. The problem seems to be as it was there, when deleting entries and having
a serializer that does not return null when null is passed in, the state store doesn't actually
delete that key/value pair but the iterator will return null value for that key.
> When I modified our serilizer to return null when null is passed in, the problem went
away. However, I believe this should be fixed in kafka streams, perhaps with a similar approach
as SAMZA-94.



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