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https://issues.apache.org/jira/browse/KAFKA-3910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15361212#comment-15361212
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ASF GitHub Bot commented on KAFKA-3910:
---------------------------------------
GitHub user johnhofman opened a pull request:
https://github.com/apache/kafka/pull/1582
KAFKA-3910: Cyclic schema support in ConnectSchema and SchemaBuilder
This feature uses a FutureSchema as a placeholder to be resolved later.
Resolution is attempted whenever a ConnectSchema is constructed, it attempts to
resolve all its children (fields, keySchema, or valueSchema) and recurses until
the end of the tree.
A FutureSchema is resolved when it finds a parent schema that matches its
name, and optional flag. If a FutureSchema is accessed before being resolved,
it will throw a DataException.
The SchemaBuilder constructs a FutureSchema if a field is added with only a
type name.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/johnhofman/kafka cyclic
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/kafka/pull/1582.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1582
----
commit d932db4544cc2d20a46bf873fbd92f2c09450276
Author: John Hofman <johnhof...@users.noreply.github.com>
Date: 2016-06-30T20:04:19Z
Add FutureSchema to support cyclic schemas
commit 7d95c487d4a5bf3cb751deb98425e5123abb461b
Author: John Hofman <johnhof...@users.noreply.github.com>
Date: 2016-07-04T07:32:47Z
Fix resolution failure test
commit 09f1b47c238ff10f58681e44816f2ba39ed95166
Author: John Hofman <johnhof...@users.noreply.github.com>
Date: 2016-07-04T09:53:58Z
Move cyclic comparison resolution to FutureSchema
commit c1c632b51f80d81c29cb66a35c5aed867ad869e7
Author: John Hofman <johnhof...@users.noreply.github.com>
Date: 2016-07-04T11:26:35Z
Clean up unused tokens, minor spelling fixes
----
> Cyclic schema support in ConnectSchema and SchemaBuilder
> --------------------------------------------------------
>
> Key: KAFKA-3910
> URL: https://issues.apache.org/jira/browse/KAFKA-3910
> Project: Kafka
> Issue Type: Improvement
> Components: KafkaConnect
> Affects Versions: 0.10.0.0
> Reporter: John Hofman
> Assignee: Ewen Cheslack-Postava
> Priority: Blocker
>
> Cyclic schema's are not supported by ConnectSchema or SchemaBuilder.
> Subsequently the AvroConverter (confluentinc/schema-registry) hits a stack
> overflow when converting a cyclic avro schema, e.g:
> {code}
> {"type":"record",
> "name":"list","fields":[{"name":"value","type":"int"},{"name":"next","type":["null","list"]}]}
> {code}
> This is a blocking issue for all connectors running on the connect framework
> with data containing cyclic references. The AvroConverter cannot support
> cyclic schema's until the underlying ConnectSchema and SchemaBuilder do.
> To reproduce the stack-overflow (Confluent-3.0.0):
> Produce some cyclic data:
> {code}
> bin/kafka-avro-console-producer --broker-list localhost:9092 --topic test
> --property value.schema='{"type":"record",
> "name":"list","fields":[{"name":"value","type":"int"},{"name":"next","type":["null","list"]}]}'
> {"value":1,"next":null}
> {"value":1,"next":{"list":{"value":2,"next":null}}}
> {code}
> Then try to consume it with connect:
> {code:title=connect-console-sink.properties}
> name=local-console-sink
> connector.class=org.apache.kafka.connect.file.FileStreamSinkConnector
> tasks.max=1
> topics=test
> {code}
> {code}
> ./bin/connect-standalone
> ./etc/schema-registry/connect-avro-standalone.properties
> connect-console-sink.properties
> … start up logging …
> java.lang.StackOverflowError
> at org.apache.avro.JsonProperties.getJsonProp(JsonProperties.java:54)
> at org.apache.avro.JsonProperties.getProp(JsonProperties.java:45)
> at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1055)
> at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1103)
> at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1137)
> at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1103)
> at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1137)
> {code}
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