Konstantine Karantasis created KAFKA-6467:
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Summary: Enforce layout of dependencies within a Connect plugin to
be deterministic
Key: KAFKA-6467
URL: https://issues.apache.org/jira/browse/KAFKA-6467
Project: Kafka
Issue Type: Bug
Components: KafkaConnect
Affects Versions: 0.11.0.2, 1.0.0
Reporter: Konstantine Karantasis
Assignee: Konstantine Karantasis
Fix For: 1.0.1, 0.11.0.3
In principle, Connect plugins that intend to load their dependencies in
isolation should not contain any conflicts among the classes they package as
dependencies. In other words, the order in which a plugin's dependencies are
laid out and passed to its plugin class loader should not matter.
However, in practice, there are rare and suboptimal situations where a plugin
needs to bundle a few packages with conflicting dependencies because it doesn't
control packaging of third-party modules. In those cases depending on a
deterministic ordering within the class loader's path can help the Connect
plugin enforce loading of the desired classes as needed. (For example, see
[HDFS connector with MapR
libs|https://github.com/confluentinc/kafka-connect-hdfs/issues/270] or [HDFS
connector with Hive's extended
jar|https://github.com/confluentinc/kafka-connect-hdfs/issues/261)
To achieve such ordering, this improvement suggests ordering a plugin's
dependencies in a nested directory structure by sorting such paths
alphanumerically. This way the deterministic order is implicit (no extra
configuration is required) and a specific dependency can be put earlier or
later in the class loader's path with appropriate naming of its package path
(e.g. within the plugin's directory).
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