[
https://issues.apache.org/jira/browse/KAFKA-12704?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Kalpesh Patel updated KAFKA-12704:
----------------------------------
Description:
Concurrent requests to the {{PUT
/connector-plugins/\{connectorType}/config/validate}} endpoint are [delegated
to the
herder|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/resources/ConnectorPluginsResource.java#L81],
which [caches connector
instances|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L536-L544]
that are used [during config
validation|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L310].
This has the effect that, should concurrent requests to that endpoint occur
for the same connector type and the connector isn't created yet then there is
also a race condition in the {{AbstractHerder::getConnector}} method that
potentially fails to detect that an instance of the connector has already been
created and, as a result, creates another instance.
This can be solved by using computeIfAbsent to create the connector
was:
Requests to the {{PUT /connector-plugins/\{connectorType}/config/validate}}
endpoint are [delegated to the
herder|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/resources/ConnectorPluginsResource.java#L81],
which [caches connector
instances|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L536-L544]
that are used [during config
validation|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L310].
This has the effect that, should concurrent requests to that endpoint occur
for the same connector type, the same connector instance may be responsible for
[validating those
configurations|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L334]
concurrently _(may_ instead of _will_ because there is also a race condition
in the {{AbstractHerder::getConnector}} method that potentially fails to detect
that an instance of the connector has already been created and, as a result,
creates a second instance).
This is slightly problematic because the
[Connector::validate|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/api/src/main/java/org/apache/kafka/connect/connector/Connector.java#L122-L127]
method is not marked as thread-safe. However, because a lot of connectors out
there tend to use the default implementation for that method, it's probably not
super urgent that we patch this immediately.
A couple of options are:
# Update the docs for that method to specify that it must be thread-safe
# Rewrite the connector validation logic in the framework to avoid
concurrently invoking {{Connector::validate}} on the same instance.
> Concurrent calls to AbstractHerder::getConnector can potentially create two
> connector instances
> -----------------------------------------------------------------------------------------------
>
> Key: KAFKA-12704
> URL: https://issues.apache.org/jira/browse/KAFKA-12704
> Project: Kafka
> Issue Type: Bug
> Components: KafkaConnect
> Reporter: Kalpesh Patel
> Assignee: Kalpesh Patel
> Priority: Minor
>
> Concurrent requests to the {{PUT
> /connector-plugins/\{connectorType}/config/validate}} endpoint are [delegated
> to the
> herder|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/resources/ConnectorPluginsResource.java#L81],
> which [caches connector
> instances|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L536-L544]
> that are used [during config
> validation|https://github.com/apache/kafka/blob/16ee326755e3f13914a0ed446c34c84e65fc0bc4/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/AbstractHerder.java#L310].
> This has the effect that, should concurrent requests to that endpoint occur
> for the same connector type and the connector isn't created yet then there is
> also a race condition in the {{AbstractHerder::getConnector}} method that
> potentially fails to detect that an instance of the connector has already
> been created and, as a result, creates another instance.
>
> This can be solved by using computeIfAbsent to create the connector
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