C0urante commented on a change in pull request #11775:
URL: https://github.com/apache/kafka/pull/11775#discussion_r819939810
##########
File path:
connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java
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@@ -28,4 +30,46 @@
protected SourceConnectorContext context() {
return (SourceConnectorContext) context;
}
+
+ /**
+ * Signals whether the connector supports exactly-once delivery guarantees
with a proposed configuration.
+ * Developers can assume that worker-level exactly-once support is enabled
when this method is invoked.
+ *
+ * <p>For backwards compatibility, the default implementation will return
{@code null}, but connector developers are
+ * strongly encouraged to override this method to return a non-null value
such as
+ * {@link ExactlyOnceSupport#SUPPORTED SUPPORTED} or {@link
ExactlyOnceSupport#UNSUPPORTED UNSUPPORTED}.
+ *
+ * <p>Similar to {@link #validate(Map) validate}, this method may be
called by the runtime before the
+ * {@link #start(Map) start} method is invoked when the connector will be
run with exactly-once support.
+ *
+ * @param connectorConfig the configuration that will be used for the
connector.
+ * @return {@link ExactlyOnceSupport#SUPPORTED} if the connector can
provide exactly-once support with the given
+ * configuration, and {@link ExactlyOnceSupport#UNSUPPORTED} if it cannot.
If this method is overridden by a
+ * connector, should not be {@code null}, but if {@code null}, it will be
assumed that the connector cannot provide
+ * exactly-once guarantees.
+ * @since 3.2
+ */
+ public ExactlyOnceSupport exactlyOnceSupport(Map<String, String>
connectorConfig) {
+ return null;
+ }
+
+ /**
+ * Signals whether the connector implementation is capable of defining the
transaction boundaries for a
+ * connector with the given configuration. This method is called before
{@link #start(Map)}, only when the
+ * runtime supports exactly-once and the connector configuration includes
{@code transaction.boundary=connector}.
+ *
+ * <p>This method need not be implemented if the connector implementation
does not support defining
+ * transaction boundaries.
+ *
+ * @param connectorConfig the configuration that will be used for the
connector
+ * @return {@link ConnectorTransactionBoundaries#SUPPORTED} if the
connector will define its own transaction boundaries,
+ * or {@link ConnectorTransactionBoundaries#UNSUPPORTED} otherwise. If
this method is overridden by a
+ * connector, should not be {@code null}, but if {@code null}, it will be
assumed that the connector cannot define its own
+ * transaction boundaries.
Review comment:
I think it's reasonable to completely disallow `null` here since the
default implementation returns a non-null value and there's no need to allow
for the possibility that the connector might support custom transaction
boundaries even if it doesn't return `SUPPORTED`. This differs from the case
with `SourceConnector::exactlyOnceSupport`, where it's possible that a
connector might already be capable of providing exactly-once guarantees as-is
without having to implement any new framework APIs.
Thoughts on prohibiting `null` as a return value and both documenting that
fact here and adding a preflight validation step to enforce it?
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