markusthoemmes commented on a change in pull request #2414: SPI approach for pluggable implementations URL: https://github.com/apache/incubator-openwhisk/pull/2414#discussion_r131064319
########## File path: common/scala/src/main/scala/whisk/connector/kafka/KafkaMessagingProvider.scala ########## @@ -0,0 +1,43 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package whisk.connector.kafka + +import scala.concurrent.ExecutionContext +import scala.concurrent.duration.FiniteDuration +import whisk.common.Logging +import whisk.core.WhiskConfig +import whisk.core.connector.MessageConsumer +import whisk.core.connector.MessageProducer +import whisk.core.connector.MessagingProvider +import whisk.spi.Dependencies +import whisk.spi.SingletonSpiFactory + +/** + * A Kafka based implementation of MessagingProvider + */ +class KafkaMessagingProvider() extends MessagingProvider { + def getConsumer(config: WhiskConfig, groupId: String, topic: String, maxPeek: Int, maxPollInterval: FiniteDuration)(implicit logging: Logging): MessageConsumer = { + new KafkaConsumerConnector(config.kafkaHost, groupId, topic, maxPeek, maxPollInterval = maxPollInterval) + } + + def getProducer(config: WhiskConfig, ec:ExecutionContext)(implicit logging: Logging): MessageProducer = new KafkaProducerConnector(config.kafkaHost, ec) +} + +object KafkaMessagingProvider extends SingletonSpiFactory[MessagingProvider] { + override def buildInstance(dependencies: Dependencies): MessagingProvider = new KafkaMessagingProvider +} Review comment: We could just have `object KafkaMessagingProvider extends MessagingProvider` and implement the `getConsumer`/`getProducer` there. Singletons are guaranteed by the underlying JVM then, making the SingletonSpiFactory (and SpiFactory itself) unnecessary. The question at hand is: What is the interface for us? To me it was more like I do: ```scala SpiLoader.instanceOf[MessageProducer]("openwhisk.KafkaProducer") ``` and get an instance of the `KafkaProducer`. Of course that is non-sensical in that Producer and Consumer should be off the same implementation, so I think you're approach is valid. I wonder though if we can generalize then, that each `Spi` needs to be a `Provider`, that is: A factory object providing methods to actually generate the instances. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
