Decaton code reading
https://github.com/line/decaton
org.apache.kafka.clients.consumer.ConsumerConfig は一部上書きされる
https://github.com/line/decaton/blob/0489884d071d5dfd24313c696c8a9b6028ddb3c7/processor/src/main/java/com/linecorp/decaton/processor/runtime/ConsumerSupplier.java#L35-L37
DecatonProcessor の config
https://github.com/line/decaton/blob/0489884d071d5dfd24313c696c8a9b6028ddb3c7/processor/src/main/java/com/linecorp/decaton/processor/ProcessorProperties.java
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SubscriptionBuilder(subscriptionId, ProcessorProperties, ProcessorsBuilder)
ProcessorsBuilder (topic, extractor, DecatonProcessor)
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Executors.newSingleThreadExecutor が partition の数 * 並列度だけ呼ばれる
https://github.com/line/decaton/blob/0489884d071d5dfd24313c696c8a9b6028ddb3c7/processor/src/main/java/com/linecorp/decaton/processor/runtime/ProcessorUnit.java#L43