August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
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204
10 章 Spark Streaming
};
JavaPairDStream<Integer, Long> responseCodeCountDStream = accessLogsDStream.mapToPair(
new PairFunction<ApacheAccessLog, Integer, Long>() {
public Tuple2<Integer, Long> call(ApacheAccessLog log) {
return new Tuple2(log.getResponseCode(), 1L);
}})
.updateStateByKey(new UpdateRunningSum());
10.4
出力操作は、最終的に変換されたストリーム中のデータに対して行わなければならないこと（例
えば外部のデータベースへの書き込みや、画面への出力）を指定します。
RDD が遅延評価されるのと同様に、DStream やその子孫の DStream も、出力操作が行われる
までは評価されません。そして、StreamingContext に出力操作が設定されていなければ、その
StreamingContext は起動しません。
すでに使いましたが、一般的にデバッグ出力の操作として使われるのが
print()
です。
print()
は、
DStream
の各バッチの先頭の
10
個の要素を取得して出力します。
プログラムをデバッグすることができたら、結果をセーブするために出力操作を使うこともで ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.