May 2019
Intermediate to advanced
464 pages
9h 22m
Japanese
Content preview from Node.jsデザインパターン 第2版
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130
5
章 ストリーム
ここで
urlList.txt
には次のような
URL
のリストが含まれています。
http://www.mariocasciaro.me
http://loige.co
http://thiswillbedownforsure.com
コマンドの実行が終了すると、ファイル
results.txt
が作成されています。このファイルにはたと
えば次のような結果が入ります。
http://thiswillbedownforsure.com is down
http://loige.co is up
http://www.mariocasciaro.me is up
結果の順序は入力ファイルの
URL
の順番と異なっている可能性があります（処理が並行に行われる
ため）。
ParallelStream
を
through2
ス ト リ ー ム で 置 き 換 え て 実 行 し て み て く だ さ い。
through2
のほうが遅くなるでしょう。なぜなら
URL
が順番にチェックされるからです。
しかしこの場合
results.txt
の順番は保存されることになります。
5.3.3
順序なしの制限付き並行実行
checkUrls
を何千、何万もの
URL
を含むファイルに対して実行すると問題が生じます。アプリケー
ションが安定的に動作するかも保証ができません。そこで、並行に実行するタスクの数を制限すること
になります。
モ ジ ュ ー ル
limitedParallelStream.js
を 作 成 し ま し ょ う（
15_
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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.