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Python print の内容が docker logs に見えない件について

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下記のように Dockerfile があります

CMD ["python", "/app.py"]

app.py にこんな処理があります:

print 'some log'

docker run で起動します:

docker run -d xxx

Logをみます:

docke logs -f yyy

なかなか期待の Log が出てきません。

調べたところ、Python による標準出力のバッファーのが原因だそうです。

バッファーをしなくて直ちに Log を見たい場合、 python -u でアプリを起動すればいいことです。

下記のように修正したら、 docker logs も無事に Log を見ることができました。

CMD ["python", "-u", "/app.py"]
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