dingweiqings

GUACAMOLE-1589: To apt install software using ubuntu repository is too slow in China

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### This PR is intended to use mirror when a guy stunk in apt install stage as he build docker image. - And here is another point, I found that...

Update design doc

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## Description After I read your good code and try to understand your design , I add some notes in your design md doc and fix some typos. This PR...

[FLINK-29092][tests] use day format for date time ass…

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## What is the purpose of the change Fix FLINK-29092 in unit test ## Brief change log Use ``yyyy-MM-dd`` format instead of default format, ```yyyy-MM-dd--HH``` ## Verifying this change Test...