Nginx cannot be accessed after running for a period of time

A nginx, is installed on the CentOS6.8 system to forward the background management platform and the api interface. Access is fine after the nginx restart, but not through the browser after running for a period of time. At the beginning, I could not find the reason, so I restarted nginx, and then I could access it again. Today, the test girl said that the server could not be accessed. After looking for it all afternoon, I still couldn"t find the reason. I looked it up on the Internet and said that the log file was too large and should be cut regularly. I don"t know if it is this. I would like to trouble you to understand the great god of Nginx to help solve it. Thank you

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Nov.08,2021

look at the nginx log.
look at the background application server log.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e5ac11-44e14.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e5ac11-44e14.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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