What's going on with Failed to read FastCGI header?

there are a lot of errors in the log that Failed to read FastCGI header does not understand under what circumstances. On the surface of the website, there is no access exception

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Php
Mar.14,2021
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-64f5-1b37873-2b81a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b37873-2b81a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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