$ php -f lock.php 
[2018-10-24 10:40:29] EXCEPTION: (AphrontConnectionLostQueryException) #2006: MySQL server has gone away

This error may occur if your configured MySQL "wait_timeout" or "max_allowed_packet" values are too small. This may also indicate that something used the MySQL "KILL <process>" command to kill the connection running the query. at [<phutil>/src/aphront/storage/connection/mysql/AphrontBaseMySQLDatabaseConnection.php:304]
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