Thinkphp cannot read the cache. Runtime must be deleted to be normal.

A normal branch of a project has been in a normal branch for 2 years, but there has been a sudden error in these two days. The
test found that thinkphp could not read the cache, and runtime must be deleted to be normal.
I even restarted the server, but it didn"t work out. The
code is as follows, please take a look at it.

        $code = I("get.nt");
        $key = C("authcodekey");
        $id = a_decode($code,$key);
        // var_dump($code); die(); 
        
        if ((null == $code)||("" == $code)){
            redirect("/Home/Index/home.html");            
            // redirect("/home.html"); 
        }  

        //runtime
        if(!S($code)){ //
            M("notes")->cache($code,120)->where(array("note_id"=>$id))->find();            
        } 
        
        $result=S($code);     
        if($result["code"]!=$code){ 
            // redirect("/Home/Error/index/error/"."");
            //20181211 test begin
            echo "string1111111111<br>";
            var_dump($code); //
            var_dump($id); //
            echo "result_code-->".$result["code"]."<br>";  //
            M("notes")->cache($code,120)->where(array("note_id"=>$id))->find(); 
            //runtime          
            //20181211 test end            
        }

the environmental background of the problems and what methods you have tried

runtime must be deleted to be normal.
I even restarted the server, but it didn"t work out.

related codes

/ / Please paste the code text below (do not replace the code with pictures)

what result do you expect? What is the error message actually seen?

Mar.11,2022

A possibility that your disk space is full and the runtime directory can no longer be written to

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-64f5-1e3236e-4419a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e3236e-4419a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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