Readv () failed to execute PROPFIND request while reading php: // input (PHP 7, nginx)

Question

After upgrading my server to PHP 7, I get a few errors when starting ownCloud in the current version 8.1.1.

I tried to find out what the problem was, and I went to Sapi.phpSaber lib.

I wrote a very small test script to isolate the error. When I run the following code using the PROPFIND request, I see errors in the log and I am not getting output from php: // input.

<?php 
    fopen("php://input", 'r+');
    echo "Done";
?>

Request using cURL:

curl -i -X PROPFIND https://cloud.example.com/readv-demo.php  -d 'Demo'

Error in nginx error log:

*285599 readv() failed (104: Connection reset by peer) while reading upstream, client: 5.35.252.37, server: cloud.example.com, request: "PROPFIND /readv-demo.php HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.0-fpm.sock:", host: "cloud.example.com"

The server worked like a charm using PHP 5.6, and I tried to run PHP 7 without changes. Everything on the server side is fine, but this error.

I also tried suggestions to get around errors readv()and changed several settings, for example:

max_input_time = ...
max_execution_time = ...
default_socket_timeout = ...
request_terminate_timeout = ...