I just learned Redis and have never understood stand-alone testing. . . . The Redis cluster worked fine before. After I enabled the sentry mode, I found that sentile was not easy to use and restored some Redis configurations. When I used PHP to connect to Redis, I used $redis->connect( '127.0.0.1'); There was a problem with this code. The centos system did not report an error (even if I started the error reporting function of PHP, it was useless). The code just ran to $redis->connect('127.0. 0.1'); unable to run