So if some of the hosted websites have Error 503 while accessing them and in the error LOG you find:
[box type=”warning”] relocation error: symbol deflateInit2_, version libmysqlclient_16 not defined in file libmysqlclient.so.16 with link time reference
This is caused by a corrupted libmysqlclient.so and in order to fix the issue quickly you will have to replace it by executing the following commands:
mv /usr/lib64/libmysqlclient.so.16.0.0 /usr/lib64/__libmysqlclient.so.16.0.0
cp /usr/lib64/mysql/libmysqlclient.so.16.0.0 /usr/lib64/libmysqlclient.so.16.0.0
In my particular situation, the server that had this issue was a cPanel server with LiteSpeed web server and Percona MySQL server.
If the Database server wasn’t Percona, just a plain mysql, I’m pretty confident that the fix would be just running an forced upcp so that the mysql libraries would get reinstalled as well.