Mysql thread connected is 1-3 but experienced too many connections -

yesterday can see in log within 1 minute timespan, there alot of mysql errors many connections failures. running default setting: 151 max_connections , have not experienced before.

when checking current state, thread connections 1 , 3 @ max.

should increase max_connections or did temporary suffer ddos?

note: solved , worked after minute.

update 2: happend again. can see multiple errors within seconds timeframe error log. why happen?

decrease max_connect_errors to, say, 100. small protection against hackers.

threads_running @ least 1 because includes show.

with max_connections = 151, max_used_connections = 152 means 151 user connections came in, plus 1 "extra" connection allowed , used. reason, not run application root (or other super user).

grant ... on your_database.* ..., not ... on *.* ... application logins. slows down hackers getting @ mysql database.

root should allowed localhost. safety measure.

if web server has "access" log, @ it. may see hundreds of similar looking hack attacks in row. , may similar set of them often.

be sure escape data coming html forms. build inserts. without this, wide open attack.

addenda

select user, host mysql.user super_priv = 'y'; 

will show has super. first cut, should include host values of localhost, 127.0.0.1, or ::1, of localhost. not prevent hackers first hacking client, may on localhost.

this may list way in:

select user, host mysql.user grant_priv = 'y'; 

back question

the web server's (nginx's?) limit on number of connections should less mysql's max_connections. stop hackers (and users) @ door, rather letting them clog both web server , mysql.

even on running system, 20 reasonable max how many should allowed web server simultaneously. if there more, stumbling on each other; better let few resources need rather take longer because of battling on resources.