Is mysqld_safe supposed to run always?

Question

In my server I noticed that I have mysqld and mysqld_safe processes running simultaneously. Is mysqld_safe supposed to run always, together with mysqld?

Answer 1

It is best that does. If you read the the code for mysqld_safe, there is basic startup initialization in the beginning and an indefinite loop at the bottom. Here is the pseudocode description of the Loop

Start the Loop

• run mysqld inside the loop
• once mysqld terminates, check for how terrmination occurred
  • if normally terminated, exit loop (such as service mysql stop)
  • if abnormally terminated on startup, exit loop (errmsg posted in error file)
  • if abnormally terminated otherwise, errmsg posted why mysqld died
• retry mysqld

End of Loop

This is an oversimplified description of what mysqld_safe does