mysqld_safe how does the instance check work

daniel_hauke

Hi everybody,

can anyone please explain me how the mysqld_safe process is doing the check of the mysqld process.

Does it use mysqladmin ping or something like that?

Greetings Daniel

Gaz in Oz

...can anyone please explain me how the mysqld_safe process is doing the check of the mysqld process.

Looking at the /usr/bin/mysqld_safe shell script, it checks to see if mysqld is running via:

## If there exists an old pid file, check if the daemon is already running# Note: The switches to 'ps' may depend on your operating systemif test -f "$pid_file"then  PID=`cat "$pid_file"`  if /usr/bin/kill -0 $PID > /dev/null 2> /dev/null  then    if /bin/ps wwwp $PID | grep -v " grep" | grep -v mysqld_safe | grep -- "$MYSQLD" > /dev/null    then    # The pid contains a mysqld process      log_error "A mysqld process already exists"      exit 1    fi  fi  rm -f "$pid_file"  if test -f "$pid_file"  then    log_error "Fatal error: Can't remove the pid file:$pid_filePlease remove it manually and start $0 again;mysqld daemon not started"    exit 1  fifi

Lines 07. to 14.

Does it use mysqladmin ping or something like that?

No.

   https://dev.mysql.com/doc/refman/5.7/en/mysqld-safe.html

Gaz in Oz

...can anyone please explain me how the mysqld_safe process is doing the check of the mysqld process.

Looking at the /usr/bin/mysqld_safe shell script, it checks to see if mysqld is running via:

## If there exists an old pid file, check if the daemon is already running# Note: The switches to 'ps' may depend on your operating systemif test -f "$pid_file"then  PID=`cat "$pid_file"`  if /usr/bin/kill -0 $PID > /dev/null 2> /dev/null  then    if /bin/ps wwwp $PID | grep -v " grep" | grep -v mysqld_safe | grep -- "$MYSQLD" > /dev/null    then    # The pid contains a mysqld process      log_error "A mysqld process already exists"      exit 1    fi  fi  rm -f "$pid_file"  if test -f "$pid_file"  then    log_error "Fatal error: Can't remove the pid file:$pid_filePlease remove it manually and start $0 again;mysqld daemon not started"    exit 1  fifi

Lines 07. to 14.

Does it use mysqladmin ping or something like that?

No.

   https://dev.mysql.com/doc/refman/5.7/en/mysqld-safe.html

daniel_hauke

Hi,

thanks fot the hint and your answer. That was very helpful.

Greetings Daniel