rvalle commented on issue #3973: systemd dependency on db
URL: https://github.com/apache/cloudstack/pull/3973#issuecomment-602026825
 
 
   ok I did run the install test with restart after install.
   The database was not corrupted with Wants.
   
   So, this is the status:
   
   **Wants** seems sufficient for startup, shutdown and reboot. While still 
works if no mysql is installed. as @weizhouapache  is pointing. 
   
   **Requires** is stronger and will deal with things like shutting down CSM 
automatically if you happen to stop mysql (perhaps during a mysql update). Will 
also start mysql automatically at CSM startup even if is stopped, or will not 
start CSM if mysql is misconfigured. However it does require mysql to be 
present in the system. And you need to know if it is mysql or mariadb.
   
   What we can do from here?
   
   I think we should include Wants in the distribution file, because it causes 
no harm, and serves as a safeward. It will work and provide protection for most 
of the use cases.
   
   We still have the option to modify the service unit from  /etc/systemd as 
discussed in #3954 adding a **Requires** once we know that the  mysql/mariadb 
runs on localhost for sure. This could be dome from the script 
**cloudstack-setup-databases**.
   
   Another posibilty is simply to include an additional comment with 
instructions in the at the distrubuted Systemd. This comment could be extended 
to other depndencies, something like this in the provided Systemd script:
   
   ```
   # Do not modify this file as your changes will be lost in the next CSM 
update.
   # If you need to add specific dependencies to this service unit do it in the
   # /etc/systemd/system/cloudstack-management.service.d/ directory
   # If you know that either mysql or mariadb is running on this system is a 
good idea to
   # add a Requires dependency there. Check systemd documentation for details
   ```

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