Minor edits to "improved systemd integration"

[mamoep]

Is your feature request related to a problem? Please describe.
Monitoring poller instance health via systemd units. The provided solution can be improved further.

Describe the solution you'd like

• The description of the improved systemd integration should be linked into the README (https://github.com/NetApp/harvest/tree/main/service/contrib)
• Poller service Unit file should be modified
  1. improve description
  2. change path to default
  3. add user/group to avoid unix poller /proc issue and improve security
  4. add "WantedBy" to correctly stop when harvest.target is stopped
     Suggestion:

[Unit]
Description="Netapp Harvest Poller instance %I"
PartOf=harvest.target

[Service]
User=harvest
Group=harvest
Type=simple
Restart=on-failure
WorkingDirectory=/opt/harvest
ExecStart=/opt/harvest/bin/harvest --config /opt/harvest/harvest.yml start -f %i

[Install]
WantedBy=harvest.target

-harvest generate systemd output should be modified to allow piping directly to unit file

• harvest.target unit file should use Requires instead of Wants. That way the target will fail if any poller fails to start.
• harvest.target unit file should reference unix poller as last unit to avoid instance discovery error messages. (skip instance [ontap], process: process not found)
  Suggestion

[Unit]
Description="NetApp Harvest Meta Service"
[email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected]

[Install]
WantedBy=multi-user.target' | sudo tee /etc/systemd/system/harvest.target

Describe alternatives you've considered
None

Additional context
None

[cgrinds]

Verified on release/22.02.0 727e0b5 :

• documentation was updated
• description was improved
• default path printed to console is standard service location
• harvest user and group are included in service file
• service file includes WantedBy clause. Pollers are stopped when harvest.target is stopped
• unix poller is added last in the service list