Split discovery intervals

[rtorrero]

This PR superseedes #876 and in addition to just splitting the subscription discovery, it splits all the discoveries into separately configurable variables:

ClusterDiscoveryPeriod      time.Duration
SAPSystemDiscoveryPeriod    time.Duration
CloudDiscoveryPeriod        time.Duration
HostDiscoveryPeriod         time.Duration
SubscriptionDiscoveryPeriod time.Duration

Some notes:

• The subscription discovery interval is kept as a hidden parameter
• All others are visible in the trento CLI when using --help

• We add the interval as part of the BaseDiscovery struct in the interval field and access them through the GetInterval() method

  @abravosuse min/max limits on the intervals have not been added as have a few questions:

  • Do we add the limits to all discoveries or just the subscription one?
  • What do you think about the default values? (10 for all execept subscription which is 900)

[abravosuse]

@rtorrero sorry for the late reply:

• Do we add the limits to all discoveries or just the subscription one? I think all discoveries should have, at least, a min limit. No so sure about the max limit: users should be able to adjust them to whatever value comfortable with. If a user is OK having their cluster info updated every 10m, who are we to say no?

• What do you think about the default values? (10 for all except subscription which is 900) Good.

[rtorrero]

The changes that we discussed should be there. Regarding the default and minimal values: I've set all defaults to 10 seconds, except the discovery which is set at 900s. The minimal values are 1 for all except for the discovery where we have a min allowed value of 500s.

@abravosuse if you want to change these let me know

[abravosuse]

The changes that we discussed should be there. Regarding the default and minimal values: I've set all defaults to 10 seconds, except the discovery which is set at 900s. The minimal values are 1 for all except for the discovery where we have a min allowed value of 500s.

@abravosuse if you want to change these let me know

I'm fine with these values @rtorrero.