[Project Monitors] Support multiple hosts/urls/ports in lightweight monitors.

[andrewvc]

Lightweight monitors in the synthetics agent currently do not support the popular multiple hosts feature. When users want to check a list of hosts with the same config, they can use a config like:

- type: tcp 
  id: special-monitors
  name: Special Monitors
  hosts: ["10.0.0.1:8080", "10.0.0.2:8080", "10.0.0.3:8080"]
  schedule: "@every 5m"
  tags: ["special"]

and easily monitor all three. We currently prevent that in our Kibana validation, because it would move us from a 1:1 saved object -> monitor relationship to a 1:N relationship. This issue would solve that by having the synthetics agent essentially treat the hosts and urls fields as a macro, expanding it before communicating to the API.

This requires us to also add the host to both the id and name fields to prevent clashes. This is done today in heartbeat by hashing the host then appending it to the ID in wrappers.go. We currently do not do something similar for the name, relying on the UI to show the name and the URL consistently side-by-side. I propose we change this, and include the plain text URL in the name as a suffix, so, in the example above we'd have names like Special Monitors - 10.0.0.1:8080.

ACs:

• Add support for multiple urls
• Add support for multiple hosts
• Add support for multiple ports

[robdiluca]

Are there any updates about this issue?

[paulb-elastic]

@robdiluca we don't have an update about when this will be prioritised that we can share at the moment (aside from updating the docs to clarify this is not currently possible).

For now, the work around would be to create multiple monitors for each of the hosts/endpoints.

[paulb-elastic]

Added this is also needed for ports