Check connection response format when adding External Service to monitoring

User story:

 As a user I want to be able to check connection to external exporter

UI/UX: 

 

Acceptance criteria

• If metrics mode is pull
  • Connection checker checks that pmm-server can connect to external exporter.
• If metrics mode is push
  • Connection checker checks that vm-agent on  a node can connect to external exporter.
• skip-connection-check skips connection check and adds external service

Out of scope:

 

Suggested implementation:

1. Add new flag skip-connection-check to the `pmm-admin add external` command
2. If metrics mode is push
   1. Send request to pmm-agent to check connection with external exporter
3. If metrics mode is pull
   1. Check connection to external exporter from pmm-managed

Out of Scope:

1. Check that data given from the URL is Prometheus metrics

Try to find ready libraries to check for Prometheus metrics.

How to test:

• Case 1
  • Setup external exporter
  • Add external exporter via pmm-admin add external
  • Make ensure that no error is the return
  • Stop external exporter
  • Add external exporter via pmm-admin add external
  • Check that error is returned
  • Add external exporter via pmm-admin add external --skip-connection-checks
  • Check that external exporter is added
• Case 2
  • Setup external exporter
  • Add external exporter via pmm-admin add external-serverless
  • Make ensure that no error is the return
  • Stop external exporter
  • Add external exporter via pmm-admin add external-serverless
  • Check that error is returned
  • Add external exporter via pmm-admin add external-serverless --skip-connection-checks
  • Check that external exporter is added

Details:

In Management API we should check the connection to an external exporter

If API got skip-connection-check parameter connection checking should be skipped.

 

We should add new flag skip-connection-check to the `pmm-admin add external` command