[Antithesis] Refactor recording client management

[serathius]

What would you like to be added?

Current recording client management has a problem. It's easy to create a client and then forget to collect report from it.

Would be better if we had some higher level structure for creating clients that collects all clients and is able to return report for all clients constructed.

Why is this needed?

Make it harder to forget collecting report from client.

[nwnt]

Not sure if you want to discuss this in the weekly robustness call, but I can have a look at this in the meantime too.

[serathius]

Goal is to replace something like:

reports := []report.ClientReport{}
var mux sync.Mutex
var wg sync.WaitGroup
for i:=0;i<6;i++{
  c := client.NewRecordingClient(hosts[i%len(hosts)], ids, baseTime)
  defer c.Close()
  wg.Add(1)
  go func() {
    defer wg.Done()
    traffic.RunTraffic(c...)
    mux.Lock()
    reports = append(reports, c.Report())
    mux.Unlock()
  }()
}
wg.Wait()
return reports

With

clientSet := client.NewSet(ids, baseTime)
defer clientSet.Close()
var wg sync.WaitGroup
for i:=0;i<6;i++{
  c := clientSet.NewClient(hosts[i%len(hosts)])
  wg.Add(1)
  go func() {
    defer wg.Done()
    traffic.RunTraffic(c...)
  }()
}
wg.Wait()
return clientSet.Reports()

[serathius]

So:

• Add a ClientSet struct that manages livecycle of clients
• Move common arguments like ids, baseTime to ClientSet
• All clients created are recorded within clientSet, allowing as to collect reports via clientset for all clients created by it.
• [optional] Allow for closing clients directly or via clientset.
• [optional] Safeguard collecting reports before all clients are closed. Prevent Creation of new clients after clientset is closed.

Note, RecordingClient is used around the code, but we don't need to refactor everything at once. Let's do it in smaller steps.