Fix List of the Environments with fetch.

Before the List function dropped all idleRunners of all environments when fetch was set.

Additionally, the replaced environment was not destroyed properly so that a goroutine for it and for all its idle runners remained running.

internal/environment/nomad_manager.go

@@ -87,14 +87,50 @@ func (m *NomadEnvironmentManager) Get(id dto.EnvironmentID, fetch bool) (
 
 func (m *NomadEnvironmentManager) List(fetch bool) ([]runner.ExecutionEnvironment, error) {
 	if fetch {
-		err := m.Load()
+		if err := m.fetchEnvironments(); err != nil {
-		if err != nil {
 			return nil, err
 		}
 	}
 	return m.runnerManager.ListEnvironments(), nil
 }
 
+func (m *NomadEnvironmentManager) fetchEnvironments() error {
+	remoteEnvironmentList, err := m.api.LoadEnvironmentJobs()
+	if err != nil {
+		return fmt.Errorf("failed fetching environments: %w", err)
+	}
+	remoteEnvironments := make(map[string]*nomadApi.Job)
+
+	// Update local environments from remote environments.
+	for _, job := range remoteEnvironmentList {
+		remoteEnvironments[*job.ID] = job
+		id, err := nomad.EnvironmentIDFromTemplateJobID(*job.ID)
+		if err != nil {
+			return fmt.Errorf("cannot parse environment id: %w", err)
+		}
+
+		if localEnvironment, ok := m.runnerManager.GetEnvironment(id); ok {
+			fetchedEnvironment := newNomadEnvironmentFromJob(job, m.api)
+			localEnvironment.SetConfigFrom(fetchedEnvironment)
+			// We destroy only this (second) local reference to the environment.
+			if err = fetchedEnvironment.Delete(true); err != nil {
+				log.WithError(err).Warn("Failed to remove environment locally")
+			}
+		} else {
+			m.runnerManager.StoreEnvironment(newNomadEnvironmentFromJob(job, m.api))
+		}
+	}
+
+	// Remove local environments that are not remote environments.
+	for _, localEnvironment := range m.runnerManager.ListEnvironments() {
+		if _, ok := remoteEnvironments[localEnvironment.ID().ToString()]; !ok {
+			err := localEnvironment.Delete(true)
+			log.WithError(err).Warn("Failed to remove environment locally")
+		}
+	}
+	return nil
+}
+
 func (m *NomadEnvironmentManager) CreateOrUpdate(
 	id dto.EnvironmentID, request dto.ExecutionEnvironmentRequest, ctx context.Context) (created bool, err error) {
 	// Check if execution environment is already existing (in the local memory).