Improve crash on failed agent initialization (#326)

* Move fact gathering up and block on failed listen

* Add test to check for error on invalid amqp url

internal/agent/agent.go

@@ -74,8 +74,25 @@ func GetAgentID(fileSystem afero.Fs) (string, error) {
 
 // Start the Agent. This will start the discovery ticker and the heartbeat ticker
 func (a *Agent) Start(ctx context.Context) error {
+	gathererRegistry := gatherers.NewRegistry(gatherers.StandardGatherers())
+
+	c := factsengine.NewFactsEngine(a.config.AgentID, a.config.FactsServiceURL, *gathererRegistry)
+	log.Info("Starting fact gathering service...")
+	if err := c.Subscribe(); err != nil {
+		return err
+	}
+
 	g, groupCtx := errgroup.WithContext(ctx)
 
+	g.Go(func() error {
+		if err := c.Listen(groupCtx); err != nil {
+			return err
+		}
+
+		log.Info("fact gathering stopped.")
+		return nil
+	})
+
 	for _, d := range a.discoveries {
 		dLoop := d
 		g.Go(func() error {
@@ -93,8 +110,6 @@ func (a *Agent) Start(ctx context.Context) error {
 		return nil
 	})
 
-	gathererRegistry := gatherers.NewRegistry(gatherers.StandardGatherers())
-
 	log.Info("loading plugins")
 
 	pluginLoaders := gatherers.PluginLoaders{
@@ -111,22 +126,6 @@ func (a *Agent) Start(ctx context.Context) error {
 
 	gathererRegistry.AddGatherers(gatherersFromPlugins)
 
-	c := factsengine.NewFactsEngine(a.config.AgentID, a.config.FactsServiceURL, *gathererRegistry)
-
-	g.Go(func() error {
-		log.Info("Starting fact gathering service...")
-		if err := c.Subscribe(); err != nil {
-			return err
-		}
-
-		if err := c.Listen(groupCtx); err != nil {
-			return err
-		}
-
-		log.Info("fact gathering stopped.")
-		return nil
-	})
-
 	return g.Wait()
 }
 

internal/agent/agent_test.go

@@ -1,10 +1,13 @@
 package agent_test
 
 import (
+	"context"
 	"testing"
 
 	"github.com/stretchr/testify/suite"
 	"github.com/trento-project/agent/internal/agent"
+	"github.com/trento-project/agent/internal/discovery"
+	"github.com/trento-project/agent/internal/discovery/collector"
 	"github.com/trento-project/agent/test/helpers"
 )
 
@@ -23,3 +26,22 @@ func (suite *AgentTestSuite) TestAgentGetAgentID() {
 	suite.NoError(err)
 	suite.Equal(helpers.DummyAgentID, agentID)
 }
+
+func (suite *AgentTestSuite) TestAgentFailsWithInvalidFactsServiceURL() {
+	config := &agent.Config{
+		AgentID:      helpers.DummyAgentID,
+		InstanceName: "test",
+		DiscoveriesConfig: &discovery.DiscoveriesConfig{
+			DiscoveriesPeriodsConfig: &discovery.DiscoveriesPeriodConfig{},
+			CollectorConfig:          &collector.Config{},
+		},
+		FactsServiceURL: "amqp://trento:trento@localhost:12345/somevhost",
+		PluginsFolder:   "/usr/etc/trento/plugins/",
+	}
+
+	agent, _ := agent.NewAgent(config)
+	ctx := context.Background()
+	err := agent.Start(ctx)
+
+	suite.ErrorContains(err, "connect: connection refused")
+}