[code] reduce Gather() cyclomatic complexity

plugins/inputs/vcstat/vcstat.go

@@ -179,67 +179,38 @@ func (vcs *VCstatConfig) Description() string {
 // the data collection and writes all metrics into the Accumulator passed as an argument.
 func (vcs *VCstatConfig) Gather(acc telegraf.Accumulator) error {
 	var (
-		col       *vccollector.VcCollector
 		startTime time.Time
 		err       error
 	)
 
-	//--- re-Init if needed
-	if vcs.ctx == nil || vcs.ctx.Err() != nil || vcs.vcc == nil {
-		if err = vcs.Init(); err != nil {
-			return gatherError(acc, err)
-		}
-	}
-	col = vcs.vcc
-	if !col.IsActive(vcs.ctx) {
-		if vcs.SessionsCreated.Get() > 0 {
-			acc.AddError(fmt.Errorf("vCenter session not active, re-authenticating..."))
-		}
-		if err = col.Open(vcs.ctx, time.Duration(vcs.Timeout)); err != nil {
-			return gatherError(acc, err)
-		}
-		vcs.SessionsCreated.Incr(1)
+	if err = vcs.keepActiveSession(acc); err != nil {
+		return gatherError(acc, err)
 	}
 	acc.SetPrecision(getPrecision(vcs.pollInterval))
+
 	// poll using a context with timeout
 	ctx1, cancel1 := context.WithTimeout(vcs.ctx, time.Duration(vcs.Timeout))
 	defer cancel1()
 	startTime = time.Now()
 
-	//--- Get vCenter basic stats
-	if err = col.CollectVcenterInfo(ctx1, acc); err != nil {
-		return gatherError(acc, err)
-	}
-
-	//--- Get Datacenters info
-	if vcs.ClusterInstances || vcs.HostInstances {
-		if err = col.CollectDatacenterInfo(ctx1, acc); err != nil {
-			return gatherError(acc, err)
-		}
-	}
 
-	//--- Get Clusters info
-	if vcs.ClusterInstances {
-		if err = col.CollectClusterInfo(ctx1, acc); err != nil {
-			return gatherError(acc, err)
-		}
+	//--- Get vCenter, DCs and Clusters info
+	if err = vcs.gatherHighLevelEntities(ctx1, acc); err != nil {
+		return gatherError(acc, err)
 	}
 
-	//--- Get Hosts, Network,... info
+	//--- Get Hosts, Networks and Storage info
 	if err = vcs.gatherHost(ctx1, acc); err != nil {
 		return gatherError(acc, err)
 	}
 	if err = vcs.gatherNetwork(ctx1, acc); err != nil {
 		return gatherError(acc, err)
 	}
-
-	//--- Get Datastores info
-	if vcs.DatastoreInstances {
-		if err = col.CollectDatastoresInfo(ctx1, acc); err != nil {
-			return gatherError(acc, err)
-		}
+	if err = vcs.gatherStorage(ctx1, acc); err != nil {
+		return gatherError(acc, err)
 	}
 
+
 	// selfmonitoring
 	vcs.GatherTime.Set(int64(time.Since(startTime).Nanoseconds()))
 	vcs.NotRespondingHosts.Set(int64(vcs.vcc.GetNumberNotRespondingHosts()))
@@ -252,6 +223,63 @@ func (vcs *VCstatConfig) Gather(acc telegraf.Accumulator) error {
 	return nil
 }
 
+// keepActiveSession keeps an active session with vsphere
+func (vcs *VCstatConfig) keepActiveSession(acc telegraf.Accumulator) error {
+	var (
+		col *vccollector.VcCollector
+		err error
+	)
+
+	if vcs.ctx == nil || vcs.ctx.Err() != nil || vcs.vcc == nil {
+		if err = vcs.Init(); err != nil {
+			return err
+		}
+	}
+	col = vcs.vcc
+	if !col.IsActive(vcs.ctx) {
+		if vcs.SessionsCreated.Get() > 0 {
+			acc.AddError(fmt.Errorf("vCenter session not active, re-authenticating..."))
+		}
+		if err = col.Open(vcs.ctx, time.Duration(vcs.Timeout)); err != nil {
+			return err
+		}
+		vcs.SessionsCreated.Incr(1)
+	}
+
+	return nil
+}
+
+// gatherHighLevelEntities gathers datacenters and clusters stats
+func (vcs *VCstatConfig) gatherHighLevelEntities(ctx context.Context, acc telegraf.Accumulator) error {
+	var (
+		col *vccollector.VcCollector
+		err error
+	)
+
+	col = vcs.vcc
+
+	//--- Get vCenter basic stats
+	if err = col.CollectVcenterInfo(ctx, acc); err != nil {
+		return err
+	}
+
+	//--- Get Datacenters info
+	if vcs.ClusterInstances || vcs.HostInstances {
+		if err = col.CollectDatacenterInfo(ctx, acc); err != nil {
+			return err
+		}
+	}
+
+	//--- Get Clusters info
+	if vcs.ClusterInstances {
+		if err = col.CollectClusterInfo(ctx, acc); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // gatherHost gathers info and stats per host
 func (vcs *VCstatConfig) gatherHost(ctx context.Context, acc telegraf.Accumulator) error {
 	var (
@@ -316,6 +344,23 @@ func (vcs *VCstatConfig) gatherNetwork(ctx context.Context, acc telegraf.Accumul
 	return nil
 }
 
+// gatherStorage gathers storage entities info
+func (vcs *VCstatConfig) gatherStorage(ctx context.Context, acc telegraf.Accumulator) error {
+	var (
+		col *vccollector.VcCollector
+		err error
+	)
+
+	col = vcs.vcc
+	if vcs.DatastoreInstances {
+		if err = col.CollectDatastoresInfo(ctx, acc); err != nil {
+			return gatherError(acc, err)
+		}
+	}
+
+	return nil
+}
+
 // gatherError adds the error to the telegraf accumulator
 func gatherError(acc telegraf.Accumulator, err error) error {
 	// No need to signal errors if we were merely canceled.