Revert "Reduce logical complexity"

This reverts commit fd2c7d2.

pkg/monitoring/collector.go

@@ -46,10 +46,18 @@ type typedFactoryDesc struct {
 }
 
 type basicCollector struct {
-	name   string
-	logger logr.Logger
+	name     string
+	mu       sync.Mutex
+	wg       sync.WaitGroup
+	channels []chan<- prometheus.Metric
+	logger   logr.Logger
 }
 
+// only use with Lock called before.
+func (c *basicCollector) clearChannels() {
+	defer c.mu.Unlock()
+	c.channels = []chan<- prometheus.Metric{}
+}
 func (d *typedFactoryDesc) mustNewConstMetric(value float64, labels ...string) prometheus.Metric {
 	return prometheus.MustNewConstMetric(d.desc, d.valueType, value, labels...)
 }

pkg/monitoring/frr.go

@@ -3,6 +3,7 @@ package monitoring
 import (
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/telekom/das-schiff-network-operator/pkg/frr"
@@ -238,10 +239,36 @@ func (c *frrCollector) updateBGPNeighbors(ch chan<- prometheus.Metric, bgpNeighb
 		}
 	}
 }
+func (c *frrCollector) updateChannels(vrfs []frr.VrfVniSpec, routes []route.Information, neighbors frr.BGPVrfSummary) {
+	for _, ch := range c.channels {
+		c.updateVrfs(ch, vrfs)
+		c.updateRoutes(ch, routes)
+		c.updateBGPNeighbors(ch, neighbors)
+	}
+}
 
 func (c *frrCollector) Update(ch chan<- prometheus.Metric) error {
-	c.updateVrfs(ch, c.getVrfs())
-	c.updateRoutes(ch, c.getRoutes())
-	c.updateBGPNeighbors(ch, c.getBGPNeighbors())
+	c.mu.Lock()
+	c.channels = append(c.channels, ch)
+	if len(c.channels) == 1 {
+		c.wg = sync.WaitGroup{}
+		c.wg.Add(1)
+		// Ensure all other function calls will wait.
+		c.mu.Unlock()
+		routes, neighbors, vrfs := func() ([]route.Information, frr.BGPVrfSummary, []frr.VrfVniSpec) {
+			return c.getRoutes(), c.getBGPNeighbors(), c.getVrfs()
+		}()
+		go func(routes []route.Information, neighbors frr.BGPVrfSummary, vrfs []frr.VrfVniSpec) {
+			c.mu.Lock()
+			// unlock is done after return using defer.
+			defer c.wg.Done()
+			c.updateChannels(vrfs, routes, neighbors)
+		}(routes, neighbors, vrfs)
+		// unlock is done in this function.
+		defer c.clearChannels()
+	} else {
+		c.mu.Unlock()
+	}
+	c.wg.Wait()
 	return nil
 }

pkg/monitoring/nl.go

@@ -2,6 +2,7 @@ package monitoring
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/telekom/das-schiff-network-operator/pkg/nl"
@@ -79,8 +80,35 @@ func (c *netlinkCollector) updateNeighbors(ch chan<- prometheus.Metric, neighbor
 	}
 }
 
+func (c *netlinkCollector) updateChannels(neighbors []nl.NeighborInformation, routes []route.Information) {
+	for _, ch := range c.channels {
+		c.updateNeighbors(ch, neighbors)
+		c.updateRoutes(ch, routes)
+	}
+}
+
 func (c *netlinkCollector) Update(ch chan<- prometheus.Metric) error {
-	c.updateNeighbors(ch, c.getNeighbors())
-	c.updateRoutes(ch, c.getRoutes())
+	c.mu.Lock()
+	c.channels = append(c.channels, ch)
+	if len(c.channels) == 1 {
+		c.wg = sync.WaitGroup{}
+		c.wg.Add(1)
+		// Ensure all other function calls will wait.
+		c.mu.Unlock()
+		routes, neighbors := func() ([]route.Information, []nl.NeighborInformation) {
+			return c.getRoutes(), c.getNeighbors()
+		}()
+		go func(routes []route.Information, neighbors []nl.NeighborInformation) {
+			c.mu.Lock()
+			// unlock is done after return using defer.
+			defer c.wg.Done()
+			c.updateChannels(neighbors, routes)
+		}(routes, neighbors)
+		// unlock is done in this function.
+		defer c.clearChannels()
+	} else {
+		c.mu.Unlock()
+	}
+	c.wg.Wait()
 	return nil
 }