1 files changed, 93 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/agent/confgroup/cache.go b/src/go/collectors/go.d.plugin/agent/confgroup/cache.go
new file mode 100644
index 000000000..40c8071d5
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/agent/confgroup/cache.go
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package confgroup
+
+func NewCache() *Cache {
+	return &Cache{
+		hashes:  make(map[uint64]uint),
+		sources: make(map[string]map[uint64]Config),
+	}
+}
+
+type Cache struct {
+	hashes  map[uint64]uint              // map[cfgHash]cfgCount
+	sources map[string]map[uint64]Config // map[cfgSource]map[cfgHash]cfg
+}
+
+func (c *Cache) Add(group *Group) (added, removed []Config) {
+	if group == nil {
+		return nil, nil
+	}
+
+	if len(group.Configs) == 0 {
+		return c.addEmpty(group)
+	}
+
+	return c.addNotEmpty(group)
+}
+
+func (c *Cache) addEmpty(group *Group) (added, removed []Config) {
+	set, ok := c.sources[group.Source]
+	if !ok {
+		return nil, nil
+	}
+
+	for hash, cfg := range set {
+		c.hashes[hash]--
+		if c.hashes[hash] == 0 {
+			removed = append(removed, cfg)
+		}
+		delete(set, hash)
+	}
+
+	delete(c.sources, group.Source)
+
+	return nil, removed
+}
+
+func (c *Cache) addNotEmpty(group *Group) (added, removed []Config) {
+	set, ok := c.sources[group.Source]
+	if !ok {
+		set = make(map[uint64]Config)
+		c.sources[group.Source] = set
+	}
+
+	seen := make(map[uint64]struct{})
+
+	for _, cfg := range group.Configs {
+		hash := cfg.Hash()
+		seen[hash] = struct{}{}
+
+		if _, ok := set[hash]; ok {
+			continue
+		}
+
+		set[hash] = cfg
+		if c.hashes[hash] == 0 {
+			added = append(added, cfg)
+		}
+		c.hashes[hash]++
+	}
+
+	if !ok {
+		return added, nil
+	}
+
+	for hash, cfg := range set {
+		if _, ok := seen[hash]; ok {
+			continue
+		}
+
+		delete(set, hash)
+		c.hashes[hash]--
+		if c.hashes[hash] == 0 {
+			removed = append(removed, cfg)
+		}
+	}
+
+	if ok && len(set) == 0 {
+		delete(c.sources, group.Source)
+	}
+
+	return added, removed
+}