In-memory cache for speed-up (#88)

* Experiment with local cache

* Commit

* Cache all we can, invalidate later

* Commit

* separate cache class

* More cached

* Proper invalidate

* Complete the repos

* Fix the build

* Fix build

* Status reporting

pkg/dashboard/subproc/cache.go

@@ -0,0 +1,100 @@
+package subproc
+
+import (
+	"context"
+	"errors"
+	"github.com/eko/gocache/v3/marshaler"
+	"github.com/eko/gocache/v3/store"
+	gocache "github.com/patrickmn/go-cache"
+	log "github.com/sirupsen/logrus"
+	"time"
+)
+
+type CacheKey = string
+
+const CacheKeyRelList CacheKey = "installed-releases-list"
+const CacheKeyShowChart CacheKey = "show-chart"
+const CacheKeyRelHistory CacheKey = "release-history"
+const CacheKeyRevManifests CacheKey = "rev-manifests"
+const CacheKeyRevNotes CacheKey = "rev-notes"
+const CacheKeyRevValues CacheKey = "rev-values"
+const CacheKeyRepoChartValues CacheKey = "chart-values"
+const CacheKeyAllRepos CacheKey = "all-repos"
+
+type Cache struct {
+	Marshaler *marshaler.Marshaler `json:"-"`
+	HitCount  int
+	MissCount int
+}
+
+func NewCache() *Cache {
+	gocacheClient := gocache.New(5*time.Minute, 10*time.Minute)
+	gocacheStore := store.NewGoCache(gocacheClient)
+
+	// TODO: use tiered cache with some disk backend, allow configuring that static cache folder
+
+	// Initializes marshaler
+	marshal := marshaler.New(gocacheStore)
+	return &Cache{
+		Marshaler: marshal,
+	}
+}
+
+func (c *Cache) String(key CacheKey, tags []string, callback func() (string, error)) (string, error) {
+	if tags == nil {
+		tags = make([]string, 0)
+	}
+	tags = append(tags, key)
+
+	ctx := context.Background()
+	out := ""
+	_, err := c.Marshaler.Get(ctx, key, &out)
+	if err == nil {
+		log.Debugf("Using cached value for %s", key)
+		c.HitCount++
+		return out, nil
+	} else if !errors.Is(err, store.NotFound{}) {
+		return "", err
+	}
+	c.MissCount++
+
+	out, err = callback()
+	if err != nil {
+		return "", err
+	}
+
+	err = c.Marshaler.Set(ctx, key, out, store.WithTags(tags))
+	if err != nil {
+		return "", err
+	}
+	return out, nil
+}
+
+func (c *Cache) Invalidate(tags ...CacheKey) {
+	log.Debugf("Invalidating tags %v", tags)
+	err := c.Marshaler.Invalidate(context.Background(), store.WithInvalidateTags(tags))
+	if err != nil {
+		log.Warnf("Failed to invalidate tags %v: %s", tags, err)
+	}
+}
+
+func (c *Cache) Clear() error {
+	c.HitCount = 0
+	c.MissCount = 0
+	return c.Marshaler.Clear(context.Background())
+}
+
+func cacheTagRelease(namespace string, name string) CacheKey {
+	return "release" + "\v" + namespace + "\v" + name
+}
+func cacheTagRepoVers(chartName string) CacheKey {
+	return "repo-versions" + "\v" + chartName
+}
+
+func cacheTagRepoCharts(name string) CacheKey {
+	return "repo-charts" + "\v" + name
+}
+
+func cacheTagRepoName(name string) CacheKey {
+	return "repo-name" + "\v" + name
+}