Restore cache.go

pkg/cache/memory/cache.go

@@ -0,0 +1,134 @@
+// Copyright 2022, 2024 The kpt and Nephio Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package memorycache
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	configapi "github.com/nephio-project/porch/api/porchconfig/v1alpha1"
+	cachetypes "github.com/nephio-project/porch/pkg/cache/types"
+	"github.com/nephio-project/porch/pkg/externalrepo"
+	"github.com/nephio-project/porch/pkg/repository"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/trace"
+)
+
+var tracer = otel.Tracer("memorycache")
+
+// Cache allows us to keep state for repositories, rather than querying them every time.
+//
+// Cache Structure:
+// <cacheDir>/git/
+// * Caches bare git repositories in directories named based on the repository address.
+// <cacheDir>/oci/
+// * Caches oci images with further hierarchy underneath
+// * We Cache image layers in <cacheDir>/oci/layers/ (this might be obsolete with the flattened Cache)
+// * We Cache flattened tar files in <cacheDir>/oci/ (so we don't need to pull to read resources)
+// * We poll the repositories periodically (configurable) and cache the discovered images in memory.
+type Cache struct {
+	mutex        sync.Mutex
+	repositories map[string]*cachedRepository
+	options      cachetypes.CacheOptions
+}
+
+var _ cachetypes.Cache = &Cache{}
+
+func (c *Cache) OpenRepository(ctx context.Context, repositorySpec *configapi.Repository) (repository.Repository, error) {
+	ctx, span := tracer.Start(ctx, "Cache::OpenRepository", trace.WithAttributes())
+	defer span.End()
+
+	key, err := externalrepo.RepositoryKey(repositorySpec)
+	if err != nil {
+		return nil, err
+	}
+
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	if cachedRepo := c.repositories[key]; cachedRepo != nil {
+		// If there is an error from the background refresh goroutine, return it.
+		if err := cachedRepo.getRefreshError(); err == nil {
+			return cachedRepo, nil
+		} else {
+			return nil, err
+		}
+	}
+
+	externalRepo, err := externalrepo.CreateRepositoryImpl(ctx, repositorySpec, c.options.ExternalRepoOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	cachedRepo := newRepository(key, repositorySpec, externalRepo, c.options)
+	c.repositories[key] = cachedRepo
+
+	return cachedRepo, nil
+}
+
+func (c *Cache) UpdateRepository(ctx context.Context, repositorySpec *configapi.Repository) error {
+	return errors.New("update on memory cached repositories is not supported")
+}
+
+func (c *Cache) CloseRepository(ctx context.Context, repositorySpec *configapi.Repository, allRepos []configapi.Repository) error {
+	_, span := tracer.Start(ctx, "Cache::CloseRepository", trace.WithAttributes())
+	defer span.End()
+
+	key, err := externalrepo.RepositoryKey(repositorySpec)
+	if err != nil {
+		return err
+	}
+
+	// check if repositorySpec shares the underlying cached repo with another repository
+	for _, r := range allRepos {
+		if r.Name == repositorySpec.Name && r.Namespace == repositorySpec.Namespace {
+			continue
+		}
+		otherKey, err := externalrepo.RepositoryKey(&r)
+		if err != nil {
+			return err
+		}
+		if otherKey == key {
+			// do not close cached repo if it is shared
+			return nil
+		}
+	}
+
+	var repository *cachedRepository
+	{
+		c.mutex.Lock()
+		if r, ok := c.repositories[key]; ok {
+			delete(c.repositories, key)
+			repository = r
+		}
+		c.mutex.Unlock()
+	}
+
+	if repository != nil {
+		return repository.Close()
+	} else {
+		return nil
+	}
+}
+
+func (c *Cache) GetRepositories(ctx context.Context) []configapi.Repository {
+	repoSlice := []configapi.Repository{}
+
+	for _, repo := range c.repositories {
+		repoSlice = append(repoSlice, *repo.repoSpec)
+	}
+	return repoSlice
+}