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package zip
import (
"context"
"errors"
"net/url"
"sync"
"time"
"github.com/patrickmn/go-cache"
"gitlab.com/gitlab-org/gitlab-pages/internal/vfs"
"gitlab.com/gitlab-org/gitlab-pages/metrics"
)
const (
// TODO: make these configurable https://gitlab.com/gitlab-org/gitlab-pages/-/issues/464
defaultCacheExpirationInterval = time.Minute
defaultCacheCleanupInterval = time.Minute / 2
defaultCacheRefreshInterval = time.Minute / 2
// we assume that each item costs around 100 bytes
// this gives around 5MB of raw memory needed without acceleration structures
defaultDataOffsetItems = 50000
defaultDataOffsetExpirationInterval = time.Hour
// we assume that each item costs around 200 bytes
// this gives around 2MB of raw memory needed without acceleration structures
defaultReadlinkItems = 10000
defaultReadlinkExpirationInterval = time.Hour
)
var (
errAlreadyCached = errors.New("archive already cached")
)
// zipVFS is a simple cached implementation of the vfs.VFS interface
type zipVFS struct {
cache *cache.Cache
cacheLock sync.Mutex
dataOffsetCache *lruCache
readlinkCache *lruCache
archiveCount int64
}
// New creates a zipVFS instance that can be used by a serving request
func New() vfs.VFS {
zipVFS := &zipVFS{
cache: cache.New(defaultCacheExpirationInterval, defaultCacheCleanupInterval),
dataOffsetCache: newLruCache("data-offset", defaultDataOffsetItems, defaultDataOffsetExpirationInterval),
readlinkCache: newLruCache("readlink", defaultReadlinkItems, defaultReadlinkExpirationInterval),
}
zipVFS.cache.OnEvicted(func(s string, i interface{}) {
metrics.ZipCachedEntries.WithLabelValues("archive").Dec()
i.(*zipArchive).onEvicted()
})
return zipVFS
}
// Root opens an archive given a URL path and returns an instance of zipArchive
// that implements the vfs.VFS interface.
// To avoid using locks, the findOrOpenArchive function runs inside of a for
// loop until an archive is either found or created and saved.
// If findOrOpenArchive returns errAlreadyCached, the for loop will continue
// to try and find the cached archive or return if there's an error, for example
// if the context is canceled.
func (fs *zipVFS) Root(ctx context.Context, path string) (vfs.Root, error) {
urlPath, err := url.Parse(path)
if err != nil {
return nil, err
}
// we do it in loop to not use any additional locks
for {
root, err := fs.findOrOpenArchive(ctx, urlPath.String())
if err == errAlreadyCached {
continue
}
return root, err
}
}
func (fs *zipVFS) Name() string {
return "zip"
}
// findOrCreateArchive if found in fs.cache refresh if needed and return it.
// otherwise creates the archive entry in a cache and try to save it,
// if saving fails it's because the archive has already been cached
// (e.g. by another concurrent request)
func (fs *zipVFS) findOrCreateArchive(ctx context.Context, path string) (*zipArchive, error) {
// This needs to happen in lock to ensure that
// concurrent access will not remove it
// it is needed due to the bug https://github.com/patrickmn/go-cache/issues/48
fs.cacheLock.Lock()
defer fs.cacheLock.Unlock()
archive, expiry, found := fs.cache.GetWithExpiration(path)
if found {
metrics.ZipCacheRequests.WithLabelValues("archive", "hit").Inc()
// TODO: do not refreshed errored archives https://gitlab.com/gitlab-org/gitlab-pages/-/merge_requests/351
if time.Until(expiry) < defaultCacheRefreshInterval {
// refresh item
fs.cache.SetDefault(path, archive)
}
} else {
archive = newArchive(fs, path, DefaultOpenTimeout)
// We call delete to ensure that expired item
// is properly evicted as there's a bug in a cache library:
// https://github.com/patrickmn/go-cache/issues/48
fs.cache.Delete(path)
// if adding the archive to the cache fails it means it's already been added before
// this is done to find concurrent additions.
if fs.cache.Add(path, archive, cache.DefaultExpiration) != nil {
return nil, errAlreadyCached
}
metrics.ZipCacheRequests.WithLabelValues("archive", "miss").Inc()
metrics.ZipCachedEntries.WithLabelValues("archive").Inc()
}
return archive.(*zipArchive), nil
}
// findOrOpenArchive gets archive from cache and tries to open it
func (fs *zipVFS) findOrOpenArchive(ctx context.Context, path string) (*zipArchive, error) {
zipArchive, err := fs.findOrCreateArchive(ctx, path)
if err != nil {
return nil, err
}
err = zipArchive.openArchive(ctx)
if err != nil {
return nil, err
}
return zipArchive, nil
}
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