+// ResetSession unloads any potentially stale state. Should be called
+// after write operations, so subsequent reads don't return stale
+// data.
+func (c *cache) ResetSession(token string) {
+ c.setupOnce.Do(c.setup)
+ c.sessions.Remove(token)
+}
+
+// Get a long-lived CustomFileSystem suitable for doing a read operation
+// with the given token.
+func (c *cache) GetSession(token string) (arvados.CustomFileSystem, error) {
+ c.setupOnce.Do(c.setup)
+ now := time.Now()
+ ent, _ := c.sessions.Get(token)
+ sess, _ := ent.(*cachedSession)
+ if sess == nil {
+ c.metrics.sessionMisses.Inc()
+ sess = &cachedSession{
+ expire: now.Add(c.config.TTL.Duration()),
+ }
+ c.sessions.Add(token, sess)
+ } else if sess.expire.Before(now) {
+ c.metrics.sessionMisses.Inc()
+ sess.fs.Store(nil)
+ } else {
+ c.metrics.sessionHits.Inc()
+ }
+ go c.pruneSessions()
+ fs, _ := sess.fs.Load().(arvados.CustomFileSystem)
+ if fs != nil {
+ return fs, nil
+ }
+ ac, err := arvados.NewClientFromConfig(c.cluster)
+ if err != nil {
+ return nil, err
+ }
+ ac.AuthToken = token
+ arv, err := arvadosclient.New(ac)
+ if err != nil {
+ return nil, err
+ }
+ kc := keepclient.New(arv)
+ fs = ac.SiteFileSystem(kc)
+ fs.ForwardSlashNameSubstitution(c.cluster.Collections.ForwardSlashNameSubstitution)
+ sess.fs.Store(fs)
+ return fs, nil
+}
+
+func (c *cache) pruneSessions() {
+ now := time.Now()
+ var size int64
+ for _, token := range c.sessions.Keys() {
+ ent, ok := c.sessions.Peek(token)
+ if !ok {
+ continue
+ }
+ s := ent.(*cachedSession)
+ if s.expire.Before(now) {
+ c.sessions.Remove(token)
+ continue
+ }
+ fs, _ := s.fs.Load().(arvados.CustomFileSystem)
+ if fs == nil {
+ continue
+ }
+ size += fs.MemorySize()
+ }
+ if size > c.cluster.Collections.WebDAVCache.MaxCollectionBytes/2 {
+ for _, token := range c.sessions.Keys() {
+ c.sessions.Remove(token)
+ }
+ }
+}
+