21697: Don't hold session lock while processing read requests.

[arvados.git] / services / keep-web / handler.go

diff --git a/services/keep-web/handler.go b/services/keep-web/handler.go
index cdd51f0bb7c7fcee60dd21970192fbd3a65aa6d0..4fae0aee5f1e1fec81186f5206d3cd06ea41a4ea 100644 (file)
--- a/services/keep-web/handler.go
+++ b/services/keep-web/handler.go
@@ -430,11 +430,18 @@ func (h *handler) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
                        return
                }
                defer f.Close()
-               defer sess.Release()
 
                collectionDir, sessionFS, session, tokenUser = f, fs, sess, user
                break
        }
+
+       releaseSession := func() {}
+       if session != nil {
+               var releaseSessionOnce sync.Once
+               releaseSession = func() { releaseSessionOnce.Do(func() { session.Release() }) }
+       }
+       defer releaseSession()
+
        if forceReload && collectionDir != nil {
                err := collectionDir.Sync()
                if err != nil {
@@ -522,6 +529,7 @@ func (h *handler) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
        if r.Method == http.MethodGet || r.Method == http.MethodHead {
                targetfnm := fsprefix + strings.Join(pathParts[stripParts:], "/")
                if fi, err := sessionFS.Stat(targetfnm); err == nil && fi.IsDir() {
+                       releaseSession() // because we won't be writing anything
                        if !strings.HasSuffix(r.URL.Path, "/") {
                                h.seeOtherWithCookie(w, r, r.URL.Path+"/", credentialsOK)
                        } else {
@@ -591,6 +599,15 @@ func (h *handler) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
                                collectionDir.Splice(snap)
                                return nil
                        }}
+       } else {
+               // When writing, we need to block session renewal
+               // until we're finished, in order to guarantee the
+               // effect of the write is visible in future responses.
+               // But if we're not writing, we can release the lcok
+               // early.  This enables us to keep renewing sessions
+               // and processing more requests even if a slow client
+               // takes a long time to download a large file.
+               releaseSession()
        }
        if r.Method == http.MethodGet {
                applyContentDispositionHdr(w, r, basename, attachment)