[GitHub] markusthoemmes commented on a change in pull request #4183: Ensure cache gets properly updated with concurrent access for action with attachments

[GitBox <gi...@apache.org>]

markusthoemmes commented on a change in pull request #4183: Ensure cache gets properly updated with concurrent access for action with attachments
URL: https://github.com/apache/incubator-openwhisk/pull/4183#discussion_r242122269
 
 

 ##########
 File path: common/scala/src/main/scala/org/apache/openwhisk/core/database/DocumentFactory.scala
 ##########
 @@ -198,23 +198,40 @@ trait DocumentFactory[W <: DocumentRevisionProvider] extends MultipleReadersSing
     doc: DocId,
     rev: DocRevision = DocRevision.empty,
     fromCache: Boolean = cacheEnabled)(implicit transid: TransactionId, mw: Manifest[W]): Future[W] = {
-    getWithAttachment(db, doc, rev, fromCache, None)
+    Try {
+      require(db != null, "db undefined")
+    } map {
+      implicit val logger = db.logging
+      implicit val ec = db.executionContext
+      val key = doc.asDocInfo(rev)
+      _ =>
+        cacheLookup(CacheKey(key), db.get[W](key, None), fromCache)
+    } match {
+      case Success(f) => f
+      case Failure(t) => Future.failed(t)
+    }
   }
 
+  /**
+   *  Fetches document along with attachment. `postProcess` would be used to process the fetched document
+   *  before adding it to cache. This ensures that for documents having attachment the cache is updated only
+   *  post fetch of the attachment
+   */
   protected def getWithAttachment[Wsuper >: W](
     db: ArtifactStore[Wsuper],
     doc: DocId,
     rev: DocRevision = DocRevision.empty,
     fromCache: Boolean,
-    attachmentHandler: Option[(W, Attached) => W])(implicit transid: TransactionId, mw: Manifest[W]): Future[W] = {
+    attachmentHandler: (W, Attached) => W,
+    postProcess: W => Future[W])(implicit transid: TransactionId, mw: Manifest[W]): Future[W] = {
     Try {
       require(db != null, "db undefined")
     } map {
       implicit val logger = db.logging
       implicit val ec = db.executionContext
       val key = doc.asDocInfo(rev)
       _ =>
-        cacheLookup(CacheKey(key), db.get[W](key, attachmentHandler), fromCache)
+        cacheLookup(CacheKey(key), db.get[W](key, Some(attachmentHandler)) flatMap { postProcess }, fromCache)
 
 Review comment:
   Nit: I find the combinators a bit hard to read
   
   ```scala
   db.get[W](key, Some(attachmentHandler)).flatMap(postProcess)
   ```
   
   Is imo a bit clearer.

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