Minor Description
When use PeriodicGraphCheckpointer to persist graph, sometimes the edge isn't persisted. As currently only when vertices's storage level is none, graph is persisted. However there is a chance vertices's storage level is not none while edges's is none. Eg. graph created by a outerJoinVertices operation, vertices is automatically cached while edges is not. In this way, edges will not be persisted if we use PeriodicGraphCheckpointer do persist.
See below minimum example:
val graphCheckpointer = new PeriodicGraphCheckpointer[Array[String], Int](2, sc)
val users = sc.textFile("data/graphx/users.txt")
.map(line => line.split(",")).map(parts => (parts.head.toLong, parts.tail))
val followerGraph = GraphLoader.edgeListFile(sc, "data/graphx/followers.txt")
val graph = followerGraph.outerJoinVertices(users)
{ case (uid, deg, Some(attrList)) => attrList case (uid, deg, None) => Array.empty[String] }graphCheckpointer.update(graph)
