+1 for the wiki page
On May 12, 2018 at 10:52:43, Matt Burgess (mattyb...@apache.org) wrote: All, As Joe implied, I'm very happy that we are discussing graph tech in relation to NiFi! NiFi and Graph theory/tech/analytics are passions of mine. Mike, the examples you list are great, I would add Titan (and its fork Janusgraph as Kay-Uwe mentioned) and Azure CosmosDB (these and others are at [1]). I think there are at least four aspects to this: 1) Graph query/traversal: This deals with getting data out of a graph database and into flow file(s) for further processing. Here I agree with Kay-Uwe that we should consider Apache Tinkerpop as the main library for graph query/traversal, for a few reasons. The first as Kay-Uwe said is that there are many adapters for Tinkerpop (TP) to connect to various databases, from Mike's list I believe ArangoDB is the only one that does not yet have a TP adapter. The second is informed by the first, TP is a standard interface and graph traversal engine with a common DSL in Gremlin. A third is that Gremlin is a Groovy-based DSL, and Groovy syntax is fairly close to Java 8+ syntax and you can call Groovy/Gremlin from Java and vice versa. A third is that Tinkerpop is an Apache TLP with a very active and vibrant community, so we will be able to reap the benefits of all the graph goodness they develop moving forward. I think a QueryGraph processor could be appropriate, perhaps with a GraphDBConnectionPool controller service or something of the like. Apache DBCP can't do the pooling for us, but we could implement something similar to that for pooling TP connections. 2) Graph ingest: This one IMO is the long pole in the tent. Gremlin is a graph traversal language, and although its API has addVertex() and addEdge() methods and such, it seems like an inefficient solution, akin to using individual INSERTs in an RDBMS rather than a PreparedStatement or a bulk load. Keeping the analogy, bulk loading in RDBMSs is usually specific to that DB, and the same goes for graphs. The Titan-based ones have Titan-Hadoop (formerly Faunus), Neo4j has external tools (not sure if there's a Java API or not) and Cypher, OrientDB has an ETL pipeline system, etc. If we have a standard Graph concept, we could have controller services / writers that are system-specific (see aspect #4). 3) Arbitrary data -> Graph: Converting non-graph data into a graph almost always takes domain knowledge, which NiFi itself won't have and will thus have to be provided by the user. We'd need to make it as simple as possible but also as powerful and flexible as possible in order to get the most value. We can investigate how each of the systems in aspect #2 approaches this, and perhaps come up with a good user experience around it. 4) Organization and implementation: I think we should make sure to keep the capabilities very loosely coupled in terms of which modules/NARs/JARs provide which capabilities, to allow for maximum flexibility and ease of future development. I would prefer an API/libraries module akin to nifi-hadoop-libraries-nar, which would only include Apache Tinkerpop and any dependencies needed to do "pure" graph stuff, so probably no TP adapters except tinkergraph (and/or its faster fork from ShiftLeft [2]). The reason I say that is so NiFi components (and even the framework!) could use graphs in a lightweight manner, without lots of heavy and possibly unnecessary dependencies. Imagine being able to query your own flows using Gremlin or Cypher! I also envision an API much like the Record API in NiFi but for graphs, so we'd have GraphReaders and GraphWriters perhaps, they could convert from GraphML to GraphSON or Kryo for example, or in conjunction with a ConvertRecordToGraph processor, could be used to support the capability in aspect #3 above. I'd also be looking at bringing in Gremlin to the scripting processors, or having a Gremlin based scripting bundle as NiFi's graph capabilities mature. You might be able to tell I'm excited about this discussion ;) Should we get a Wiki page going for ideas, and/or keep it going here, or something else? I'm all ears for thoughts, questions, and ideas (especially the ones that might seem crazy!) Regards, Matt [1] http://tinkerpop.apache.org/providers.html [2] https://github.com/ShiftLeftSecurity/tinkergraph-gremlin On Sat, May 12, 2018 at 8:02 AM, u...@moosheimer.com <u...@moosheimer.com> wrote: > Hi Mike, > > graph database support is not quite as easy as it seems. > Unlike relational databases, graphs have not only defined vertices and edges (labeled vertices and edges), they are directed or not and might have attributes at the nodes and edges, too. > > This makes it a bit confusing for a general interface. > > In general, a graph database should always be accessed via TinkerPop 3 (or higher), since every professional graph database supports TinkerPop. > TinkerPop is for graph databases what jdbc is for relational databases. > > I tried to create a general NiFi processor for graph databases myself and then quit. > Unlike relational databases, graph databases usually have many dependencies. > > You do not simply create a data set but search for a particular vertex (which may still have certain edges) and create further edges and vertices at that. > And the search for the correct node is usually context-related. > > This makes it difficult to do something general for all requirements. > > In any case I am looking forward to your concept and how you want to solve it. > It's definitely a good idea but hard to solve. > > Btw.: You forgot the most important graph database - Janusgraph. > > Mit freundlichen Grüßen / best regards > Kay-Uwe Moosheimer > >> Am 12.05.2018 um 13:01 schrieb Mike Thomsen <mikerthom...@gmail.com>: >> >> I was wondering if anyone on the dev list had given much thought to graph >> database support in NiFi. There are a lot of graph databases out there, and >> many of them seem to be half-baked or barely supported. Narrowing it down, >> it looks like the best candidates for a no fuss, decent sized graph that we >> could build up with NiFi processors would be OrientDB, Neo4J and ArangoDB. >> The first two are particularly attractive because they offer JDBC drivers >> which opens the potential to making them even part of the standard >> JDBC-based processors. >> >> Anyone have any opinions or insights on this issue? I might have to do >> OrientDB anyway, but if someone has a good feel for the market and can make >> recommendations that would be appreciated. >> >> Thanks, >> >> Mike >
