Janus supports "properties of properties", ie. properties defined on other properties. How is this represented with graphml? Should I use nested elements like this

<node>
<data key="foo">
bar
<data key="xxx">yyy</data>
</data>
</node>

or should I use attributes like this?

<node>
<data key="foo" xxx="yyy">bar</data>
</node>

janusgraph-full includes Gremlin Server

What is the difference between janusgraph-<version>.zip and janusgraph-full-<version>.zip?

Hi Laura,

Your assumption about ordering of nodes and edges is correct, see the warning at: https://tinkerpop.apache.org/docs/current/reference/#graphml

For your use case it seems that you can simply edit the nodes and edges out of order and now and then save an ordered version of the graph using the sort function of your editor. If you do a lot of editing, it is probably more convenient to write a custom csv import script for networkx and then save as graphml.

Best wishes,    Marc

Hi Ronnie
No idea what is going on here, but just being pragmatic:

the bin/janusgraph.sh script starts Cassandra, Elasticsearch and Gremlin Server using the conf/janusgraph-cql-es.conf graph configuration. As you can check in the janusgraph distribution files, this config does not specify the graph.timestamps  property (so defaults to MICRO).

So some things to try:

• does your Cassandra cluster have custom settings for the timestamp type? Then you hit an existing janusgraph issue.
• does your system have a locale different than english-international and does changing the locale recover the issue? Then you discovered a janusgraph issue!
• does removing the graph.timestamps=MICRO line help? Note that you can only try this on a new graph, because this setting is FIXED.

Best wishes,    Marc

Sorry I'm asking to this list because I can't find this information anywhere else.
Is it possible to have an <edge> element nested inside a <node> element with graphml? And will Janus be able to read it correctly? Basically, instead of

<node id="1"></node>
<node id="2"></node>
<edge source="1" target="2"></edge>

I would like to use

<node id="1">
<edge target="2"></edge>
</node>
<node id="2"></node>

This would be very useful to me because I have a file (in graphml format) that I'm editing manually, and nesting edges will help me keep all the information "bundled" within a <node>; it would also reduce the verbosity by a lot. Unfortunately I have a feeling that this is not defined by the graphml spec, but I wonder if Janus can parse it?

Thank you Boxuan for the response. I will create a feature request.

Regards,
Radhika

Hi Radhika,

Unfortunately, there is no such API. If you are willing to dive into JanusGraph source code, you can modify StandardTransactionLogProcessor::fixSecondaryFailure method and build JanusGraph by yourself.

You are also welcome to create a feature request on GitHub issues. Probably we should allow users to register a callback method when recovery is done.

Best,
Boxuan

Hi Team,

I am using JanusGraphFactory.startTransactionRecovery to recover secondary failure entries.
We need to perform some other action once recovery is completed, I couldn't find any API to know the status of recovery.
Is there any way to know if the recovery of all the failure entries is completed.

I would appreciate you help.

Thanks,
Radhika

Hi,

Environment
- JanusGraph 0.5.3 on JDK: 1.8
- Backend: Cassandra 3.11.3 running on JDK 1.8

Warning and error during first time server startup

2021-08-17T22:26:20,861 - WARN  [main:o.j.d.l.c.ConsistentKeyLocker@510] - Skipping outdated lock on KeyColumn [k=0x 16-165-160-103-105- 30- 71-114- 97-112-104- 95- 78- 97-109-101- 95- 73-110-100-101-248, c=0x  0] with our rid ( 48- 97- 55- 50- 97- 97- 57- 57- 49- 56- 57- 56- 57- 45-115-104- 97-114-101-100-106- 97-110-117-115-103-114- 97-112-104- 48- 49- 45-112- 50- 55- 45-101-110-103- 45-105-110- 48- 51- 45-113-117- 97-108-121-115- 45- 99-111-109- 49) but mismatched timestamp (actual ts 2021-08-17T22:26:20.755981Z, expected ts 2021-08-17T22:26:20.755981926Z)

2021-08-17T22:26:20,863 - ERROR [main:o.j.g.d.StandardJanusGraph@724] - Could not commit transaction [1] due to storage exception in system-commit

Caused by: org.janusgraph.diskstorage.PermanentBackendException: Read 1 locks with our rid  48- 97- 55- 50- 97- 97- 57- 57- 49- 56- 57- 56- 57- 45-115-104- 97-114-101-100-106- 97-110-117-115-103-114- 97-112-104- 48- 49- 45-112- 50- 55- 45-101-110-103- 45-105-110- 48- 51- 45-113-117- 97-108-121-115- 45- 99-111-109- 49 but mismatched timestamps; no lock column contained our timestamp (2021-08-17T22:26:20.755981926Z)

at org.janusgraph.diskstorage.locking.consistentkey.ConsistentKeyLocker.checkSeniority(ConsistentKeyLocker.java:542)

at org.janusgraph.diskstorage.locking.consistentkey.ConsistentKeyLocker.checkSingleLock(ConsistentKeyLocker.java:468)

at org.janusgraph.diskstorage.locking.consistentkey.ConsistentKeyLocker.checkSingleLock(ConsistentKeyLocker.java:118)

at org.janusgraph.diskstorage.locking.AbstractLocker.checkLocks(AbstractLocker.java:351)

... 27 more

2021-08-17T22:26:20,864 - ERROR [main:o.a.t.g.s.u.ServerGremlinExecutor@87] - Could not invoke constructor on class org.janusgraph.graphdb.management.JanusGraphManager (defined by the 'graphManager' setting) with one argument of class Settings

Thanks. I opened the PR here: https://github.com/JanusGraph/janusgraph/pull/2760

I confirm, adding lucene-backward-codecs-8.9.0.jar in lib folder solves my problem.

Toom.

Hi, we upgraded Lucene to 8.9.0 version. Do you think the problem will be resolved if we include `lucene-backward-codecs.jar` in the classpath?

Hi,

I'm testing the new pre-release of Janusgraph (from https://github.com/JanusGraph/janusgraph/releases/download/v0.6.0/janusgraph-0.6.0.zip) with the Berkeley/Lucene database created from JG 0.5.3 and all calls of index fail (below the full stacktrace).
Is there a migration process, maybe a reindex ? The error message contains "Could not load codec 'Lucene70'.  Did you forget to add lucene-backward-codecs.jar?". Do you plan to include this jar in your JanusGraph distribution ?

Hi Laura,

One code example says more than 1000 words:

gremlin> graph = TinkerFactory.createModern()
==>tinkergraph[vertices:6 edges:6]
gremlin> g=graph.traversal(
traversal(    traversal()   
gremlin> g=graph.traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.addV().property("lang", 45)
==>v[13]
gremlin> g.V().elementMap()
==>[id:1,label:person,name:marko,age:29]
==>[id:2,label:person,name:vadas,age:27]
==>[id:3,label:software,name:lop,lang:java]
==>[id:4,label:person,name:josh,age:32]
==>[id:5,label:software,name:ripple,lang:java]
==>[id:6,label:person,name:peter,age:35]
==>[id:13,label:vertex,lang:45]
gremlin> g.V().values("lang")
==>java
==>java
==>45
gremlin> g.V().values("lang").group().by(map{it->it.get().getClass()}).by(count())
==>[class java.lang.String:2,class java.lang.Integer:1]
gremlin>

So, this query shows you all occurring data types of a specific property in the graph.
Strictly speaking, gremlin OLAP queries are queries using withComputer(). I tend to use the term a bit looser including analytical queries requiring a full table scan.

Best wishes,

Marc

your graph will be more difficult to use if you do not know what data type is in a property. Users would have to explore for themselves what object types are in the graph. This means a lot of OLAP queries with lots of waiting time and a large load on the graph system.

What would be an example of a OLAP query? There is a way to get a property's type in a gremlin query?

Hi Laura,

Some remarks:

• primitive types can be stored more efficiently than general objects (an integer is exactly 32 bits, an object an be any size)
• for the CompositeIndex the objects are fine as long as they implement the equals() method
• your graph will be more difficult to use if you do not know what data type is in a property. Users would have to explore for themselves what object types are in the graph. This means a lot of OLAP queries with lots of waiting time and a large load on the graph system. If users only use their own data, you can give each user its own graph.
• if you use Gremlin Server, the supported protocols will not know how to serialize arbitrary objects, so you have to instruct the client to request the string values of objects only. Then, you could have asked your users to enter object strings into janusgraph in the first place.

Best wishes,    Marc

ERRATA

The composite index does not work when searching by comparison, ie. .has('name', lt(50)) (I get the usual warning "Query requires iterating over all vertices" and it returns zero vertexes)

I get the warning but the vertex with name=42 *is* returned correctly

I'd like to understand a little bit more about what's going on under the hood when creating a new property with .dataType(Object.class) vs any other specific type eg. .dataType(String.class) or .dataType(Integer.class)
I'm able to create a "name" property like this:

mgmt.makePropertyKey('name').dataType(Object.class).make()

and this is what I've noticed:

- it allows me to create these vertexes
g.addV('alice').property('name', 'Alice')
g.addV('terminator').property('name', 42)
- it allows me to create a composite index, but not a mixed index (confirming what was said in the other thread)
- the composite index works when searching for an exact match, ie. .has('name', 'Alice') and .has('name', 42). The composite index does not work when searching by comparison, ie. .has('name', lt(50)) (I get the usual warning "Query requires iterating over all vertices" and it returns zero vertexes)

I'm only interested into this because I have a graph where multiple people contribute, it would be very nice to not having to deal with explicit property types, if Object.class is an option. For my particular use case I could live without mixed indexes, and I wouldn't mind a small performance deficit (size and/or speed) introduced by the usage of Object as a general type. But I really struggle to understand what's going on. What's the difference between Object and specific types from Janus' point of view? Are types only useful for enforcing a particular schema when inserting data, or there's more to it?



Sent: Wednesday, July 21, 2021 at 10:34 AM
From: hadoopmarc@...
To: janusgraph-users@...
Subject: Re: [janusgraph-users] What are the implications of using Object.class property type?
Hi Laura,

A similar question was posed recently:
https://lists.lfaidata.foundation/g/janusgraph-users/message/5986[https://lists.lfaidata.foundation/g/janusgraph-users/message/5986?p=,,,20,0,0,0::recentpostdate%252Fsticky,,mixedindex,20,2,0,83929827]

So,
1. Only for the CompositeIndex
2. In your specific example, you could use the java Integer class ( https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html[https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html] ), because its constructor takes either integer type or string type and it has the equals() method implemented.

Best wishes,    Marc

Hi!

As far as I know, your assumption is correct. However, Janusgraph-GRPC is still in the early stages of development and I guess it will still take a few versions before it will become available. That's also the reason, why the feature is still undocumented. If you have any specific questsions, I would recommend to reach out to Jan Jansen (@farodin91 on GitHub) because he drives the development behind Janusgraph-GRPC.

Best regards,
Florian