Graham Wallis created ATLAS-2262:
------------------------------------
Summary: EntityGraphMapper update semantics
Key: ATLAS-2262
URL: https://issues.apache.org/jira/browse/ATLAS-2262
Project: Atlas
Issue Type: Bug
Reporter: Graham Wallis
Priority: Minor
Intermittent failures in AtlasRelationshipStoreV1Test occur during modification
of the 'friends' relationships between sample Employee and Manager entities.
The intermittent failures are seen as different numbers of updated entities
being reported, which causes the test assertion to fail. The failures are
intermittent because they are caused by non-deterministic behaviour during
UPDATE of an entity's relationships. The non-determinism is caused by the order
in which results are returned by a graph query, although any order should be
considered valid.
When built with graph provider titan0, the order of edges returned from the
graph is always the same, and the current EntityGraphMapper returns a
consistent result. The way it achieves it is slightly odd, with existing edge
reuse depending on the position of the edge in the returned list. But with
titan0, the behaviour is consistent, and correct.
When using the janus graph provider, the order of edges returned from the graph
varies. This is valid behaviour on the part of the graph, but the
EntityGraphMapper does not behave the same when the edges are returned in a
different order compared to titan0.
There are two levels of problem: The first is accuracy of the returned count of
updated entities; the second and in my opinion more important is the semantics
of an update operation that presents the same array of entity relationships in
an order that is not the same as the order returned by the graph. In my opinion
the result of the UPDATE operation should not vary depending on the order of
the edges returned by the internal graph query. If the set of related entities
presented matches the set already recorded then the existing related entities
should be reused, rather than replaced. It is therefore the latter problem that
I have been working on.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
