ElasticSearch is not using the most recent scroll_id

[cdegroc]

ElasticSearch documentation has the following statement about Scroll Searches:

Important. The initial search request and each subsequent scroll request each return a _scroll_id. While the _scroll_id may change between requests, it doesn’t always change — in any case, only the most recently received _scroll_id should be used.

If I'm not mistaken, I don't think the latest scroll_id is used in JanusGraph.

In ElasticSearchScroll:

• this.scrollId is set to the _scroll_id from the initial request's response: https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/ElasticSearchScroll.java#L41
• new scroll requests are made using this.scrollId: https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/ElasticSearchScroll.java#L65
• this.scrollId is not updated when a new response is received: https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/ElasticSearchScroll.java#L46-L54

Can someone please confirm this is an issue? Then I can submit a PR if needed.

[li-boxuan]

I think you are correct. This looks like a bug to me. Although scrollId does not change most of the time (https://discuss.elastic.co/t/scroll-id-is-not-changing-while-querying/106202/3), we should definitely follow what the official documentation says. It would be great if you could submit a PR!