Why use /_doc/_mget as request path when try to multi get documentation?

[ivyxjc]

ElasticSearch api documentation informs that multi-get request path is /_mget. But in V7DocumentFactory, it use the path /_doc/_mget.

skywalking/oap-server/server-library/library-elasticsearch-client/src/main/java/org/apache/skywalking/library/elasticsearch/requests/factory/v7plus/V7DocumentFactory.java

Lines 112 to 115 in 04c4fed

	return HttpRequest.builder()
	.get("/_doc/_mget")
	.content(MediaType.JSON, content)
	.build();

And in AWS OpenSearch, it will return {"Message":"Your request: '/_doc/_mget' is not allowed."}.

[wu-sheng]

@kezhenxu94

[kezhenxu94]

@ivyxjc can you share which OpenSearch version are you using?

[ivyxjc]

AWS-host opensearch 1.3.
I just checked in self-host opensearh (run with docker), /_doc/_mget is ok. But in aws host opensearch, it will return the error response.

[wu-sheng]

I think this seems something AWS changed privately?
OpenSearch actually is a fork of ElasticSearch 7.10 or another 7.x minor version. We could only tested with open source versions.

[wu-sheng]

@ivyxjc It is better you could ask OpenSearch Community, they should have a lot of AWS engineers.

[weiguo-tough]

We also encountered the same problem, our solution is to change to "/_mget", build a private image, and then replace the image in the helm install configuration.

[ivyxjc]

Both elasticsearch/opensearch multi get documentation only have the following two apis

GET _mget
GET <index>/_mget

For path /_doc/_mget , Opensearch/Elastisearch should see _doc as index name, but _doc cannot be index name since index name should not start with _.

Opensearch/Elasticsearch real action has some conflicts with documentation. I recommend we'd better following the documentation.

I raise one related issue in opensearch project

[wu-sheng]

The key point is the following docs. Some compatible ways may be provided and may be removed without any warning.
If this specific path is required by AWS-hosted OpenSearch, we should only consider adopting it in that case only. Especially, you mentioned, the current way is correct for ElasticSearch and OpenSearch. A cloud-vendor hosted version is a black box.

[ivyxjc]

Current way can work correctly for ElasticSearch and OpenSearch, but it uses one way that is not listed in OpenSearch/ElasticSearch documentation. Recommend to use the same-function way listed in the documentation.

[wu-sheng]

but it uses one way that is not listed in OpenSearch/ElasticSearch documentation.

Could you be more clear about this? Such as what we are using, what is doc saying, and the doc ref? This could help us to adjust codes.

[ivyxjc]

Now skywalking are using path_doc/_mget:

skywalking/oap-server/server-library/library-elasticsearch-client/src/main/java/org/apache/skywalking/library/elasticsearch/requests/factory/v7plus/V7DocumentFactory.java

Lines 112 to 115 in f9e23eb

	return HttpRequest.builder()
	.get("/_doc/_mget")
	.content(MediaType.JSON, content)
	.build();

docs-multi-get does not have documenation about path _doc/_mget

[wu-sheng]

@kezhenxu94 Could you recheck? I think consistent with docs is better. Be careful about version differences.

[kezhenxu94]

For record, this happens for AWS-hosted ElasticSearch 7.10 too, and should be fixed by #10031

[wu-sheng]

FYI @ivyxjc

[ivyxjc]

We deploy with the version(9.3.0-7ad0406), and it works perfect.