feat: implement datastream support on elasticsearch-logger plugin

[jr-instantsystem]

Description

The current plugin allows to push messages to raw indices in ElasticSearch, using the "POST _bulk" endpoint, with the "_index" action.
It not compatible with DataSteams according to https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-bulk, where action have to be "_create" to push on DataStream.

The PR add a second plugin param for a datastream name. The user must choose between "index name" or "datastream name" to define the method used to push to ElasticSearch.

Tested on 3.12

Which issue(s) this PR fixes:

N/A

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[Baoyuantop]

We also need to add tests for this feature.

[Copilot]

Pull request overview

This PR updates the elasticsearch-logger plugin to support writing logs to either a classic Elasticsearch index or a DataStream target, and aligns the plugin documentation with the new configuration options.

Changes:

• Extend the plugin schema to allow configuring either field.index or field.datastream (mutually exclusive).
• Update bulk action generation to emit index vs create actions depending on the configured target.
• Document the new field.datastream attribute and update notes around required field configuration.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/en/latest/plugins/elasticsearch-logger.md	Documents field.index / field.datastream options and updates notes about required configuration.
apisix/plugins/elasticsearch-logger.lua	Adds schema support and runtime logic to generate bulk entries for index vs datastream targets.

Comments suppressed due to low confidence (1)

apisix/plugins/elasticsearch-logger.lua:231

• When field.datastream is used, body is built with a create action and has no body.index, but the ES 5/6 compatibility block unconditionally writes body.index._type. This will throw a runtime error; set _type on the actual action present (e.g., body.index vs body.create) or restructure to avoid accessing body.index when using datastream.

    -- for older version type is required
    if conf._version == "6" or conf._version == "5" then
        body.index._type = "_doc"
    end

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[Baoyuantop]

Please add test case

[Baoyuantop]

When datastream is configured, the body only contains the "create" key, not the "index" key. For version compatibility, accessing nil.index with body.index._type = "_doc" will trigger a runtime error: "attempt to index a nil value".

[jr-instantsystem]

ho, right... fix pushed
datastreams are available for ES 7+ only

[Baoyuantop]

Hi @jr-instantsystem, please fix the failed CI

[github-actions]

This pull request has been marked as stale due to 60 days of inactivity. It will be closed in 4 weeks if no further activity occurs. If you think that's incorrect or this pull request should instead be reviewed, please simply write any comment. Even if closed, you can still revive the PR at any time or discuss it on the dev@apisix.apache.org list. Thank you for your contributions.

[github-actions]

This pull request has been marked as stale due to 60 days of inactivity. It will be closed in 4 weeks if no further activity occurs. If you think that's incorrect or this pull request should instead be reviewed, please simply write any comment. Even if closed, you can still revive the PR at any time or discuss it on the dev@apisix.apache.org list. Thank you for your contributions.