Auto-reload synonym analyzers on synonyms updates

[mayya-sharipova]

Synonym Management API project

On changes of synonyms in a synonym set, auto-reload analyzers.
Note that currently all updateable analyzers will be reloaded, even
those that are not relevant for a synonyms set being updated.

Responses from PUT and DELETE synonyms set are enhanced to
contain reload analyzers details.

For a PUT synonyms set request, an example of response:
PUT _synonyms/set1

{
    "result": "created",
    "reload_analyzers_details": {
        "_shards": {
            "total": 0,
            "successful": 0,
            "failed": 0
        },
        "reload_details": []
    }
}

or an update:

{
    "result": "updated",
    "reload_analyzers_details": {
        "_shards": {
            "total": 2,
            "successful": 1,
            "failed": 0
        },
        "reload_details": [
            {
                "index": "index1",
                "reloaded_analyzers": [
                    "my_analyzer"
                ],
                "reloaded_node_ids": [
                    "vxKVyIRJQuO4DPj8Y70ijg"
                ]
            }
        ]
    }
}

For a DELETE synonyms set request, if the deleted synonyms set is in use, a response
will contain reload failures, like below:

{
    "acknowledged": true,
    "reload_analyzers_details": {
        "_shards": {
            "total": 2,
            "successful": 0,
            "failed": 1,
            "failures": [
                {
                    "shard": 0,
                    "index": "index1",
                    "status": "NOT_FOUND",
                    "reason": {
                        "type": "resource_not_found_exception",
                        "reason": "Synonym set [set1] not found"
                    }
                }
            ]
        },
        "reload_details": []
    }
}

And it is left for a user to fix affected indices.

[elasticsearchmachine]

Pinging @elastic/es-search (Team:Search)

[carlosdelest]

I like this test ❤️

[carlosdelest]

What are your thoughts for reloading just the analyzers for the specific syonyms set? Do it in a follow up PR? Or do we need some additional infra for retrieving the analyzers that use it?

[mayya-sharipova]

Right, we can do this in a follow-up. It is not trivial how to do this efficiently.