Allow multiple hosts for elasticsearch connector

[zhaoyim]

Description

Is this change a fix, improvement, new feature, refactoring, or other?

improvement

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

No

How would you describe this change to a non-technical end user or system administrator?

Allow multiple hosts for elasticsearch connector (elasticsearch.host property)

Related issues, pull requests, and links

Fixes #11889

Documentation

( ) No documentation is needed.
( ) Sufficient documentation is included in this PR.
( ) Documentation PR is available with #prnumber.
(X) Documentation issue #12528 is filed, and can be handled later.

Release notes

(x) Release notes entries required with the following suggested text:

# Elasticsearch
* Add support for multiple hosts in `elasticsearch.host` configuration property. ({issue}`12530`)

[ebyhr]

Quote from the issue:

There is property for sniffing elasticsearch.node-refresh-interval but in many cases, sniffing is not the best choice and a hardcoded list of hosts in elasticsearch.host would work best

I suppose this PR still find nodes by schedule.

[zhaoyim]

When the first start trino server, it can try all configed elasticsearch.host hosts to makes sure the es connector worked well, and the schedule nodes can get successfully.
For example:
Before:

1. elasticsearch.host config one node, but the node is not started
2. start trino, can NOT connect to es, the scheduler also can NOT get nodes
3. the es query can NOT run, until the config es node started

After:

1. elasticsearch.host config several nodes, if one node is started
2. start trino, can connect to es, the scheduler also can get nodes
3. the es query can run successfully

[zhaoyim]

@bitsondatadev Could you help review this pr? Thanks!

[martint]

This should be a List<String> not a String. The splitting on , will be done by the configuration system. It shouldn't be done by ElasticsearchClient. Otherwise, it's hard to do any validation and error reporting at startup time.

[zhaoyim]

Thanks for review! @martint Did the changes, could you help review again? Thanks in advance!

[ebyhr]

The above comment means changing the argument to List<String> instead of splitting by yourself.

[zhaoyim]

@ebyhr Thanks for clarify! Did the changes. Thanks again!

[martint]

This test is unnecessary. It doesn't validate anything about the state of the client or that it works -- just that it can be constructed.

Let's remove it.

[zhaoyim]

@martint Thanks for your comments! Remove the test.