Elasticsearch JavaScript Client breaking changes

In 8.x, every API function had a body property that would provide a place to put arbitrary values that should go in the HTTP request body, even if they were not noted in the specification or documentation. In 9.0, each API function still includes an optional body property, but TypeScript's type checker will disallow properties that should go in the root of the object. A querystring parameter has also been added that behaves the same as body, but inserts its values into the request querystring.

Impact
Some adjustments to API calls may be necessary for code that used a body property 8.x, especially to appease the TypeScript type checker, but it should not have any impact on any code that was not using a body property.

Action
Check existing code for use of the body property, and move any properties that should be in the root object according to the API function's request type definition. If using TypeScript, the TypeScript type checker will surface most of these issues for you.

The logic for where each parameter in an API function call should be added to its HTTP request has been updated:

1. If recognized as a body parameter according to the Elasticsearch specification, put it in the JSON body
2. If recognized as a path parameter, put it in the URL path
3. If recognized as a query parameter or a "common" query parameter (e.g. pretty, error_trace), put it in the querystring
4. If not recognized, and this API accepts a JSON body, put it in the JSON body
5. If not recognized and this API does not accept a JSON body, put it in the querystring

The first two steps are identical in 8.x. The final three steps replace the logic from 8.x that put all unrecognized parameters in the querystring.

Impact
Some parameters that were sent via querystring to Elasticsearch may be sent in the JSON request body, and vice versa.

Action
If Elasticsearch sends back an error response due to a request not being valid, verify with the client's TypeScript type definitions, or via the docs, that the parameters your code passes are correct.

The default 30-second timeout on all HTTP requests sent to Elasticsearch has been dropped in favor of having no timeout set at all. The previous behavior still works as it did when setting the requestTimeout value.

See pull request #2573 for more information.

Impact
Requests to Elasticsearch that used to time out after 30 seconds will now wait for as long as it takes for Elasticsearch to respond.

Action
In environments where it is not ideal to wait for an API response indefinitely, manually setting the requestTimeout option when instantiating the client still works as it did in 8.x.