[FEATURE] Add child client support AwsSigv4

[bandinib-amzn]

Currently we have child client support for Basic Authentication. Similarly we should have child client support for AwsSigv4.

[dblock]

Do you mean this code isn't propagating sigv4 options?

opensearch-js/index.js

Line 257 in 282fb51

child(opts) {

[bandinib-amzn]

Yes. Below lines of code will only work for Basic Auth.

opensearch-js/index.js

Lines 269 to 271 in 5ecad79

	if (options.auth !== undefined) {
	options.headers = prepareHeaders(options.headers, options.auth);
	}

I think type of auth should also support static IAM credentials authentication methods (accesskey and secret key)

opensearch-js/lib/Connection.d.ts

Line 51 in 5ecad79

auth?: BasicAuth;

For basic auth, prepareHeaders method updates header of child client with nee credentials. Similarly we can signed the request with credentials in case of IAM credentials.

opensearch-js/index.js

Line 270 in 5ecad79

options.headers = prepareHeaders(options.headers, options.auth);

opensearch-js/lib/Connection.js

Lines 329 to 337 in 5ecad79

	function prepareHeaders(headers = {}, auth) {
	if (auth != null && headers.authorization == null) {
	/* istanbul ignore else */
	if (auth.username && auth.password) {
	headers.authorization =
	'Basic ' + Buffer.from(`${auth.username}:${auth.password}`).toString('base64');
	}
	}
	return headers;

This is just off the top of my head. But we can build PoC and propose the solution.

[dblock]

When is child even used and why is it not a full, deep clone of the client instance?

[dblock]

@bandinib-amzn Want to help? Try to implement a unit test for your scenario alone and maybe a fix?

[bandinib-amzn]

@bandinib-amzn Want to help? Try to implement a unit test for your scenario alone and maybe a fix?

Sure. I can give a try.

[bandinib-amzn]

When is child even used and why is it not a full, deep clone of the client instance?

It is being used in multi data source plugin. We discovered this issue when we wanted to implement similar in AWSSigV4 authentication method.
https://github.com/opensearch-project/OpenSearch-Dashboards/blob/e83b7ee42831d7e62b81ad906b998ff035355640/src/plugins/data_source/server/client/configure_client.ts#L145-L160

[bandinib-amzn]

@bandinib-amzn Want to help? Try to implement a unit test for your scenario alone and maybe a fix?

Hi @dblock. I raised PR. Can you please take a look when you get a chance?