SOLR-18065: ConcurrentUpdateBaseSolrClient: support for HttpJdkSolrClient

[jdyer1]

This adds ConcurrentUpdateJdkSolrClient.java and refactors the main unit tests to test both the Jetty and the JDK clients.

Unlike with LBAsyncSolrClient and CloudHttp2SolrClient, this new client requires an HttpJdkSolrClient and not any subclass of HttpSolrClientBase. It did not seem possible to implement the abstract method ConcurrentUpdateBaseSolrClient#doSendUpdateStream without requiring the concrete client.

Unlike with ConcurrentUpdateJettySolrClient, this implementation does not loop through the queue in doSendUpdateStream (the base class does this).

I did not extend the tests ConcurrentUpdateSolrClientBadInputTest or ConcurrentUpdateSolrClientMultiCollectionTest to test this new client. These are testing the legacy client only.

[Copilot]

Pull request overview

This PR adds support for ConcurrentUpdateJdkSolrClient to enable concurrent update operations using the JDK HTTP client. The implementation follows the existing pattern established by ConcurrentUpdateJettySolrClient, but adapts it to work with the JDK client's asynchronous API.

Changes:

• Added ConcurrentUpdateJdkSolrClient implementation supporting concurrent updates with the JDK HTTP client
• Refactored existing Jetty client tests into a shared ConcurrentUpdateSolrClientTestBase to support testing both Jetty and JDK client implementations
• Modified HttpJdkSolrClient to expose a requestInputStreamAsync method for streaming responses
• Updated CustomBlockingQueue constructor to remove unused maxConsumers parameter

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
ConcurrentUpdateJdkSolrClient.java	New implementation of concurrent update client using JDK HTTP client
ConcurrentUpdateSolrClientTestBase.java	Extracted shared test logic to enable testing both Jetty and JDK client implementations
ConcurrentUpdateJdkSolrClientTest.java	Test implementation for JDK concurrent update client
ConcurrentUpdateJettySolrClientTest.java	Refactored to extend shared test base class
HttpJdkSolrClient.java	Added protected method to expose async input stream responses
ConcurrentUpdateBaseSolrClient.java	Removed unused maxConsumers parameter from CustomBlockingQueue
solr-tests.policy	Added URL permissions for JDK HTTP client test

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 11 comments.

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[dsmiley]

+1 Looks good!

I checked the test refactorings in my IDE and saw things were retained as they were.

I think there's an adoc ref guide page to update and add this client to a list of other known clients.

[janhoy]

Thanks for this new client. It would be easier to review if all comments were resolved and precommit passing. But here are some initial comments.