upgrade to Java-21 #267

	name: Multi-node Test Workflow
	# This workflow is triggered on pull requests and pushes to main or an OpenSearch release branch
	on:
	pull_request:
	branches:
	- "*"
	push:
	branches:
	- "*"
	env:
	ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true

	jobs:
	Get-CI-Image-Tag:
	uses: opensearch-project/opensearch-build/.github/workflows/get-ci-image-tag.yml@main
	with:
	product: opensearch

	build-linux:
	needs: Get-CI-Image-Tag
	strategy:
	matrix:
	java: [ 21 ]
	# Job name
	name: Build and test Alerting
	# This job runs on Linux
	runs-on: ubuntu-latest
	container:
	# using the same image which is used by opensearch-build team to build the OpenSearch Distribution
	# this image tag is subject to change as more dependencies and updates will arrive over time
	image: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-version-linux }}
	# need to switch to root so that github actions can install runner binary on container without permission issues.
	options: --user root

	steps:
	# This step uses the setup-java Github action: https://github.com/actions/setup-java
	- name: Set Up JDK ${{ matrix.java }}
	uses: actions/setup-java@v1
	with:
	java-version: ${{ matrix.java }}
	# This step uses the checkout Github action: https://github.com/actions/checkout
	- name: Checkout Branch
	uses: actions/checkout@v2
	- name: Run integration tests with multi node config
	run: \|
	chown -R 1000:1000 `pwd`
	su `id -un 1000` -c "whoami && java -version && ./gradlew integTest -PnumNodes=3"

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