Add validation for the search backpressure cancellation settings

[gaobinlong]

Description

Updating the cluster level setting search_backpressure.cancellation_burst(deprecated), search_backpressure.search_task.cancellation_burst or search_backpressure.search_shard_task.cancellation_burst to an non-default value cause the cluster crash, the reason is that the value of cancellationRate is always 0 here:

OpenSearch/server/src/main/java/org/opensearch/search/backpressure/SearchBackpressureState.java

Line 101 in 2b84305

onRateChanged(cancellationRate);

, so an exception is thrown here:

OpenSearch/server/src/main/java/org/opensearch/common/util/TokenBucket.java

Line 51 in 2b84305

if (rate <= 0.0) {

.

Just like cancellationRatio, we also need to get the value of cancellationRate from the cluster settings and pass it to the constructor method of SearchBackpressureState.

Another issue is that we don't have some validations for the setting cancellationRate and cancellationRatio, so when updating these two settings to 0, the same exception "rate must be greater than zero" is also thrown and then crash the cluster.

Related Issues

#15495

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[gaobinlong]

@reta @dblock could you help to review this PR, thank you!

[github-actions]

❌ Gradle check result for adcf328: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for f518b2e: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 575303c: SUCCESS

[reta]

Sorry @gaobinlong , completely forgot about this change

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-15501-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 8347d0ec22aa865dea3bc4b2027fb7bdf486fab2
# Push it to GitHub
git push --set-upstream origin backport/backport-15501-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-15501-to-2.x.

[reta]

@gaobinlong could you please backport to 2.x manually? thank you!