Add template snippets support for field and target_field in KV ingest processor

[gaobinlong]

Description

Add template snippets support for field and target_field parameters in KV ingest processor so that users can use mustache script like {{some filed}} to set those parameters.

Here is an example:

POST /_ingest/pipeline/_simulate
{
  "pipeline": {
    "description": "_description",
    "processors": [
      {
        "kv": {
          "field": "{{key}}",
          "field_split": " ",
          "value_split": "=",
          "target_field": "{{target_field}}"
        }
      }
    ]
  },
  "docs": [
    {
      "_index": "index",
      "_id": "id",
      "_source": {
        "key":"foo",
        "foo": "bar=x",
        "target_field":"zoo"
      }
    },
    {
      "_index": "index",
      "_id": "id",
      "_source": {
        "key":"foo",
        "foo": "rab=x",
        "target_field":"zoo"
      }
    }
  ]
}

The response is:

{
  "docs": [
    {
      "doc": {
        "_index": "index",
        "_id": "id",
        "_source": {
          "zoo": {
            "bar": "x"
          },
          "target_field": "zoo",
          "key": "foo",
          "foo": "bar=x"
        },
        "_ingest": {
          "timestamp": "2023-09-14T03:37:21.612363Z"
        }
      }
    },
    {
      "doc": {
        "_index": "index",
        "_id": "id",
        "_source": {
          "zoo": {
            "rab": "x"
          },
          "target_field": "zoo",
          "key": "foo",
          "foo": "rab=x"
        },
        "_ingest": {
          "timestamp": "2023-09-14T03:37:21.612463Z"
        }
      }
    }
  ]
}

The main changes of this PR are:

1. Add template snippets support for field and target_field parameters in KV ingest processor.
2. Same to Fix ignore_missing parameter has no effect in rename ingest processor #9725, we also need to avoid ignore_missing parameter taking no effect when the filed in template snippet doesn't exist.
3. Add some yml tests for the change.

Related Issues

#9964

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Compatibility status:

Checks if related components are compatible with change cd50504

Incompatible components

Incompatible components: [https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/performance-analyzer.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/alerting.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/25568/
• CommitID: 3dc65b3
  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 (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/25569/
• CommitID: 597a265

[github-actions]

❌ Gradle check result for e4a31b7: 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?

[reta]

@msfroh another one for you :)

[github-actions]

❕ Gradle check result for cd50504: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.index.IndexServiceTests.testAsyncTranslogTrimTaskOnClosedIndex

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[dblock]

@reta you good with this?

[reta]

@gaobinlong could you please create a documentation issue update for this processor? (https://github.com/opensearch-project/documentation-website/) Thank you.

[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-10040-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7f4537c3d4068a117576e6e2214eaf924db6748f
# Push it to GitHub
git push --set-upstream origin backport/backport-10040-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-10040-to-2.x.

[reta]

@gaobinlong could you please send a manual backport to 2.x? thank you

[gaobinlong]

@reta, sure, I'll create a backport PR and documentation PR for this change later.