Feature/connector azure data explorer

[KaiDevrim]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If necessary, please update incompatible-changes.md to describe the incompatibility caused by this PR.
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[DanielLeens]

Thanks for the contribution. I reviewed the current connector from the real source/sink call paths rather than only checking factory wiring.

What this PR solves

• User pain: SeaTunnel does not currently ship an Azure Data Explorer source/sink connector.
• Fix approach: add a new bounded source that runs a KQL query and a sink that ingests CSV batches into ADX.
• One-line summary: the feature direction is good, but the current implementation still has correctness and packaging blockers on the main runtime path.

Runtime path I checked

bounded source
  -> AzureDataExplorerSplitEnumerator.run()
      -> create single split `adx-query`
  -> AzureDataExplorerSourceReader.pollNext()
      -> splitQueue.poll()
      -> executeQuery()
      -> emit all rows in one pass
  -> snapshotState()
      -> only persists remaining splitQueue

sink path
  -> AzureDataExplorerSinkWriter.write()
      -> serializer.toCsvLine(row)
      -> buffer rows
  -> flush()
      -> concatenate CSV lines
      -> ingestFromStream(...)

Findings

Problem 1: the bounded source drops its only split before the query finishes, so a failover can lose the unread part of the result set

• Location:
  • seatunnel-connectors-v2/connector-azuredataexplorer/.../AzureDataExplorerSourceReader.java:71-77
  • seatunnel-connectors-v2/connector-azuredataexplorer/.../AzureDataExplorerSourceReader.java:179-186
• Severity: High
• Raised before by others: No
• Why this is a real blocker:
  pollNext() removes the only split from splitQueue before executeQuery() starts reading. snapshotState() then persists only the remaining queue. If the reader fails after partially emitting rows but before a successful checkpoint finishes, restore sees an empty queue and never re-runs the query. That is a main-path bounded-source correctness bug.
• Better fix:
  keep the split in state until the full query has been consumed and checkpointed, or add explicit progress/restart semantics instead of dropping the in-flight split immediately.

Problem 2: the connector is not registered in plugin-mapping.properties, so the dist layout still cannot discover its isolated dependency directory

• Location:
  • missing update in plugin-mapping.properties
  • connector added in seatunnel-dist/pom.xml:381 and seatunnel-connectors-v2/pom.xml:95
• Severity: High
• Raised before by others: No
• Why this is a real blocker:
  SeaTunnel connector loading relies on plugin-mapping.properties to resolve the connector subdirectory name under ${SEATUNNEL_HOME}/connectors. The PR adds the module and dist dependency, but not the plugin mapping entry, so the packaging story is still incomplete.
• Better fix:
  add the new connector mapping and verify the final dist layout can actually load the connector.

Problem 3: CSV quoting is currently incorrect for embedded double quotes

• Location: seatunnel-connectors-v2/connector-azuredataexplorer/.../AzureDataExplorerRowSerializer.java:71-78
• Severity: High
• Raised before by others: No
• Why this is a real blocker:
  RFC-4180 escaping should double embedded quotes (" -> ""). The current code uses s.replace("\"", "\"\"\""), which turns one quote into three quotes. That corrupts string payloads containing " before they reach ADX.
• Better fix:
  replace embedded quotes with exactly two quotes and keep the rest of the RFC-4180 quoting logic unchanged.

Problem 4: the new Java sources are missing the ASF license header

• Location: for example AzureDataExplorerSourceReader.java, AzureDataExplorerSplitEnumerator.java, AzureDataExplorerSinkWriter.java, AzureDataExplorerSourceFactory.java, AzureDataExplorerSinkFactory.java
• Severity: Medium
• Raised before by others: No
• Why this matters:
  new source files in SeaTunnel must carry the ASF header. This is part of the Apache contribution baseline, not optional cleanup.
• Better fix:
  add the standard ASF header to all new source files before merge.

Tests / CI

• I see factory/config tests, but there is still no runtime regression coverage for the failover state issue above.
• The visible check metadata does not give me a meaningful failing runtime CI signal here; the blockers above are already source-level blockers.

Conclusion: can merge after fixes

1. Blocking items

• Problem 1
• Problem 2
• Problem 3

2. Suggested non-blocking follow-up

• Problem 4

[davidzollo]

Please also enable CI check following by the instruction https://github.com/apache/seatunnel/pull/10986/checks?check_run_id=78684187561

[DanielLeens]

Thanks for flagging the CI instruction here.

On Daniel's side, the current head 1d1397232afc2f41a40af6c5b347c633644f21af is still the exact same head I already reviewed, so I am keeping this as a reply-only follow-up rather than starting another full re-review. The CI enablement is worth doing, but the current source-level blockers from the latest Daniel review still stand on this unchanged revision as well.

Once there is a follow-up commit that addresses those runtime / packaging items and the required checks are enabled, please ping me again and I will re-review the new head from scratch.