Gatewayservice 1

[xyuanlu]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

(No specific issue number mentioned in the description)

Description

• Here are some details about my PR, including screenshots of any UI changes:

This pull request introduces significant enhancements to the Helix Gateway Service, particularly focusing on implementing a poll-mode channel for the gateway service. The main changes include:

1. Implementation of HelixGatewayServicePollModeChannel class, which periodically polls for updates on participant states and liveness.
2. Addition of new configuration options in GatewayServiceChannelConfig to support poll mode operations.
3. Updates to GatewayServiceManager to handle poll mode operations and manage target state caches.
4. Introduction of utility classes like PollChannelUtil for file-based operations and health checks.
5. Modifications to existing classes to support the new poll mode functionality.

These changes aim to provide an alternative method for managing participant states and liveness in the Helix Gateway Service, allowing for file-based and polling approaches alongside the existing gRPC-based methods.

Tests

• The following tests are written for this issue:

1. TestHelixGatewayServicePollModeChannel: Tests the new poll mode channel implementation, including connection events, state updates, and disconnection scenarios.
2. TestGatewayServiceChannelConfig: Updated to include tests for invalid configurations in both gRPC and file-based modes.

Existing tests in TestHelixGatewayParticipant and TestGatewayCurrentStateCache have been modified to accommodate the new method signatures and functionality.

• The following is the result of the "mvn test" command on the appropriate module:

(If CI test fails due to known issue, please specify the issue and test PR locally. Then copy & paste the result of "mvn test" to here.)

Changes that Break Backward Compatibility

• My PR contains changes that break backward compatibility or previous assumptions for certain methods or API. They include:

1. The method signatures in HelixGatewayServiceChannel interface have been updated to include clusterName parameter:

   • closeConnectionWithError(String clusterName, String instanceName, String reason)
   • completeConnection(String clusterName, String instanceName)

2. The serializeTargetAssignmentsToJSON() method in GatewayCurrentStateCache has been renamed to serializeTargetAssignmentsToJSONNode().

Documentation

• In case of new functionality, my PR adds documentation in the following wiki page:

(No documentation changes mentioned in the description)

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml
  (helix-style-intellij.xml if IntelliJ IDE is used)

Created with Palmier

[xyuanlu]

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