[grid] Revert default standalone config

[VietND96]

🔗 Related Issues

💥 What does this PR do?

Revert the default config for Standalone has been done in PR #17015

🔧 Implementation Notes

💡 Additional Considerations

🔄 Types of changes

• Cleanup (formatting, renaming)
• Bug fix (backwards compatible)
• New feature (non-breaking change which adds functionality and tests!)
• Breaking change (fix or feature that would cause existing functionality to change)

[qodo-code-review]

PR Type

Enhancement

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Description

• Simplify EventBus default implementation selection logic

• Add explicit GuavaEventBus configuration to standalone mode

• Remove conditional logic for automatic EventBus selection

• Always use ZeroMqEventBus as default fallback implementation

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File Walkthrough

	Relevant files
Configuration changes	DefaultStandaloneConfig.java Add explicit GuavaEventBus to standalone config                    java/src/org/openqa/selenium/grid/commands/DefaultStandaloneConfig.java Add explicit "events" configuration mapping to GuavaEventBus Reformat "sessions" configuration for improved readability Ensure standalone mode uses in-process event bus by default +4/-1
Refactoring	EventBusOptions.java Simplify EventBus default selection logic                                java/src/org/openqa/selenium/grid/server/EventBusOptions.java Replace GUAVA_BUS_CLASS and ZEROMQ_BUS_CLASS constants with single DEFAULT_CLASS Remove conditional logic that selected EventBus based on publish/subscribe configuration Simplify createBus() method to always use ZeroMqEventBus as default Remove explanatory comments about EventBus selection strategy +2/-10

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[qodo-code-review]

PR Compliance Guide 🔍

Below is a summary of compliance checks for this PR:

Security Compliance
🟢	No security concerns identified No security vulnerabilities detected by AI analysis. Human verification advised for critical code.
Ticket Compliance
🟡	🎫 #5678 🔴 Address repeated ChromeDriver instantiation causing console errors "Error: ConnectFailure (Connection refused)" after the first instance.
🟡	🎫 #1234 🔴 Ensure click() triggers JavaScript in a link's href (regression between 2.47.1 and 2.48.x) in Firefox.
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[qodo-code-review]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Reinstate dynamic default event bus selection Restore the previous, more robust logic for selecting the default event bus. The new hardcoded default to ZeroMqEventBus can cause runtime errors if ZeroMQ dependencies are missing; the old logic intelligently defaulted to GuavaEventBus in such cases. java/src/org/openqa/selenium/grid/server/EventBusOptions.java [58-60] private EventBus createBus() { - return config.getClass(EVENTS_SECTION, "implementation", EventBus.class, DEFAULT_CLASS); + // Determine default implementation based on EventBus configuration: + // - If publish/subscribe endpoints are configured: use ZeroMqEventBus (distributed mode) + // - Otherwise: use GuavaEventBus (standalone mode, in-process, more efficient) + String ZEROMQ_BUS_CLASS = "org.openqa.selenium.events.zeromq.ZeroMqEventBus"; + String GUAVA_BUS_CLASS = "org.openqa.selenium.events.local.GuavaEventBus"; + + boolean hasZmqConfig = + config.get(EVENTS_SECTION, "publish").isPresent() + || config.get(EVENTS_SECTION, "subscribe").isPresent(); + String defaultClass = hasZmqConfig ? ZEROMQ_BUS_CLASS : GUAVA_BUS_CLASS; + return config.getClass(EVENTS_SECTION, "implementation", EventBus.class, defaultClass); } Apply / Chat Suggestion importance[1-10]: 9 __ Why: The suggestion correctly identifies a potential breaking change where the new default to ZeroMqEventBus could cause runtime errors for users without ZeroMQ dependencies, and it proposes reverting to the previous, safer logic.	High
General	Use class literal for event bus name Replace the hardcoded class name string "org.openqa.selenium.events.local.GuavaEventBus" with the safer GuavaEventBus.class.getName() to improve maintainability and prevent potential runtime errors from refactoring. java/src/org/openqa/selenium/grid/commands/DefaultStandaloneConfig.java [27-28] Map.of( - "events", Map.of("implementation", "org.openqa.selenium.events.local.GuavaEventBus"), + "events", Map.of("implementation", org.openqa.selenium.events.local.GuavaEventBus.class.getName()), Apply / Chat Suggestion importance[1-10]: 4 __ Why: The suggestion improves maintainability by replacing a "magic string" with a type-safe class literal, which helps prevent runtime errors if the class is ever refactored.	Low
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[Copilot]

Pull request overview

This PR aims to revert Selenium Grid Standalone’s default event bus configuration back to an in-process implementation, undoing a defaulting change introduced in #17015.

Changes:

• Set Standalone’s default events.implementation to GuavaEventBus.
• Change EventBusOptions to always default to ZeroMqEventBus when events.implementation is not explicitly configured.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
java/src/org/openqa/selenium/grid/server/EventBusOptions.java	Alters the default event bus selection logic (now always defaults to ZeroMQ).
java/src/org/openqa/selenium/grid/commands/DefaultStandaloneConfig.java	Forces Standalone’s default event bus implementation to Guava.