fix metallb e2e

[changluyi]

Pull Request

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What type of this PR

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• Features
• Bug fixes
• Docs
• Tests

Which issue(s) this PR fixes

Fixes #(issue-number)

[gemini-code-assist]

Hello @changluyi, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

This pull request addresses an issue in the MetalLB end-to-end tests. Specifically, it adds a command to explicitly check the ARP table using arping before proceeding with the VIP node verification. This is done to ensure the ARP table is stable, as it may not be immediately after the system starts, which could lead to test failures.

Highlights

• Bug Fix: Addresses an intermittent failure in MetalLB E2E tests due to unstable ARP tables.
• ARP Check: Introduces an arping command to stabilize the ARP table before checking VIP node reachability.

Changelog

• test/e2e/metallb/e2e_test.go
  • Added arping command to check ARP table stability before verifying VIP node reachability.
  • The arping command is executed with a count of 5 to ensure stability.
  • The output of the arping command is logged for debugging purposes.

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---

The ARP table's fickle state,
Can cause our tests to meet their fate.
So arping we send,
A fix to extend,
And make our E2E tests great.

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[gemini-code-assist]

Code Review

The pull request introduces a change to the e2e test for MetalLB, specifically adding an arping command before the curl command to ensure ARP is stable. This is a good addition to improve the reliability of the test. However, there are a few things that can be improved.

Summary of Findings

• ARP stability: The added arping command aims to improve ARP stability before checking VIP reachability. While the intention is good, the implementation could be more robust by checking the result of the arping command.
• Error handling: The code logs the output of the arping command but doesn't check for errors. It's important to handle errors to ensure the test behaves as expected.

Merge Readiness

The change seems reasonable and addresses a potential flakiness in the e2e test. However, the error handling for the arping command should be improved before merging. I am unable to approve this pull request, and recommend that others review and approve this code before merging.

[gemini-code-assist]

The arping command is executed, and its output is logged, but the code doesn't check if the arping command was successful. It's important to check the error returned by docker.Exec to ensure that arping completed successfully before proceeding with the curl command. If arping fails, the test should fail or retry, rather than continuing with potentially unstable ARP entries. Consider adding a check for err != nil after the docker.Exec call, and failing the test if the error is present.

Suggested change

	// the arp may not be stable when just started
	cmd = strings.Fields(fmt.Sprintf("arping -c 5 %s", targetIP))
	output, _, err = docker.Exec(containerID, nil, cmd...)
	framework.Logf("arping result is %s ", output)
	// the arp may not be stable when just started
	cmd = strings.Fields(fmt.Sprintf("arping -c 5 %s", targetIP))
	output, _, err = docker.Exec(containerID, nil, cmd...)
	if err != nil {
	framework.Failf("arping failed: %v, output: %s", err, output)
	}
	framework.Logf("arping result is %s ", output)