clarify unmentioned constraint port.name equalness

[tedli]

Please provide a description for what this PR is for.

In our multi cluster mesh, we found that, even we meet the namespace-sameness, cross cluster calls to remote cluster through eastwest gateway never happen in some cases. (calls always invoke to primary cluster) After some digging, we found that the same kubernetes Service had different port.name, and the code that aggregating eds reads the port.name to match endpoint with service. And if we correct the Service.spec.ports[_].name to be same as what in primary cluster (literally equal, both name no specified consider equal "" == "" ), cross cluster calls act as expect. So as namespace-sameness, the addition constraint should be documented.

https://github.com/istio/istio/blob/93e4ec424b52da807228bd7784c59d646ec73733/pilot/pkg/xds/endpoint_builder.go#L240-L242

for _, ep := range endpoints {
			// TODO(nmittler): Consider merging discoverability policy with cluster-local
			if !ep.IsDiscoverableFromProxy(b.proxy) {
				continue
			}
			if svcPort.Name != ep.ServicePortName {
				continue
			}

And to help us figure out who should review this PR, please put an X in all the areas that this PR affects.

• [ ] Configuration Infrastructure
• [x] Docs
• [x] Installation
• [x] Networking
• [ ] Performance and Scalability
• [ ] Policies and Telemetry
• [ ] Security
• [ ] Test and Release
• [ ] User Experience
• [ ] Developer Infrastructure

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[istio-testing]

Hi @tedli. Thanks for your PR.

I'm waiting for a istio member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[tedli]

/ok-to-test

[istio-testing]

@tedli: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/ok-to-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[zirain]

/ok-to-test

[tedli]

/retest

[craigbox]

WG Network, PTAL

[ericvn]

This PR is targeted for the release-1.14 branch which will shortly be archived and likely not archived again. Thus this PR will not show up in the 1.14 version of the documentation. This PR should be rebased on the main branch (and cherry-picked to 1.15 if needed).

[craigbox]

@tedli could you please rebase this on master or release-1.15?

[tedli]

@tedli could you please rebase this on master or release-1.15?

Hi craigbox,

Thanks for reply. I cherry-picked this to master and release-1.15. Please have a look.

https://github.com/istio/istio.io/pull/11892 https://github.com/istio/istio.io/pull/11891

[ericvn]

@craigbox If we approve this one, it will be cp'd to the other releases. This PR won't matter too much, unless we rebuild the 1.14 archive. But at least the tooling should cherry-pick to the istio and preliminary istio branches.

Else, we could close this and approve the one in master and cherry-pick that to 1.15.