Change to use shouldFetchRegistry.

[aftersss]

When I have two nodes to form a eurekaServer cluster,
If I set eureka.client.fetch-registry=false and eureka.client.register-with-eureka=true,
then eurekaClient inside the eurekaServer will never fetch registry from another eurekaServer upon startup.

Refer to PeerAwareInstanceRegistryImpl.syncUp:

public int syncUp() {
        // Copy entire entry from neighboring DS node
        int count = 0;

        for (int i = 0; ((i < serverConfig.getRegistrySyncRetries()) && (count == 0)); i++) {
            if (i > 0) {
                try {
                    Thread.sleep(serverConfig.getRegistrySyncRetryWaitMs());
                } catch (InterruptedException e) {
                    logger.warn("Interrupted during registry transfer..");
                    break;
                }
            }
            Applications apps = eurekaClient.getApplications();
            for (Application app : apps.getRegisteredApplications()) {
                for (InstanceInfo instance : app.getInstances()) {
                    try {
                        if (isRegisterable(instance)) {
                            register(instance, instance.getLeaseInfo().getDurationInSecs(), true);
                            count++;
                        }
                    } catch (Throwable t) {
                        logger.error("During DS init copy", t);
                    }
                }
            }
        }
        return count;
    }

Because eureka.client.fetch-registry=false, eurekaClient.getApplications().getRegisteredApplications() here will always be empty, so wait for 5 times here is meaningless. so clientConfig.shouldRegisterWithEureka() should be changed to use clientConfig.shouldFetchRegistry() just as what this PR shows.

[codecov]

Codecov Report

Merging #3627 into master will not change coverage.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #3627   +/-   ##
=========================================
  Coverage     65.04%   65.04%           
  Complexity     1508     1508           
=========================================
  Files           191      191           
  Lines          7286     7286           
  Branches        871      871           
=========================================
  Hits           4739     4739           
  Misses         2236     2236           
  Partials        311      311

Impacted Files	Coverage Δ	Complexity Δ
...x/eureka/server/EurekaServerAutoConfiguration.java	85.71% <0%> (ø)	16 <0> (ø)	⬇️

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[codecov]

Codecov Report

Merging #3627 into master will not change coverage.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #3627   +/-   ##
=========================================
  Coverage     65.04%   65.04%           
  Complexity     1508     1508           
=========================================
  Files           191      191           
  Lines          7286     7286           
  Branches        871      871           
=========================================
  Hits           4739     4739           
  Misses         2236     2236           
  Partials        311      311

Impacted Files	Coverage Δ	Complexity Δ
...x/eureka/server/EurekaServerAutoConfiguration.java	85.71% <0%> (ø)	16 <0> (ø)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #3627 into master will not change coverage.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #3627   +/-   ##
=========================================
  Coverage     65.04%   65.04%           
  Complexity     1508     1508           
=========================================
  Files           191      191           
  Lines          7286     7286           
  Branches        871      871           
=========================================
  Hits           4739     4739           
  Misses         2236     2236           
  Partials        311      311

Impacted Files	Coverage Δ	Complexity Δ
...x/eureka/server/EurekaServerAutoConfiguration.java	85.71% <0%> (ø)	16 <0> (ø)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 455c60c...94aad12. Read the comment docs.

[spencergibb]

I think that makes sense. Is there a way to test this change?

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 65.04%. Comparing base (455c60c) to head (94aad12).
⚠️ Report is 1062 commits behind head on main.

Files with missing lines	Patch %	Lines
...x/eureka/server/EurekaServerAutoConfiguration.java	0.00%	0 Missing and 1 partial ⚠️
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Additional details and impacted files

@@            Coverage Diff            @@
##               main    #3627   +/-   ##
=========================================
  Coverage     65.04%   65.04%           
  Complexity     1508     1508           
=========================================
  Files           191      191           
  Lines          7286     7286           
  Branches        871      871           
=========================================
  Hits           4739     4739           
  Misses         2236     2236           
  Partials        311      311           

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