Prevent infinite recursion when migrating secrets to credentials while loading GitLab server configuration

[dwnusbaum]

I recently ran into a case where the migration code in https://github.com/jenkinsci/gitlab-branch-source-plugin/pull/267 was causing an infinite loop while loading extensions during Jenkins startup, leading to various issues.

The problem is that readResolve on a class that is part of a @Extension PersistentDescriptor will be called while extensions are being loaded because PersistentDescriptor.load is annotated with @PostConstruct which gets called here when the extension is loaded. This means that it is not safe to do anything that requires other extensions to be loaded from within load and any other methods that loading may trigger. In this case the problem was the call to CredentialsProvider.lookupCredentials in GitLabServer.readResolve. To avoid this issue, I moved the migration to a static @Initializer method that runs after EXTENSIONS_AUGMENTED, so all extensions have already been loaded at that point.

Here is what the OldDataMonitor warning looked like, filtered to just the repeating stack frames:

INFO    hudson.diagnosis.OldDataMonitor#report: Trouble loading io.jenkins.plugins.gitlabserverconfig.servers.GitLabServers@4a65323
java.lang.StackOverflowError
    ... everything below repeats after this ...
    at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at hudson.ExtensionFinder$GuiceFinder$SezpozModule.onProvision(ExtensionFinder.java:634)
    at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:117)
    at com.google.inject.internal.ProvisionListenerStackCallback.provision(ProvisionListenerStackCallback.java:66)
    at com.google.inject.internal.ConstructorInjector.construct(ConstructorInjector.java:93)
    at com.google.inject.internal.ConstructorBindingImpl$Factory.get(ConstructorBindingImpl.java:300)
    at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
    at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:169)
    at hudson.ExtensionFinder$GuiceFinder$FaultTolerantScope$1.get(ExtensionFinder.java:445)
    at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:45)
    at com.google.inject.internal.InjectorImpl$1.get(InjectorImpl.java:1148)
    at hudson.ExtensionFinder$GuiceFinder._find(ExtensionFinder.java:403)
    at hudson.ExtensionFinder$GuiceFinder.find(ExtensionFinder.java:394)
    at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:335)
    at hudson.ExtensionList.load(ExtensionList.java:384)
    at hudson.ExtensionList.ensureLoaded(ExtensionList.java:320)
    at hudson.ExtensionList.iterator(ExtensionList.java:172)
    at jenkins.model.Jenkins.getDescriptor(Jenkins.java:1649)
    at io.jenkins.plugins.gitlabserverconfig.servers.GitLabServersTest$CredentialsProviderThatRequiresDescriptorLookup.getCredentials(GitLabServersTest.java:71)
    at com.cloudbees.plugins.credentials.CredentialsProvider.getCredentialsInItemGroup(CredentialsProvider.java:1191)
    at com.cloudbees.plugins.credentials.CredentialsProvider.lookupCredentialsInItemGroup(CredentialsProvider.java:389)
    at com.cloudbees.plugins.credentials.CredentialsProvider.lookupCredentials(CredentialsProvider.java:348)
    at io.jenkins.plugins.gitlabserverconfig.servers.GitLabServer.migrateWebhookSecretCredentials(GitLabServer.java:421)
    at io.jenkins.plugins.gitlabserverconfig.servers.GitLabServer.readResolve(GitLabServer.java:412)
    at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at com.thoughtworks.xstream.core.util.SerializationMembers.callReadResolve(SerializationMembers.java:78)
    at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:290)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:74)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:68)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:52)
    at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readBareItem(AbstractCollectionConverter.java:132)
    at hudson.util.RobustCollectionConverter.populateCollection(RobustCollectionConverter.java:87)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.unmarshal(CollectionConverter.java:81)
    at hudson.util.RobustCollectionConverter.unmarshal(RobustCollectionConverter.java:78)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:74)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:68)
    at hudson.util.RobustReflectionConverter.unmarshalField(RobustReflectionConverter.java:454)
    at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:350)
    at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:289)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:74)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:68)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:52)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:136)
    at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1464)
    at hudson.util.XStream2.unmarshal(XStream2.java:230)
    at hudson.util.XStream2.unmarshal(XStream2.java:201)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1441)
    at hudson.XmlFile.unmarshal(XmlFile.java:196)
    at hudson.XmlFile.unmarshal(XmlFile.java:179)
    at hudson.model.Descriptor.load(Descriptor.java:935)
    ...

There was also this Guice exception in the logs:

WARNING h.ExtensionFinder$GuiceFinder$FaultTolerantScope$1#error: Failed to instantiate Key[type=io.jenkins.plugins.gitlabserverconfig.servers.GitLabServers, annotation=[none]]; skipping this component
java.lang.IllegalStateException: Singleton is called recursively returning different results

Testing done

See new automated test.

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