Missing equals/hashCode in HttpVersionSelection class generates a memory leak

[jpbempel]

Expected Behavior

no memory leak

Actual Behaviour

io.micronaut.http.client.netty.DefaultHttpClient instances are leaking and are retained in unbalancedClients map in io.micronaut.http.client.netty.DefaultNettyHttpClientRegistry

Steps To Reproduce

In our application we have defined a http client like this:

@Client(
    id = "rc-api",
    path = "/api/unstable/remote_config/products/product1",
    alpnModes = [HttpVersionSelection.ALPN_HTTP_1],
)
interface RcApiClient {
}

We have noticed after a certain time, that the Java Heap was filling up to the maximum.
By analysis of the heap dump we noticed a large amount of DefaultHttpClient instances stored into the unbalancedClients map in DefaultNettyHttpClientRegistry.

Insertion into the map is done by this:

private DefaultHttpClient getClient(ClientKey key, BeanContext beanContext, AnnotationMetadata annotationMetadata) {
        return unbalancedClients.computeIfAbsent(key, clientKey -> {

and the key of this unbalancedClients map is io.micronaut.http.client.netty.DefaultNettyHttpClientRegistry.ClientKey

ClientKey class is made from the following fields:

        final HttpVersionSelection httpVersion;
        final String clientId;
        final List<String> filterAnnotations;
        final String path;
        final Class<?> configurationClass;
        final JsonFeatures jsonFeatures;

and equals and hashCode:

       @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            ClientKey clientKey = (ClientKey) o;
            return httpVersion == clientKey.httpVersion &&
                    Objects.equals(clientId, clientKey.clientId) &&
                    Objects.equals(filterAnnotations, clientKey.filterAnnotations) &&
                    Objects.equals(path, clientKey.path) &&
                    Objects.equals(configurationClass, clientKey.configurationClass) &&
                    Objects.equals(jsonFeatures, clientKey.jsonFeatures);
        }

        @Override
        public int hashCode() {
            return Objects.hash(httpVersion, clientId, filterAnnotations, path, configurationClass, jsonFeatures);
        }

The problem is that httpVersion field when not null is using the type io.micronaut.http.client.HttpVersionSelection that does not provide any equals and hashCode methods.
So in the case of the ClientKey::hashCode it means that we are using an identityHashCode and using @client annotation with alpn will create a new instance of HttpVersionSelection (through DefaultNettyHttpClientRegistry#getClientKey -> HttpVersionSelection#forClientAnnotation.
Then every http client have a different hashCode that will spread across the unbalancedClients map.
Moreover the ClientKey::equals use reference equality (==) for the httpVersion field which will be always false.

It ends up creating a new http client for every request and stored into the map.

Environment Information

No response

Example Application

No response

Version

4.1.5

[yawkat]

thanks for the report and figuring out the cause.