nhenneaux/resilient-httpclient

Java HTTP client with pooling and auto refresh of underlying IP addresses

Resilient HTTP with java.net.http.HttpClient

Client using a pool of HTTP clients targeting each a single IP. Each of them is refreshed based on HTTP health check and DNS query. It has the following features.

• Client side load balancing between all the IP behind the hostname
• Monitoring of all the IP behind the hostname at HTTP level
• Monitoring of the DNS
• TCP failover
• HTTP/2 with seamless fallback to HTTP/1

A presentation detailing the features of the client and comparing it with other Java HTTP clients (HttpUrlConnection, Apache, Jetty) Presentation.

Usage

HttpClientPool singletonByHost = HttpClientPool.newHttpClientPool(new ServerConfiguration("openjdk.java.net"));
java.net.http.HttpClient resilientClient = singletonByHost.resilientClient();

HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://openjdk.java.net/"))
        .build();
resilientClient.sendAsync(request, HttpResponse.BodyHandlers.ofString())
        .thenApply(HttpResponse::body)
        .thenAccept(System.out::println)
        .join();

resilient-httpclient's Issues

refreshTheListWrappedInTryCatch should not re-throw an exception because it is used in the scheduled executor service

Please observe this javadoc comment for the scheduleAtFixedRate::scheduleAtFixedRate method:

The sequence of task executions continues indefinitely until one of the following exceptional completions occur:
The task is explicitly cancelled via the returned future.
The executor terminates, also resulting in task cancellation.
An execution of the task throws an exception. In this case calling get on the returned future will throw ExecutionException, holding the exception as its cause.

Therefore the HttpClientPool::refreshTheListWrappedInTryCatch method used within
this.scheduledFutureDnsRefresh = scheduledExecutorService.scheduleAtFixedRate( () -> refreshTheListWrappedInTryCatch( dnsLookupWrapper, serverConfiguration, httpClientsCache, singleHttpClientProvider, scheduledExecutorService ), dnsLookupRefreshPeriodInSeconds, dnsLookupRefreshPeriodInSeconds, TimeUnit.SECONDS );

should not re-throw an exception