I'm just playing and testing a bit with the Restlet Client Api 2.2, but I don't get a non-blocking asynchronous request with a callback to work. I already have googled extensively
but really not found an answer to a (working) non-blocking solution.
I have the following two approaches:
Approach 1 ( Client - Request ):
Client c = new Client(Protocol.HTTP);
Request r = new Request(Method.GET, url);
System.out.println("START1");
c.handle(r, new Uniform() {
#Override
public void handle(Request request, Response response) {
int statusCode = response.getStatus().getCode();
System.out.println(statusCode);
}
});
System.out.println("START2");
Approach 2 ( ClientResource - setOnResponse() - get() ):
ClientResource cr = new ClientResource(url);
cr.setOnResponse(new Uniform() {
#Override
public void handle(Request request, Response response) {
int statusCode = response.getStatus().getCode();
System.out.println(statusCode);
}
});
System.out.println("START1");
cr.get();
System.out.println("START2");
The Console-Output for both approaches is always:
START1
Starting the internal HTTP client
SOME WAITING HERE
200
START2
Can anyone give me a hint to make one of these approaches non-blocking? Is that at all possible with the Restlet API? What am I missing, do I need another connector or must I define a seperate thread for the request myself?
I make a quick answer, an issue has been created: https://github.com/restlet/restlet-framework-java/issues/943
Initially the support of asynchronous was available using the internal nio connector.
As this connector is not fully stabilized, it has been decided to extract it from the core module and expose it inside a dedicated org.restlet.ext.nio module.
This explains why your code is blocking, as the current internal connector (in both 2.2 and 2.3 branches) does not support it.
At this time, the support is available using the nio extension, but this extension is not fully stabilized yet. So we are not inclined to encourage you to use it.
We are working on another scenario where we rely on the client connector provided by Jetty.
Stay tuned.
Related
I'm working on a micro service powered by SpringMVC and Spring Cloud Kafka.
For simplicity I will only focus on the part that makes HTTP request.
I have a binding function like the following (please note that I'm using the functional style binding).
#SpringBootApplication
public class ExampleApplication {
// PayloadSender uses RestTemplate to send HTTP request.
#Autowired
private PayloadSender payloadSender;
#Bean
public Function<KStream<String, Input>, KStream<String, Output>> process() {
// payloadSender.send() is a blocking call which sends payload using RestTemplate,
// once response is received it will collect all info and create "Output" object
return input -> input
.map((k,v) -> KeyValue.pair(k, payloadSender.send(v))); // "send" is a blocking call
// Question: if autoCommitOffset is set to true, would offset automatically commit right after the "map" function from KStream?
}
public static void main(String[] args) {
SpringApplication.run(ExampleApplication.class, args);
}
}
From this example you can see that the payloadSender is sending the payload from the input stream using RestTemplate and upon receiving the response creating the "Output" object and produce to the output topic.
Since payloadSender.send() is blocking, I'm worried that this will cause performance issue. Most importantly if the HTTP request gets timed out, I'm afraid it will exceed the commit interval (usually the HTTP timeout interval is much much greater than the consumer commit interval) and cause the kafka broker to think the consumer is dead (please correct me if I'm wrong).
So is there a better solution for this case? I would eventually switch over to spring-reactive but for the time being I need to make sure the MVC model works. Although I'm not sure spring-reactive would have magically solve this issue.
The default max.poll.interval is 5 minutes; you can increase it or reduce max.poll.records. You can also set a timeout on the rest call.
I have two query :
1. Can we have non blocking async routes in camel. I do see async with seda but then if offloads work to other thread that blocks.
2. If so can we use multicast in such routes.
Following is my multistep camel route which seems to work. But not sure if it is async or non blocking async.
from("direct:multiStep")
.to("bean:routeHandler?method=monoReturningMethod1")
.process(new UnwrapStreamProcessor())
.to("bean:routeHandler?method=monoReturningMethod2")
.process(new UnwrapStreamProcessor())
Above works and web request has response from both monoReturningMethod. In this case I want to make sure all process is non blocking.
For multicast I am experimenting with following route. Not sure where to put UnwrapStreamProcessor. I have tried to put it after end() but it does not work. Do I need a custom Processor ? Or how can I tie all Mono returns in one ?
from("direct:incoming")
.multicast()
.parallelProcessing()
.to("bean:routeHandler?method=monoReturningMethod1", "bean:routeHandler?method=monoReturningMethod2")
.end()
I am using apache `camel 3.0.1 with spring boot starter.
#Component("routeHandler")
public class RouteHandler {
Mono<Entity> monoReturningMethod1(Exchange exchange) {
//make some WebClient request which returns Mono.
}
Mono<Entity> monoReturningMethod2(Exchange exchange) {
//make some WebClient request which returns Mono.
}
}
This route handles incoming web request. How to make all route processing non blocking and async. I have tried using process(new UnwrapStreamProcessor()) as process step after monoReturningMehtod and if I do in sequence it works. But it does not work with multicast and give original message overwrite not allowed.
Any suggestions ?
PS : I am initiating my async flow like following :
producerTemplate.asyncSend("RouteName", exchange)
According to this page, all EIPs are supported by the async routing engine, but not all endpoint types (components). Some components have only limited support, i.e. they can only consume or produce asynchronous.
You can use the Threads DSL in your route to tell Camel that from the point forwards, the messages should be routed asynchronous in a new thread.
This article shows a well-known problem with HttpClient that can lead to socket exhaustion.
I have an ASP.NET Core 3.1 web application. In a .NET Standard 2.0 class library I've added a WCF web service reference in Visual Studio 2019 following this instructions.
In a service I'm using the WCF client the way it's described in the documentation. Creating an instance of the WCF client and then closing the client for every request.
public class TestService
{
public async Task<int> Add(int a, int b)
{
CalculatorSoapClient client = new CalculatorSoapClient();
var resultat = await client.AddAsync(a, b);
//this is a bad way to close the client I should also check
//if I need to call Abort()
await client.CloseAsync();
return resultat;
}
}
I know it's bad practice to close the client without any checks but for the purpose of this example it does not matter.
When I start the application and make five requests to an action method that uses the WCF client and then take a look at the result from netstat I discover open connections with status TIME_WAIT, much like the problems in the article above about HttpClient.
It looks to me like using the WCF client out-of-the-box like this can lead to socket exhaustion or am I missing something?
The WCF client inherits from ClientBase<TChannel>. Reading this article it looks to me like the WCF client uses HttpClient. If that is the case then I probably shouldn't create a new client for every request, right?
I've found several articles (this and this) talking about using a singleton or reusing the WCF client in some way. Is this the way to go?
###UPDATE
Debugging the appropriate parts of the WCF source code I discovered that a new HttpClient and HttpClientHandler were created each time I created a new WCF client which I do for every request.
You can inspect the code here
internal virtual HttpClientHandler GetHttpClientHandler(EndpointAddress to, SecurityTokenContainer clientCertificateToken)
{
return new HttpClientHandler();
}
This handler is used in to create a new HttpClient in the GetHttpClientAsync method:
httpClient = new HttpClient(handler);
This explains why the WCF client in my case behaves just like a HttpClient that is created and disposed for every request.
Matt Connew writes in an issue in the WCF repo that he has made it possible to inject your own HttpMessage factory into the WCF client.
He writes:
I implemented the ability to provide a Func<HttpClientHandler,
HttpMessageHandler> to enable modifying or replacing the
HttpMessageHandler. You provide a method which takes an
HttpClientHandler and returns an HttpMessageHandler.
Using this information I injected my own factory to be able to control the generation of HttpClientHandlers in HttpClient.
I created my own implementation of IEndpointBehavior that injects IHttpMessageHandlerFactory to get a pooled HttpMessageHandler.
public class MyEndpoint : IEndpointBehavior
{
private readonly IHttpMessageHandlerFactory messageHandlerFactory;
public MyEndpoint(IHttpMessageHandlerFactory messageHandlerFactory)
{
this.messageHandlerFactory = messageHandlerFactory;
}
public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
{
Func<HttpClientHandler, HttpMessageHandler> myHandlerFactory = (HttpClientHandler clientHandler) =>
{
return messageHandlerFactory.CreateHandler();
};
bindingParameters.Add(myHandlerFactory);
}
<other empty methods needed for implementation of IEndpointBehavior>
}
As you can see in AddBindingParameters I add a very simple factory that returns a pooled HttpMessageHandler.
I add this behavior to my WCF client like this.
public class TestService
{
private readonly MyEndpoint endpoint;
public TestService(MyEndpoint endpoint)
{
this.endpoint = endpoint;
}
public async Task<int> Add(int a, int b)
{
CalculatorSoapClient client = new CalculatorSoapClient();
client.Endpoint.EndpointBehaviors.Add(endpoint);
var resultat = await client.AddAsync(a, b);
//this is a bad way to close the client I should also check
//if I need to call Abort()
await client.CloseAsync();
return resultat;
}
}
Be sure to update any package references to System.ServiceModel.* to at least version 4.5.0 for this to work. If you're using Visual Studio's 'Add service reference' feature, VS will pull in the 4.4.4 versions of these packages (tested with Visual Studio 16.8.4).
When I run the applications with these changes I no longer have an open connection for every request I make.
You should consider disposing your CalculatorSoapClient. Be aware that a simple Dispose() is usually not enough, becaue of the implementation of the ClientBase.
Have a look at https://learn.microsoft.com/en-us/dotnet/framework/wcf/samples/use-close-abort-release-wcf-client-resources?redirectedfrom=MSDN, there the problem is explained.
Also consider that the underlying code is managing your connections, sometimes it will keep them alive for later use. Try calling the server a lot of times to see, if there is a new connection for each call, or if the connections are being reused.
The meaning TIME_WAIT is also discussed here:
https://superuser.com/questions/173535/what-are-close-wait-and-time-wait-states
https://serverfault.com/questions/450055/lot-of-fin-wait2-close-wait-last-ack-and-time-wait-in-haproxy
It looks like your client has done everything required to close the connection and is just waiting for the confirmation of the server.
You should not have to use a singleton since the framework is (usually) taking good care of the connections.
I created an issue in the WCF repository in Github and got some great answers.
According to Matt Connew and Stephen Bonikowsky who are authorities in this area the best solution is to reuse the client or the ChannelFactory.
Bonikowsky writes:
Create a single client and re-use it.
var client = new ImportSoapClient();
And Connew adds:
Another possibility is you could create a channel proxy instance from
the underlying channelfactory. You would do this with code similar to
this:
public void Init()
{
_client?.Close();
_factory?.Close();
_client = new ImportSoapClient();
_factory = client.ChannelFactory;
}
public void DoWork()
{
var proxy = _factory.CreateChannel();
proxy.MyOperation();
((IClientChannel)proxy).Close();
}
According to Connew there is no problem reusing the client in my ASP.NET Core web application with potentially concurrent requests.
Concurrent requests all using the same client is not a problem as long
as you explicitly open the channel before any requests are made. If
using a channel created from the channel factory, you can do this with
((IClientChannel)proxy).Open();. I believe the generated client also
adds an OpenAsync method that you can use.
UPDATE
Since reusing the WCF Client also means reusing the HttpClient instance and that could lead to the known DNS problem I decided to go with my original solution using my own implementation of IEndpointBehavior as described in the question.
I am trying to track the HTTP request and response time in Jetty. I have extended the jetty server and i am able to get the request timestamp using following snippet :
public void handle(HttpChannel connection) throws IOException,
ServletException {
super.handle(connection);
connection.getRequest().getTimeStamp();
}
I need to get the exact time of the response for the request.
How can i achieve it by extending jetty server ?
If any way of doing other than extending jetty. please let me know
Thank you
Since you seem to only be interested in the latency, do this.
The RequestLog mechanism is now to do this.
Instantiate a new RequestLogHandler and add it as the root of your server Handler tree (think nested, not collection).
Add a custom implementation of RequestLog to the RequestLogHandler
In your custom RequestLog.log(Request,Response) method, grab the Request.getTimeStamp() and work out the latency.
This approach is more durable to changes internally in Jetty, and does not require a fork Jetty + modify approach to work.
Having some problem developing a SignalR client for a Hub hosted in asp.net website with gzip compression enabled. Since we are using IIS compression, the response from SignalR also gets compressed, but, the client does not understand the response and we get a Json parsing error on the client side.
SignalR internally uses HttpWebRequest to make make http requests and HttpWebRequest can be configured to automatically decompress the response using AutomaticDecompression property. So, if somehow I can get hold of the HttpWebRequest object used by SignalR to make the request, I should be able to set the enable automatic decompression.
I thought I should be able to get access to the HttpWebRequest by providing HubConnection.Start with my custom implementation of IHttpClient, IHttpClient.GetAsync takes a prepareRequest action which I thought should give me access to the HttpWebRequest, but, HttpHelper.GetAsync wraps the HttpWebRequest with HttpWebRequestWrapper before passing to prepareRequest and HttpWebRequestWrapper does not provide access to HttpWebRequest.
HttpHelper class is internal so can't use it as well, so, I am not exactly sure how to enable automatic decompression with SignalR.
I can expose the HttpWebRequest in HttpWebRequestWrapper, but, would prefer a simpler solution if one exists. Any thougths?
I am using SignalR version 0.5.1.10822
My auto decompression HttpClient:
public class HttpClientWithAutoDecompression : IHttpClient
{
readonly DefaultHttpClient _httpClient = new DefaultHttpClient();
private readonly DecompressionMethods _decompressionMethods;
public HttpClientWithAutoDecompression(DecompressionMethods decompressionMethods)
{
_decompressionMethods = decompressionMethods;
}
public Task<IResponse> GetAsync(string url, Action<IRequest> prepareRequest)
{
Task<IResponse> task = _httpClient.GetAsync(url,
request =>
{
[ERROR: request is actually HttpRequestWrapper and
does not expose HttpWebRequest]** ]
var httpWebRequest = (HttpWebRequest) request;
httpWebRequest.AutomaticDecompression = _decompressionMethods;
prepareRequest(request);
});
return task.ContinueWith(response =>
{
Log.Debug(this, "Response: {0}", response.Result.ReadAsString());
return response.Result;
});
}
....
}
To the best of my knowledge GZip encoding and streaming do not mix. In the case of the forever frame transport the client wouldn't be able to decode any on the streaming content until the entire response, or at least a significant block of data, is received (due to the way the data is decoded). In the case of web sockets there is not support for encoding of any kind at this time, although there is apparently an extension to the specification for per message encoding being worked on.
That said, if you wanted to attempt to provide support for the LongPolling transport, the only way I can see this being possible is to provide your own SignalR IHttpClient implementation. You can see right now that the DefaultHttpClient class uses HttpHelper::GetAsync which creates the HttpWebRequest internally and you can never get your hands on that because you only have access to the IRequest which is HttpWebRequestWrapper at that point.
By creating your own IHttpClient you can take over the initial instantiation of the HttpWebRequest, set the AutomaticDecompression and then wrap that up yourself with the HttpWebRequestWrapper.