brian clozel created HTTPCLIENT-2281:
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Summary: AsyncExecChain is not aware of cancellations
Key: HTTPCLIENT-2281
URL: https://issues.apache.org/jira/browse/HTTPCLIENT-2281
Project: HttpComponents HttpClient
Issue Type: Bug
Components: HttpClient (async)
Affects Versions: 5.2.1
Reporter: brian clozel
When working on a AsyncExecChain implementation, the "execute" method is tied
to the lifecycle of the exchange through the AsyncExecCallback that is provided
to the next element in the chain.
It's not clear how the AsyncExecChain is supposed to be notified of
cancellations and how it should clear resources. None of the AsyncExecCallback
contracts are not called when a cancellation occurs.
Given the following sample implementation, that allocates resources when the
execution starts. The handler is not notified of cancellations and resources
cannot be cleared as a result.
{code:java}
public class CustomHandler implements AsyncExecChainHandler {
@Override
public void execute(HttpRequest request, AsyncEntityProducer
entityProducer, AsyncExecChain.Scope scope,
AsyncExecChain chain, AsyncExecCallback asyncExecCallback) throws
HttpException, IOException {
CustomResource resource = CustomResource.allocate();
chain.proceed(request, entityProducer, newScope, new
AsyncExecCallback() {
@Override
public AsyncDataConsumer handleResponse(HttpResponse response,
EntityDetails entityDetails)
throws HttpException, IOException {
// not called in case of cancellation
resource.clear();
return asyncExecCallback.handleResponse(response,
entityDetails);
}
@Override
public void handleInformationResponse(HttpResponse response) throws
HttpException, IOException {
// not called in case of cancellation
}
@Override
public void completed() {
// not called in case of cancellation
resource.clear();
}
@Override
public void failed(Exception cause) {
resource.clear();
}
});
}
{code}
Here is a concrete sample using the custom handler:
{code:java}
CustomHandler customHandler = new CustomHandler();
CloseableHttpAsyncClient client = HttpAsyncClients.custom()
.addExecInterceptorFirst("custom", customHandler)
.build();
client.start();
final SimpleHttpRequest request =
SimpleRequestBuilder.get("http://localhost/delay/10";).build();
final Future<SimpleHttpResponse> future = client.execute(request,
new FutureCallback<SimpleHttpResponse>() {
@Override
public void completed(final SimpleHttpResponse response) {
}
@Override
public void failed(final Exception ex) {
}
@Override
public void cancelled() {
// this method is called but the custom handler is not made aware of
cancellations
System.out.println(request + " cancelled");
}
});
future.cancel(true);
{code}
So far I have used the AsyncExecChain.Scope CancellableDependency and tried to
wrap it to be notified of cancellations but I'm not sure this is the right
choice.
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