aws-sdk-cpp: how to use CurlHttpClient? - aws-sdk

Question

I need to make signed requests to AWS ES, but am stuck at the first hurdle in that I cannot seem to be able to use CurlHttpClient. Here is my code (verb, path, and body defined elsewhere):
Aws::Client::ClientConfiguration clientConfiguration;
clientConfiguration.scheme = Aws::Http::Scheme::HTTPS;
clientConfiguration.region = Aws::Region::US_EAST_1;
auto client = Aws::MakeShared<Aws::Http::CurlHttpClient>(ALLOCATION_TAG, clientConfiguration);
Aws::Http::URI uri;
uri.SetScheme(Aws::Http::Scheme::HTTPS);
uri.SetAuthority(ELASTIC_SEARCH_DOMAIN);
uri.SetPath(path);
Aws::Http::Standard::StandardHttpRequest req(uri, verb);
req.AddContentBody(body);
auto res = client->MakeRequest(req);
Aws::Http::HttpResponseCode resCode = res->GetResponseCode();
if (resCode == Aws::Http::HttpResponseCode::OK) {
Aws::IOStream &body = res->GetResponseBody();
rejoiceAndBeMerry();
}
else {
gotoPanicStations();
}
When executed, the code throws a bad_function_call deep from within the sdk mixed up with a lot of shared_ptr this and allocate that. My guess is that I am just using the SDK wrong, but I've been unable to find any examples that use the CurlHttpClient directly such as I need to do here.
How can I use CurlHttpClient?

Answer 1

You shouldn't be using the HTTP client directly, but the supplied wrappers with the aws-cpp-sdk-es package. Like previous answer(s), I would recommend evaluating the test cases shipped with the library to see how the original authors intended to implement the API (at least until the documents catch-up).
How can I use CurlHttpClient?
Your on the right track with managed shared resources and helper functions. Just need to create a static factory/client to reference. Here's a generic example.
using namespace Aws::Client;
using namespace Aws::Http;
static std::shared_ptr<HttpClientFactory> MyClientFactory; // My not be needed
static std::shared_ptr<HttpClient> MyHttpClient;
// ... jump ahead to method body ...
ClientConfiguration clientConfiguration;
MyHttpClient = CreateHttpClient(clientConfiguration);
Aws::String uri("https://example.org");
std::shared_ptr<HttpRequest> req(
CreateHttpRequest(uri,
verb, // i.e. HttpMethod::HTTP_POST
Utils::Stream::DefaultResponseStreamFactoryMethod));
req.AddContentBody(body); //<= remember `body' should be `std::shared_ptr<Aws::IOStream>',
// and can be created with `Aws::MakeShared<Aws::StringStream>("")';
req.SetContentLength(body_size);
req.SetContentType(body_content_type);
std::shared_ptr<HttpResponse> res = MyHttpClient->MakeRequest(*req);
HttpResponseCode resCode = res->GetResponseCode();
if (resCode == HttpResponseCode::OK) {
Aws::StringStream resBody;
resBody << res->GetResponseBody().rdbuf();
rejoiceAndBeMerry();
} else {
gotoPanicStations();
}

Answer 2

I encountered exactly the same error when trying to download from S3 using CurlHttpClient.
I fixed it by instead modelling my code after the integration test found in the cpp sdk:
aws-sdk-cpp/aws-cpp-sdk-s3-integration-tests/BucketAndObjectOperationTest.cpp
Search for the test called TestObjectOperationsWithPresignedUrls.