James Clampffer created HDFS-9326:
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Summary: Create a generic function to synchronize async functions
and methods.
Key: HDFS-9326
URL: https://issues.apache.org/jira/browse/HDFS-9326
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: James Clampffer
The majority of the functionality in libhdfs++ is asynchronous, but some
applications need synchronous operations. At the time of filing this only
happens in 3 places in the C API, however that number is going to grow a lot
once the C and high level C++ APIs expose all of the namenode functions.
This synchronization is typically implemented like this:
auto promise = std::make_shared<std::promise<T>>()
std::future<T> = future(promise->get_future());
auto async_callback = [promise] () {promise->set_value(val);};
SomeClass::AsyncMethod(async_callback);
auto result = future.get()
Ideally this could all be pushed into a templated function so that the promise
and future don't need to be defined at the call site. This would probably take
the form of doing a std::bind to get all the arguments in place at the call
site and then passing that to the synchronize function.
This appears to require some template magic that isn't always well supported;
see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51979.
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