do we have an example of syn watch?

[danielzhanghl]

hi, all the watch operation examples are asynchronous, do we have a way to sync the watch?
I tried below, but it return right way, instead of block there.
thanks for any suggestions!

static std::string etcd_uri("http: 127.0.0.1:2379");
etcd::Client etcd(etcd_uri);
etcd::Response response;
pplx::tasketcd::Response response_task = etcd.watch("/test/key1",true);
try
{
std::cout << "start watch" << std::endl;
response = response_task.get(); // can throw
if (response.is_ok())
std::cout << "successful action is: "<<response.action()<<" value= " << response.value().as_string() << std::endl;
else
std::cout << "operation failed, details: " << response.error_message();
}
catch (std::exception const & ex)
{
std::cerr << "communication problem, details: " << ex.what();
}

---

result is as below:

start watch
successful action is: value=

[danielzhanghl]

after some dig into the code, it seems the watch can not be cancelled, that is a bug.

[sighingnow]

Hi @danielzhanghl,

You could find sync-watch examples in

etcd-cpp-apiv3/tst/EtcdSyncTest.cpp

Lines 111 to 179 in a00a06d

	TEST_CASE("wait for a value change")
	{
	etcd::SyncClient etcd(etcd_uri);
	etcd.set("/test/key1", "42");
	std::thread watch_thrd([&]() {
	etcd::Response res = etcd.watch("/test/key1");
	REQUIRE("set" == res.action());
	CHECK("43" == res.value().as_string());
	});
	sleep(1);
	etcd.set("/test/key1", "43");
	watch_thrd.join();
	REQUIRE(0 == etcd.rmdir("/test", true).error_code());
	}
	TEST_CASE("wait for a directory change")
	{
	etcd::SyncClient etcd(etcd_uri);
	std::thread watch_thrd1([&]() {
	etcd::Response res = etcd.watch("/test", true);
	CHECK("create" == res.action());
	CHECK("44" == res.value().as_string());
	});
	sleep(1);
	etcd.add("/test/key4", "44");
	watch_thrd1.join();
	std::thread watch_thrd2([&]() {
	etcd::Response res2 = etcd.watch("/test", true);
	CHECK("set" == res2.action());
	CHECK("45" == res2.value().as_string());
	});
	sleep(1);
	etcd.set("/test/key4", "45");
	watch_thrd2.join();
	REQUIRE(0 == etcd.rmdir("/test", true).error_code());
	}
	TEST_CASE("watch changes in the past")
	{
	etcd::SyncClient etcd(etcd_uri);
	int index = etcd.set("/test/key1", "42").index();
	etcd.set("/test/key1", "43");
	etcd.set("/test/key1", "44");
	etcd.set("/test/key1", "45");
	etcd::Response res = etcd.watch("/test/key1", ++index);
	CHECK("set" == res.action());
	CHECK("43" == res.value().as_string());
	res = etcd.watch("/test/key1", ++index);
	CHECK("set" == res.action());
	CHECK("44" == res.value().as_string());
	res = etcd.watch("/test", ++index, true);
	CHECK("set" == res.action());
	CHECK("45" == res.value().as_string());
	REQUIRE(0 == etcd.rmdir("/test", true).error_code());
	}

.