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[core] allow creating optional requests
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Introduces "optional" requests. These should be fulfilled by the FileSource only there's a low-cost/easy way to obtain the data (e.g. from a local cache). If the data for an optional request cannot be found, it *must* return a Response object with a NotFound error.

Traditional "required" requests still work the same way, with one change: If you set any prior* field in the Resource (i.e. priorModified, priorEtag, or priorExpires), the DefaultFileSource assumes that you already have the cache value and will not consult the cache before performing the request. If a prior cache lookup didn't turn up any data, and you therefore don't have an Etag or Modified value, you can still skip the cache by setting priorExpires. This will of course always result in a non-conditional HTTP request.
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@kkaefer
kkaefer committed May 13, 2016
1 parent cd65a43 commit 25f5c4e
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Showing 2 changed files with 277 additions and 11 deletions.
36 changes: 25 additions & 11 deletions platform/default/default_file_source.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,21 +82,35 @@ class DefaultFileSource::Impl {
}

void request(AsyncRequest* req, Resource resource, Callback callback) {
auto offlineResponse = offlineDatabase.get(resource);

Resource revalidation = resource;

if (offlineResponse) {
revalidation.priorModified = offlineResponse->modified;
revalidation.priorExpires = offlineResponse->expires;
revalidation.priorEtag = offlineResponse->etag;
callback(*offlineResponse);
const bool hasPrior = resource.priorEtag || resource.priorModified || resource.priorExpires;
if (!hasPrior || resource.necessity == Resource::Optional) {
auto offlineResponse = offlineDatabase.get(resource);

if (resource.necessity == Resource::Optional && !offlineResponse) {
// Ensure there's always a response that we can send, so the caller knows that
// there's no optional data available in the cache.
offlineResponse.emplace();
offlineResponse->noContent = true;
offlineResponse->error = std::make_unique<Response::Error>(
Response::Error::Reason::NotFound, "Not found in offline database");
}

if (offlineResponse) {
revalidation.priorModified = offlineResponse->modified;
revalidation.priorExpires = offlineResponse->expires;
revalidation.priorEtag = offlineResponse->etag;
callback(*offlineResponse);
}
}

tasks[req] = onlineFileSource.request(revalidation, [=] (Response onlineResponse) {
this->offlineDatabase.put(revalidation, onlineResponse);
callback(onlineResponse);
});
if (resource.necessity == Resource::Required) {
tasks[req] = onlineFileSource.request(revalidation, [=] (Response onlineResponse) {
this->offlineDatabase.put(revalidation, onlineResponse);
callback(onlineResponse);
});
}
}

void cancel(AsyncRequest* req) {
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252 changes: 252 additions & 0 deletions test/storage/default_file_source.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -208,3 +208,255 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(HTTPIssue1369)) {

loop.run();
}

TEST(DefaultFileSource, OptionalNonExpired) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };

using namespace std::chrono_literals;

Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(optionalResource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(optionalResource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
ASSERT_TRUE(res.data.get());
EXPECT_EQ("Cached value", *res.data);
ASSERT_TRUE(bool(res.expires));
EXPECT_EQ(*response.expires, *res.expires);
EXPECT_FALSE(bool(res.modified));
EXPECT_FALSE(bool(res.etag));
loop.stop();
});

loop.run();
}

TEST(DefaultFileSource, OptionalExpired) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };

using namespace std::chrono_literals;

Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() - 1h;
fs.put(optionalResource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(optionalResource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
ASSERT_TRUE(res.data.get());
EXPECT_EQ("Cached value", *res.data);
ASSERT_TRUE(bool(res.expires));
EXPECT_EQ(*response.expires, *res.expires);
EXPECT_FALSE(bool(res.modified));
EXPECT_FALSE(bool(res.etag));
loop.stop();
});

loop.run();
}

TEST(DefaultFileSource, OptionalNotFound) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };

using namespace std::chrono_literals;

std::unique_ptr<AsyncRequest> req;
req = fs.request(optionalResource, [&](Response res) {
req.reset();
ASSERT_TRUE(res.error.get());
EXPECT_EQ(Response::Error::Reason::NotFound, res.error->reason);
EXPECT_EQ("Not found in offline database", res.error->message);
EXPECT_FALSE(res.data);
EXPECT_FALSE(bool(res.expires));
EXPECT_FALSE(bool(res.modified));
EXPECT_FALSE(bool(res.etag));
loop.stop();
});

loop.run();
}

// Test that we can make a request with etag data that doesn't first try to load
// from cache like a regular request
TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagNotModified)) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
resource.priorEtag.emplace("snowfall");

using namespace std::chrono_literals;

// Put a fake value into the cache to make sure we're not retrieving anything from the cache.
Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(resource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(resource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
EXPECT_TRUE(res.notModified);
EXPECT_FALSE(res.data.get());
ASSERT_TRUE(bool(res.expires));
EXPECT_LT(util::now(), *res.expires);
EXPECT_FALSE(bool(res.modified));
ASSERT_TRUE(bool(res.etag));
EXPECT_EQ("snowfall", *res.etag);
loop.stop();
});

loop.run();
}

// Test that we can make a request with etag data that doesn't first try to load
// from cache like a regular request
TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagModified)) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
resource.priorEtag.emplace("sunshine");

using namespace std::chrono_literals;

// Put a fake value into the cache to make sure we're not retrieving anything from the cache.
Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(resource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(resource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
EXPECT_FALSE(res.notModified);
ASSERT_TRUE(res.data.get());
EXPECT_EQ("Response", *res.data);
EXPECT_FALSE(bool(res.expires));
EXPECT_FALSE(bool(res.modified));
ASSERT_TRUE(bool(res.etag));
EXPECT_EQ("snowfall", *res.etag);
loop.stop();
});

loop.run();
}

// Test that we can make a request that doesn't first try to load
// from cache like a regular request.
TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheFull)) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
// Setting any prior field results in skipping the cache.
resource.priorExpires.emplace(Seconds(0));

using namespace std::chrono_literals;

// Put a fake value into the cache to make sure we're not retrieving anything from the cache.
Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(resource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(resource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
EXPECT_FALSE(res.notModified);
ASSERT_TRUE(res.data.get());
EXPECT_EQ("Response", *res.data);
EXPECT_FALSE(bool(res.expires));
EXPECT_FALSE(bool(res.modified));
ASSERT_TRUE(bool(res.etag));
EXPECT_EQ("snowfall", *res.etag);
loop.stop();
});

loop.run();
}

// Test that we can make a request with a Modified field that doesn't first try to load
// from cache like a regular request
TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshModifiedNotModified)) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-modified" };
resource.priorModified.emplace(Seconds(1420070400)); // January 1, 2015

using namespace std::chrono_literals;

// Put a fake value into the cache to make sure we're not retrieving anything from the cache.
Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(resource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(resource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
EXPECT_TRUE(res.notModified);
EXPECT_FALSE(res.data.get());
ASSERT_TRUE(bool(res.expires));
EXPECT_LT(util::now(), *res.expires);
ASSERT_TRUE(bool(res.modified));
EXPECT_EQ(Timestamp{ Seconds(1420070400) }, *res.modified);
EXPECT_FALSE(bool(res.etag));
loop.stop();
});

loop.run();
}

// Test that we can make a request with a Modified field that doesn't first try to load
// from cache like a regular request
TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshModifiedModified)) {
util::RunLoop loop;
DefaultFileSource fs(":memory:", ".");

Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-modified" };
resource.priorModified.emplace(Seconds(1417392000)); // December 1, 2014

using namespace std::chrono_literals;

// Put a fake value into the cache to make sure we're not retrieving anything from the cache.
Response response;
response.data = std::make_shared<std::string>("Cached value");
response.expires = util::now() + 1h;
fs.put(resource, response);

std::unique_ptr<AsyncRequest> req;
req = fs.request(resource, [&](Response res) {
req.reset();
EXPECT_EQ(nullptr, res.error);
EXPECT_FALSE(res.notModified);
ASSERT_TRUE(res.data.get());
EXPECT_EQ("Response", *res.data);
EXPECT_FALSE(bool(res.expires));
EXPECT_EQ(Timestamp{ Seconds(1420070400) }, *res.modified);
EXPECT_FALSE(res.etag);
loop.stop();
});

loop.run();
}

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