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#include <mbgl/storage/online_file_source.hpp>
#include <mbgl/storage/http_context_base.hpp>
#include <mbgl/storage/network_status.hpp>
#include <mbgl/storage/response.hpp>
#include <mbgl/platform/log.hpp>
#include <mbgl/util/thread.hpp>
#include <mbgl/util/mapbox.hpp>
#include <mbgl/util/exception.hpp>
#include <mbgl/util/chrono.hpp>
#include <mbgl/util/async_task.hpp>
#include <mbgl/util/noncopyable.hpp>
#include <mbgl/util/timer.hpp>
#include <algorithm>
#include <cassert>
#include <set>
#include <unordered_map>
namespace mbgl {
class OnlineFileRequestImpl : public util::noncopyable {
public:
using Callback = std::function<void (Response)>;
OnlineFileRequestImpl(const Resource&, Callback, OnlineFileSource::Impl&);
~OnlineFileRequestImpl();
void networkIsReachableAgain(OnlineFileSource::Impl&);
private:
void schedule(OnlineFileSource::Impl&, bool forceImmediate = false);
Resource resource;
HTTPRequestBase* request = nullptr;
util::Timer timer;
Callback callback;
// Counts the number of subsequent failed requests. We're using this value for exponential
// backoff when retrying requests.
uint32_t failedRequests = 0;
Response::Error::Reason failedRequestReason = Response::Error::Reason::Success;
};
class OnlineFileSource::Impl {
public:
// Dummy parameter is a workaround for a gcc 4.9 bug.
Impl(int) {
NetworkStatus::Subscribe(&reachability);
}
~Impl() {
NetworkStatus::Unsubscribe(&reachability);
}
void request(FileRequest* req, Resource resource, Callback callback) {
pending[req] = std::make_unique<OnlineFileRequestImpl>(resource, callback, *this);
}
void cancel(FileRequest* req) {
pending.erase(req);
}
private:
friend OnlineFileRequestImpl;
void networkIsReachableAgain() {
for (auto& req : pending) {
req.second->networkIsReachableAgain(*this);
}
}
std::unordered_map<FileRequest*, std::unique_ptr<OnlineFileRequestImpl>> pending;
const std::unique_ptr<HTTPContextBase> httpContext { HTTPContextBase::createContext() };
util::AsyncTask reachability { std::bind(&Impl::networkIsReachableAgain, this) };
};
OnlineFileSource::OnlineFileSource()
: thread(std::make_unique<util::Thread<Impl>>(
util::ThreadContext{ "OnlineFileSource", util::ThreadType::Unknown, util::ThreadPriority::Low }, 0)) {
}
OnlineFileSource::~OnlineFileSource() = default;
std::unique_ptr<FileRequest> OnlineFileSource::request(const Resource& resource, Callback callback) {
Resource res = resource;
switch (resource.kind) {
case Resource::Kind::Unknown:
break;
case Resource::Kind::Style:
res.url = mbgl::util::mapbox::normalizeStyleURL(resource.url, accessToken);
break;
case Resource::Kind::Source:
res.url = util::mapbox::normalizeSourceURL(resource.url, accessToken);
break;
case Resource::Kind::Glyphs:
res.url = util::mapbox::normalizeGlyphsURL(resource.url, accessToken);
break;
case Resource::Kind::SpriteImage:
case Resource::Kind::SpriteJSON:
res.url = util::mapbox::normalizeSpriteURL(resource.url, accessToken);
break;
case Resource::Kind::Tile:
res.url = util::mapbox::normalizeTileURL(resource.url, accessToken);
break;
}
class OnlineFileRequest : public FileRequest {
public:
OnlineFileRequest(Resource resource_, FileSource::Callback callback_, util::Thread<OnlineFileSource::Impl>& thread_)
: thread(thread_),
workRequest(thread.invokeWithCallback(&OnlineFileSource::Impl::request, callback_, this, resource_)) {
}
~OnlineFileRequest() {
thread.invoke(&OnlineFileSource::Impl::cancel, this);
}
util::Thread<OnlineFileSource::Impl>& thread;
std::unique_ptr<WorkRequest> workRequest;
};
return std::make_unique<OnlineFileRequest>(res, callback, *thread);
}
OnlineFileRequestImpl::OnlineFileRequestImpl(const Resource& resource_, Callback callback_, OnlineFileSource::Impl& impl)
: resource(resource_),
callback(callback_) {
// Force an immediate first request if we don't have an expiration time.
schedule(impl, !resource.priorExpires);
}
OnlineFileRequestImpl::~OnlineFileRequestImpl() {
if (request) {
request->cancel();
}
}
static Duration errorRetryTimeout(Response::Error::Reason failedRequestReason, uint32_t failedRequests) {
if (failedRequestReason == Response::Error::Reason::Server) {
// Retry after one second three times, then start exponential backoff.
return Seconds(failedRequests <= 3 ? 1 : 1 << std::min(failedRequests - 3, 31u));
} else if (failedRequestReason == Response::Error::Reason::Connection) {
// Immediate exponential backoff.
assert(failedRequests > 0);
return Seconds(1 << std::min(failedRequests - 1, 31u));
} else {
// No error, or not an error that triggers retries.
return Duration::max();
}
}
static Duration expirationTimeout(optional<SystemTimePoint> expires) {
if (expires) {
return std::max(SystemDuration::zero(), *expires - SystemClock::now());
} else {
return Duration::max();
}
}
void OnlineFileRequestImpl::schedule(OnlineFileSource::Impl& impl, bool forceImmediate) {
if (request) {
// There's already a request in progress; don't start another one.
return;
}
// If we're not being asked for a forced refresh, calculate a timeout that depends on how many
// consecutive errors we've encountered, and on the expiration time, if present.
Duration timeout = forceImmediate
? Duration::zero()
: std::min(errorRetryTimeout(failedRequestReason, failedRequests),
expirationTimeout(resource.priorExpires));
if (timeout == Duration::max()) {
return;
}
timer.start(timeout, Duration::zero(), [this, &impl] {
assert(!request);
request = impl.httpContext->createRequest(resource, [this, &impl](Response response) {
request = nullptr;
// If we didn't get various caching headers in the response, continue using the
// previous values. Otherwise, update the previous values to the new values.
if (!response.modified) {
response.modified = resource.priorModified;
} else {
resource.priorModified = response.modified;
}
if (!response.expires) {
response.expires = resource.priorExpires;
} else {
resource.priorExpires = response.expires;
}
if (!response.etag) {
response.etag = resource.priorEtag;
} else {
resource.priorEtag = response.etag;
}
if (response.error) {
failedRequests++;
failedRequestReason = response.error->reason;
} else {
failedRequests = 0;
failedRequestReason = Response::Error::Reason::Success;
}
callback(response);
schedule(impl);
});
});
}
void OnlineFileRequestImpl::networkIsReachableAgain(OnlineFileSource::Impl& impl) {
// We need all requests to fail at least once before we are going to start retrying
// them, and we only immediately restart request that failed due to connection issues.
if (failedRequestReason == Response::Error::Reason::Connection) {
schedule(impl, true);
}
}
} // namespace mbgl
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