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Fix sporadic crash in JSON API async calls

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In Restbed one is not supposed to call session->yield outside the
  threads controlled by Restbed. RetroShare JSON API async call were
  calling session->yield from threads controlled by RetroShare all the
  times, this caused crashes in some cases, like when the JSON API
  socket timed out concurrently with the session->yield call .
  To solve this problem session->yield from async
  calls are now wrapped insto mService->schedule to ensure they are
  executed on the right thread (aka one of the threads controlled by
  Restbed).
While solving this issue I realized also that passing RsEvents as const
  references around was quite limiting in cases where the event need to
  be finally handled in another thread, in that case passing by const
  reference the RsEvent needed to be copied by value into the thread
  that process it, in this copy by value process the information of
  which was the original specific type is lost, and then only the data
  and methods from general RsEvents are available, unless the handler
  does tricky stuff with type coercion etc. To solve this limitation
  pass the events as std::shared_ptr<const RsEvent> seems the safer and
  more elegant solution.
This commit is contained in:
Gioacchino Mazzurco 2019-08-27 11:59:38 +02:00
parent 202cee687e
commit 9b8d0afacb
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GPG key ID: A1FBCA3872E87051
8 changed files with 94 additions and 79 deletions
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36
libretroshare/src/jsonapi/jsonapi.cpp
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@ -280,7 +280,7 @@ JsonApiServer::JsonApiServer(uint16_t port, const std::string& bindAddress,
}, true);
registerHandler("/rsEvents/registerEventsHandler",
[](const std::shared_ptr<rb::Session> session)
[this](const std::shared_ptr<rb::Session> session)
{
const std::multimap<std::string, std::string> headers
{
@ -291,7 +291,7 @@ JsonApiServer::JsonApiServer(uint16_t port, const std::string& bindAddress,
size_t reqSize = static_cast<size_t>(
session->get_request()->get_header("Content-Length", 0) );
session->fetch( reqSize, [](
session->fetch( reqSize, [this](
const std::shared_ptr<rb::Session> session,
const rb::Bytes& body )
{
@ -303,24 +303,28 @@ JsonApiServer::JsonApiServer(uint16_t port, const std::string& bindAddress,
const std::weak_ptr<rb::Session> weakSession(session);
RsEventsHandlerId_t hId = rsEvents->generateUniqueHandlerId();
std::function<void(const RsEvent&)> multiCallback =
[weakSession, hId](const RsEvent& event)
std::function<void(std::shared_ptr<const RsEvent>)> multiCallback =
[this, weakSession, hId](std::shared_ptr<const RsEvent> event)
{
auto session = weakSession.lock();
if(!session || session->is_closed())
mService.schedule( [weakSession, hId, event]()
{
if(rsEvents) rsEvents->unregisterEventsHandler(hId);
return;
}
auto session = weakSession.lock();
if(!session || session->is_closed())
{
if(rsEvents) rsEvents->unregisterEventsHandler(hId);
return;
}
RsGenericSerializer::SerializeContext ctx;
RsTypeSerializer::serial_process(
RsGenericSerializer::TO_JSON, ctx,
const_cast<RsEvent&>(event), "event" );
RsGenericSerializer::SerializeContext ctx;
RsTypeSerializer::serial_process(
RsGenericSerializer::TO_JSON, ctx,
*const_cast<RsEvent*>(event.get()), "event" );
std::stringstream message;
message << "data: " << compactJSON << ctx.mJson << "\n\n";
session->yield(message.str());
std::stringstream message;
message << "data: " << compactJSON << ctx.mJson << "\n\n";
session->yield(message.str());
} );
};
bool retval = rsEvents->registerEventsHandler(multiCallback, hId);