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IXDNSLookup. Uses weak pointer + smart_ptr + shared_from_this instead of static sets + mutex to handle object going away before dns lookup has resolved

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This commit is contained in:
Benjamin Sergeant
2019-06-19 00:43:59 -07:00
parent dbd62b8622
commit b26e9d0338
6 changed files with 28 additions and 52 deletions
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47
ixwebsocket/IXDNSLookup.cpp
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@ -14,27 +14,15 @@ namespace ix
{
const int64_t DNSLookup::kDefaultWait = 10; // ms
std::atomic<uint64_t> DNSLookup::_nextId(0);
std::set<uint64_t> DNSLookup::_activeJobs;
std::mutex DNSLookup::_activeJobsMutex;
DNSLookup::DNSLookup(const std::string& hostname, int port, int64_t wait) :
_port(port),
_wait(wait),
_res(nullptr),
_done(false),
_id(_nextId++)
_done(false)
{
setHostname(hostname);
}
DNSLookup::~DNSLookup()
{
// Remove this job from the active jobs list
std::lock_guard<std::mutex> lock(_activeJobsMutex);
_activeJobs.erase(_id);
}
struct addrinfo* DNSLookup::getAddrInfo(const std::string& hostname,
int port,
std::string& errMsg)
@ -94,17 +82,14 @@ namespace ix
// if you need a second lookup.
}
// Record job in the active Job set
{
std::lock_guard<std::mutex> lock(_activeJobsMutex);
_activeJobs.insert(_id);
}
//
// Good resource on thread forced termination
// https://www.bo-yang.net/2017/11/19/cpp-kill-detached-thread
//
_thread = std::thread(&DNSLookup::run, this, _id, getHostname(), _port);
auto ptr = shared_from_this();
std::weak_ptr<DNSLookup> self(ptr);
_thread = std::thread(&DNSLookup::run, this, self, getHostname(), _port);
_thread.detach();
std::unique_lock<std::mutex> lock(_conditionVariableMutex);
@ -138,7 +123,7 @@ namespace ix
return getRes();
}
void DNSLookup::run(uint64_t id, const std::string& hostname, int port) // thread runner
void DNSLookup::run(std::weak_ptr<DNSLookup> self, const std::string& hostname, int port) // thread runner
{
// We don't want to read or write into members variables of an object that could be
// gone, so we use temporary variables (res) or we pass in by copy everything that
@ -146,21 +131,15 @@ namespace ix
std::string errMsg;
struct addrinfo* res = getAddrInfo(hostname, port, errMsg);
// if this isn't an active job, and the control thread is gone
// there is nothing to do, and we don't want to touch the defunct
// object data structure such as _errMsg or _condition
std::lock_guard<std::mutex> lock(_activeJobsMutex);
if (_activeJobs.count(id) == 0)
if (self.lock())
{
return;
// Copy result into the member variables
setRes(res);
setErrMsg(errMsg);
_condition.notify_one();
_done = true;
}
// Copy result into the member variables
setRes(res);
setErrMsg(errMsg);
_condition.notify_one();
_done = true;
}
void DNSLookup::setHostname(const std::string& hostname)