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resolves #19: laminard crashes under load

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reading into a static buffer is a race condition that is only
manifested under load. There's no guarantee the clause in then()
will run before another task overwrites the buffer. Allocating
a local string is the only correct solution
This commit is contained in:
Oliver Giles 2017-12-04 20:29:19 +02:00
parent 7dce535264
commit d91816097a
3 changed files with 11 additions and 10 deletions
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4
src/laminar.cpp
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@ -371,7 +371,7 @@ void Laminar::run() {
sigaddset(&mask, SIGCHLD);
sigprocmask(SIG_BLOCK, &mask, NULL);
int sigchld = signalfd(-1, &mask, 0);
srv->addDescriptor(sigchld, [this](char* buf, size_t sz){
srv->addDescriptor(sigchld, [this](const char* buf, size_t sz){
struct signalfd_siginfo* siginfo = (struct signalfd_siginfo*) buf;
// TODO: re-enable assertion when the cause for its triggering
// is discovered and solved
@ -505,7 +505,7 @@ std::shared_ptr<Run> Laminar::queueJob(std::string name, ParamMap params) {
bool Laminar::stepRun(std::shared_ptr<Run> run) {
bool complete = run->step();
if(!complete) {
srv->addDescriptor(run->fd, [=](char* b,size_t n){
srv->addDescriptor(run->fd, [=](const char* b,size_t n){
std::string s(b,n);
run->log += s;
for(LaminarClient* c : clients) {

13
src/server.cpp
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@ -420,7 +420,7 @@ void Server::stop() {
eventfd_write(efd_quit, 1);
}
void Server::addDescriptor(int fd, std::function<void(char*,size_t)> cb) {
void Server::addDescriptor(int fd, std::function<void(const char*,size_t)> cb) {
auto event = this->ioContext.lowLevelProvider->wrapInputFd(fd, kj::LowLevelAsyncIoProvider::TAKE_OWNERSHIP);
tasks.add(handleFdRead(event, cb).attach(std::move(event)));
}
@ -455,13 +455,14 @@ void Server::acceptRpcClient(kj::Own<kj::ConnectionReceiver>&& listener) {
// returns a promise which will read a chunk of data from the file descriptor
// wrapped by stream and invoke the provided callback with the read data.
// Repeats until ::read returns <= 0
kj::Promise<void> Server::handleFdRead(kj::AsyncInputStream* stream, std::function<void(char*,size_t)> cb) {
static char* buffer = new char[PROC_IO_BUFSIZE];
return stream->tryRead(buffer, 1, PROC_IO_BUFSIZE).then([this,stream,cb](size_t sz) {
kj::Promise<void> Server::handleFdRead(kj::AsyncInputStream* stream, std::function<void(const char*,size_t)> cb) {
std::string buffer;
buffer.reserve(PROC_IO_BUFSIZE);
return stream->tryRead((void*)buffer.data(), 1, PROC_IO_BUFSIZE).then(kj::mvCapture(kj::mv(buffer), [this,stream,cb](std::string&& buffer, size_t sz) {
if(sz > 0) {
cb(buffer, sz);
cb(buffer.data(), sz);
return handleFdRead(stream, cb);
}
return kj::Promise<void>(kj::READY_NOW);
});
})).attach(kj::mv(buffer));
}

4
src/server.h
View File

@ -41,12 +41,12 @@ public:
// add a file descriptor to be monitored for output. The callback will be
// invoked with the read data
void addDescriptor(int fd, std::function<void(char*,size_t)> cb);
void addDescriptor(int fd, std::function<void(const char*,size_t)> cb);
private:
void acceptHttpClient(kj::Own<kj::ConnectionReceiver>&& listener);
void acceptRpcClient(kj::Own<kj::ConnectionReceiver>&& listener);
kj::Promise<void> handleFdRead(kj::AsyncInputStream* stream, std::function<void(char*,size_t)> cb);
kj::Promise<void> handleFdRead(kj::AsyncInputStream* stream, std::function<void(const char*,size_t)> cb);
void taskFailed(kj::Exception&& exception) override {
kj::throwFatalException(kj::mv(exception));