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rgw: detect and work around a curl_multi_wait bug

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Fixes: http://tracker.ceph.com/issues/15915
Fixes: http://tracker.ceph.com/issues/16695

Signed-off-by: Casey Bodley <cbodley@redhat.com>
This commit is contained in:
Casey Bodley 2016-09-09 16:46:54 -04:00
parent 1101fcc750
commit 0359be62b7
1 changed files with 72 additions and 2 deletions
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74
src/rgw/rgw_http_client.cc
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@ -421,7 +421,8 @@ int RGWHTTPTransceiver::send_data(void* ptr, size_t len)
static int clear_signal(int fd)
{
// since we're in non-blocking mode, we can try to read a lot more than
// one signal from signal_thread() to avoid later wakeups
// one signal from signal_thread() to avoid later wakeups. non-blocking reads
// are also required to support the curl_multi_wait bug workaround
std::array<char, 256> buf;
int ret = ::read(fd, (void *)buf.data(), buf.size());
if (ret < 0) {
@ -433,6 +434,67 @@ static int clear_signal(int fd)
#if HAVE_CURL_MULTI_WAIT
static std::once_flag detect_flag;
static bool curl_multi_wait_bug_present = false;
static int detect_curl_multi_wait_bug(CephContext *cct, CURLM *handle,
int write_fd, int read_fd)
{
int ret = 0;
// write to write_fd so that read_fd becomes readable
uint32_t buf = 0;
ret = ::write(write_fd, &buf, sizeof(buf));
if (ret < 0) {
ret = -errno;
ldout(cct, 0) << "ERROR: " << __func__ << "(): write() returned " << ret << dendl;
return ret;
}
// pass read_fd in extra_fds for curl_multi_wait()
int num_fds;
struct curl_waitfd wait_fd;
wait_fd.fd = read_fd;
wait_fd.events = CURL_WAIT_POLLIN;
wait_fd.revents = 0;
ret = curl_multi_wait(handle, &wait_fd, 1, 0, &num_fds);
if (ret != CURLM_OK) {
ldout(cct, 0) << "ERROR: curl_multi_wait() returned " << ret << dendl;
return -EIO;
}
// curl_multi_wait should flag revents when extra_fd is readable. if it
// doesn't, the bug is present and we can't rely on revents
if (wait_fd.revents == 0) {
curl_multi_wait_bug_present = true;
ldout(cct, 0) << "WARNING: detected a version of libcurl which contains a "
"bug in curl_multi_wait(). enabling a workaround that may degrade "
"performance slightly. please upgrade to a more recent version of "
"libcurl." << dendl;
}
return clear_signal(read_fd);
}
static bool is_signaled(const curl_waitfd& wait_fd)
{
if (wait_fd.fd < 0) {
// no fd to signal
return false;
}
if (curl_multi_wait_bug_present) {
// we can't rely on revents, so we always return true if a wait_fd is given.
// this means we'll be trying a non-blocking read on this fd every time that
// curl_multi_wait() wakes up
return true;
}
return wait_fd.revents > 0;
}
static int do_curl_wait(CephContext *cct, CURLM *handle, int signal_fd)
{
int num_fds;
@ -448,7 +510,7 @@ static int do_curl_wait(CephContext *cct, CURLM *handle, int signal_fd)
return -EIO;
}
if (wait_fd.revents > 0) {
if (is_signaled(wait_fd)) {
ret = clear_signal(signal_fd);
if (ret < 0) {
ldout(cct, 0) << "ERROR: " << __func__ << "(): read() returned " << ret << dendl;
@ -810,6 +872,14 @@ int RGWHTTPManager::set_threaded()
return r;
}
#ifdef HAVE_CURL_MULTI_WAIT
// on first initialization, use this pipe to detect whether we're using a
// buggy version of libcurl
std::call_once(detect_flag, detect_curl_multi_wait_bug, cct,
static_cast<CURLM*>(multi_handle),
thread_pipe[1], thread_pipe[0]);
#endif
is_threaded = true;
reqs_thread = new ReqsThread(this);
reqs_thread->create("http_manager");