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#include "mds/QuiesceAgent.h"
#include "common/debug.h"
#include "include/ceph_assert.h"
#include <future>
#define dout_context g_ceph_context
#define dout_subsys ceph_subsys_mds_quiesce
#undef dout_prefix
#define dout_prefix *_dout << "quiesce.agt <" << __func__ << "> "
#undef dout
#define dout(lvl) \
do { \
auto subsys = ceph_subsys_mds; \
if ((dout_context)->_conf->subsys.should_gather(dout_subsys, lvl)) { \
subsys = dout_subsys; \
} \
dout_impl(dout_context, ceph::dout::need_dynamic(subsys), lvl) dout_prefix
#undef dendl
#define dendl \
dendl_impl; \
} \
while (0)
template <class CharT, class Traits>
std::basic_ostream<CharT, Traits>&
operator<<(std::basic_ostream<CharT, Traits>& os, const QuiesceAgent::TrackedRootsVersion& tr)
{
return os << "tracked_roots[armed: " << tr.armed << ", v: " << tr.db_version << " r: " << tr.roots.size() << "]";
}
bool QuiesceAgent::db_update(QuiesceMap& map)
{
// copy of the current roots
TrackedRoots current_roots = tracked_roots();
TrackedRoots new_roots;
dout(20) << "got a db update version " << map.db_version << " with " << map.roots.size() << " roots" << dendl;
for (auto their_it = map.roots.begin(); their_it != map.roots.end();) {
auto &[root, info] = *their_it;
TrackedRootRef tracked_root_ref;
ceph_assert(info.state > QS__INVALID);
if (info.state >= QS__FAILURE) {
// we don't care about roots in failed states
dout(5) << "ignoring a root in a failed state: '" << root << "', " << info.state << dendl;
their_it = map.roots.erase(their_it);
continue;
}
if (const auto& my_it = current_roots.find(root); my_it != current_roots.end()) {
// keep the existing root
new_roots.insert(*my_it);
tracked_root_ref = my_it->second;
} else {
// introduce a new root
tracked_root_ref = std::make_shared<TrackedRoot>(info.state, info.ttl);
new_roots[root] = tracked_root_ref;
}
std::lock_guard l(*tracked_root_ref);
tracked_root_ref->update_committed(info);
auto actual_state = tracked_root_ref->get_actual_state();
if (actual_state != info.state) {
// we have an update for the state
info.state = actual_state;
info.ttl = tracked_root_ref->get_ttl();
} else {
// our tracked root has the same state as the db
// we can just drop it from the response
their_it = map.roots.erase(their_it);
continue;
}
++their_it;
}
// ack with the known state stored in `map`
set_pending_roots(map.db_version, std::move(new_roots));
// to avoid ack races with the agent_thread,
// never send a synchronous ack
return false;
}
void* QuiesceAgent::agent_thread_main() {
std::unique_lock agent_lock(agent_mutex);
while (!stop_agent_thread) {
TrackedRootsVersion old;
if (pending.armed) {
std::swap(old, current);
current.roots.swap(pending.roots);
current.db_version = pending.db_version;
}
dout(20)
<< "old = " << old.db_version
<< ", current = " << current.db_version
<< dendl;
// it's safe to clear the pending roots under agent_lock because it shouldn't
// ever hold a last shared ptr to quiesced tracked roots, causing their destructors to run cancel.
pending.clear();
current.armed = true;
upkeep_needed = false;
// for somebody waiting for the internal state to progress
agent_cond.notify_all();
agent_lock.unlock();
_agent_thread_will_work();
QuiesceMap ack(current.db_version);
// upkeep what we believe is the current state.
for (auto& [root, info] : current.roots) {
info->lock();
bool should_quiesce = info->should_quiesce();
bool issue_quiesce = should_quiesce && !info->quiesce_request && !info->quiesce_result;
std::optional<QuiesceInterface::RequestHandle> cancel_handle;
if (!should_quiesce && !info->cancel_result) {
cancel_handle = info->quiesce_request;
}
auto actual_state = info->get_actual_state();
if (info->committed_state != actual_state) {
ack.roots[root] = { actual_state, info->get_ttl() };
}
info->unlock();
if (issue_quiesce) {
std::weak_ptr<TrackedRoot> weak_info = info;
auto request_handle = quiesce_control.submit_request(root, new LambdaContext([weak_info, submitted_root = root, this](int rc) {
if (auto info = weak_info.lock()) {
dout(20) << "completing request (rc=" << rc << ") for '" << submitted_root << "'" << dendl;
info->lock();
info->quiesce_result = rc;
info->unlock();
// TODO: capturing QuiesceAgent& `this` is potentially dangerous
// the assumption is that since the tracked root pointer is weak
// it will have been deleted by the QuiesceAgent shutdown sequence
set_upkeep_needed();
}
dout(20) << "done with submit callback for '" << submitted_root << "'" << dendl;
}));
dout(10) << "got request handle <" << request_handle << "> for '" << root << "'" << dendl;
info->lock();
info->quiesce_request = request_handle;
info->cancel = quiesce_control.cancel_request;
info->unlock();
} else if (cancel_handle) {
dout(10) << "Calling `cancel` on `" << root << "` with handle <" << *cancel_handle << ">" << dendl;
int rc = quiesce_control.cancel_request(*cancel_handle);
if (rc != 0) {
dout(1) << "ERROR (" << rc << ") when trying to cancel quiesce request id: " << *cancel_handle << dendl;
}
info->lock();
info->cancel_result = rc;
info->unlock();
}
}
_agent_thread_did_work();
// send the ack and clear the old roots outside of the lock
bool new_version = current.db_version != old.db_version;
if (new_version || !ack.roots.empty()) {
dout(20) << "asynchronous ack for " << (new_version ? "a new" : "the current") << " version: " << ack << dendl;
int rc = quiesce_control.agent_ack(std::move(ack));
if (rc != 0) {
dout(3) << "got error: " << rc << " trying to send " << ack << dendl;
}
}
old.clear();
ack.clear();
agent_lock.lock();
current.armed = false;
// a new pending version could be set while we weren't locked
// if that's the case just go for another pass
// otherwise, wait for updates
while (!pending.armed && !current.armed && !upkeep_needed && !stop_agent_thread) {
// for somebody waiting for the thread to idle
agent_cond.notify_all();
agent_cond.wait(agent_lock);
}
}
agent_cond.notify_all();
return nullptr;
}
void QuiesceAgent::set_pending_roots(QuiesceDbVersion version, TrackedRoots&& new_roots)
{
std::unique_lock l(agent_mutex);
bool rollback = current.db_version > version;
if (rollback) {
dout(5) << "version rollback to " << version
<< ". current = " << current.db_version
<< ", pending = " << pending.db_version << dendl;
}
// set the pending version unconditionally
pending.db_version = version;
pending.roots = std::move(new_roots);
pending.armed = true;
agent_cond.notify_all();
}
void QuiesceAgent::set_upkeep_needed()
{
std::unique_lock l(agent_mutex);
dout(20)
<< "current = " << current.db_version
<< ", pending = " << pending.db_version << dendl;
upkeep_needed = true;
agent_cond.notify_all();
}
QuiesceAgent::TrackedRoot::~TrackedRoot()
{
std::optional<QuiesceInterface::RequestHandle> request_handle;
lock();
request_handle.swap(quiesce_request);
bool should_cancel = !cancel_result.has_value();
unlock();
if (should_cancel && request_handle && cancel) {
dout(10) << "Calling `cancel` on an abandoned root with handle <" << request_handle << ">" << dendl;
cancel(*request_handle);
}
dout(20) << "done with request handle <" << request_handle << ">" << dendl;
}
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