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Fix using locks in ProcessList #51348

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Merged
vitlibar merged 3 commits into from
Jun 27, 2023
Merged

Fix using locks in ProcessList #51348

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fad07bf
Fix using locks in ProcessList.
vitlibar Jun 23, 2023
c01d5ed
Fix after review.
vitlibar Jun 26, 2023
1ae51ff
Merge branch 'master' into fix-using-locks-in-process-list
vitlibar Jun 27, 2023
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33 changes: 23 additions & 10 deletions src/Interpreters/ProcessList.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -246,6 +246,7 @@ ProcessList::insert(const String & query_, const IAST * ast, ContextMutablePtr q
priorities.insert(static_cast<int>(settings.priority)),
std::move(thread_group),
query_kind,
settings,
watch_start_nanoseconds));

increaseQueryKindAmount(query_kind);
Expand Down Expand Up @@ -342,6 +343,7 @@ QueryStatus::QueryStatus(
QueryPriorities::Handle && priority_handle_,
ThreadGroupPtr && thread_group_,
IAST::QueryKind query_kind_,
const Settings & query_settings_,
UInt64 watch_start_nanoseconds)
: WithContext(context_)
, query(query_)
Expand All @@ -353,9 +355,11 @@ QueryStatus::QueryStatus(
, query_kind(query_kind_)
, num_queries_increment(CurrentMetrics::Query)
{
auto settings = getContext()->getSettings();
limits.max_execution_time = settings.max_execution_time;
overflow_mode = settings.timeout_overflow_mode;
/// We have to pass `query_settings_` to this constructor because we can't use `context_->getSettings().max_execution_time` here:
/// a QueryStatus is created with `ProcessList::mutex` locked (see ProcessList::insert) and calling `context_->getSettings()`
/// would lock the context's lock too, whereas holding two those locks simultaneously is not good.
limits.max_execution_time = query_settings_.max_execution_time;
overflow_mode = query_settings_.timeout_overflow_mode;
}

QueryStatus::~QueryStatus()
Expand Down Expand Up @@ -589,10 +593,13 @@ QueryStatusInfo QueryStatus::getInfo(bool get_thread_list, bool get_profile_even
res.profile_counters = std::make_shared<ProfileEvents::Counters::Snapshot>(thread_group->performance_counters.getPartiallyAtomicSnapshot());
}

if (get_settings && getContext())
if (get_settings)
{
res.query_settings = std::make_shared<Settings>(getContext()->getSettings());
res.current_database = getContext()->getCurrentDatabase();
if (auto ctx = context.lock())
{
res.query_settings = std::make_shared<Settings>(ctx->getSettings());
res.current_database = ctx->getCurrentDatabase();
}
}

return res;
Expand All @@ -601,12 +608,18 @@ QueryStatusInfo QueryStatus::getInfo(bool get_thread_list, bool get_profile_even

ProcessList::Info ProcessList::getInfo(bool get_thread_list, bool get_profile_events, bool get_settings) const
{
Info per_query_infos;
/// We have to copy `processes` first because `process->getInfo()` below can access the context to get the query settings,
/// and it's better not to keep the process list's lock while doing that.
std::vector<QueryStatusPtr> processes_copy;

auto lock = safeLock();
{
auto lock = safeLock();
processes_copy.assign(processes.begin(), processes.end());
}

per_query_infos.reserve(processes.size());
for (const auto & process : processes)
Info per_query_infos;
per_query_infos.reserve(processes_copy.size());
for (const auto & process : processes_copy)
per_query_infos.emplace_back(process->getInfo(get_thread_list, get_profile_events, get_settings));

return per_query_infos;
Expand Down
1 change: 1 addition & 0 deletions src/Interpreters/ProcessList.h
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Original file line number Diff line number Diff line change
Expand Up @@ -164,6 +164,7 @@ class QueryStatus : public WithContext
QueryPriorities::Handle && priority_handle_,
ThreadGroupPtr && thread_group_,
IAST::QueryKind query_kind_,
const Settings & query_settings_,
UInt64 watch_start_nanoseconds);

~QueryStatus();
Expand Down