Function StacksHandler

be/src/util/default-path-handlers.cc:188–260

Registered to handle "/stacks", and produces a plain text dump of all thread stacks.

// Registered to handle "/stacks", and produces a plain text dump of all thread stacks.
void StacksHandler(const Webserver::WebRequest& req, Document* document) {
  // Tell the webserver to render as plain text instead of HTML
  document->AddMember(rapidjson::StringRef(Webserver::ENABLE_RAW_HTML_KEY), true,
      document->GetAllocator());

  // Use MonoTime to measure elapsed time
  kudu::StackTraceSnapshot snapshot;
  // Disable automatic thread name collection - we'll use Impala's ThreadMgr instead
  // to get consistent names with the /thread-group page
  snapshot.set_capture_thread_names(false);

  kudu::MonoTime start = kudu::MonoTime::Now();
  kudu::Status status = snapshot.SnapshotAllStacks();

  stringstream output;
  if (!status.ok()) {
    output << "Error collecting stack traces: " << status.ToString() << "\n";
  } else {
    kudu::MonoDelta elapsed = kudu::MonoTime::Now() - start;
    output << "Collected stacks from " << snapshot.num_threads() << " threads in "
      << elapsed.ToSeconds() << "s\n";

    if (snapshot.num_failed() > 0) {
      output << "Failed to collect stacks for " << snapshot.num_failed() << " threads "
        << "(they may have exited while we were iterating over the threads)\n";
    }
    output << "\n";

    // Visit groups of threads with the same stack trace
    snapshot.VisitGroups(
      [&output](kudu::ArrayView<kudu::StackTraceSnapshot::ThreadInfo> group) {
      // Print the thread count if there are multiple threads with the same stack
      if (group.size() > 1) {
        output << group.size() << " threads with same stack:\n";
      }

      // Print thread IDs and names
      string thread_name;
      kudu::faststring buf;
      for (auto& info : group) {
        // Try to get the thread name from Impala's ThreadMgr first for consistency
        // with the /thread-group page. If not found (e.g., JVM threads or library
        // threads), fall back to reading from /proc.
        if (!GetThreadNameByTid(info.tid, &thread_name)) {
          // Thread not managed by Impala - read from /proc/self/task/[tid]/comm
          kudu::Status s = kudu::ReadFileToString(kudu::Env::Default(),
              strings::Substitute("/proc/self/task/$0/comm", info.tid), &buf);
          if (!s.ok()) {
            thread_name = "<unknown>";
          } else {
            thread_name = buf.ToString();
            StripTrailingNewline(&thread_name);
          }
        }
        output << "TID " << info.tid << " (" << thread_name << "):\n";
      }

      // Print the stack trace (or error if collection failed)