perf(symbolizer): Cache unsuccessful debug help resolutions

If the process handle can't be acquired or the symbol handler initialization fails, we cache the symbol info to avoid hammering the OpenProcess API indefinitely.

Author: rabbitstack

pkg/symbolize/symbolizer.go

@@ -535,12 +535,16 @@ func (s *Symbolizer) produceFrame(addr va.Address, e *event.Event) callstack.Fra
 	if !ok {
 		handle, err := windows.OpenProcess(windows.SYNCHRONIZE|windows.PROCESS_QUERY_INFORMATION, false, pid)
 		if err != nil {
+			// symbol handler initalization fails, cache
+			// the symbol for future lookups
+			s.cacheSymbolUnbacked(pid, addr, &frame)
 			return frame
 		}
 		// initialize symbol handler
 		opts := uint32(sys.SymUndname | sys.SymCaseInsensitive | sys.SymAutoPublics | sys.SymOmapFindNearest | sys.SymDeferredLoads)
 		err = s.r.Initialize(handle, opts)
 		if err != nil {
+			s.cacheSymbolUnbacked(pid, addr, &frame)
 			return frame
 		}
 		proc = &process{pid, handle, time.Now(), 1}
@@ -654,6 +658,13 @@ func (s *Symbolizer) cacheSymbol(pid uint32, addr va.Address, frame *callstack.F
 	}
 }
 
+func (s *Symbolizer) cacheSymbolUnbacked(pid uint32, addr va.Address, frame *callstack.Frame) {
+	if frame.Module == "?" {
+		frame.Module = "unbacked"
+	}
+	s.cacheSymbol(pid, addr, frame)
+}
+
 func (s *Symbolizer) cleanSym() {
 	s.mu.Lock()
 	defer s.mu.Unlock()