pkg/manager: omit fs images from big coverage reports

In the presence of numerous program seeds that mount fs images, our html
coverage reports end up being as big as 1GB, which makes it problematic
to render/manipulate them in the web browser.

Adjust coverage report generation: once the total size of program seeds
exceeds 100MB, switch to the compact seed serialization mode.

Author: a-nogikh

pkg/manager/http.go

@@ -517,7 +517,7 @@ func (serv *HTTPServer) httpCoverCover(w http.ResponseWriter, r *http.Request, f
 		}()
 	}
 
-	var progs []cover.Prog
+	var progs []coverProgRaw
 	if sig := r.FormValue("input"); sig != "" {
 		inp := corpus.Item(sig)
 		if inp == nil {
@@ -530,16 +530,16 @@ func (serv *HTTPServer) httpCoverCover(w http.ResponseWriter, r *http.Request, f
 				http.Error(w, "bad call_id", http.StatusBadRequest)
 				return
 			}
-			progs = append(progs, cover.Prog{
-				Sig:  sig,
-				Data: string(inp.Prog.Serialize()),
-				PCs:  CoverToPCs(serv.Cfg, inp.Updates[updateID].RawCover),
+			progs = append(progs, coverProgRaw{
+				sig:  sig,
+				prog: inp.Prog,
+				pcs:  CoverToPCs(serv.Cfg, inp.Updates[updateID].RawCover),
 			})
 		} else {
-			progs = append(progs, cover.Prog{
-				Sig:  sig,
-				Data: string(inp.Prog.Serialize()),
-				PCs:  CoverToPCs(serv.Cfg, inp.Cover),
+			progs = append(progs, coverProgRaw{
+				sig:  sig,
+				prog: inp.Prog,
+				pcs:  CoverToPCs(serv.Cfg, inp.Cover),
 			})
 		}
 	} else {
@@ -548,10 +548,10 @@ func (serv *HTTPServer) httpCoverCover(w http.ResponseWriter, r *http.Request, f
 			if call != "" && call != inp.StringCall() {
 				continue
 			}
-			progs = append(progs, cover.Prog{
-				Sig:  inp.Sig,
-				Data: string(inp.Prog.Serialize()),
-				PCs:  CoverToPCs(serv.Cfg, inp.Cover),
+			progs = append(progs, coverProgRaw{
+				sig:  inp.Sig,
+				prog: inp.Prog,
+				pcs:  CoverToPCs(serv.Cfg, inp.Cover),
 			})
 		}
 	}
@@ -566,7 +566,7 @@ func (serv *HTTPServer) httpCoverCover(w http.ResponseWriter, r *http.Request, f
 	}
 
 	params := cover.HandlerParams{
-		Progs:  progs,
+		Progs:  serv.serializeCoverProgs(progs),
 		Filter: coverFilter,
 		Debug:  r.FormValue("debug") != "",
 		Force:  r.FormValue("force") != "",
@@ -599,6 +599,44 @@ func (serv *HTTPServer) httpCoverCover(w http.ResponseWriter, r *http.Request, f
 	}
 }
 
+type coverProgRaw struct {
+	sig  string
+	prog *prog.Prog
+	pcs  []uint64
+}
+
+// Once the total size of corpus programs exceeds 100MB, skip fs images from it.
+const compactProgsCutOff = 100 * 1000 * 1000
+
+func (serv *HTTPServer) serializeCoverProgs(rawProgs []coverProgRaw) []cover.Prog {
+	skipImages := false
+outerLoop:
+	for {
+		var flags []prog.SerializeFlag
+		if skipImages {
+			flags = append(flags, prog.SkipImages)
+		}
+		totalSize := 0
+		var ret []cover.Prog
+		for _, item := range rawProgs {
+			prog := cover.Prog{
+				Sig:  item.sig,
+				Data: string(item.prog.Serialize(flags...)),
+				PCs:  item.pcs,
+			}
+			totalSize += len(prog.Data)
+			if totalSize > compactProgsCutOff && !skipImages {
+				log.Logf(0, "total size of corpus programs is too big,"+
+					"fullfs image won't be included in the cover reports")
+				skipImages = true
+				continue outerLoop
+			}
+			ret = append(ret, prog)
+		}
+		return ret
+	}
+}
+
 func (serv *HTTPServer) httpCoverFallback(w http.ResponseWriter, r *http.Request) {
 	corpus := serv.Corpus.Load()
 	if corpus == nil {