abstract dumpFsm

Signed-off-by: Wangchong Zhou <fffonion@gmail.com>

main.go

@@ -14,8 +14,10 @@
 package main
 
 import (
+	"bufio"
 	"net"
 	"net/http"
+	"os"
 	"strconv"
 
 	"github.com/howeyc/fsnotify"
@@ -118,6 +120,20 @@ func watchConfig(fileName string, mapper *mapper.MetricMapper) {
 	}
 }
 
+func dumpFSM(mapper *mapper.MetricMapper, dumpFilename string) error {
+	f, err := os.Create(dumpFilename)
+	if err != nil {
+		return err
+	}
+	log.Infoln("Start dumping FSM to", dumpFilename)
+	w := bufio.NewWriter(f)
+	mapper.FSM.DumpFSM(w)
+	w.Flush()
+	f.Close()
+	log.Infoln("Finish dumping FSM")
+	return nil
+}
+
 func main() {
 	var (
 		listenAddress   = kingpin.Flag("web.listen-address", "The address on which to expose the web interface and generated Prometheus metrics.").Default(":9102").String()
@@ -179,17 +195,17 @@ func main() {
 	}
 
 	mapper := &mapper.MetricMapper{MappingsCount: mappingsCount}
-	if *dumpFSMPath != "" {
-		err := mapper.FSM.SetDumpFSMPath(*dumpFSMPath)
-		if err != nil {
-			log.Fatal("Error setting dump FSM path:", err)
-		}
-	}
 	if *mappingConfig != "" {
 		err := mapper.InitFromFile(*mappingConfig)
 		if err != nil {
 			log.Fatal("Error loading config:", err)
 		}
+		if *dumpFSMPath != "" {
+			err := dumpFSM(mapper, *dumpFSMPath)
+			if err != nil {
+				log.Fatal("Error dumpping FSM:", err)
+			}
+		}
 		go watchConfig(*mappingConfig, mapper)
 	}
 	exporter := NewExporter(mapper)

pkg/mapper/fsm/fsm.go

@@ -1,9 +1,8 @@
 package fsm
 
 import (
-	"bufio"
 	"fmt"
-	"os"
+	"io"
 	"regexp"
 	"strings"
 
@@ -38,17 +37,11 @@ type fsmBacktrackStackCursor struct {
 type FSM struct {
 	root              *mappingState
 	needsBacktracking bool
-	dumpFSMPath       string
 	metricTypes       []string
 	disableOrdering   bool
 	statesCount       int
 }
 
-func (fsm *FSM) SetDumpFSMPath(path string) error {
-	fsm.dumpFSMPath = path
-	return nil
-}
-
 func NewFSM(metricTypes []string, maxPossibleTransitions int, disableOrdering bool) *FSM {
 	fsm := FSM{}
 	root := &mappingState{}
@@ -128,40 +121,32 @@ func (f *FSM) AddState(match string, name string, labels prometheus.Labels, matc
 
 }
 
-func (f *FSM) DumpFSM() {
+func (f *FSM) DumpFSM(w io.Writer) {
-	if f.dumpFSMPath == "" {
-		return
-	}
-	log.Infoln("Start dumping FSM to", f.dumpFSMPath)
 	idx := 0
 	states := make(map[int]*mappingState)
 	states[idx] = f.root
 
-	fd, _ := os.Create(f.dumpFSMPath)
+	w.Write([]byte("digraph g {\n"))
-	w := bufio.NewWriter(fd)
+	w.Write([]byte("rankdir=LR\n"))                                                    // make it vertical
-	w.WriteString("digraph g {\n")
+	w.Write([]byte("node [ label=\"\",style=filled,fillcolor=white,shape=circle ]\n")) // remove label of node
-	w.WriteString("rankdir=LR\n")                                                    // make it vertical
-	w.WriteString("node [ label=\"\",style=filled,fillcolor=white,shape=circle ]\n") // remove label of node
 
 	for idx < len(states) {
 		for field, transition := range states[idx].transitions {
 			states[len(states)] = transition
-			w.WriteString(fmt.Sprintf("%d -> %d  [label = \"%s\"];\n", idx, len(states)-1, field))
+			w.Write([]byte(fmt.Sprintf("%d -> %d  [label = \"%s\"];\n", idx, len(states)-1, field)))
 			if idx == 0 {
 				// color for metric types
-				w.WriteString(fmt.Sprintf("%d [color=\"#D6B656\",fillcolor=\"#FFF2CC\"];\n", len(states)-1))
+				w.Write([]byte(fmt.Sprintf("%d [color=\"#D6B656\",fillcolor=\"#FFF2CC\"];\n", len(states)-1)))
 			} else if transition.transitions == nil || len(transition.transitions) == 0 {
 				// color for end state
-				w.WriteString(fmt.Sprintf("%d [color=\"#82B366\",fillcolor=\"#D5E8D4\"];\n", len(states)-1))
+				w.Write([]byte(fmt.Sprintf("%d [color=\"#82B366\",fillcolor=\"#D5E8D4\"];\n", len(states)-1)))
 			}
 		}
 		idx++
 	}
 	// color for start state
-	w.WriteString(fmt.Sprintf("0 [color=\"#a94442\",fillcolor=\"#f2dede\"];\n"))
+	w.Write([]byte(fmt.Sprintf("0 [color=\"#a94442\",fillcolor=\"#f2dede\"];\n")))
-	w.WriteString("}")
+	w.Write([]byte("}"))
-	w.Flush()
-	log.Infoln("Finish dumping FSM")
 }
 
 func (f *FSM) TestIfNeedBacktracking(mappings []string) bool {