From 2896a36e3aa9cfc8f3429f36253de24556baf61e Mon Sep 17 00:00:00 2001
From: Jeremy Jay <jeremy@pbnjay.com>
Date: Sun, 14 Feb 2021 14:17:25 -0500
Subject: [PATCH] implement concurrent search and sync aggregation

---
 cmd/grate2tsv/main.go | 99 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 80 insertions(+), 19 deletions(-)

diff --git a/cmd/grate2tsv/main.go b/cmd/grate2tsv/main.go
index 762c640..9801f1d 100644
--- a/cmd/grate2tsv/main.go
+++ b/cmd/grate2tsv/main.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"crypto/md5"
 	"flag"
 	"fmt"
 	"io"
@@ -13,6 +14,7 @@ import (
 	"runtime"
 	"runtime/pprof"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/pbnjay/grate"
@@ -30,10 +32,23 @@ var (
 	skipBlanks     = flag.Bool("b", true, "discard blank rows from the output")
 	cpuprofile     = flag.String("cpuprofile", "", "write cpu profile to file")
 	memprofile     = flag.String("memprofile", "", "write memory profile to file")
+
+	timeFormat = "2006-01-02 15:04:05"
+	fstats     *os.File
+
+	procWG  sync.WaitGroup
+	cleanup = make(chan *output, 100)
+	outpool = sync.Pool{New: func() interface{} {
+		return &output{}
+	}}
 )
 
+type output struct {
+	f *os.File
+	b *bufio.Writer
+}
+
 func main() {
-	timeFormat := "2006-01-02 15:04:05"
 	flag.Parse()
 
 	if *memprofile != "" {
@@ -66,7 +81,18 @@ func main() {
 		log.SetOutput(fo)
 	}
 
-	fstats, err := os.OpenFile(*infoFile, os.O_CREATE|os.O_RDWR, 0644)
+	done := make(chan int)
+	go func() {
+		for x := range cleanup {
+			x.b.Flush()
+			x.f.Close()
+			outpool.Put(x)
+		}
+		done <- 1
+	}()
+
+	var err error
+	fstats, err = os.OpenFile(*infoFile, os.O_CREATE|os.O_RDWR, 0644)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -78,12 +104,36 @@ func main() {
 	if pos == 0 {
 		fmt.Fprintf(fstats, "time\tfilename\tsheet\trows\tcolumns\terrors\n")
 	}
+
+	filenameChan := make(chan string)
+
+	// fan out to 1/2 of CPU cores
+	// (e.g. each file-processor can use 2 cpus)
+	outMu := &sync.Mutex{}
+	nparallel := runtime.NumCPU() / 2
+	procWG.Add(nparallel)
+	for i := 0; i < nparallel; i++ {
+		go runProcessor(filenameChan, outMu)
+	}
 	for _, fn := range flag.Args() {
+		filenameChan <- fn
+	}
+
+	close(filenameChan)
+	procWG.Wait()
+	close(cleanup)
+	<-done
+}
+
+func runProcessor(from chan string, mu *sync.Mutex) {
+	for fn := range from {
 		nowFmt := time.Now().Format(timeFormat)
 		results, err := processFile(fn)
+		mu.Lock()
 		if err != nil {
 			// returned errors are fatal
 			fmt.Fprintf(fstats, "%s\t%s\t-\t-\t-\t%s\n", nowFmt, fn, err.Error())
+			mu.Unlock()
 			continue
 		}
 
@@ -95,7 +145,9 @@ func main() {
 			fmt.Fprintf(fstats, "%s\t%s\t%s\t%d\t%d\t%s\n", nowFmt, res.Filename, res.SheetName,
 				res.NumRows, res.NumCols, e)
 		}
+		mu.Unlock()
 	}
+	procWG.Done()
 }
 
 var (
@@ -105,27 +157,29 @@ var (
 
 type stats struct {
 	Filename  string
+	Hash      string
 	SheetName string
 	NumRows   int
 	NumCols   int
 	Err       error
 }
 
-type Flusher interface {
-	Flush() error
-}
-
 func processFile(fn string) ([]stats, error) {
-	log.Printf("Opening file '%s' ...", fn)
+	//log.Printf("Opening file '%s' ...", fn)
 	wb, err := grate.Open(fn)
 	if err != nil {
 		return nil, err
 	}
+	defer wb.Close()
 
 	results := []stats{}
 
 	ext := filepath.Ext(fn)
 	fn2 := filepath.Base(strings.TrimSuffix(fn, ext))
+	subparts := fmt.Sprintf("%x", md5.Sum([]byte(fn2)))
+	subdir := filepath.Join("results", subparts[:2], subparts[2:4])
+	os.MkdirAll(subdir, 0755)
+	log.Printf(subparts[:8]+"  Processing file '%s'", fn2)
 
 	sheets, err := wb.List()
 	if err != nil {
@@ -134,9 +188,10 @@ func processFile(fn string) ([]stats, error) {
 	for _, s := range sheets {
 		ps := stats{
 			Filename:  fn,
+			Hash:      subparts[:8],
 			SheetName: s,
 		}
-		log.Printf("  Opening Sheet '%s'...", s)
+		log.Printf(subparts[:8]+"  Opening Sheet '%s'...", s)
 		sheet, err := wb.Get(s)
 		if err != nil {
 			ps.Err = err
@@ -144,7 +199,7 @@ func processFile(fn string) ([]stats, error) {
 			continue
 		}
 		if sheet.IsEmpty() {
-			log.Println("    Empty sheet. Skipping.")
+			log.Println(subparts[:8] + "    Empty sheet. Skipping.")
 			results = append(results, ps)
 			continue
 		}
@@ -152,14 +207,17 @@ func processFile(fn string) ([]stats, error) {
 		if s == fn {
 			s2 = "main"
 		}
+		var ox *output
 		var w io.Writer = ioutil.Discard
 		if !*pretend {
-			f, err := os.Create(fn2 + "." + s2 + ".tsv")
+			f, err := os.Create(subdir + "/" + fn2 + "." + s2 + ".tsv")
 			if err != nil {
 				return nil, err
 			}
-			defer f.Close()
-			w = bufio.NewWriter(f)
+			ox = outpool.Get().(*output)
+			ox.f = f
+			ox.b = bufio.NewWriter(f)
+			w = ox.b
 		}
 
 		for sheet.Next() {
@@ -181,17 +239,20 @@ func processFile(fn string) ([]stats, error) {
 				}
 			}
 			if nonblank || !*skipBlanks {
-				fmt.Fprintln(w, strings.Join(row, "\t"))
+				for i, v := range row {
+					if i != 0 {
+						w.Write([]byte{'\t'})
+					}
+					w.Write([]byte(v))
+				}
+				w.Write([]byte{'\n'})
+				//fmt.Fprintln(w, strings.Join(row, "\t"))
 				ps.NumRows++
 			}
 		}
 		results = append(results, ps)
-
-		if ff, ok := w.(Flusher); ok {
-			ff.Flush()
-		}
-		if c, ok := w.(io.Closer); ok {
-			c.Close()
+		if ox != nil {
+			cleanup <- ox
 		}
 	}
 	return results, nil