From 7e6174126f5d01547cee13a2cdae902e837298c6 Mon Sep 17 00:00:00 2001
From: Alexander Neumann <alexander@bumpern.de>
Date: Sun, 12 Jul 2015 00:25:42 +0200
Subject: [PATCH] checker: run Packs() in parallel

---
 checker/checker.go | 103 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 83 insertions(+), 20 deletions(-)

diff --git a/checker/checker.go b/checker/checker.go
index c449bde9e..aff7c1ef7 100644
--- a/checker/checker.go
+++ b/checker/checker.go
@@ -4,6 +4,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"sync"
 
 	"github.com/restic/restic"
 	"github.com/restic/restic/backend"
@@ -63,7 +64,7 @@ func New(repo *repository.Repository) *Checker {
 	}
 }
 
-const loadIndexParallelism = 20
+const defaultParallelism = 20
 
 // LoadIndex loads all index files.
 func (c *Checker) LoadIndex() error {
@@ -94,7 +95,7 @@ func (c *Checker) LoadIndex() error {
 	go func() {
 		defer close(indexCh)
 		debug.Log("LoadIndex", "start loading indexes in parallel")
-		perr = repository.FilesInParallel(c.repo.Backend(), backend.Index, loadIndexParallelism, worker)
+		perr = repository.FilesInParallel(c.repo.Backend(), backend.Index, defaultParallelism, worker)
 		debug.Log("LoadIndex", "loading indexes finished, error: %v", perr)
 	}()
 
@@ -140,33 +141,95 @@ func (e PackError) Error() string {
 	return "pack " + e.ID.String() + ": " + e.error.Error()
 }
 
+func packIDTester(repo *repository.Repository, inChan <-chan mapID, errChan chan<- error, wg *sync.WaitGroup, done <-chan struct{}) {
+	debug.Log("Checker.testPackID", "worker start")
+	defer debug.Log("Checker.testPackID", "worker done")
+
+	defer wg.Done()
+
+	for id := range inChan {
+		ok, err := repo.Backend().Test(backend.Data, map2str(id))
+		if err != nil {
+			err = PackError{map2id(id), err}
+		} else {
+			if !ok {
+				err = PackError{map2id(id), errors.New("does not exist")}
+			}
+		}
+
+		if err != nil {
+			debug.Log("Checker.testPackID", "error checking for pack %s: %v", map2id(id).Str(), err)
+			select {
+			case <-done:
+				return
+			case errChan <- err:
+			}
+
+			continue
+		}
+
+		debug.Log("Checker.testPackID", "pack %s exists", map2id(id).Str())
+	}
+}
+
+func collectErrors(in <-chan error, out chan<- []error, done <-chan struct{}) {
+	var errs []error
+
+outer:
+	for {
+		select {
+		case err, ok := <-in:
+			if !ok {
+				break outer
+			}
+			errs = append(errs, err)
+		case <-done:
+			break outer
+		}
+	}
+
+	out <- errs
+}
+
 // Packs checks that all packs referenced in the index are still available and
 // there are no packs that aren't in an index.
-func (c *Checker) Packs() (errs []error) {
+func (c *Checker) Packs() []error {
 	debug.Log("Checker.Packs", "checking for %d packs", len(c.packs))
 	seenPacks := make(map[mapID]struct{})
 
-	for id := range c.packs {
-		seenPacks[id] = struct{}{}
-		ok, err := c.repo.Backend().Test(backend.Data, map2str(id))
-		if err != nil {
-			debug.Log("Checker.Packs", "error checking for pack %s", map2id(id).Str())
-			errs = append(errs, PackError{map2id(id), err})
-			continue
-		}
-
-		if !ok {
-			debug.Log("Checker.Packs", "pack %s does not exist", map2id(id).Str())
-			errs = append(errs, PackError{map2id(id), errors.New("does not exist")})
-			continue
-		}
-		debug.Log("Checker.Packs", "pack %s exists", map2id(id).Str())
-	}
-
 	done := make(chan struct{})
 	defer close(done)
 
+	var workerWG sync.WaitGroup
+
+	IDChan := make(chan mapID)
+	errChan := make(chan error)
+
+	for i := 0; i < defaultParallelism; i++ {
+		workerWG.Add(1)
+		go packIDTester(c.repo, IDChan, errChan, &workerWG, done)
+	}
+
+	errsChan := make(chan []error, 1)
+
+	go collectErrors(errChan, errsChan, done)
+
+	for id := range c.packs {
+		seenPacks[id] = struct{}{}
+		IDChan <- id
+	}
+	close(IDChan)
+
+	debug.Log("Checker.Packs", "waiting for %d workers to terminate", defaultParallelism)
+	workerWG.Wait()
+	debug.Log("Checker.Packs", "workers terminated")
+	close(errChan)
+
+	errs := <-errsChan
+	debug.Log("Checker.Packs", "error worker terminated")
+
 	for id := range c.repo.List(backend.Data, done) {
+		debug.Log("Checker.Packs", "check data blob %v", id)
 		if _, ok := seenPacks[id2map(id)]; !ok {
 			errs = append(errs, PackError{id, errors.New("not referenced in any index")})
 		}