Add concurrency to healing objects on a fresh disk (#15575)

internal/jobtokens/jobtokens.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2022 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package jobtokens
+
+import (
+	"errors"
+	"sync"
+)
+
+// JobTokens provides a bounded semaphore with the ability to wait until all
+// concurrent jobs finish.
+type JobTokens struct {
+	wg     sync.WaitGroup
+	tokens chan struct{}
+}
+
+// New creates a JobTokens object which allows up to n jobs to proceed
+// concurrently. n must be > 0.
+func New(n int) (*JobTokens, error) {
+	if n <= 0 {
+		return nil, errors.New("n must be > 0")
+	}
+
+	tokens := make(chan struct{}, n)
+	for i := 0; i < n; i++ {
+		tokens <- struct{}{}
+	}
+	return &JobTokens{
+		tokens: tokens,
+	}, nil
+}
+
+// Take is how a job (goroutine) can Take its turn.
+func (jt *JobTokens) Take() {
+	jt.wg.Add(1)
+	<-jt.tokens
+}
+
+// Give is how a job (goroutine) can give back its turn once done.
+func (jt *JobTokens) Give() {
+	jt.wg.Done()
+	jt.tokens <- struct{}{}
+}
+
+// Wait waits for all ongoing concurrent jobs to complete
+func (jt *JobTokens) Wait() {
+	jt.wg.Wait()
+}

internal/jobtokens/jobtokens_test.go

@@ -0,0 +1,148 @@
+// Copyright (c) 2022 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package jobtokens
+
+import (
+	"fmt"
+	"sync"
+	"testing"
+)
+
+func TestJobTokens(t *testing.T) {
+	tests := []struct {
+		n        int
+		jobs     int
+		mustFail bool
+	}{
+		{
+			n:        0,
+			jobs:     5,
+			mustFail: true,
+		},
+		{
+			n:        -1,
+			jobs:     5,
+			mustFail: true,
+		},
+		{
+			n:    1,
+			jobs: 5,
+		},
+		{
+			n:    2,
+			jobs: 5,
+		},
+		{
+			n:    5,
+			jobs: 10,
+		},
+		{
+			n:    10,
+			jobs: 5,
+		},
+	}
+	testFn := func(n, jobs int, mustFail bool) {
+		var mu sync.Mutex
+		var jobsDone int
+		// Create jobTokens for n concurrent workers
+		jt, err := New(n)
+		if err == nil && mustFail {
+			t.Fatal("Expected test to return error")
+		}
+		if err != nil && mustFail {
+			return
+		}
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		for i := 0; i < jobs; i++ {
+			jt.Take()
+			go func() { // Launch a worker after acquiring a token
+				defer jt.Give() // Give token back once done
+				mu.Lock()
+				jobsDone++
+				mu.Unlock()
+			}()
+		}
+		jt.Wait() // Wait for all workers to complete
+		if jobsDone != jobs {
+			t.Fatalf("Expected %d jobs to be done but only %d were done", jobs, jobsDone)
+		}
+	}
+
+	for i, test := range tests {
+		t.Run(fmt.Sprintf("test-%d", i), func(t *testing.T) {
+			testFn(test.n, test.jobs, test.mustFail)
+		})
+	}
+
+	// Verify that jobTokens can be reused after full drain
+	t.Run("test-jobTokens-reuse", func(t *testing.T) {
+		var mu sync.Mutex
+		jt, _ := New(5)
+		for reuse := 0; reuse < 3; reuse++ {
+			var jobsDone int
+			for i := 0; i < 10; i++ {
+				jt.Take()
+				go func() {
+					defer jt.Give()
+					mu.Lock()
+					jobsDone++
+					mu.Unlock()
+				}()
+			}
+			jt.Wait()
+			if jobsDone != 10 {
+				t.Fatalf("Expected %d jobs to be complete but only %d were", 10, jobsDone)
+			}
+		}
+	})
+}
+
+func benchmarkJobTokens(b *testing.B, n, jobs int) {
+	b.ReportAllocs()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			var mu sync.Mutex
+			var jobsDone int
+			jt, _ := New(n)
+			for i := 0; i < jobs; i++ {
+				jt.Take()
+				go func() {
+					defer jt.Give()
+					mu.Lock()
+					jobsDone++
+					mu.Unlock()
+				}()
+			}
+			jt.Wait()
+			if jobsDone != jobs {
+				b.Fail()
+			}
+		}
+	})
+}
+
+func BenchmarkJobTokens_N5_J10(b *testing.B) {
+	benchmarkJobTokens(b, 5, 10)
+}
+
+func BenchmarkJobTokens_N5_J100(b *testing.B) {
+	benchmarkJobTokens(b, 5, 100)
+}