content: added direct code coverage for mergedIndex (#1580)

go.mod

@@ -111,7 +111,7 @@ require (
 	github.com/prometheus/statsd_exporter v0.22.2 // indirect
 	github.com/rs/xid v1.3.0 // indirect
 	go.uber.org/atomic v1.9.0 // indirect
-	go.uber.org/multierr v1.7.0 // indirect
+	go.uber.org/multierr v1.7.0
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20211021150943-2b146023228c // indirect

repo/content/merged.go

@@ -4,10 +4,9 @@
 	"container/heap"
 
 	"github.com/pkg/errors"
+	"go.uber.org/multierr"
 )
 
-const iterateParallelism = 16
-
 // mergedIndex is an implementation of Index that transparently merges returns from underlying Indexes.
 type mergedIndex []packIndex
 
@@ -23,13 +22,13 @@ func (m mergedIndex) ApproximateCount() int {
 
 // Close closes all underlying indexes.
 func (m mergedIndex) Close() error {
+	var err error
+
 	for _, ndx := range m {
-		if err := ndx.Close(); err != nil {
-			return errors.Wrap(err, "error closing index shard")
-		}
+		err = multierr.Append(err, ndx.Close())
 	}
 
-	return nil
+	return errors.Wrap(err, "closing index shards")
 }
 
 func contentInfoGreaterThan(a, b Info) bool {
@@ -107,7 +106,7 @@ func (h *nextInfoHeap) Pop() interface{} {
 }
 
 func iterateChan(r IDRange, ndx packIndex, done chan bool) <-chan Info {
-	ch := make(chan Info, iterateParallelism)
+	ch := make(chan Info, 1)
 
 	go func() {
 		defer close(ch)

repo/content/merged_test.go

@@ -2,6 +2,7 @@
 
 import (
 	"bytes"
+	"fmt"
 	"reflect"
 	"testing"
 
@@ -37,14 +38,13 @@ func TestMerged(t *testing.T) {
 
 	m := mergedIndex{i1, i2, i3}
 
-	i, err := m.GetInfo("aabbcc")
-	if err != nil || i == nil {
-		t.Fatalf("unable to get info: %v", err)
-	}
+	require.Equal(t, m.ApproximateCount(), 11)
 
-	if got, want := i.GetPackOffset(), uint32(33); got != want {
-		t.Errorf("invalid pack offset %v, wanted %v", got, want)
-	}
+	i, err := m.GetInfo("aabbcc")
+	require.NoError(t, err)
+	require.NotNil(t, i)
+
+	require.Equal(t, uint32(33), i.GetPackOffset())
 
 	require.NoError(t, m.Iterate(AllIDs, func(i Info) error {
 		if i.GetContentID() == "de1e1e" {
@@ -55,11 +55,28 @@ func TestMerged(t *testing.T) {
 		return nil
 	}))
 
-	if i, err := m.GetInfo("de1e1e"); err != nil {
-		t.Errorf("error getting deleted content info: %v", err)
-	} else if i.GetDeleted() {
-		t.Errorf("GetInfo preferred deleted content over non-deleted")
-	}
+	fmt.Println("=========== START")
+
+	// error is propagated.
+	someErr := errors.Errorf("some error")
+	require.ErrorIs(t, m.Iterate(AllIDs, func(i Info) error {
+		if i.GetContentID() == "aabbcc" {
+			return someErr
+		}
+
+		return nil
+	}), someErr)
+
+	fmt.Println("=========== END")
+
+	// empty merged index does not invoke callback during iteration.
+	require.NoError(t, mergedIndex{}.Iterate(AllIDs, func(i Info) error {
+		return someErr
+	}))
+
+	i, err = m.GetInfo("de1e1e")
+	require.NoError(t, err)
+	require.False(t, i.GetDeleted())
 
 	cases := []struct {
 		r IDRange
@@ -130,6 +147,25 @@ func TestMerged(t *testing.T) {
 	}
 }
 
+type failingIndex struct {
+	packIndex
+	err error
+}
+
+func (i failingIndex) GetInfo(contentID ID) (Info, error) {
+	return nil, i.err
+}
+
+func TestMergedGetInfoError(t *testing.T) {
+	someError := errors.Errorf("some error")
+
+	m := mergedIndex{failingIndex{nil, someError}}
+
+	info, err := m.GetInfo("some-id")
+	require.ErrorIs(t, err, someError)
+	require.Nil(t, info)
+}
+
 func TestMergedIndexIsConsistent(t *testing.T) {
 	i1, err := indexWithItems(
 		&InfoStruct{ContentID: "aabbcc", TimestampSeconds: 1, PackBlobID: "xx", PackOffset: 11},