fix: discard excessive errors (influxdata#22379) (influxdata#22391)

The tsmBatchKeyIterator discards excessive errors to avoid
out-of-memory crashes when compacting very corrupt files.
Any error beyond DefaultMaxSavedErrors (100) will be
discarded instead of appended to the error slice.

closes influxdata#22328

(cherry picked from commit e53f75e)

closes influxdata#22381

tsdb/engine/tsm1/compact.go

@@ -40,6 +40,10 @@ const (
 
 	// TSMFileExtension is the extension used for TSM files.
 	TSMFileExtension = "tsm"
+
+	// DefaultMaxSavedErrors is the number of errors that are stored by a TSMBatchKeyReader before
+	// subsequent errors are discarded
+	DefaultMaxSavedErrors = 100
 )
 
 var (
@@ -954,7 +958,7 @@ func (c *Compactor) compact(fast bool, tsmFiles []string, logger *zap.Logger) ([
 		return nil, nil
 	}
 
-	tsm, err := NewTSMBatchKeyIterator(size, fast, intC, tsmFiles, trs...)
+	tsm, err := NewTSMBatchKeyIterator(size, fast, DefaultMaxSavedErrors, intC, tsmFiles, trs...)
 	if err != nil {
 		return nil, err
 	}
@@ -1660,15 +1664,28 @@ type tsmBatchKeyIterator struct {
 	// without decode
 	merged    blocks
 	interrupt chan struct{}
+
+	// maxErrors is the maximum number of errors to store before discarding.
+	maxErrors int
+	// overflowErrors is the number of errors we have ignored.
+	overflowErrors int
 }
 
-func (t *tsmBatchKeyIterator) AppendError(err error) {
-	t.errs = append(t.errs, err)
+func (t *tsmBatchKeyIterator) AppendError(err error) bool {
+	if t.maxErrors > len(t.errs) {
+		t.errs = append(t.errs, err)
+		// Was the error stored?
+		return true
+	} else {
+		// Was the error dropped
+		t.overflowErrors++
+		return false
+	}
 }
 
 // NewTSMBatchKeyIterator returns a new TSM key iterator from readers.
 // size indicates the maximum number of values to encode in a single block.
-func NewTSMBatchKeyIterator(size int, fast bool, interrupt chan struct{}, tsmFiles []string, readers ...*TSMReader) (KeyIterator, error) {
+func NewTSMBatchKeyIterator(size int, fast bool, maxErrors int, interrupt chan struct{}, tsmFiles []string, readers ...*TSMReader) (KeyIterator, error) {
 	var iter []*BlockIterator
 	for _, r := range readers {
 		iter = append(iter, r.BlockIterator())
@@ -1689,6 +1706,7 @@ func NewTSMBatchKeyIterator(size int, fast bool, interrupt chan struct{}, tsmFil
 		mergedBooleanValues:  &tsdb.BooleanArray{},
 		mergedStringValues:   &tsdb.StringArray{},
 		interrupt:            interrupt,
+		maxErrors:            maxErrors,
 	}, nil
 }
 
@@ -1916,7 +1934,12 @@ func (k *tsmBatchKeyIterator) Err() error {
 	if len(k.errs) == 0 {
 		return nil
 	}
-	return k.errs
+	// Copy the errors before appending the dropped error count
+	var errs TSMErrors
+	errs = make([]error, 0, len(k.errs)+1)
+	errs = append(errs, k.errs...)
+	errs = append(errs, fmt.Errorf("additional errors dropped: %d", k.overflowErrors))
+	return errs
 }
 
 type cacheKeyIterator struct {

tsdb/engine/tsm1/reader_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -1864,6 +1865,98 @@ func TestTSMReader_References(t *testing.T) {
 	}
 }
 
+func TestBatchKeyIterator_Errors(t *testing.T) {
+	const MaxErrors = 10
+
+	dir, name := createTestTSM(t)
+	defer os.RemoveAll(dir)
+	fr, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("unexpected error opening file %s: %v", name, err)
+	}
+	r, err := NewTSMReader(fr)
+	if err != nil {
+		// Only have a deferred close if we could not create the TSMReader
+		defer func() {
+			if e := fr.Close(); e != nil {
+				t.Fatalf("unexpected error closing %s: %v", name, e)
+			}
+		}()
+
+		t.Fatalf("unexpected error creating TSMReader for %s: %v", name, err)
+	}
+	defer func() {
+		if e := r.Close(); e != nil {
+			t.Fatalf("error closing TSMReader for %s: %v", name, e)
+		}
+	}()
+	interrupts := make(chan struct{})
+	var iter KeyIterator
+	if iter, err = NewTSMBatchKeyIterator(3, false, MaxErrors, interrupts, []string{name}, r); err != nil {
+		t.Fatalf("unexpected error creating tsmBatchKeyIterator: %v", err)
+	}
+	var i int
+	for i = 0; i < MaxErrors*2; i++ {
+		saved := iter.(*tsmBatchKeyIterator).AppendError(fmt.Errorf("fake error: %d", i))
+		if i < MaxErrors && !saved {
+			t.Fatalf("error unexpectedly not saved: %d", i)
+		}
+		if i >= MaxErrors && saved {
+			t.Fatalf("error unexpectedly saved: %d", i)
+		}
+	}
+	errs := iter.Err()
+	if errCnt := len(errs.(TSMErrors)); errCnt != (MaxErrors + 1) {
+		t.Fatalf("saved wrong number of errors: expected %d, got %d", MaxErrors, errCnt)
+	}
+	expected := fmt.Sprintf("additional errors dropped: %d", i-MaxErrors)
+	if strings.Compare(errs.(TSMErrors)[MaxErrors].Error(), expected) != 0 {
+		t.Fatalf("expected: '%s', got: '%s", expected, errs.(TSMErrors)[MaxErrors].Error())
+	}
+}
+
+func createTestTSM(t *testing.T) (dir string, name string) {
+	dir = MustTempDir()
+	f := mustTempFile(dir)
+	name = f.Name()
+	w, err := NewTSMWriter(f)
+	if err != nil {
+		f.Close()
+		t.Fatalf("unexpected error creating writer for %s: %v", name, err)
+	}
+	defer func() {
+		if e := w.Close(); e != nil {
+			t.Fatalf("write TSM close of %s: %v", name, err)
+		}
+	}()
+
+	var data = map[string][]Value{
+		"float":  []Value{NewValue(1, 1.0)},
+		"int":    []Value{NewValue(1, int64(1))},
+		"uint":   []Value{NewValue(1, ^uint64(0))},
+		"bool":   []Value{NewValue(1, true)},
+		"string": []Value{NewValue(1, "foo")},
+	}
+
+	keys := make([]string, 0, len(data))
+	for k := range data {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	for _, k := range keys {
+		if err := w.Write([]byte(k), data[k]); err != nil {
+			t.Fatalf("write TSM value: %v", err)
+		}
+	}
+
+	if err := w.WriteIndex(); err != nil {
+		t.Fatalf("write TSM index: %v", err)
+	}
+
+	return dir, name
+}
+
 func BenchmarkIndirectIndex_UnmarshalBinary(b *testing.B) {
 	index := NewIndexWriter()
 	for i := 0; i < 100000; i++ {