Fixed TestChunkDiskMapper_WriteChunk_Chunk_IterateChunks for go1.16 (#8538)

Fixes https://github.com/prometheus/prometheus/issues/8403

Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>

tsdb/chunks/head_chunks.go

@@ -605,12 +605,14 @@ func (cdm *ChunkDiskMapper) IterateAllChunks(f func(seriesRef, chunkRef uint64,
 					}
 				}
 				if allZeros {
+					// End of segment chunk file content.
 					break
 				}
 				return &CorruptionErr{
 					Dir:       cdm.dir.Name(),
 					FileIndex: segID,
-					Err:       errors.Errorf("head chunk file doesn't include enough bytes to read the chunk header - required:%v, available:%v, file:%d", idx+MaxHeadChunkMetaSize, fileEnd, segID),
+					Err: errors.Errorf("head chunk file has some unread data, but doesn't include enough bytes to read the chunk header"+
+						" - required:%v, available:%v, file:%d", idx+MaxHeadChunkMetaSize, fileEnd, segID),
 				}
 			}
 			chkCRC32.Reset()

tsdb/chunks/head_chunks_test.go

@@ -118,11 +118,6 @@ func TestChunkDiskMapper_WriteChunk_Chunk_IterateChunks(t *testing.T) {
 	fileEnd := HeadChunkFileHeaderSize + len(expectedBytes)
 	require.Equal(t, expectedBytes, actualBytes[HeadChunkFileHeaderSize:fileEnd])
 
-	// Test for the next chunk header to be all 0s. That marks the end of the file.
-	for _, b := range actualBytes[fileEnd : fileEnd+MaxHeadChunkMetaSize] {
-		require.Equal(t, byte(0), b)
-	}
-
 	// Testing reading of chunks.
 	for _, exp := range expectedData {
 		actChunk, err := hrw.Chunk(exp.chunkRef)
@@ -137,7 +132,7 @@ func TestChunkDiskMapper_WriteChunk_Chunk_IterateChunks(t *testing.T) {
 	require.NoError(t, err)
 
 	idx := 0
-	err = hrw.IterateAllChunks(func(seriesRef, chunkRef uint64, mint, maxt int64, numSamples uint16) error {
+	require.NoError(t, hrw.IterateAllChunks(func(seriesRef, chunkRef uint64, mint, maxt int64, numSamples uint16) error {
 		t.Helper()
 
 		expData := expectedData[idx]
@@ -153,10 +148,8 @@ func TestChunkDiskMapper_WriteChunk_Chunk_IterateChunks(t *testing.T) {
 
 		idx++
 		return nil
-	})
-	require.NoError(t, err)
+	}))
 	require.Equal(t, len(expectedData), idx)
-
 }
 
 // TestChunkDiskMapper_Truncate tests