From e70b9af3e41662cd0c5dd246b0b097f13acdc84c Mon Sep 17 00:00:00 2001
From: Alex Grintsvayg <grin@lbry.com>
Date: Sat, 21 Nov 2020 11:39:15 -0500
Subject: [PATCH] dont overallocate ram when reading blobs from disk

ReadFile checks the file size and allocates a bit more space than we
expect we'll need. ReadAll uses Go's standard resizing algo, which
doubles the underlying array each time you hit the end. So ReadAll
ends up allocating 4MB for a full blob, while ReadFile allocates
slightly over 2MB.
---
 store/disk.go      |  8 +++-----
 store/disk_test.go | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 5 deletions(-)
 create mode 100644 store/disk_test.go

diff --git a/store/disk.go b/store/disk.go
index 4ac2a0f..2234971 100644
--- a/store/disk.go
+++ b/store/disk.go
@@ -58,17 +58,15 @@ func (d *DiskStore) Get(hash string) (stream.Blob, error) {
 		return nil, err
 	}
 
-	file, err := os.Open(d.path(hash))
+	blob, err := ioutil.ReadFile(d.path(hash))
 	if err != nil {
 		if os.IsNotExist(err) {
 			return nil, errors.Err(ErrBlobNotFound)
 		}
-		return nil, err
+		return nil, errors.Err(err)
 	}
-	defer file.Close()
 
-	blob, err := ioutil.ReadAll(file)
-	return blob, errors.Err(err)
+	return blob, nil
 }
 
 // Put stores the blob on disk
diff --git a/store/disk_test.go b/store/disk_test.go
new file mode 100644
index 0000000..3bc088a
--- /dev/null
+++ b/store/disk_test.go
@@ -0,0 +1,45 @@
+package store
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"testing"
+
+	"github.com/lbryio/lbry.go/v2/extras/errors"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDiskStore_Get(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "reflector_test_*")
+	require.NoError(t, err)
+	defer os.RemoveAll(tmpDir)
+	d := NewDiskStore(tmpDir, 2)
+
+	hash := "1234567890"
+	data := []byte("oyuntyausntoyaunpdoyruoyduanrstjwfjyuwf")
+
+	expectedPath := path.Join(tmpDir, hash[:2], hash)
+	err = os.MkdirAll(filepath.Dir(expectedPath), os.ModePerm)
+	require.NoError(t, err)
+	err = ioutil.WriteFile(expectedPath, data, os.ModePerm)
+	require.NoError(t, err)
+
+	blob, err := d.Get(hash)
+	assert.NoError(t, err)
+	assert.EqualValues(t, data, blob)
+}
+
+func TestDiskStore_GetNonexistentBlob(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "reflector_test_*")
+	require.NoError(t, err)
+	defer os.RemoveAll(tmpDir)
+	d := NewDiskStore(tmpDir, 2)
+
+	blob, err := d.Get("nonexistent")
+	assert.Nil(t, blob)
+	assert.True(t, errors.Is(err, ErrBlobNotFound))
+}