Add large bucket support for erasure coded backend (#5160)

This PR implements an object layer which
combines input erasure sets of XL layers
into a unified namespace.

This object layer extends the existing
erasure coded implementation, it is assumed
in this design that providing > 16 disks is
a static configuration as well i.e if you started
the setup with 32 disks with 4 sets 8 disks per
pack then you would need to provide 4 sets always.

Some design details and restrictions:

- Objects are distributed using consistent ordering
  to a unique erasure coded layer.
- Each pack has its own dsync so locks are synchronized
  properly at pack (erasure layer).
- Each pack still has a maximum of 16 disks
  requirement, you can start with multiple
  such sets statically.
- Static sets set of disks and cannot be
  changed, there is no elastic expansion allowed.
- Static sets set of disks and cannot be
  changed, there is no elastic removal allowed.
- ListObjects() across sets can be noticeably
  slower since List happens on all servers,
  and is merged at this sets layer.

Fixes #5465
Fixes #5464
Fixes #5461
Fixes #5460
Fixes #5459
Fixes #5458
Fixes #5460
Fixes #5488
Fixes #5489
Fixes #5497
Fixes #5496

pkg/bpool/bpool_test.go

@@ -0,0 +1,96 @@
+// Original work https://github.com/oxtoacart/bpool borrowed
+// only bpool.go licensed under Apache 2.0.
+
+// This file modifies original bpool.go to add one more option
+// to provide []byte capacity for better GC management.
+
+/*
+ * Minio Cloud Storage (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package bpool
+
+import "testing"
+
+// Tests - bytePool functionality.
+func TestBytePool(t *testing.T) {
+	var size = 4
+	var width = 10
+	var capWidth = 16
+
+	bufPool := NewBytePoolCap(size, width, capWidth)
+
+	// Check the width
+	if bufPool.Width() != width {
+		t.Fatalf("bytepool width invalid: got %v want %v", bufPool.Width(), width)
+	}
+
+	// Check with width cap
+	if bufPool.WidthCap() != capWidth {
+		t.Fatalf("bytepool capWidth invalid: got %v want %v", bufPool.WidthCap(), capWidth)
+	}
+
+	// Check that retrieved buffer are of the expected width
+	b := bufPool.Get()
+	if len(b) != width {
+		t.Fatalf("bytepool length invalid: got %v want %v", len(b), width)
+	}
+	if cap(b) != capWidth {
+		t.Fatalf("bytepool length invalid: got %v want %v", cap(b), capWidth)
+	}
+
+	bufPool.Put(b)
+
+	// Fill the pool beyond the capped pool size.
+	for i := 0; i < size*2; i++ {
+		bufPool.Put(make([]byte, bufPool.w))
+	}
+
+	b = bufPool.Get()
+	if len(b) != width {
+		t.Fatalf("bytepool length invalid: got %v want %v", len(b), width)
+	}
+	if cap(b) != capWidth {
+		t.Fatalf("bytepool length invalid: got %v want %v", cap(b), capWidth)
+	}
+
+	bufPool.Put(b)
+
+	// Close the channel so we can iterate over it.
+	close(bufPool.c)
+
+	// Check the size of the pool.
+	if len(bufPool.c) != size {
+		t.Fatalf("bytepool size invalid: got %v want %v", len(bufPool.c), size)
+	}
+
+	bufPoolNoCap := NewBytePoolCap(size, width, 0)
+	// Check the width
+	if bufPoolNoCap.Width() != width {
+		t.Fatalf("bytepool width invalid: got %v want %v", bufPool.Width(), width)
+	}
+
+	// Check with width cap
+	if bufPoolNoCap.WidthCap() != 0 {
+		t.Fatalf("bytepool capWidth invalid: got %v want %v", bufPool.WidthCap(), 0)
+	}
+	b = bufPoolNoCap.Get()
+	if len(b) != width {
+		t.Fatalf("bytepool length invalid: got %v want %v", len(b), width)
+	}
+	if cap(b) != width {
+		t.Fatalf("bytepool length invalid: got %v want %v", cap(b), width)
+	}
+}