Support MinIO to be deployed on more than 32 nodes (#8492)

This PR implements locking from a global entity into
a more localized set level entity, allowing for locks
to be held only on the resources which are writing
to a collection of disks rather than a global level.

In this process this PR also removes the top-level
limit of 32 nodes to an unlimited number of nodes. This
is a precursor change before bring in bucket expansion.

pkg/dsync/retry_test.go

@@ -0,0 +1,82 @@
+/*
+ * Minio Cloud Storage, (C) 2017 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 dsync
+
+import (
+	"testing"
+	"time"
+)
+
+// Tests for retry timer.
+func TestRetryTimerSimple(t *testing.T) {
+	doneCh := make(chan struct{})
+	attemptCh := newRetryTimerSimple(doneCh)
+	i := <-attemptCh
+	if i != 0 {
+		close(doneCh)
+		t.Fatalf("Invalid attempt counter returned should be 0, found %d instead", i)
+	}
+	i = <-attemptCh
+	if i <= 0 {
+		close(doneCh)
+		t.Fatalf("Invalid attempt counter returned should be greater than 0, found %d instead", i)
+	}
+	close(doneCh)
+	_, ok := <-attemptCh
+	if ok {
+		t.Fatal("Attempt counter should be closed")
+	}
+}
+
+// Test retry time with no jitter.
+func TestRetryTimerWithNoJitter(t *testing.T) {
+	doneCh := make(chan struct{})
+	// No jitter
+	attemptCh := newRetryTimerWithJitter(time.Millisecond, 5*time.Millisecond, NoJitter, doneCh)
+	i := <-attemptCh
+	if i != 0 {
+		close(doneCh)
+		t.Fatalf("Invalid attempt counter returned should be 0, found %d instead", i)
+	}
+	// Loop through the maximum possible attempt.
+	for i = range attemptCh {
+		if i == 30 {
+			close(doneCh)
+		}
+	}
+	_, ok := <-attemptCh
+	if ok {
+		t.Fatal("Attempt counter should be closed")
+	}
+}
+
+// Test retry time with Jitter greater than MaxJitter.
+func TestRetryTimerWithJitter(t *testing.T) {
+	doneCh := make(chan struct{})
+	// Jitter will be set back to 1.0
+	attemptCh := newRetryTimerWithJitter(time.Second, 30*time.Second, 2.0, doneCh)
+	i := <-attemptCh
+	if i != 0 {
+		close(doneCh)
+		t.Fatalf("Invalid attempt counter returned should be 0, found %d instead", i)
+	}
+	close(doneCh)
+	_, ok := <-attemptCh
+	if ok {
+		t.Fatal("Attempt counter should be closed")
+	}
+}