Event persistence for MQTT (#7268)

- The events will be persisted in queueStore if `queueDir` is set.
- Else, if queueDir is not set events persist in memory.

The events are replayed back when the mqtt broker is back online.

pkg/event/target/memorystore_test.go

@@ -0,0 +1,106 @@
+/*
+ * Minio Cloud Storage, (C) 2019 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 target
+
+import (
+	"reflect"
+	"testing"
+)
+
+// TestMemoryStorePut - Tests for store.Put
+func TestMemoryStorePut(t *testing.T) {
+	store := NewMemoryStore(1000)
+	defer func() {
+		store = nil
+	}()
+	for i := 0; i < 100; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	if len(store.ListAll()) != 100 {
+		t.Fatalf("ListAll() Expected: 100, got %d", len(store.ListAll()))
+	}
+}
+
+// TestMemoryStoreGet - Tests for store.Get.
+func TestMemoryStoreGet(t *testing.T) {
+	store := NewMemoryStore(1000)
+	defer func() {
+		store = nil
+	}()
+	for i := 0; i < 10; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	eventKeys := store.ListAll()
+	if len(eventKeys) == 10 {
+		for _, key := range eventKeys {
+			event, eErr := store.Get(key)
+			if eErr != nil {
+				t.Fatal("Failed to Get the event from the queue store ", eErr)
+			}
+			if !reflect.DeepEqual(testEvent, event) {
+				t.Fatalf("Failed to read the event: error: expected = %v, got = %v", testEvent, event)
+			}
+		}
+	} else {
+		t.Fatalf("ListAll() Expected: 10, got %d", len(eventKeys))
+	}
+}
+
+// TestMemoryStoreDel - Tests for store.Del.
+func TestMemoryStoreDel(t *testing.T) {
+	store := NewMemoryStore(1000)
+	defer func() {
+		store = nil
+	}()
+	for i := 0; i < 20; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	eventKeys := store.ListAll()
+	if len(eventKeys) == 20 {
+		for _, key := range eventKeys {
+			store.Del(key)
+		}
+	} else {
+		t.Fatalf("ListAll() Expected: 20, got %d", len(eventKeys))
+	}
+
+	if len(store.ListAll()) != 0 {
+		t.Fatalf("ListAll() Expected: 0, got %d", len(store.ListAll()))
+	}
+}
+
+// TestMemoryStoreLimit - tests for store limit.
+func TestMemoryStoreLimit(t *testing.T) {
+	store := NewMemoryStore(5)
+	defer func() {
+		store = nil
+	}()
+	for i := 0; i < 5; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	if err := store.Put(testEvent); err == nil {
+		t.Fatalf("Expected to fail with %s, but passes", ErrLimitExceeded)
+	}
+}