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/queuestore_test.go

@@ -0,0 +1,162 @@
+/*
+ * 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 (
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	"github.com/minio/minio/pkg/event"
+)
+
+// TestDir
+var queueDir = filepath.Join(os.TempDir(), "minio_test")
+
+// Sample test event.
+var testEvent = event.Event{EventVersion: "1.0", EventSource: "test_source", AwsRegion: "test_region", EventTime: "test_time", EventName: event.ObjectAccessedGet}
+
+// Initialize the store.
+func setUpStore(directory string, limit uint16) (Store, error) {
+	store := NewQueueStore(queueDir, limit)
+	if oErr := store.Open(); oErr != nil {
+		return nil, oErr
+	}
+	return store, nil
+}
+
+// Tear down store
+func tearDownStore() error {
+	if err := os.RemoveAll(queueDir); err != nil {
+		return err
+	}
+	return nil
+}
+
+// TestQueueStorePut - tests for store.Put
+func TestQueueStorePut(t *testing.T) {
+	defer func() {
+		if err := tearDownStore(); err != nil {
+			t.Fatal("Failed to tear down store ", err)
+		}
+	}()
+	store, err := setUpStore(queueDir, 10000)
+	if err != nil {
+		t.Fatal("Failed to create a queue store ", err)
+
+	}
+	// Put 100 events.
+	for i := 0; i < 100; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	// Count the events.
+	if len(store.ListAll()) != 100 {
+		t.Fatalf("ListAll() Expected: 100, got %d", len(store.ListAll()))
+	}
+}
+
+// TestQueueStoreGet - tests for store.Get
+func TestQueueStoreGet(t *testing.T) {
+	defer func() {
+		if err := tearDownStore(); err != nil {
+			t.Fatal("Failed to tear down store ", err)
+		}
+	}()
+	store, err := setUpStore(queueDir, 10000)
+	if err != nil {
+		t.Fatal("Failed to create a queue store ", err)
+	}
+	// Put 10 events
+	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()
+	// Get 10 events.
+	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))
+	}
+}
+
+// TestQueueStoreDel - tests for store.Del
+func TestQueueStoreDel(t *testing.T) {
+	defer func() {
+		if err := tearDownStore(); err != nil {
+			t.Fatal("Failed to tear down store ", err)
+		}
+	}()
+	store, err := setUpStore(queueDir, 10000)
+	if err != nil {
+		t.Fatal("Failed to create a queue store ", err)
+	}
+	// Put 20 events.
+	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()
+	// Remove all the events.
+	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()))
+	}
+}
+
+// TestQueueStoreLimit - tests the event limit for the store.
+func TestQueueStoreLimit(t *testing.T) {
+	defer func() {
+		if err := tearDownStore(); err != nil {
+			t.Fatal("Failed to tear down store ", err)
+		}
+	}()
+	// The max limit is set to 5.
+	store, err := setUpStore(queueDir, 5)
+	if err != nil {
+		t.Fatal("Failed to create a queue store ", err)
+	}
+	for i := 0; i < 5; i++ {
+		if err := store.Put(testEvent); err != nil {
+			t.Fatal("Failed to put to queue store ", err)
+		}
+	}
+	// Should not allow 6th Put.
+	if err := store.Put(testEvent); err == nil {
+		t.Fatalf("Expected to fail with %s, but passes", ErrLimitExceeded)
+	}
+}