1 files changed, 103 insertions, 0 deletions
diff --git a/aai-traversal/src/main/java/org/onap/aai/rest/util/AaiGraphChecker.java b/aai-traversal/src/main/java/org/onap/aai/rest/util/AaiGraphChecker.java
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+++ b/aai-traversal/src/main/java/org/onap/aai/rest/util/AaiGraphChecker.java
@@ -0,0 +1,103 @@
+/*
+ * ============LICENSE_START=======================================================
+ * Copyright (C) 2022 Bell Canada
+ * Modification Copyright (C) 2022 Deutsche Telekom SA
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+package org.onap.aai.rest.util;
+
+import java.util.Iterator;
+
+import org.janusgraph.core.JanusGraphException;
+import org.janusgraph.core.JanusGraphTransaction;
+import org.onap.aai.dbmap.AAIGraph;
+import org.onap.aai.logging.ErrorLogHelper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.config.ConfigurableBeanFactory;
+import org.springframework.context.annotation.Scope;
+import org.springframework.stereotype.Component;
+
+import com.google.common.collect.Iterators;
+
+/**
+ * Singleton class responsible to check that AAI service is able to connect to its back-end
+ * database.
+ */
+@Component
+@Scope(ConfigurableBeanFactory.SCOPE_SINGLETON)
+public class AaiGraphChecker {
+    private static final Logger LOGGER = LoggerFactory.getLogger(AaiGraphChecker.class);
+
+    private AaiGraphChecker() {
+    }
+
+    /**
+     * Checks whether a connection to the graph database can be made.
+     * 
+     * @return
+     *         <li>true, if database is available</li>
+     *         <li>false, if database is NOT available</li>
+     */
+    public Boolean isAaiGraphDbAvailable() {
+        Boolean dbAvailable;
+        JanusGraphTransaction transaction = null;
+        try {
+            transaction = AAIGraph.getInstance().getGraph().newTransaction();
+            final Iterator<?> vertexIterator = transaction.query().limit(1).vertices().iterator();
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.debug("Number of vertices retrieved while checking db: {}",
+                    Iterators.size(vertexIterator));
+            }
+            vertexIterator.hasNext();
+            LOGGER.debug("Database is available");
+            dbAvailable = Boolean.TRUE;
+        } catch (JanusGraphException e) {
+            String message = "Database is not available (after JanusGraph exception)";
+            ErrorLogHelper.logError("500", message + ": " + e.getMessage());
+            LOGGER.error(message, e);
+            dbAvailable = Boolean.FALSE;
+        } catch (Error e) {
+            // Following error occurs when aai resources is starting:
+            // - UnsatisfiedLinkError (for org.onap.aai.dbmap.AAIGraph$Helper instantiation)
+            // Following errors are raised when aai resources is starting and cassandra is not
+            // running:
+            // - ExceptionInInitializerError
+            // - NoClassDefFoundError (definition for org.onap.aai.dbmap.AAIGraph$Helper is not
+            // found)
+            String message = "Database is not available (after error)";
+            ErrorLogHelper.logError("500", message + ": " + e.getMessage());
+            LOGGER.error(message, e);
+            dbAvailable = Boolean.FALSE;
+        } catch (Exception e) {
+            String message = "Database availability can not be determined";
+            ErrorLogHelper.logError("500", message + ": " + e.getMessage());
+            LOGGER.error(message, e);
+            dbAvailable = null;
+        } finally {
+            if (transaction != null && !transaction.isClosed()) {
+                // check if transaction is open then closed instead of flag
+                try {
+                    transaction.rollback();
+                } catch (Exception e) {
+                    String message = "Exception occurred while closing transaction";
+                    LOGGER.error(message, e);
+                    ErrorLogHelper.logError("500", message + ": " + e.getMessage());
+                }
+            }
+        }
+        return dbAvailable;
+    }
+}