[GitHub] [nifi] mattyb149 commented on a change in pull request #4635: NIFI-7821 Added Cassandra-based DMC.

[GitBox <gi...@apache.org>]

mattyb149 commented on a change in pull request #4635:
URL: https://github.com/apache/nifi/pull/4635#discussion_r528962136



##########
File path: nifi-nar-bundles/nifi-cassandra-bundle/nifi-cassandra-distributedmapcache-service/src/main/java/org/apache/nifi/controller/cassandra/CassandraDistributedMapCache.java
##########
@@ -0,0 +1,241 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.nifi.controller.cassandra;
+
+import com.datastax.driver.core.BoundStatement;
+import com.datastax.driver.core.PreparedStatement;
+import com.datastax.driver.core.ResultSet;
+import com.datastax.driver.core.Row;
+import com.datastax.driver.core.Session;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnDisabled;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.cassandra.CassandraSessionProviderService;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.controller.AbstractControllerService;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.distributed.cache.client.Deserializer;
+import org.apache.nifi.distributed.cache.client.DistributedMapCacheClient;
+import org.apache.nifi.distributed.cache.client.Serializer;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import static org.apache.nifi.controller.cassandra.QueryUtils.createDeleteStatement;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createExistsQuery;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createFetchQuery;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createInsertStatement;
+
+@Tags({"map", "cache", "distributed", "cassandra"})
+@CapabilityDescription("Provides a DistributedMapCache client that is based on Apache Cassandra.")
+public class CassandraDistributedMapCache extends AbstractControllerService implements DistributedMapCacheClient {
+    public static final PropertyDescriptor SESSION_PROVIDER = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-session-provider")
+            .displayName("Session Provider")
+            .description("The client service that will configure the cassandra client connection.")
+            .required(true)
+            .identifiesControllerService(CassandraSessionProviderService.class)
+            .build();
+
+    public static final PropertyDescriptor TABLE_NAME = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-table-name")
+            .displayName("Table Name")
+            .description("The name of the table where the cache will be stored.")
+            .required(true)
+            .addValidator(StandardValidators.NON_EMPTY_EL_VALIDATOR)
+            .build();
+
+    public static final PropertyDescriptor KEY_FIELD_NAME = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-key-field-name")
+            .displayName("Key Field Name")
+            .description("The name of the field that acts as the unique key. (The CQL type should be \"blob\")")

Review comment:
       Is there a necessary restriction on the CQL type to blob? I would think TEXT, VARCHAR, or other string-based fields would be acceptable? Or is that so we can use a single serializer/deserializer?

##########
File path: nifi-nar-bundles/nifi-cassandra-bundle/nifi-cassandra-distributedmapcache-service/src/main/java/org/apache/nifi/controller/cassandra/CassandraDistributedMapCache.java
##########
@@ -0,0 +1,241 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.nifi.controller.cassandra;
+
+import com.datastax.driver.core.BoundStatement;
+import com.datastax.driver.core.PreparedStatement;
+import com.datastax.driver.core.ResultSet;
+import com.datastax.driver.core.Row;
+import com.datastax.driver.core.Session;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnDisabled;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.cassandra.CassandraSessionProviderService;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.controller.AbstractControllerService;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.distributed.cache.client.Deserializer;
+import org.apache.nifi.distributed.cache.client.DistributedMapCacheClient;
+import org.apache.nifi.distributed.cache.client.Serializer;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import static org.apache.nifi.controller.cassandra.QueryUtils.createDeleteStatement;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createExistsQuery;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createFetchQuery;
+import static org.apache.nifi.controller.cassandra.QueryUtils.createInsertStatement;
+
+@Tags({"map", "cache", "distributed", "cassandra"})
+@CapabilityDescription("Provides a DistributedMapCache client that is based on Apache Cassandra.")
+public class CassandraDistributedMapCache extends AbstractControllerService implements DistributedMapCacheClient {
+    public static final PropertyDescriptor SESSION_PROVIDER = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-session-provider")
+            .displayName("Session Provider")
+            .description("The client service that will configure the cassandra client connection.")
+            .required(true)
+            .identifiesControllerService(CassandraSessionProviderService.class)
+            .build();
+
+    public static final PropertyDescriptor TABLE_NAME = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-table-name")
+            .displayName("Table Name")
+            .description("The name of the table where the cache will be stored.")
+            .required(true)
+            .addValidator(StandardValidators.NON_EMPTY_EL_VALIDATOR)
+            .build();
+
+    public static final PropertyDescriptor KEY_FIELD_NAME = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-key-field-name")
+            .displayName("Key Field Name")
+            .description("The name of the field that acts as the unique key. (The CQL type should be \"blob\")")
+            .required(true)
+            .addValidator(StandardValidators.NON_EMPTY_EL_VALIDATOR)
+            .build();
+
+    public static final PropertyDescriptor VALUE_FIELD_NAME = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-value-field-name")
+            .displayName("Value Field Name")
+            .description("The name of the field that will store the value. (The CQL type should be \"blob\")")
+            .required(true)
+            .addValidator(StandardValidators.NON_EMPTY_EL_VALIDATOR)
+            .build();
+
+    public static final PropertyDescriptor TTL = new PropertyDescriptor.Builder()
+            .name("cassandra-dmc-ttl")
+            .displayName("TTL")
+            .description("If configured, this will set a TTL (Time to Live) for each row inserted into the table so that " +
+                    "old cache items expire after a certain period of time.")
+            .addValidator(StandardValidators.TIME_PERIOD_VALIDATOR)
+            .required(false)
+            .build();
+
+    public static final List<PropertyDescriptor> DESCRIPTORS = Collections.unmodifiableList(Arrays.asList(
+        SESSION_PROVIDER, TABLE_NAME, KEY_FIELD_NAME, VALUE_FIELD_NAME, TTL
+    ));
+
+    private CassandraSessionProviderService sessionProviderService;
+    private String tableName;
+    private String keyField;
+    private String valueField;
+    private Long ttl;
+
+    private Session session;
+    private PreparedStatement deleteStatement;
+    private PreparedStatement existsStatement;
+    private PreparedStatement fetchStatement;
+    private PreparedStatement insertStatement;
+
+    @Override
+    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return DESCRIPTORS;
+    }
+
+    @OnEnabled
+    public void onEnabled(ConfigurationContext context) {
+        sessionProviderService = context.getProperty(SESSION_PROVIDER).asControllerService(CassandraSessionProviderService.class);
+        tableName = context.getProperty(TABLE_NAME).evaluateAttributeExpressions().getValue();
+        keyField = context.getProperty(KEY_FIELD_NAME).evaluateAttributeExpressions().getValue();
+        valueField = context.getProperty(VALUE_FIELD_NAME).evaluateAttributeExpressions().getValue();
+        if (context.getProperty(TTL).isSet()) {
+            ttl = context.getProperty(TTL).evaluateAttributeExpressions().asTimePeriod(TimeUnit.SECONDS);
+        }
+
+        session = sessionProviderService.getCassandraSession();
+
+        deleteStatement = session.prepare(createDeleteStatement(keyField, tableName));
+        existsStatement = session.prepare(createExistsQuery(keyField, tableName));
+        fetchStatement = session.prepare(createFetchQuery(keyField, valueField, tableName));
+        insertStatement = session.prepare(createInsertStatement(keyField, valueField, tableName, ttl));
+    }
+
+    @OnDisabled
+    public void onDisabled() {
+        session = null;
+        deleteStatement = null;
+        existsStatement = null;
+        fetchStatement = null;
+        insertStatement = null;
+    }
+
+    @Override
+    public <K, V> boolean putIfAbsent(K k, V v, Serializer<K> keySerializer, Serializer<V> valueSerializer) throws IOException {
+        if (containsKey(k, keySerializer)) {
+            return false;
+        } else {
+            put(k, v, keySerializer, valueSerializer);
+            return true;
+        }
+    }
+
+    @Override
+    public <K, V> V getAndPutIfAbsent(K k, V v, Serializer<K> keySerializer, Serializer<V> valueSerializer, Deserializer<V> deserializer) throws IOException {
+        V got = get(k, keySerializer, deserializer);
+        boolean wasPresent = putIfAbsent(k, v, keySerializer, valueSerializer);

Review comment:
       Shouldn't this be the inverse? `putIfAbsent` will return false if the value was present in the cache, so `wasPresent` should be true. The HBase versions do:
   
   ```
   final boolean wasAbsent = putIfAbsent(key, value, keySerializer, valueSerializer);
   
   if (! wasAbsent) return got;
   else return null;
   ```
   Would be good to add a unit test around this as well.




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