Github user JPercivall commented on a diff in the pull request:
https://github.com/apache/nifi/pull/392#discussion_r61949743
--- Diff:
nifi-nar-bundles/nifi-mqtt-bundle/nifi-mqtt-processors/src/main/java/org/apache/nifi/processors/mqtt/PublishMQTT.java
---
@@ -0,0 +1,288 @@
+/*
+ * 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.processors.mqtt;
+
+import org.apache.nifi.annotation.behavior.SupportsBatching;
+import org.apache.nifi.annotation.lifecycle.OnStopped;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.PropertyValue;
+import org.apache.nifi.expression.AttributeExpression;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.SeeAlso;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.logging.ProcessorLog;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessorInitializationContext;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.io.InputStreamCallback;
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
+
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.processors.mqtt.common.AbstractMQTTProcessor;
+import org.apache.nifi.ssl.SSLContextService;
+import org.apache.nifi.stream.io.StreamUtils;
+import org.eclipse.paho.client.mqttv3.MqttCallback;
+import org.eclipse.paho.client.mqttv3.MqttClient;
+import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
+import org.eclipse.paho.client.mqttv3.MqttException;
+import org.eclipse.paho.client.mqttv3.MqttMessage;
+import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
+import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Properties;
+import java.util.Set;
+import java.io.InputStream;
+import java.io.IOException;
+
+@SupportsBatching
+@InputRequirement(Requirement.INPUT_REQUIRED)
+@Tags({"publish", "MQTT", "IOT"})
+@CapabilityDescription("Publishes a message to an MQTT topic")
+@SeeAlso({SubscribeMQTT.class})
+public class PublishMQTT extends AbstractMQTTProcessor {
+
+ private String broker;
+ private MemoryPersistence persistence = new MemoryPersistence();
+ private MqttClient mqttClient;
+ private final Object mqttClientLock = new Object();
+
+ public static final PropertyDescriptor PROP_TOPIC = new
PropertyDescriptor.Builder()
+ .name("Topic")
+ .description("The topic to publish the message to.")
+ .expressionLanguageSupported(true)
+ .required(true)
+
.addValidator(StandardValidators.createAttributeExpressionLanguageValidator(AttributeExpression.ResultType.STRING,
true))
+ .addValidator(StandardValidators.NON_BLANK_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor PROP_QOS = new
PropertyDescriptor.Builder()
+ .name("Quality of Service(QoS)")
+ .description("The Quality of Service(QoS) to send the message
with. Accepts three values '0', '1' and '2'; '0' for 'at most once', '1' for
'at least once', '2' for 'exactly once'.")
+ .required(true)
+ .expressionLanguageSupported(true)
+ .addValidator(QoSValidator)
+ .build();
+
+ public static final PropertyDescriptor PROP_RETAIN = new
PropertyDescriptor.Builder()
+ .name("Retain Message")
+ .description("Whether or not the retain flag should be set on
the MQTT message.")
+ .required(true)
+ .expressionLanguageSupported(true)
+ .addValidator(RetainValidator)
+ .build();
+
+ public static final PropertyDescriptor PROP_TIMEOUT = new
PropertyDescriptor.Builder()
+ .name("QoS Timeout")
+ .description("How many milliseconds to wait for the broker to
acknowledge delivery of a message before routing the message back to the source
queue for retry. Only applicable " +
+ "when QoS is 1 or 2")
+ .required(true)
+
.addValidator(StandardValidators.NON_NEGATIVE_INTEGER_VALIDATOR)
+ .build();
+
+ private List<PropertyDescriptor> descriptors;
+
+ public static final Relationship REL_SUCCESS = new
Relationship.Builder()
+ .name("success")
+ .description("FlowFiles that are sent successfully to the
destination are sent out this relationship.")
+ .build();
+ public static final Relationship REL_FAILURE = new
Relationship.Builder()
+ .name("failure")
+ .description("FlowFiles that failed to send to the destination
are sent out this relationship.")
+ .build();
+
+ private Set<Relationship> relationships;
+ private ProcessorLog logger;
+ private MqttConnectOptions connOpts;
+
+ @Override
+ protected void init(final ProcessorInitializationContext context) {
+ logger = getLogger();
+ final List<PropertyDescriptor> descriptors =
getAbstractPropertyDescriptors();
+ descriptors.add(PROP_TOPIC);
+ descriptors.add(PROP_QOS);
+ descriptors.add(PROP_RETAIN);
+ descriptors.add(PROP_TIMEOUT);
+ this.descriptors = Collections.unmodifiableList(descriptors);
+
+ final Set<Relationship> relationships = new
HashSet<Relationship>();
+ relationships.add(REL_SUCCESS);
+ relationships.add(REL_FAILURE);
+ this.relationships = Collections.unmodifiableSet(relationships);
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+ return this.relationships;
+ }
+
+ @Override
+ public final List<PropertyDescriptor>
getSupportedPropertyDescriptors() {
+ return descriptors;
+ }
+
+ @OnScheduled
+ public void onScheduled(final ProcessContext context) {
+ try {
+ broker = context.getProperty(PROP_BROKER_URI).getValue();
+ String clientID =
context.getProperty(PROP_CLIENTID).getValue();
+
+ connOpts = new MqttConnectOptions();
+ connOpts.setCleanSession(true);
+
+ PropertyValue sslProp =
context.getProperty(PROP_SSL_CONTEXT_SERVICE);
+ if (sslProp.isSet()) {
+ Properties sslProps =
transformSSLContextService((SSLContextService) sslProp.asControllerService());
+ connOpts.setSSLProperties(sslProps);
+ }
+
+ PropertyValue lastWillTopicProp =
context.getProperty(PROP_LAST_WILL_TOPIC);
+ if (lastWillTopicProp.isSet()){
+ PropertyValue lastWillMessage =
context.getProperty(PROP_LAST_WILL_TOPIC);
+ PropertyValue lastWillRetain =
context.getProperty(PROP_LAST_WILL_TOPIC);
+ connOpts.setWill(lastWillTopicProp.getValue(),
lastWillMessage.getValue().getBytes(), LAST_WILL_QOS, lastWillRetain.isSet() ?
lastWillRetain.asBoolean() : false);
+ }
+
+ PropertyValue usernameProp =
context.getProperty(PROP_USERNAME);
+ if(usernameProp.isSet()) {
+ connOpts.setUserName(usernameProp.getValue());
+
connOpts.setPassword(context.getProperty(PROP_PASSWORD).getValue().toCharArray());
+ }
+
+ synchronized (mqttClientLock) {
+ mqttClient = new MqttClient(broker, clientID, persistence);
+
+ mqttClient.setCallback(new PublishMQTTCallback());
+ getLogger().info("Connecting to broker: " + broker);
+ mqttClient.connect(connOpts);
+ }
+ } catch(MqttException me) {
+ logger.error("Failed to initialize the connection to the
"+me.getMessage());
+ }
+ }
+
+ @OnStopped
+ public void onStop(final ProcessContext context) {
+ try {
+ synchronized (mqttClientLock) {
+ if (mqttClient != null && mqttClient.isConnected()) {
+ mqttClient.disconnect();
+ }
+ }
+ logger.info("Disconnected the MQTT client.");
+ } catch(MqttException me) {
+ logger.error("Failed when disconnecting the MQTT client.", me);
+ }
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSession session) throws ProcessException {
+ FlowFile flowfile = session.get();
+ if (flowfile == null) {
+ return;
+ }
--- End diff --
PublishMQTT won't spin "without any delay (yield)" because it requires
input and under normal circumstances will only get triggered by the controller
when there are flowfiles to process. This check is more or less a fail-safe.
Yielding is for when there is something wrong with the processor for which
waiting may help resolve (failing to reconnect). I don't see this as an
instance that warrants yielding.
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