PublishMQTT.java

/*
 * 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.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.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.stream.io.StreamUtils;
import org.apache.nifi.util.StopWatch;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.io.InputStream;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

@SupportsBatching
@InputRequirement(Requirement.INPUT_REQUIRED)
@Tags({"publish", "MQTT", "IOT"})
@CapabilityDescription("Publishes a message to an MQTT topic")
@SeeAlso({ConsumeMQTT.class})
public class PublishMQTT extends AbstractMQTTProcessor {

    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'. " +
                    "Expression language is allowed in order to support publishing messages with different QoS but the end value of the property must be either '0', '1' or '2'. ")
            .required(true)
            .expressionLanguageSupported(true)
            .addValidator(QOS_VALIDATOR)
            .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(RETAIN_VALIDATOR)
            .build();

    public static final Relationship REL_SUCCESS = new Relationship.Builder()
            .name("success")
            .description("FlowFiles that are sent successfully to the destination are transferred to this relationship.")
            .build();
    public static final Relationship REL_FAILURE = new Relationship.Builder()
            .name("failure")
            .description("FlowFiles that failed to send to the destination are transferred to this relationship.")
            .build();

    private static final List<PropertyDescriptor> descriptors;
    private static final Set<Relationship> relationships;

    static {
        final List<PropertyDescriptor> innerDescriptorsList = getAbstractPropertyDescriptors();
        innerDescriptorsList.add(PROP_TOPIC);
        innerDescriptorsList.add(PROP_QOS);
        innerDescriptorsList.add(PROP_RETAIN);
        descriptors = Collections.unmodifiableList(innerDescriptorsList);

        final Set<Relationship> innerRelationshipsSet = new HashSet<>();
        innerRelationshipsSet.add(REL_SUCCESS);
        innerRelationshipsSet.add(REL_FAILURE);
        relationships = Collections.unmodifiableSet(innerRelationshipsSet);
    }

    @Override
    protected void init(final ProcessorInitializationContext context) {
        logger = getLogger();
    }

    @Override
    public Set<Relationship> getRelationships() {
        return relationships;
    }

    @Override
    public final List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return descriptors;
    }

    @OnScheduled
    public void onScheduled(final ProcessContext context) {
        buildClient(context);
    }

    @OnStopped
    public void onStop(final ProcessContext context) {
        mqttClientConnectLock.writeLock().lock();
        try {
            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);
        } finally {
            mqttClientConnectLock.writeLock().unlock();
        }
    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {
        FlowFile flowfile = session.get();
        if (flowfile == null) {
            return;
        }

        if(mqttClient == null || !mqttClient.isConnected()){
            logger.info("Was disconnected from client or was never connected, attempting to connect.");
            try {
                reconnect();
            } catch (MqttException e) {
                context.yield();
                session.transfer(flowfile, REL_FAILURE);
                logger.error("MQTT client is disconnected and re-connecting failed. Transferring FlowFile to fail and yielding", e);
                return;
            }
        }

        // get the MQTT topic
        String topic = context.getProperty(PROP_TOPIC).evaluateAttributeExpressions(flowfile).getValue();

        if (topic == null || topic.isEmpty()) {
            logger.warn("Evaluation of the topic property returned null or evaluated to be empty, routing to failure");
            session.transfer(flowfile, REL_FAILURE);
            return;
        }

        // do the read
        final byte[] messageContent = new byte[(int) flowfile.getSize()];
        session.read(flowfile, new InputStreamCallback() {
            @Override
            public void process(final InputStream in) throws IOException {
                StreamUtils.fillBuffer(in, messageContent, true);
            }
        });

        int qos = context.getProperty(PROP_QOS).evaluateAttributeExpressions(flowfile).asInteger();
        final MqttMessage mqttMessage = new MqttMessage(messageContent);
        mqttMessage.setQos(qos);
        mqttMessage.setPayload(messageContent);
        mqttMessage.setRetained(context.getProperty(PROP_RETAIN).evaluateAttributeExpressions(flowfile).asBoolean());

        try {
            mqttClientConnectLock.readLock().lock();
            final StopWatch stopWatch = new StopWatch(true);
            try {
                /*
                 * Underlying method waits for the message to publish (according to set QoS), so it executes synchronously:
                 *     MqttClient.java:361 aClient.publish(topic, message, null, null).waitForCompletion(getTimeToWait());
                 */
                mqttClient.publish(topic, mqttMessage);
            } finally {
                mqttClientConnectLock.readLock().unlock();
            }

            session.getProvenanceReporter().send(flowfile, broker, stopWatch.getElapsed(TimeUnit.MILLISECONDS));
            session.transfer(flowfile, REL_SUCCESS);
        } catch(MqttException me) {
            logger.error("Failed to publish message.", me);
            session.transfer(flowfile, REL_FAILURE);
        }
    }

    private class PublishMQTTCallback  implements MqttCallback {

        @Override
        public void connectionLost(Throwable cause) {
            logger.warn("Connection to " + broker + " lost", cause);
            try {
                reconnect();
            } catch (MqttException e) {
                logger.error("Connection to " + broker + " lost and re-connect failed");
            }
        }

        @Override
        public void messageArrived(String topic, MqttMessage message) throws Exception {
            logger.error("Message arrived to a PublishMQTT processor { topic:'" + topic +"; payload:"+ Arrays.toString(message.getPayload())+"}");
        }

        @Override
        public void deliveryComplete(IMqttDeliveryToken token) {
            // Client.publish waits for message to be delivered so this token will always have a null message and is useless in this application.
            logger.trace("Received 'delivery complete' message from broker for:" + token.toString());
        }
    }


    private void reconnect() throws MqttException {
        mqttClientConnectLock.writeLock().lock();
        try {
            if (!mqttClient.isConnected()) {
                setAndConnectClient(new PublishMQTTCallback());
                getLogger().info("Connecting to broker: " + broker);
            }
        } finally {
            mqttClientConnectLock.writeLock().unlock();
        }
    }
}