Github user lresende commented on a diff in the pull request:
https://github.com/apache/bahir/pull/13#discussion_r73405744
--- Diff:
sql-streaming-mqtt/src/main/scala/org/apache/bahir/sql/streaming/mqtt/MQTTStreamSource.scala
---
@@ -0,0 +1,191 @@
+/*
+ * 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.bahir.sql.streaming.mqtt
+
+import java.sql.Timestamp
+import java.text.SimpleDateFormat
+import java.util.Calendar
+import java.util.concurrent.CountDownLatch
+
+import scala.collection.concurrent.TrieMap
+import scala.collection.mutable.ArrayBuffer
+import scala.util.{Failure, Success, Try}
+
+import org.apache.bahir.utils.Logging
+import org.eclipse.paho.client.mqttv3._
+import org.eclipse.paho.client.mqttv3.persist.{MemoryPersistence,
MqttDefaultFilePersistence}
+
+import org.apache.spark.sql.{DataFrame, SQLContext}
+import org.apache.spark.sql.execution.streaming.{LongOffset, Offset,
Source}
+import org.apache.spark.sql.sources.{DataSourceRegister,
StreamSourceProvider}
+import org.apache.spark.sql.types.{StringType, StructField, StructType,
TimestampType}
+
+
+object MQTTStreamConstants {
+
+ val DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
+
+ val SCHEMA_DEFAULT = StructType(StructField("value", StringType)
+ :: StructField("timestamp", TimestampType) :: Nil)
+}
+
+class MQTTTextStreamSource(brokerUrl: String, persistence:
MqttClientPersistence,
+ topic: String, clientId: String, messageParser: Array[Byte] =>
(String, Timestamp),
+ sqlContext: SQLContext) extends Source with Logging {
+
+ override def schema: StructType = MQTTStreamConstants.SCHEMA_DEFAULT
+
+ private val store = new LocalMessageStore(persistence,
sqlContext.sparkContext.getConf)
+
+ private val messages = new TrieMap[Int, (String, Timestamp)]
+
+ private val initLock = new CountDownLatch(1)
+
+ private var offset = 0
+
+ private var client: MqttClient = _
+
+ private def fetchLastProcessedOffset(): Int = {
+ Try(store.maxProcessedOffset) match {
+ case Success(x) =>
+ log.info(s"Recovering from last stored offset $x")
+ x
+ case Failure(e) => 0
+ }
+ }
+
+ initialize()
+ private def initialize(): Unit = {
+
+ client = new MqttClient(brokerUrl, clientId, persistence)
+ val mqttConnectOptions: MqttConnectOptions = new MqttConnectOptions()
+ mqttConnectOptions.setAutomaticReconnect(true)
+ // This is required to support recovery. TODO: configurable ?
+ mqttConnectOptions.setCleanSession(false)
+
+ val callback = new MqttCallbackExtended() {
+
+ override def messageArrived(topic_ : String, message: MqttMessage):
Unit = synchronized {
+ initLock.await() // Wait for initialization to complete.
+ val temp = offset + 1
+ messages.put(temp, messageParser(message.getPayload))
+ offset = temp
+ log.trace(s"Message arrived, $topic_ $message")
+ }
+
+ override def deliveryComplete(token: IMqttDeliveryToken): Unit = {
+ }
+
+ override def connectionLost(cause: Throwable): Unit = {
+ log.warn("Connection to mqtt server lost.", cause)
+ }
+
+ override def connectComplete(reconnect: Boolean, serverURI: String):
Unit = {
+ log.info(s"Connect complete $serverURI. Is it a reconnect?:
$reconnect")
+ }
+ }
+ client.setCallback(callback)
+ client.connect(mqttConnectOptions)
+ client.subscribe(topic)
+ // It is not possible to initialize offset without `client.connect`
+ offset = fetchLastProcessedOffset()
+ initLock.countDown() // Release.
+ }
+
+ /** Stop this source and free any resources it has allocated. */
+ override def stop(): Unit = {
+ client.disconnect()
+ persistence.close()
+ client.close()
+ }
+
+ /** Returns the maximum available offset for this source. */
+ override def getOffset: Option[Offset] = {
+ if (offset == 0) {
+ None
+ } else {
+ Some(LongOffset(offset))
+ }
+ }
+
+ /**
+ * Returns the data that is between the offsets (`start`, `end`]. When
`start` is `None` then
+ * the batch should begin with the first available record. This method
must always return the
+ * same data for a particular `start` and `end` pair.
+ */
+ override def getBatch(start: Option[Offset], end: Offset): DataFrame =
synchronized {
+ val startIndex =
start.getOrElse(LongOffset(0L)).asInstanceOf[LongOffset].offset.toInt
+ val endIndex = end.asInstanceOf[LongOffset].offset.toInt
+ val data: ArrayBuffer[(String, Timestamp)] = ArrayBuffer.empty
+ // Move consumed messages to persistent store.
+ (startIndex + 1 to endIndex).foreach { id =>
+ val element: (String, Timestamp) = messages.getOrElse(id,
store.retrieve(id))
+ data += element
+ store.store(id, element)
+ messages.remove(id, element)
+ }
+ log.trace(s"Get Batch invoked, ${data.mkString}")
+ import sqlContext.implicits._
+ data.toDF("value", "timestamp")
+ }
+
+}
+
+class MQTTStreamSourceProvider extends StreamSourceProvider with
DataSourceRegister with Logging {
+
+ override def sourceSchema(sqlContext: SQLContext, schema:
Option[StructType],
+ providerName: String, parameters: Map[String, String]): (String,
StructType) = {
+ ("mqtt", MQTTStreamConstants.SCHEMA_DEFAULT)
+ }
+
+ override def createSource(sqlContext: SQLContext, metadataPath: String,
+ schema: Option[StructType], providerName: String, parameters:
Map[String, String]): Source = {
+
+ def e(s: String) = new IllegalArgumentException(s)
+
+ val brokerUrl: String = parameters.getOrElse("brokerUrl",
parameters.getOrElse("path",
+ throw e("Please provide a `brokerUrl` by specifying path or
.options(\"brokerUrl\",...)")))
+
+
+ val persistence: MqttClientPersistence = parameters.get("persistence")
match {
+ case Some("memory") => new MemoryPersistence()
+ case _ => val localStorage: Option[String] =
parameters.get("localStorage")
+ localStorage match {
+ case Some(x) => new MqttDefaultFilePersistence(x)
+ case None => new MqttDefaultFilePersistence()
+ }
+ }
+
+ val messageParserWithTimeStamp = (x: Array[Byte]) => (new String(x),
Timestamp.valueOf(
+
MQTTStreamConstants.DATE_FORMAT.format(Calendar.getInstance().getTime)))
--- End diff --
An option here would be to use something like Spark DateTimeUtils which
handles usage of these classes in ThreadLocal to avoid concurrency issues
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