Merge pull request #88 from fe2s/branch-2.3

preparing for release 2.3.1

.gitignore

@@ -1,5 +1,6 @@
 hs_err_pid*.log
 nohup.out
+scalastyle-output.xml
 .idea
 *.iml
 **/.idea
@@ -34,4 +35,6 @@ project/plugins/project/
 build/*.jar
 
 # eclipse
-.project
+.project
+.classpath
+/.settings/

README.md

@@ -1,4 +1,5 @@
 [![Build Status](https://travis-ci.org/RedisLabs/spark-redis.svg)](https://travis-ci.org/RedisLabs/spark-redis)
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.redislabs/spark-redis/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.redislabs/spark-redis)
 
 # Spark-Redis
 A library for reading and writing data from and to [Redis](http://redis.io) with [Apache Spark](http://spark.apache.org/)
@@ -7,57 +8,60 @@ Spark-Redis provides access to all of Redis' data structures - String, Hash, Lis
 
 Spark-Redis also provides Spark-Streaming support.
 
-## Minimal requirements
-You'll need the the following to use Spark-Redis:
+## Version compatibility and branching
+
+The library has several branches, each corresponds to a different supported Spark version. For example, 'branch-2.3' works with any Spark 2.3.x version.
+The master branch contains the recent development for the next release.
+
+| Spark-Redis | Spark         | Redis            | Supported Scala Versions | 
+| ----------- | ------------- | ---------------- | ------------------------ |
+| 2.3         | 2.3           | >=2.9.0          | 2.11                     | 
+| 1.4         | 1.4           |                  | 2.10                     | 
 
- - Apache Spark v1.4.0
- - Scala v2.10.4
- - Jedis v2.7
- - Redis v2.8.12 or v3.0.3
 
 ## Known limitations
 
 * Java, Python and R API bindings are not provided at this time
-* The package was only tested with the following stack:
- - Apache Spark v1.4.0
- - Scala v2.10.4
- - Jedis v2.7 and v2.8 pre-release (see [below](#jedis-and-read-only-redis-cluster-slave-nodes) for details)
- - Redis v2.8.12 and v3.0.3
 
 ## Additional considerations
 This library is work in progress so the API may change before the official release.
 
 ## Getting the library
+
+### Maven
+
+```xml
+  <dependencies>
+    <dependency>
+      <groupId>com.redislabs</groupId>
+      <artifactId>spark-redis</artifactId>
+      <version>2.3.0</version>
+    </dependency>
+  </dependencies>
+```
+
+### Build form source
 You can download the library's source and build it:
 ```
 git clone https://github.com/RedisLabs/spark-redis.git
 cd spark-redis
 mvn clean package -DskipTests
 ```
 
-### Jedis and read-only Redis cluster slave nodes
-Jedis' current version - v2.7 - does not support reading from Redis cluster's slave nodes. This functionality will only be included in its upcoming version, v2.8.
-
-To use Spark-Redis with Redis cluster's slave nodes, the library's source includes a pre-release of Jedis v2.8 under the `with-slaves` branch. Switch to that branch by entering the following before running `mvn clean install`:
-```
-git checkout with-slaves
-```
-
 ## Using the library
 Add Spark-Redis to Spark with the `--jars` command line option. For example, use it from spark-shell, include it in the following manner:
 
 ```
-$ bin/spark-shell --jars <path-to>/spark-redis-<version>.jar,<path-to>/jedis-<version>.jar
+$ bin/spark-shell --jars <path-to>/spark-redis-<version>-jar-with-dependencies.jar
 
 Welcome to
       ____              __
      / __/__  ___ _____/ /__
     _\ \/ _ \/ _ `/ __/  '_/
-   /___/ .__/\_,_/_/ /_/\_\   version 1.4.0
+   /___/ .__/\_,_/_/ /_/\_\   version 2.3.1
       /_/
 
-Using Scala version 2.10.4 (OpenJDK 64-Bit Server VM, Java 1.7.0_79)
-...
+Using Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_101)
 ```
 
 The following sections contain code snippets that demonstrate the use of Spark-Redis. To use the sample code, you'll need to replace `your.redis.server` and `6379` with your Redis database's IP address or hostname and port, respectively.
@@ -262,7 +266,8 @@ import org.apache.spark.storage.StorageLevel
 import com.redislabs.provider.redis._
 val ssc = new StreamingContext(sc, Seconds(1))
 val redisStream = ssc.createRedisStream(Array("foo", "bar"), storageLevel = StorageLevel.MEMORY_AND_DISK_2)
-redisStream.print
+redisStream.print()
+ssc.start()
 ssc.awaitTermination()
 ```
 
@@ -275,7 +280,8 @@ import org.apache.spark.storage.StorageLevel
 import com.redislabs.provider.redis._
 val ssc = new StreamingContext(sc, Seconds(1))
 val redisStream = ssc.createRedisStreamWithoutListname(Array("foo", "bar"), storageLevel = StorageLevel.MEMORY_AND_DISK_2)
-redisStream.print
+redisStream.print()
+ssc.start()
 ssc.awaitTermination()
 ```
 

pom.xml

@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.redislabs</groupId>
 	<artifactId>spark-redis</artifactId>
-	<version>2.3.0-SNAPSHOT</version>
+	<version>2.3.1-SNAPSHOT</version>
 	<name>Spark-Redis</name>
 	<description>A Spark library for Redis</description>
 	<url>http://github.com/RedisLabs/spark-redis</url>

src/main/scala/com/redislabs/provider/redis/streaming/RedisInputDStream.scala

@@ -50,8 +50,8 @@ private class RedisReceiver[T: ClassTag](keys: Array[String],
       try {
         while(!isStopped) {
           val response = conn.blpop(2, key)
-          if (response == null) {
-
+          if (response == null || response.isEmpty) {
+            // no-op
           } else if (classTag[T] == classTag[String]) {
             store(response.get(1).asInstanceOf[T])
           } else if (classTag[T] == classTag[(String, String)]) {