update spark

spark/2.3.1-yarn/README.md

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+# Deploy Spark On Yarn
+
+## Client
+
+```bash
+docker service create \
+	--name spark-client \
+	--hostname spark-client \
+	--network swarm-net \
+	--replicas 1 \
+	--detach true \
+	newnius/spark:2.3.1-yarn
+```
+
+## Validate installation
+
+#### spark-submit PI
+
+```bash
+spark-submit \
+	--master yarn \
+	--deploy-mode cluster \
+	--class org.apache.spark.examples.JavaSparkPi \
+	./examples/jars/spark-examples*.jar 100
+```
+
+#### spark-shell HDFS wordcount
+
+Enter `spark-shell --master yarn` to enter shell.
+
+```shell
+val lines = sc.textFile("hdfs://hadoop-master:8020/user/root/input")
+
+val words = lines.flatMap(_.split("\\s+"))
+
+val wc = words.map(word => (word, 1)).reduceByKey(_ + _)
+
+wc.collect()
+
+val cnt = words.map(word => 1).reduce(_ + _)
+```
+
+## Browse the web UI
+
+In Spark On Yarn mode, the spark jobs will occur in the Yarn web UI.