Add example and test for hadoopDistCache

build.sbt

@@ -307,6 +307,7 @@ lazy val scioExamples: Project = Project(
   scioCore,
   scioBigtable,
   scioSchemas,
+  scioHdfs,
   scioTest % "test"
 )
 

scio-examples/src/main/scala/com/spotify/scio/examples/extra/HadoopDistCacheExample.scala

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2016 Spotify AB.
+ *
+ * Licensed 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 com.spotify.scio.examples.extra
+
+import com.spotify.scio._
+import com.spotify.scio.bigquery._
+import com.spotify.scio.hdfs._
+import com.spotify.scio.examples.common.ExampleData
+import org.joda.time.Instant
+
+/*
+SBT
+runMain
+  com.spotify.scio.examples.extra.DistCacheExample
+  --project=[PROJECT] --runner=DataflowPipelineRunner --zone=[ZONE]
+  --stagingLocation=gs://[BUCKET]/path/to/staging
+  --input=gs://dataflow-samples/wikipedia_edits/wiki_data-*.json
+  --output=gs://[BUCKET]/[PATH]/dist_cache_example
+*/
+
+// Use distributed cache inside a job
+object HadoopDistCacheExample {
+  def main(cmdlineArgs: Array[String]): Unit = {
+    val (sc, args) = ContextAndArgs(cmdlineArgs)
+
+    // declare a HDFS file to be distributed to all workers and logic to load the file
+    val dc = sc.hadoopDistCache(args.getOrElse("months", ExampleData.MONTHS)) { f =>
+      scala.io.Source.fromFile(f).getLines().map { s =>
+        val t = s.split(" ")
+        (t(0).toInt, t(1))
+      }.toMap
+    }
+
+    sc
+      .tableRowJsonFile(args.getOrElse("input", ExampleData.EXPORTED_WIKI_TABLE))
+      .map(row => new Instant(row.getLong("timestamp") * 1000L).toDateTime.getMonthOfYear)
+      .countByValue
+      // distributed cache available inside a transform
+      .map(kv => dc().getOrElse(kv._1, "unknown") + " " + kv._2)
+      .saveAsTextFile(args("output"))
+
+    sc.close()
+  }
+}

scio-examples/src/test/scala/com/spotify/scio/examples/extra/HadoopDistCacheTest.scala

@@ -0,0 +1,33 @@
+package com.spotify.scio.examples.extra
+
+import com.spotify.scio.bigquery.TableRow
+import com.spotify.scio.examples.common.ExampleData
+import com.spotify.scio.testing._
+import org.joda.time.format.DateTimeFormat
+
+
+class HadoopDistCacheTest extends PipelineSpec {
+  val fmt = DateTimeFormat.forPattern("yyyyMMdd")
+  def d2t(date: String): Long = fmt.parseDateTime(date).getMillis / 1000
+
+  val in = Seq(
+    TableRow("timestamp" -> d2t("20150101")),
+    TableRow("timestamp" -> d2t("20150102")),
+    TableRow("timestamp" -> d2t("20150103")),
+    TableRow("timestamp" -> d2t("20150201")),
+    TableRow("timestamp" -> d2t("20150202")),
+    TableRow("timestamp" -> d2t("20150301")))
+
+  val distCache = Map(1 -> "Jan", 2 -> "Feb", 3 -> "Mar")
+
+  val expected = Seq("Jan 3", "Feb 2", "Mar 1")
+
+  "HadoopDistCacheExample" should "work" in {
+    JobTest[com.spotify.scio.examples.extra.HadoopDistCacheExample.type]
+      .args("--output=out.txt")
+      .input(TableRowJsonIO(ExampleData.EXPORTED_WIKI_TABLE), in)
+      .distCache(DistCacheIO("hdfs://dataflow-samples/samples/misc/months.txt"), distCache)
+      .output(TextIO("out.txt"))(_ should containInAnyOrder(expected))
+      .run()
+  }
+}