[flink] Add FlinkRunnerRegistrar

Expose Flink runner and options via AuteService. AuteService will
at compile time populate META-INF/services so that Dataflow sdk
can seamlessly pick up FlinkRunner.

This closes apache#40.

runners/flink/runner/pom.xml

@@ -84,11 +84,6 @@
         </exclusion>
       </exclusions>
     </dependency>
-    <dependency>
-      <groupId>com.google.auto.service</groupId>
-      <artifactId>auto-service</artifactId>
-      <version>1.0-rc2</version>
-    </dependency>
     <!-- Test scoped -->
     <dependency>
       <groupId>com.google.cloud.dataflow</groupId>
@@ -121,6 +116,13 @@
       <version>1.9.5</version>
       <scope>test</scope>
     </dependency>
+    <!-- Optional Pipeline Registration -->
+    <dependency>
+      <groupId>com.google.auto.service</groupId>
+      <artifactId>auto-service</artifactId>
+      <version>1.0-rc2</version>
+      <optional>true</optional>
+    </dependency>
   </dependencies>
 
   <build>

runners/flink/runner/src/main/java/org/apache/beam/runners/flink/FlinkRunnerRegistrar.java

@@ -0,0 +1,56 @@
+/*
+ * 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.beam.runners.flink;
+
+import com.google.auto.service.AutoService;
+import org.apache.beam.runners.flink.FlinkPipelineOptions;
+import org.apache.beam.runners.flink.FlinkPipelineRunner;
+import com.google.cloud.dataflow.sdk.options.PipelineOptions;
+import com.google.cloud.dataflow.sdk.options.PipelineOptionsRegistrar;
+import com.google.cloud.dataflow.sdk.runners.PipelineRunner;
+import com.google.cloud.dataflow.sdk.runners.PipelineRunnerRegistrar;
+import com.google.common.collect.ImmutableList;
+
+
+/**
+ * AuteService registrar - will register FlinkRunner and FlinkOptions
+ * as possible pipeline runner services.
+ *
+ * It ends up in META-INF/services and gets picked up by Dataflow.
+ *
+ */
+public class FlinkRunnerRegistrar {
+  private FlinkRunnerRegistrar() { }
+
+  @AutoService(PipelineRunnerRegistrar.class)
+  public static class Runner implements PipelineRunnerRegistrar {
+    @Override
+    public Iterable<Class<? extends PipelineRunner<?>>> getPipelineRunners() {
+      return ImmutableList.<Class<? extends PipelineRunner<?>>>of(FlinkPipelineRunner.class);
+    }
+  }
+
+  @AutoService(PipelineOptionsRegistrar.class)
+  public static class Options implements PipelineOptionsRegistrar {
+    @Override
+    public Iterable<Class<? extends PipelineOptions>> getPipelineOptions() {
+      return ImmutableList.<Class<? extends PipelineOptions>>of(FlinkPipelineOptions.class);
+    }
+  }
+}