SAMZA-1788: Add LocationIdProvider abstraction.

samza-api/src/main/java/org/apache/samza/runtime/LocationId.java

@@ -0,0 +1,60 @@
+/*
+ * 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.samza.runtime;
+
+import java.util.Objects;
+
+/**
+ * Represents the physical execution environment of the StreamProcessor.
+ * All the stream processors which run from a LocationId should be able to share (read/write)
+ * their local state stores.
+ */
+public class LocationId {
+  private final String locationId;
+
+  public LocationId(String locationId) {
+    if (locationId == null) {
+      throw new IllegalArgumentException("LocationId cannot be null");
+    }
+    this.locationId = locationId;
+  }
+
+  public String getId() {
+    return this.locationId;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+    LocationId that = (LocationId) o;
+
+    return Objects.equals(locationId, that.locationId);
+  }
+
+  @Override
+  public int hashCode() {
+    return locationId.hashCode();
+  }
+
+  @Override
+  public String toString() {
+    return locationId;
+  }
+}

samza-api/src/main/java/org/apache/samza/runtime/LocationIdProvider.java

@@ -0,0 +1,28 @@
+/*
+ * 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.samza.runtime;
+
+/**
+ * Generates {@link LocationId} that uniquely identifies the
+ * execution environment of a stream processor.
+ */
+public interface LocationIdProvider {
+
+  LocationId getLocationId();
+}

samza-api/src/main/java/org/apache/samza/runtime/LocationIdProviderFactory.java

@@ -0,0 +1,28 @@
+/*
+ * 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.samza.runtime;
+
+import org.apache.samza.config.Config;
+
+/**
+ * Builds the {@link LocationIdProvider}.
+ */
+public interface LocationIdProviderFactory {
+  LocationIdProvider getLocationIdProvider(Config config);
+}

samza-core/src/main/java/org/apache/samza/runtime/DefaultLocationIdProviderFactory.java

@@ -0,0 +1,32 @@
+/*
+ * 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.samza.runtime;
+
+import org.apache.samza.config.Config;
+import org.apache.samza.util.Util;
+
+/**
+ * Uses the address of the local host for generating {@link LocationId}. 
+ */ 
+public class DefaultLocationIdProviderFactory implements LocationIdProviderFactory {
+  @Override
+  public LocationIdProvider getLocationIdProvider(Config config) {
+    return ()  -> new LocationId(Util.getLocalHost().getHostName());
+  }
+}

samza-core/src/main/scala/org/apache/samza/config/JobConfig.scala

@@ -23,6 +23,7 @@ package org.apache.samza.config
 import java.io.File
 
 import org.apache.samza.container.grouper.stream.GroupByPartitionFactory
+import org.apache.samza.runtime.DefaultLocationIdProviderFactory
 import org.apache.samza.util.Logging
 
 object JobConfig {
@@ -77,6 +78,8 @@ object JobConfig {
   val DEFAULT_MONITOR_PARTITION_CHANGE_FREQUENCY_MS = 300000
   val JOB_SECURITY_MANAGER_FACTORY = "job.security.manager.factory"
 
+  val LOCATION_ID_PROVIDER_FACTORY = "locationid.provider.factory"
+
   // Processor Config Constants
   val PROCESSOR_ID = "processor.id"
   val PROCESSOR_LIST = "processor.list"
@@ -161,6 +164,8 @@ class JobConfig(config: Config) extends ScalaMapConfig(config) with Logging {
 
   def getSystemStreamPartitionGrouperFactory = getOption(JobConfig.SSP_GROUPER_FACTORY).getOrElse(classOf[GroupByPartitionFactory].getCanonicalName)
 
+  def getLocationIdProviderFactory = getOption(JobConfig.LOCATION_ID_PROVIDER_FACTORY).getOrElse(classOf[DefaultLocationIdProviderFactory].getCanonicalName)
+
   def getSecurityManagerFactory = getOption(JobConfig.JOB_SECURITY_MANAGER_FACTORY)
 
   def getSSPMatcherClass = getOption(JobConfig.SSP_MATCHER_CLASS)