Add EM plan and optimizer packages.

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/api/DataInfo.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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 edu.snu.cay.services.em.optimizer.api;
+
+/**
+ * Information about a dataType stored at an Evaluator.
+ */
+public interface DataInfo {
+
+  /**
+   * @return the dataType
+   */
+  String getDataType();
+
+  /**
+   * @return number of units stored with the dataType
+   */
+  int getNumUnits();
+}

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/api/EvaluatorParameters.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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 edu.snu.cay.services.em.optimizer.api;
+
+import java.util.Collection;
+
+/**
+ * The current state of an evaluator, represented as a set of input parameters for an optimizer.
+ */
+public interface EvaluatorParameters {
+  /**
+   * @return the evaluator's context ID
+   */
+  String getId();
+
+  /**
+   * @return information about all data on the evaluator
+   */
+  Collection<DataInfo> getDataInfos();
+}

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/api/Optimizer.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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 edu.snu.cay.services.em.optimizer.api;
+
+import edu.snu.cay.services.em.plan.api.Plan;
+
+import java.util.Collection;
+
+/**
+ * Given the current state of evaluators (as parameters) and available resources (as the number of available
+ * evaluators), the optimizer generates an optimized plan.
+ */
+public interface Optimizer {
+  /**
+   * @param activeEvaluators all currently active evaluators and their parameters
+   * @param availableEvaluators the total number of evaluators available for optimization.
+   *     If availableEvaluators < activeEvaluators.size(), the optimized plan must delete evaluators.
+   *     If availableEvaluators > activeEvaluators.size(), the optimized plan may add evaluators.
+   * @return the optimized plan
+   */
+  Plan optimize(Collection<EvaluatorParameters> activeEvaluators, int availableEvaluators);
+}

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/api/package-info.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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.
+ */
+/**
+ * An optimizer that takes the current state of evaluators (as parameters) and available resources
+ * (as the number of available evaluators), and generates a plan {@link edu.snu.cay.services.em.plan.api}.
+ */
+package edu.snu.cay.services.em.optimizer.api;

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/impl/DataInfoImpl.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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 edu.snu.cay.services.em.optimizer.impl;
+
+import edu.snu.cay.services.em.optimizer.api.DataInfo;
+
+/**
+ * A plain-old-data implementation of DataInfo.
+ */
+public final class DataInfoImpl implements DataInfo {
+  private final String dataType;
+  private final int numUnits;
+
+  public DataInfoImpl(final String dataType, final int numUnits) {
+    this.dataType = dataType;
+    this.numUnits = numUnits;
+  }
+
+  @Override
+  public String getDataType() {
+    return dataType;
+  }
+
+  @Override
+  public int getNumUnits() {
+    return numUnits;
+  }
+
+  @Override
+  public String toString() {
+    return "DataInfoImpl{" +
+        "dataType='" + dataType + '\'' +
+        ", numUnits=" + numUnits +
+        '}';
+  }
+}

services/elastic-memory/src/main/java/edu/snu/cay/services/em/optimizer/impl/EvaluatorParametersImpl.java

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+/*
+ * Copyright (C) 2015 Seoul National University
+ *
+ * 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 edu.snu.cay.services.em.optimizer.impl;
+
+import edu.snu.cay.services.em.optimizer.api.DataInfo;
+import edu.snu.cay.services.em.optimizer.api.EvaluatorParameters;
+
+import java.util.Collection;
+
+/**
+ * A plain-old-data implementation of EvaluatorParameters.
+ */
+public final class EvaluatorParametersImpl implements EvaluatorParameters {
+  private final String id;
+  private final Collection<DataInfo> dataInfos;
+
+  public EvaluatorParametersImpl(final String id, final Collection<DataInfo> dataInfos) {
+    this.id = id;
+    this.dataInfos = dataInfos;
+  }
+
+  @Override
+  public String getId() {
+    return id;
+  }
+
+  @Override
+  public Collection<DataInfo> getDataInfos() {
+    return dataInfos;
+  }
+}