add ML model get API

Signed-off-by: Xun Zhang <xunzh@amazon.com>

common/build.gradle

@@ -14,6 +14,8 @@ dependencies {
     compileOnly group: 'org.opensearch', name: 'opensearch', version: "${opensearch_version}"
     compile group: 'org.reflections', name: 'reflections', version: '0.9.12'
     testCompile group: 'junit', name: 'junit', version: '4.12'
+    compile "org.opensearch.client:opensearch-rest-client:${opensearch_version}"
+    compile "org.opensearch:common-utils:${common_utils_version}"
 }
 
 jacocoTestReport {

common/src/main/java/org/opensearch/ml/common/parameter/MLModel.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.common.parameter;
+
+import lombok.Builder;
+import lombok.Getter;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.io.stream.StreamOutput;
+import org.opensearch.common.xcontent.ToXContentObject;
+import org.opensearch.common.xcontent.XContentBuilder;
+import org.opensearch.common.xcontent.XContentParser;
+import org.opensearch.commons.authuser.User;
+
+import java.io.IOException;
+import java.util.Base64;
+
+import static org.opensearch.common.xcontent.XContentParserUtils.ensureExpectedToken;
+
+@Getter
+public class MLModel implements ToXContentObject {
+    public static final String ALGORITHM = "algorithm";
+    public static final String MODEL_NAME = "name";
+    public static final String MODEL_VERSION = "version";
+    public static final String MODEL_CONTENT = "content";
+    public static final String USER = "user";
+
+    private String name;
+    private FunctionName algorithm;
+    private Integer version;
+    private String content;
+    private User user;
+
+    @Builder
+    public MLModel(String name, FunctionName algorithm, Integer version, String content, User user) {
+        this.name = name;
+        this.algorithm = algorithm;
+        this.version = version;
+        this.content = content;
+        this.user = user;
+    }
+
+    public MLModel(FunctionName algorithm, Model model) {
+        this(model.getName(), algorithm, model.getVersion(), Base64.getEncoder().encodeToString(model.getContent()), null);
+    }
+
+    public MLModel(StreamInput input) throws IOException{
+        name = input.readOptionalString();
+        algorithm = input.readEnum(FunctionName.class);
+        version = input.readInt();
+        content = input.readOptionalString();
+        if (input.readBoolean()) {
+            this.user = new User(input);
+        } else {
+            user = null;
+        }
+    }
+
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeOptionalString(name);
+        out.writeEnum(algorithm);
+        out.writeInt(version);
+        out.writeOptionalString(content);
+        if (user != null) {
+            out.writeBoolean(true); // user exists
+            user.writeTo(out);
+        } else {
+            out.writeBoolean(false); // user does not exist
+        }
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject();
+        if (name != null) {
+            builder.field(MODEL_NAME, name);
+        }
+        if (algorithm != null) {
+            builder.field(ALGORITHM, algorithm);
+        }
+        if (version != null) {
+            builder.field(MODEL_VERSION, version);
+        }
+        if (content != null) {
+            builder.field(MODEL_CONTENT, content);
+        }
+        if (user != null) {
+            builder.field(USER, user);
+        }
+        builder.endObject();
+        return builder;
+    }
+
+    public static MLModel parse(XContentParser parser, String taskId) throws IOException {
+        String name = null;
+        FunctionName algorithm = null;
+        Integer version = null;
+        String content = null;
+        User user = null;
+
+        ensureExpectedToken(XContentParser.Token.START_OBJECT, parser.currentToken(), parser);
+        while (parser.nextToken() != XContentParser.Token.END_OBJECT) {
+            String fieldName = parser.currentName();
+            parser.nextToken();
+
+            switch (fieldName) {
+                case MODEL_NAME:
+                    name = parser.text();
+                    break;
+                case MODEL_CONTENT:
+                    content = parser.text();
+                    break;
+                case MODEL_VERSION:
+                    version = parser.intValue();
+                    break;
+                case USER:
+                    user = User.parse(parser);
+                    break;
+                case ALGORITHM:
+                    algorithm = FunctionName.valueOf(parser.text());
+                    break;
+                default:
+                    break;
+            }
+        }
+        return MLModel.builder()
+                .name(name)
+                .algorithm(algorithm)
+                .version(version)
+                .content(content)
+                .user(user)
+                .build();
+        }
+
+    public static MLModel fromStream(StreamInput in) throws IOException {
+        MLModel mlModel = new MLModel(in);
+        return mlModel;
+    }
+}

ml-algorithms/src/main/java/org/opensearch/ml/engine/Model.java → common/src/main/java/org/opensearch/ml/common/parameter/Model.java

@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-package org.opensearch.ml.engine;
+package org.opensearch.ml.common.parameter;
 
 import lombok.Data;
 

common/src/main/java/org/opensearch/ml/common/transport/model/MLModelGetAction.java

@@ -0,0 +1,15 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.common.transport.model;
+
+import org.opensearch.action.ActionType;
+
+public class MLModelGetAction extends ActionType<MLModelGetResponse> {
+    public static final MLModelGetAction INSTANCE = new MLModelGetAction();
+    public static final String NAME = "cluster:admin/opensearch/ml/models/get";
+
+    private MLModelGetAction() { super(NAME, MLModelGetResponse::new);}
+}

common/src/main/java/org/opensearch/ml/common/transport/model/MLModelGetRequest.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.common.transport.model;
+
+import lombok.AccessLevel;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.ToString;
+import lombok.experimental.FieldDefaults;
+import org.opensearch.action.ActionRequest;
+import org.opensearch.action.ActionRequestValidationException;
+import org.opensearch.common.io.stream.InputStreamStreamInput;
+import org.opensearch.common.io.stream.OutputStreamStreamOutput;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.io.stream.StreamOutput;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+
+import static org.opensearch.action.ValidateActions.addValidationError;
+
+@Getter
+@FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE)
+@ToString
+public class MLModelGetRequest extends ActionRequest {
+
+    String modelId;
+
+    @Builder
+    public MLModelGetRequest(String modelId) {
+        this.modelId = modelId;
+    }
+
+    public MLModelGetRequest(StreamInput in) throws IOException {
+        super(in);
+        this.modelId = in.readOptionalString();
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+        out.writeOptionalString(this.modelId);
+    }
+
+    @Override
+    public ActionRequestValidationException validate() {
+        ActionRequestValidationException exception = null;
+
+        if (this.modelId == null) {
+            exception = addValidationError("ML model id can't be null", exception);
+        }
+
+        return exception;
+    }
+
+    public static MLModelGetRequest fromActionRequest(ActionRequest actionRequest) {
+        if (actionRequest instanceof MLModelGetRequest) {
+            return (MLModelGetRequest)actionRequest;
+        }
+
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
+             OutputStreamStreamOutput osso = new OutputStreamStreamOutput(baos)) {
+            actionRequest.writeTo(osso);
+            try (StreamInput input = new InputStreamStreamInput(new ByteArrayInputStream(baos.toByteArray()))) {
+                return new MLModelGetRequest(input);
+            }
+        } catch (IOException e) {
+            throw new UncheckedIOException("failed to parse ActionRequest into MLModelGetRequest", e);
+        }
+    }
+}

common/src/main/java/org/opensearch/ml/common/transport/model/MLModelGetResponse.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.common.transport.model;
+
+import lombok.Builder;
+import org.opensearch.action.ActionResponse;
+import org.opensearch.common.io.stream.InputStreamStreamInput;
+import org.opensearch.common.io.stream.OutputStreamStreamOutput;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.io.stream.StreamOutput;
+import org.opensearch.common.xcontent.ToXContentObject;
+import org.opensearch.common.xcontent.XContentBuilder;
+import org.opensearch.ml.common.parameter.FunctionName;
+import org.opensearch.ml.common.parameter.MLModel;
+import org.opensearch.ml.common.parameter.MLOutput;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+
+public class MLModelGetResponse extends ActionResponse implements ToXContentObject {
+
+    MLModel mlModel;
+
+    @Builder
+    public MLModelGetResponse(MLModel mlModel) {
+        this.mlModel = mlModel;
+    }
+
+
+    public MLModelGetResponse(StreamInput in) throws IOException {
+        super(in);
+        mlModel = mlModel.fromStream(in);
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException{
+        mlModel.writeTo(out);
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder xContentBuilder, Params params) throws IOException {
+        return mlModel.toXContent(xContentBuilder, params);
+    }
+}

common/src/test/java/org/opensearch/ml/common/TestHelper.java

@@ -6,6 +6,7 @@
 package org.opensearch.ml.common;
 
 import org.opensearch.common.Strings;
+import org.opensearch.common.bytes.BytesReference;
 import org.opensearch.common.xcontent.LoggingDeprecationHandler;
 import org.opensearch.common.xcontent.NamedXContentRegistry;
 import org.opensearch.common.xcontent.ToXContent;
@@ -43,4 +44,8 @@ public static <T> void testParseFromString(ToXContentObject obj, String jsonStr,
         T parsedObj = function.apply(parser);
         obj.equals(parsedObj);
     }
+
+    public static String xContentBuilderToString(XContentBuilder builder) {
+        return BytesReference.bytes(builder).utf8ToString();
+    }
 }

common/src/test/java/org/opensearch/ml/common/parameter/MLModelTests.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.common.parameter;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.xcontent.XContentBuilder;
+import org.opensearch.common.xcontent.XContentType;
+import org.opensearch.commons.authuser.User;
+import org.opensearch.ml.common.TestHelper;
+
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+import static org.opensearch.common.xcontent.ToXContent.EMPTY_PARAMS;
+
+public class MLModelTests {
+
+    MLModel mlModel;
+    @Before
+    public void setUp() {
+        FunctionName algorithm = FunctionName.KMEANS;
+        User user  = new User();
+        mlModel = MLModel.builder()
+                .name("some model")
+                .algorithm(algorithm)
+                .version(1)
+                .content("some content")
+                .user(user)
+                .build();
+    }
+
+    @Test
+    public void toXContent() throws IOException {
+        MLModel mlModel = MLModel.builder().algorithm(FunctionName.KMEANS).name("model_name").version(1).content("test_content").build();
+        XContentBuilder builder = XContentBuilder.builder(XContentType.JSON.xContent());
+        mlModel.toXContent(builder, EMPTY_PARAMS);
+        String mlModelContent = TestHelper.xContentBuilderToString(builder);
+        assertEquals("{\"name\":\"model_name\",\"algorithm\":\"KMEANS\",\"version\":1,\"content\":\"test_content\"}", mlModelContent);
+    }
+
+    @Test
+    public void toXContent_NullValue() throws IOException {
+        MLModel mlModel = MLModel.builder().build();
+        XContentBuilder builder = XContentBuilder.builder(XContentType.JSON.xContent());
+        mlModel.toXContent(builder, EMPTY_PARAMS);
+        String mlModelContent = TestHelper.xContentBuilderToString(builder);
+        assertEquals("{}", mlModelContent);
+    }
+
+    @Test
+    public void readInputStream_Success() throws IOException {
+        readInputStream(mlModel);
+    }
+
+    public void readInputStream(MLModel mlModel) throws IOException {
+        BytesStreamOutput bytesStreamOutput = new BytesStreamOutput();
+        mlModel.writeTo(bytesStreamOutput);
+
+        StreamInput streamInput = bytesStreamOutput.bytes().streamInput();
+        MLModel parsedMLModel = new MLModel(streamInput);
+        assertEquals(mlModel.getName(), parsedMLModel.getName());
+        assertEquals(mlModel.getAlgorithm(), parsedMLModel.getAlgorithm());
+        assertEquals(mlModel.getVersion(), parsedMLModel.getVersion());
+        assertEquals(mlModel.getContent(), parsedMLModel.getContent());
+        assertEquals(mlModel.getUser(), parsedMLModel.getUser());
+    }
+}