Add Redis storage implementation (#547)

* Add Redis storage

* Remove staleness check; can be checked at the service level

* Remove staleness related tests

* Add dependencies to top level pom

* Clean up code

storage/api/src/main/java/feast/storage/common/retry/BackOffExecutor.java

@@ -0,0 +1,58 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2018-2020 The Feast Authors
+ *
+ * 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
+ *
+ *     https://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 feast.storage.common.retry;
+
+import java.io.Serializable;
+import org.apache.beam.sdk.util.BackOff;
+import org.apache.beam.sdk.util.BackOffUtils;
+import org.apache.beam.sdk.util.FluentBackoff;
+import org.apache.beam.sdk.util.Sleeper;
+import org.joda.time.Duration;
+
+public class BackOffExecutor implements Serializable {
+
+  private final Integer maxRetries;
+  private final Duration initialBackOff;
+
+  public BackOffExecutor(Integer maxRetries, Duration initialBackOff) {
+    this.maxRetries = maxRetries;
+    this.initialBackOff = initialBackOff;
+  }
+
+  public void execute(Retriable retriable) throws Exception {
+    FluentBackoff backoff =
+        FluentBackoff.DEFAULT.withMaxRetries(maxRetries).withInitialBackoff(initialBackOff);
+    execute(retriable, backoff);
+  }
+
+  private void execute(Retriable retriable, FluentBackoff backoff) throws Exception {
+    Sleeper sleeper = Sleeper.DEFAULT;
+    BackOff backOff = backoff.backoff();
+    while (true) {
+      try {
+        retriable.execute();
+        break;
+      } catch (Exception e) {
+        if (retriable.isExceptionRetriable(e) && BackOffUtils.next(sleeper, backOff)) {
+          retriable.cleanUpAfterFailure();
+        } else {
+          throw e;
+        }
+      }
+    }
+  }
+}

storage/api/src/main/java/feast/storage/common/retry/Retriable.java

@@ -0,0 +1,25 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2018-2020 The Feast Authors
+ *
+ * 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
+ *
+ *     https://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 feast.storage.common.retry;
+
+public interface Retriable {
+  void execute() throws Exception;
+
+  Boolean isExceptionRetriable(Exception e);
+
+  void cleanUpAfterFailure();
+}

storage/connectors/redis/pom.xml

@@ -13,6 +13,64 @@
     <name>Feast Storage Connector for Redis</name>
 
     <dependencies>
+        <dependency>
+            <groupId>io.lettuce</groupId>
+            <artifactId>lettuce-core</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.9</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.google.auto.value</groupId>
+            <artifactId>auto-value-annotations</artifactId>
+            <version>1.6.6</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.google.auto.value</groupId>
+            <artifactId>auto-value</artifactId>
+            <version>1.6.6</version>
+            <scope>provided</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>2.23.0</version>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- To run actual Redis for ingestion integration test -->
+        <dependency>
+            <groupId>com.github.kstyrc</groupId>
+            <artifactId>embedded-redis</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.beam</groupId>
+            <artifactId>beam-runners-direct-java</artifactId>
+            <version>${org.apache.beam.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-library</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>

storage/connectors/redis/src/main/java/feast/storage/connectors/redis/retrieval/FeatureRowDecoder.java

@@ -0,0 +1,95 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2018-2020 The Feast Authors
+ *
+ * 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
+ *
+ *     https://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 feast.storage.connectors.redis.retrieval;
+
+import feast.core.FeatureSetProto.FeatureSetSpec;
+import feast.core.FeatureSetProto.FeatureSpec;
+import feast.types.FeatureRowProto.FeatureRow;
+import feast.types.FieldProto.Field;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class FeatureRowDecoder {
+
+  private final String featureSetRef;
+  private final FeatureSetSpec spec;
+
+  public FeatureRowDecoder(String featureSetRef, FeatureSetSpec spec) {
+    this.featureSetRef = featureSetRef;
+    this.spec = spec;
+  }
+
+  /**
+   * A feature row is considered encoded if the feature set and field names are not set. This method
+   * is required for backward compatibility purposes, to allow Feast serving to continue serving non
+   * encoded Feature Row ingested by an older version of Feast.
+   *
+   * @param featureRow Feature row
+   * @return boolean
+   */
+  public Boolean isEncoded(FeatureRow featureRow) {
+    return featureRow.getFeatureSet().isEmpty()
+        && featureRow.getFieldsList().stream().allMatch(field -> field.getName().isEmpty());
+  }
+
+  /**
+   * Validates if an encoded feature row can be decoded without exception.
+   *
+   * @param featureRow Feature row
+   * @return boolean
+   */
+  public Boolean isEncodingValid(FeatureRow featureRow) {
+    return featureRow.getFieldsList().size() == spec.getFeaturesList().size();
+  }
+
+  /**
+   * Decoding feature row by repopulating the field names based on the corresponding feature set
+   * spec.
+   *
+   * @param encodedFeatureRow Feature row
+   * @return boolean
+   */
+  public FeatureRow decode(FeatureRow encodedFeatureRow) {
+    final List<Field> fieldsWithoutName = encodedFeatureRow.getFieldsList();
+
+    List<String> featureNames =
+        spec.getFeaturesList().stream()
+            .sorted(Comparator.comparing(FeatureSpec::getName))
+            .map(FeatureSpec::getName)
+            .collect(Collectors.toList());
+    List<Field> fields =
+        IntStream.range(0, featureNames.size())
+            .mapToObj(
+                featureNameIndex -> {
+                  String featureName = featureNames.get(featureNameIndex);
+                  return fieldsWithoutName
+                      .get(featureNameIndex)
+                      .toBuilder()
+                      .setName(featureName)
+                      .build();
+                })
+            .collect(Collectors.toList());
+    return encodedFeatureRow
+        .toBuilder()
+        .clearFields()
+        .setFeatureSet(featureSetRef)
+        .addAllFields(fields)
+        .build();
+  }
+}