Github user cestella commented on a diff in the pull request:
https://github.com/apache/incubator-metron/pull/236#discussion_r78371624
--- Diff:
metron-analytics/metron-profiler/src/main/java/org/apache/metron/profiler/hbase/SaltyRowKeyBuilder.java
---
@@ -0,0 +1,211 @@
+/*
+ *
+ * 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.metron.profiler.hbase;
+
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.metron.profiler.ProfileMeasurement;
+import org.apache.metron.profiler.ProfilePeriod;
+
+import java.nio.ByteBuffer;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A RowKeyBuilder that uses a salt to prevent hot-spotting.
+ *
+ * Responsible for building the row keys used to store profile data in
HBase. The row key is composed of the following
+ * fields in the given order.
+ * <ul>
+ * <li>salt - A salt that helps prevent hot-spotting.
+ * <li>profile - The name of the profile.
+ * <li>entity - The name of the entity being profiled.
+ * <li>group(s) - The group(s) used to sort the data in HBase. For
example, a group may distinguish between weekends and weekdays.
+ * <li>year - The year based on UTC.
+ * <li>day of year - The current day within the year based on UTC; [1, 366]
+ * <li>hour - The hour within the day based on UTC; [0, 23]
+ * </ul>period - The period within the hour. The number of periods per
hour can be defined by the user; defaults to 4.
+ */
+public class SaltyRowKeyBuilder implements RowKeyBuilder {
+
+ /**
+ * A salt can be prepended to the row key to help prevent hot-spotting.
The salt
+ * divisor is used to generate the salt. The salt divisor should be
roughly equal
+ * to the number of nodes in the Hbase cluster.
+ */
+ private int saltDivisor;
+
+ /**
+ * An hour is divided into multiple periods. This defines how many
periods
+ * will exist within each given hour.
+ */
+ private int periodsPerHour;
+
+ public SaltyRowKeyBuilder() {
+ this.saltDivisor = 1000;
+ this.periodsPerHour = 4;
+ }
+
+ public SaltyRowKeyBuilder(int saltDivisor, int periodsPerHour) {
+ this.saltDivisor = saltDivisor;
+ this.periodsPerHour = periodsPerHour;
+ }
+
+ /**
+ * Builds a list of row keys necessary to retrieve profile measurements
over
+ * a time horizon.
+ *
+ * @param profile The name of the profile.
+ * @param entity The name of the entity.
+ * @param groups The group(s) used to sort the profile data.
+ * @param durationAgo How long ago?
+ * @param unit The time units of how long ago.
+ * @return All of the row keys necessary to retrieve the profile
measurements.
+ */
+ @Override
+ public List<byte[]> rowKeys(String profile, String entity, List<Object>
groups, long durationAgo, TimeUnit unit) {
--- End diff --
Nah, I was thinking that we might compare output of a given profile against
a lookback not including the current range for outlier analysis (i.e. comparing
the current profile period against the profile period of the last month
trailing the current profile period).
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