Add Normalize Pipeline Aggregation (elastic#56399)

This aggregation will perform normalizations of metrics
for a given series of data in the form of bucket values.

The aggregations supports the following normalizations

- rescale 0-1
- rescale 0-100
- percentage of sum
- mean normalization
- z-score normalization
- softmax normalization

To specify which normalization is to be used, it can be specified
in the normalize agg's `normalizer` field.

For example:

```
{
  "normalize": {
    "buckets_path": <>,
    "normalizer": "percent"
  }
}
```

Closes elastic#51005.

docs/reference/aggregations/pipeline.asciidoc

@@ -288,3 +288,4 @@ include::pipeline/bucket-selector-aggregation.asciidoc[]
 include::pipeline/bucket-sort-aggregation.asciidoc[]
 include::pipeline/serial-diff-aggregation.asciidoc[]
 include::pipeline/moving-percentiles-aggregation.asciidoc[]
+include::pipeline/normalize-aggregation.asciidoc[]

docs/reference/aggregations/pipeline/normalize-aggregation.asciidoc

@@ -0,0 +1,182 @@
+[role="xpack"]
+[testenv="basic"]
+[[search-aggregations-pipeline-normalize-aggregation]]
+=== Normalize Aggregation
+
+A parent pipeline aggregation which calculates the specific normalized/rescaled value for a specific bucket value.
+Values that cannot be normalized, will be skipped using the <<gap-policy, skip gap policy>>.
+
+==== Syntax
+
+A `normalize` aggregation looks like this in isolation:
+
+[source,js]
+--------------------------------------------------
+{
+    "normalize": {
+        "buckets_path": "normalized",
+        "method": "percent_of_sum"
+    }
+}
+--------------------------------------------------
+// NOTCONSOLE
+
+[[normalize_pipeline-params]]
+.`normalize_pipeline` Parameters
+[options="header"]
+|===
+|Parameter Name |Description |Required |Default Value
+|`buckets_path` |The path to the buckets we wish to normalize (see <<buckets-path-syntax, `buckets_path` syntax>> for more details) |Required |
+|`method` | The specific <<normalize_pipeline-method, method>> to apply | Required |
+|`format` |format to apply to the output value of this aggregation |Optional |`null`
+|===
+
+==== Methods
+[[normalize_pipeline-method]]
+
+The Normalize Aggregation supports multiple methods to transform the bucket values. Each method definition will use
+the following original set of bucket values as examples: `[5, 5, 10, 50, 10, 20]`.
+
+_rescale_0_1_::
+                This method rescales the data such that the minimum number is zero, and the maximum number is 1, with the rest normalized
+                linearly in-between.
+
+                x' = (x - min_x) / (max_x - min_x)
+
+                [0, 0, .1111, 1, .1111, .3333]
+
+_rescale_0_100_::
+                This method rescales the data such that the minimum number is zero, and the maximum number is 1, with the rest normalized
+                linearly in-between.
+
+                x' = 100 * (x - min_x) / (max_x - min_x)
+
+                [0, 0, 11.11, 100, 11.11, 33.33]
+
+_percent_of_sum_::
+                This method normalizes each value so that it represents a percentage of the total sum it attributes to.
+
+                x' = x / sum_x
+
+                [5%, 5%, 10%, 50%, 10%, 20%]
+
+
+_mean_::
+                This method normalizes such that each value is normalized by how much it differs from the average.
+
+                x' = (x - mean_x) / (max_x - min_x)
+
+                [4.63, 4.63, 9.63, 49.63, 9.63, 9.63, 19.63]
+
+_zscore_::
+                This method normalizes such that each value represents how far it is from the mean relative to the standard deviation
+
+                x' = (x - mean_x) / stdev_x
+
+                [-0.68, -0.68, -0.39, 1.94, -0.39, 0.19]
+
+_softmax_::
+                This method normalizes such that each value is exponentiated and relative to the sum of the exponents of the original values.
+
+                x' = e^x / sum_e_x
+
+                [2.862E-20, 2.862E-20, 4.248E-18, 0.999, 9.357E-14, 4.248E-18]
+
+
+==== Example
+
+The following snippet calculates the percent of total sales for each month:
+
+[source,console]
+--------------------------------------------------
+POST /sales/_search
+{
+    "size": 0,
+    "aggs" : {
+        "sales_per_month" : {
+            "date_histogram" : {
+                "field" : "date",
+                "calendar_interval" : "month"
+            },
+            "aggs": {
+                "sales": {
+                    "sum": {
+                        "field": "price"
+                    }
+                },
+                "percent_of_total_sales": {
+                    "normalize": {
+                        "buckets_path": "sales", <1>
+                        "method": "percent_of_sum",  <2>
+                        "format": "00.00%" <3>
+                    }
+                }
+            }
+        }
+    }
+}
+--------------------------------------------------
+// TEST[setup:sales]
+
+<1> `buckets_path` instructs this normalize aggregation to use the output of the `sales` aggregation for rescaling
+<2> `method` sets which rescaling to apply. In this case, `percent_of_sum` will calculate the sales value as a percent of all sales
+    in the parent bucket
+<3> `format` influences how to format the metric as a string using Java's `DecimalFormat` pattern. In this case, multiplying by 100
+    and adding a '%'
+
+And the following may be the response:
+
+[source,console-result]
+--------------------------------------------------
+{
+   "took": 11,
+   "timed_out": false,
+   "_shards": ...,
+   "hits": ...,
+   "aggregations": {
+      "sales_per_month": {
+         "buckets": [
+            {
+               "key_as_string": "2015/01/01 00:00:00",
+               "key": 1420070400000,
+               "doc_count": 3,
+               "sales": {
+                  "value": 550.0
+               },
+               "percent_of_total_sales": {
+                  "value": 0.5583756345177665,
+                  "value_as_string": "55.84%"
+               }
+            },
+            {
+               "key_as_string": "2015/02/01 00:00:00",
+               "key": 1422748800000,
+               "doc_count": 2,
+               "sales": {
+                  "value": 60.0
+               },
+               "percent_of_total_sales": {
+                  "value": 0.06091370558375635,
+                  "value_as_string": "06.09%"
+               }
+            },
+            {
+               "key_as_string": "2015/03/01 00:00:00",
+               "key": 1425168000000,
+               "doc_count": 2,
+               "sales": {
+                  "value": 375.0
+               },
+               "percent_of_total_sales": {
+                  "value": 0.38071065989847713,
+                  "value_as_string": "38.07%"
+               }
+            }
+         ]
+      }
+   }
+}
+--------------------------------------------------
+// TESTRESPONSE[s/"took": 11/"took": $body.took/]
+// TESTRESPONSE[s/"_shards": \.\.\./"_shards": $body._shards/]
+// TESTRESPONSE[s/"hits": \.\.\./"hits": $body.hits/]

server/src/main/java/org/elasticsearch/search/aggregations/pipeline/InternalSimpleValue.java

@@ -35,7 +35,7 @@ public class InternalSimpleValue extends InternalNumericMetricsAggregation.Singl
     public static final String NAME = "simple_value";
     protected final double value;
 
-    InternalSimpleValue(String name, double value, DocValueFormat formatter, Map<String, Object> metadata) {
+    public InternalSimpleValue(String name, double value, DocValueFormat formatter, Map<String, Object> metadata) {
         super(name, metadata);
         this.format = formatter;
         this.value = value;

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/AnalyticsPlugin.java

@@ -32,6 +32,7 @@
 import org.elasticsearch.watcher.ResourceWatcherService;
 import org.elasticsearch.xpack.analytics.action.TransportAnalyticsStatsAction;
 import org.elasticsearch.xpack.analytics.aggregations.metrics.AnalyticsAggregatorFactory;
+import org.elasticsearch.xpack.analytics.normalize.NormalizePipelineAggregationBuilder;
 import org.elasticsearch.xpack.analytics.boxplot.BoxplotAggregationBuilder;
 import org.elasticsearch.xpack.analytics.boxplot.InternalBoxplot;
 import org.elasticsearch.xpack.analytics.cumulativecardinality.CumulativeCardinalityPipelineAggregationBuilder;
@@ -84,6 +85,11 @@ public List<PipelineAggregationSpec> getPipelineAggregations() {
             MovingPercentilesPipelineAggregationBuilder::new,
             usage.track(AnalyticsStatsAction.Item.MOVING_PERCENTILES,
                 checkLicense(MovingPercentilesPipelineAggregationBuilder.PARSER))));
+        pipelineAggs.add(new PipelineAggregationSpec(
+            NormalizePipelineAggregationBuilder.NAME,
+            NormalizePipelineAggregationBuilder::new,
+            usage.track(AnalyticsStatsAction.Item.NORMALIZE,
+                checkLicense(NormalizePipelineAggregationBuilder.PARSER))));
         return pipelineAggs;
     }
 

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/normalize/NormalizePipelineAggregationBuilder.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.analytics.normalize;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.ConstructingObjectParser;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.search.DocValueFormat;
+import org.elasticsearch.search.aggregations.pipeline.AbstractPipelineAggregationBuilder;
+import org.elasticsearch.search.aggregations.pipeline.BucketMetricsParser;
+import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.DoubleUnaryOperator;
+import java.util.function.Function;
+
+import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
+import static org.elasticsearch.common.xcontent.ConstructingObjectParser.optionalConstructorArg;
+import static org.elasticsearch.search.aggregations.pipeline.PipelineAggregator.Parser.FORMAT;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.Mean;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.Percent;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.RescaleZeroToOne;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.RescaleZeroToOneHundred;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.Softmax;
+import static org.elasticsearch.xpack.analytics.normalize.NormalizePipelineMethods.ZScore;
+
+public class NormalizePipelineAggregationBuilder extends AbstractPipelineAggregationBuilder<NormalizePipelineAggregationBuilder> {
+    public static final String NAME = "normalize";
+    static final ParseField METHOD_FIELD = new ParseField("method");
+
+    @SuppressWarnings("unchecked")
+    public static final ConstructingObjectParser<NormalizePipelineAggregationBuilder, String> PARSER = new ConstructingObjectParser<>(
+        NAME, false, (args, name) -> new NormalizePipelineAggregationBuilder(name, (String) args[0],
+        (String) args[1], (List<String>) args[2]));
+
+    static {
+        PARSER.declareString(optionalConstructorArg(), FORMAT);
+        PARSER.declareString(constructorArg(), METHOD_FIELD);
+        PARSER.declareStringArray(constructorArg(), BUCKETS_PATH_FIELD);
+    }
+
+    static final Map<String, Function<double[], DoubleUnaryOperator>> NAME_MAP;
+
+    static {
+        NAME_MAP = new HashMap<>();
+        NAME_MAP.put(RescaleZeroToOne.NAME, RescaleZeroToOne::new);
+        NAME_MAP.put(RescaleZeroToOneHundred.NAME, RescaleZeroToOneHundred::new);
+        NAME_MAP.put(Mean.NAME, Mean::new);
+        NAME_MAP.put(ZScore.NAME, ZScore::new);
+        NAME_MAP.put(Percent.NAME, Percent::new);
+        NAME_MAP.put(Softmax.NAME, Softmax::new);
+    }
+
+    static String validateMethodName(String name) {
+        if (NAME_MAP.containsKey(name)) {
+            return name;
+        }
+        throw new IllegalArgumentException("invalid method [" + name + "]");
+    }
+
+    private final String format;
+    private final String method;
+
+    public NormalizePipelineAggregationBuilder(String name, String format, String method, List<String> bucketsPath) {
+        super(name, NAME, bucketsPath.toArray(new String[0]));
+        this.format = format;
+        this.method = validateMethodName(method);
+    }
+
+    /**
+     * Read from a stream.
+     */
+    public NormalizePipelineAggregationBuilder(StreamInput in) throws IOException {
+        super(in, NAME);
+        format = in.readOptionalString();
+        method = in.readString();
+    }
+
+    @Override
+    protected final void doWriteTo(StreamOutput out) throws IOException {
+        out.writeOptionalString(format);
+        out.writeString(method);
+    }
+
+    /**
+     * Gets the format to use on the output of this aggregation.
+     */
+    public String format() {
+        return format;
+    }
+
+    protected DocValueFormat formatter() {
+        if (format != null) {
+            return new DocValueFormat.Decimal(format);
+        } else {
+            return DocValueFormat.RAW;
+        }
+    }
+
+    @Override
+    protected PipelineAggregator createInternal(Map<String, Object> metadata) {
+        return new NormalizePipelineAggregator(name, bucketsPaths, formatter(), NAME_MAP.get(method), metadata);
+    }
+
+    @Override
+    protected void validate(ValidationContext context) {
+        if (bucketsPaths.length != 1) {
+            context.addBucketPathValidationError("must contain a single entry for aggregation [" + name + "]");
+        }
+        context.validateHasParent(NAME, name);
+    }
+
+    @Override
+    protected final XContentBuilder internalXContent(XContentBuilder builder, Params params) throws IOException {
+        if (format != null) {
+            builder.field(BucketMetricsParser.FORMAT.getPreferredName(), format);
+        }
+        builder.field(METHOD_FIELD.getPreferredName(), method);
+        return builder;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(super.hashCode(), format, method);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null || getClass() != obj.getClass()) return false;
+        if (super.equals(obj) == false) return false;
+        NormalizePipelineAggregationBuilder other = (NormalizePipelineAggregationBuilder) obj;
+        return Objects.equals(format, other.format) && Objects.equals(method, other.method);
+    }
+
+    @Override
+    public String getWriteableName() {
+        return NAME;
+    }
+}