[ML] Write model_memory_limit with units into the cluster state (elastic/x-pack-elasticsearch#1934)

This is step 2 of elastic/x-pack-elasticsearch#1604

This change stores `model_memory_limit` as a string with `mb` unit.
I considered using the `toString` method of `ByteSizeValue` but it
can lead to accuracy loss. Adding the fixed `mb` unit maintains
the accuracy, while making clear what unit the value is in.

Original commit: elastic/x-pack-elasticsearch@4dc48f0ce8

docs/en/rest-api/ml/update-job.asciidoc

@@ -92,7 +92,7 @@ POST _xpack/ml/anomaly_detectors/it_ops_new_logs/_update
     "enabled": true
   },
   "analysis_limits": {
-    "model_memory_limit": 1024
+    "model_memory_limit": "1024mb"
   },
   "renormalization_window_days": 30,
   "background_persist_interval": "2h",
@@ -135,7 +135,7 @@ information, including the updated property values. For example:
     "influencers": []
   },
   "analysis_limits": {
-    "model_memory_limit": 1024
+    "model_memory_limit": "1024mb"
   },
   "data_description": {
     "time_field": "time",

plugin/src/main/java/org/elasticsearch/xpack/ml/job/config/AnalysisLimits.java

@@ -126,7 +126,7 @@ public class AnalysisLimits implements ToXContentObject, Writeable {
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject();
         if (modelMemoryLimit != null) {
-            builder.field(MODEL_MEMORY_LIMIT.getPreferredName(), modelMemoryLimit);
+            builder.field(MODEL_MEMORY_LIMIT.getPreferredName(), modelMemoryLimit + "mb");
         }
         if (categorizationExamplesLimit != null) {
             builder.field(CATEGORIZATION_EXAMPLES_LIMIT.getPreferredName(), categorizationExamplesLimit);

plugin/src/test/java/org/elasticsearch/xpack/ml/job/config/AnalysisLimitsTests.java

@@ -8,6 +8,8 @@ package org.elasticsearch.xpack.ml.job.config;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.unit.ByteSizeUnit;
+import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
@@ -24,6 +26,10 @@ public class AnalysisLimitsTests extends AbstractSerializingTestCase<AnalysisLim
 
     @Override
     protected AnalysisLimits createTestInstance() {
+        return createRandomized();
+    }
+
+    public static AnalysisLimits createRandomized() {
         return new AnalysisLimits(randomBoolean() ? (long) randomIntBetween(1, 1000000) : null,
                 randomBoolean() ? randomNonNegativeLong() : null);
     }

plugin/src/test/java/org/elasticsearch/xpack/ml/job/config/JobBuilderTests.java

@@ -38,8 +38,7 @@ public class JobBuilderTests extends AbstractSerializingTestCase<Job.Builder> {
             builder.setAnalysisConfig(AnalysisConfigTests.createRandomized());
         }
         if (randomBoolean()) {
-            builder.setAnalysisLimits(new AnalysisLimits(randomNonNegativeLong(),
+            builder.setAnalysisLimits(AnalysisLimitsTests.createRandomized());
-                    randomNonNegativeLong()));
         }
         if (randomBoolean()) {
             DataDescription.Builder dataDescription = new DataDescription.Builder();

plugin/src/test/java/org/elasticsearch/xpack/ml/job/config/JobTests.java

@@ -508,7 +508,7 @@ public class JobTests extends AbstractSerializingTestCase<Job> {
             builder.setLastDataTime(new Date(randomNonNegativeLong()));
         }
         builder.setAnalysisConfig(AnalysisConfigTests.createRandomized());
-        builder.setAnalysisLimits(new AnalysisLimits(randomNonNegativeLong(), randomNonNegativeLong()));
+        builder.setAnalysisLimits(AnalysisLimitsTests.createRandomized());
 
         DataDescription.Builder dataDescription = new DataDescription.Builder();
         dataDescription.setFormat(randomFrom(DataDescription.DataFormat.values()));

plugin/src/test/java/org/elasticsearch/xpack/ml/job/config/JobUpdateTests.java

@@ -51,7 +51,7 @@ public class JobUpdateTests extends AbstractSerializingTestCase<JobUpdate> {
             update.setModelPlotConfig(new ModelPlotConfig(randomBoolean(), randomAlphaOfLength(10)));
         }
         if (randomBoolean()) {
-            update.setAnalysisLimits(new AnalysisLimits(randomNonNegativeLong(), randomNonNegativeLong()));
+            update.setAnalysisLimits(AnalysisLimitsTests.createRandomized());
         }
         if (randomBoolean()) {
             update.setRenormalizationWindowDays(randomNonNegativeLong());

plugin/src/test/resources/rest-api-spec/test/ml/jobs_crud.yml

@@ -88,7 +88,7 @@
             }
           }
   - match: { job_id: "job-model-memory-limit-as-number" }
-  - match: { analysis_limits.model_memory_limit: 2048 }
+  - match: { analysis_limits.model_memory_limit: "2048mb" }
 
 ---
 "Test put job with model_memory_limit as string":
@@ -108,7 +108,7 @@
             }
           }
   - match: { job_id: "job-model-memory-limit-as-string" }
-  - match: { analysis_limits.model_memory_limit: 3072 }
+  - match: { analysis_limits.model_memory_limit: "3072mb" }
 
 ---
 "Test get job API with non existing job id":
@@ -302,7 +302,7 @@
   - match: { description: "Post update description" }
   - match: { model_plot_config.enabled: false }
   - match: { model_plot_config.terms: "foobar" }
-  - match: { analysis_limits.model_memory_limit: 20 }
+  - match: { analysis_limits.model_memory_limit: "20mb" }
   - match: { analysis_config.categorization_filters: ["cat3.*"] }
   - match: { analysis_config.detectors.0.detector_rules.0.target_field_name: "airline" }
   - match: { analysis_config.detectors.0.detector_index: 0 }