ML: changing automatic check_window calculation (#35643)

* ML: changing automatic check_window calculation

* adding docs on how we calculate the default

docs/java-rest/high-level/ml/put-datafeed.asciidoc

@@ -72,6 +72,7 @@ The window must be larger than the Job's bucket size, but smaller than 24 hours,
 and span less than 10,000 buckets.
 Defaults to `null`, which causes an appropriate window span to be calculated when
 the datafeed runs.
+The default `check_window` span calculation is the max between `2h` or `8 * bucket_span`.
 To explicitly disable, pass `DelayedDataCheckConfig.disabledDelayedDataCheckConfig()`.
 
 ["source","java",subs="attributes,callouts,macros"]

docs/reference/ml/apis/datafeedresource.asciidoc

@@ -111,6 +111,7 @@ The configuration object has the following properties:
   (time units) The window of time before the latest finalized bucket that should be searched
   for late data. Defaults to `null` which causes an appropriate `check_window` to be calculated
   when the real-time {dfeed} runs.
+  The default `check_window` span calculation is the max between `2h` or `8 * bucket_span`.
 
 [float]
 [[ml-datafeed-counts]]

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/messages/Messages.java

@@ -23,11 +23,9 @@ public final class Messages {
             "script_fields cannot be used in combination with aggregations";
     public static final String DATAFEED_CONFIG_INVALID_OPTION_VALUE = "Invalid {0} value ''{1}'' in datafeed configuration";
     public static final String DATAFEED_CONFIG_DELAYED_DATA_CHECK_TOO_SMALL =
-        "delayed_data_check_window [{0}] must be greater than the bucket_span [{1}]";
-    public static final String DATAFEED_CONFIG_DELAYED_DATA_CHECK_TOO_LARGE =
-        "delayed_data_check_window [{0}] must be less than or equal to [24h]";
+        "delayed_data_check_config: check_window [{0}] must be greater than the bucket_span [{1}]";
     public static final String DATAFEED_CONFIG_DELAYED_DATA_CHECK_SPANS_TOO_MANY_BUCKETS =
-        "delayed_data_check_window [{0}] must be less than 10,000x the bucket_span [{1}]";
+        "delayed_data_check_config: check_window [{0}] must be less than 10,000x the bucket_span [{1}]";
 
     public static final String DATAFEED_DOES_NOT_SUPPORT_JOB_WITH_LATENCY = "A job configured with datafeed cannot support latency";
     public static final String DATAFEED_NOT_FOUND = "No datafeed with id [{0}] exists";

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/datafeed/delayeddatacheck/DelayedDataDetectorFactory.java

@@ -21,8 +21,8 @@ import java.util.Objects;
 public class DelayedDataDetectorFactory {
 
     // There are eight 15min buckets in a two hour span, so matching that number as the fallback for very long buckets
-    private static final int FALLBACK_NUMBER_OF_BUCKETS_TO_SPAN = 8;
-    private static final TimeValue DEFAULT_CHECK_WINDOW = TimeValue.timeValueHours(2);
+    private static final int DEFAULT_NUMBER_OF_BUCKETS_TO_SPAN = 8;
+    private static final long DEFAULT_CHECK_WINDOW_MS = 7_200_000L; // 2 hours in Milliseconds
 
     /**
      * This will build the appropriate detector given the parameters.
@@ -57,11 +57,7 @@ public class DelayedDataDetectorFactory {
             return 0;
         }
         if (currentWindow == null) { // we should provide a good default as the user did not specify a window
-            if(bucketSpan.compareTo(DEFAULT_CHECK_WINDOW) >= 0) {
-                return FALLBACK_NUMBER_OF_BUCKETS_TO_SPAN * bucketSpan.millis();
-            } else {
-                return DEFAULT_CHECK_WINDOW.millis();
-            }
+            return Math.max(DEFAULT_CHECK_WINDOW_MS, DEFAULT_NUMBER_OF_BUCKETS_TO_SPAN * bucketSpan.millis());
         }
         if (currentWindow.compareTo(bucketSpan) < 0) {
             throw new IllegalArgumentException(

x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/datafeed/delayeddatacheck/DelayedDataDetectorFactoryTests.java

@@ -52,13 +52,13 @@ public class DelayedDataDetectorFactoryTests extends ESTestCase {
         assertEquals(Messages.getMessage(
             Messages.DATAFEED_CONFIG_DELAYED_DATA_CHECK_SPANS_TOO_MANY_BUCKETS, "12h", "2s"), e.getMessage());
 
-        Job withBigBucketSpan = createJob(TimeValue.timeValueHours(3));
+        Job withBigBucketSpan = createJob(TimeValue.timeValueHours(1));
         datafeedConfig = createDatafeed(true, null);
 
         // Should not throw
         DelayedDataDetector delayedDataDetector =
             DelayedDataDetectorFactory.buildDetector(withBigBucketSpan, datafeedConfig, mock(Client.class));
-        assertThat(delayedDataDetector.getWindow(), equalTo(TimeValue.timeValueHours(3).millis() * 8));
+        assertThat(delayedDataDetector.getWindow(), equalTo(TimeValue.timeValueHours(1).millis() * 8));
 
         datafeedConfig = createDatafeed(true, null);