Refine cold-start, window delay, and task updates (#1496)

- Skip checkpoint writes during historical/run once
- Add retryOnConflict to task updates to dodge version clashes
- Switch window-delay calculation from 20 % padding (gap × 1.2) to a bucket-based approach. Motivation: the multiplicative cushion scaled with absolute lag, so a multi-hour ingest gap could inflate the delay into days, causing cold start failures.  Tying the delay to config intervals (plus one safety bucket) keeps it proportional and restores prompt results.

Testing done:
* added IT: https://tinyurl.com/5n98z3ue

Signed-off-by: Kaituo Li <kaituo@amazon.com>
(cherry picked from commit 08dceb4)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

release-notes/opensearch-anomaly-detection.release-notes-3.1.0.0.md

@@ -9,5 +9,5 @@ Compatible with OpenSearch 3.1.0
 ### Bug Fixes
 - Fix incorrect task state handling in ForecastRunOnceTransportAction ([#1489](https://github.com/opensearch-project/anomaly-detection/pull/1489))
 - Fix incorrect task state handling in ForecastRunOnceTransportAction ([#1493](https://github.com/opensearch-project/anomaly-detection/pull/1493))
-
+- Refine cold-start, window delay, and task updates ([#1496](https://github.com/opensearch-project/anomaly-detection/pull/1496))
 

src/main/java/org/opensearch/ad/ml/ADColdStart.java

@@ -304,8 +304,10 @@ protected List<AnomalyResult> trainModelFromDataSegments(
 
         entityState.setLastUsedTime(clock.instant());
 
-        // save to checkpoint
-        checkpointWriteWorker.write(entityState, true, RequestPriority.MEDIUM);
+        // save to checkpoint for real time only
+        if (null == taskId) {
+            checkpointWriteWorker.write(entityState, true, RequestPriority.MEDIUM);
+        }
 
         return results;
     }

src/main/java/org/opensearch/forecast/ml/ForecastCheckpointDao.java

@@ -391,7 +391,8 @@ protected ModelState<RCFCaster> fromSingleStreamModelCheckpoint(Map<String, Obje
     private RCFCaster loadRCFCaster(Map<String, Object> checkpoint, String modelId) {
         String model = (String) checkpoint.get(CommonName.FIELD_MODEL);
         if (model == null || model.length() > maxCheckpointBytes) {
-            logger.warn(new ParameterizedMessage("[{}]'s model too large: [{}] bytes", modelId, model.length()));
+            logger
+                .warn(new ParameterizedMessage("[{}]'s model empty or too large: [{}] bytes", modelId, model == null ? 0 : model.length()));
             return null;
         }
         return toRCFCaster(model);

src/main/java/org/opensearch/timeseries/ml/ModelColdStart.java

@@ -233,6 +233,7 @@ private void coldStart(
         }
 
         if (lastThrottledColdStartTime.plus(Duration.ofMinutes(coolDownMinutes)).isAfter(clock.instant())) {
+            logger.info("Still in cool down.");
             listener.onResponse(null);
             return;
         }
@@ -290,8 +291,11 @@ private void coldStart(
                         logger.info("Not enough data to train model: {}, currently we have {}", modelId, dataSize);
 
                         trainingData.forEach(modelState::addSample);
-                        // save to checkpoint
-                        checkpointWriteWorker.write(modelState, true, RequestPriority.MEDIUM);
+                        // save to checkpoint for real time only
+                        if (null == coldStartRequest.getTaskId()) {
+                            checkpointWriteWorker.write(modelState, true, RequestPriority.MEDIUM);
+                        }
+
                         listener.onResponse(null);
                     }
                 } else {
@@ -376,7 +380,6 @@ private void getColdStartData(String configId, FeatureRequest coldStartRequest,
                     // [current start, current end] for training. So we fetch training data ending at current start
                     long endTimeMs = coldStartRequest.getDataStartTimeMillis();
                     int numberOfSamples = selectNumberOfSamples(config);
-
                     // we start with round 0
                     getFeatures(
                         listener,

src/main/java/org/opensearch/timeseries/task/TaskManager.java

@@ -747,6 +747,8 @@ public void updateTask(String taskId, Map<String, Object> updatedFields, ActionL
         updatedContent.put(TimeSeriesTask.LAST_UPDATE_TIME_FIELD, Instant.now().toEpochMilli());
         updateRequest.doc(updatedContent);
         updateRequest.setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE);
+        // OpenSearch will transparently re‑read the doc and retry up to 2 times.
+        updateRequest.retryOnConflict(2);
         client.update(updateRequest, listener);
     }
 

src/main/java/org/opensearch/timeseries/transport/BaseSuggestConfigParamTransportAction.java

@@ -41,7 +41,6 @@
 import org.opensearch.timeseries.rest.handler.HistorySuggest;
 import org.opensearch.timeseries.rest.handler.IntervalCalculation;
 import org.opensearch.timeseries.rest.handler.LatestTimeRetriever;
-import org.opensearch.timeseries.settings.TimeSeriesSettings;
 import org.opensearch.timeseries.util.ParseUtils;
 import org.opensearch.timeseries.util.SecurityClientUtil;
 import org.opensearch.transport.TransportService;
@@ -249,8 +248,44 @@ protected void suggestWindowDelay(Config config, User user, TimeValue timeout, A
                 // we may get future date (e.g., in testing)
                 long currentMillis = clock.millis();
 
+                // ---------------------------------------------------------------------------
+                // Adaptive window-delay calculation
+                // ---------------------------------------------------------------------------
+                // Goal: pick a delay long enough that all data for the current query
+                // window has been ingested, so the config never sees “future gaps”.
+                //
+                // Algorithm
+                // 1. Compute the raw lag (`gapMs`) between now and the newest document.
+                // 2. Convert that lag into whole config-interval “buckets” (ceil).
+                // We use the integer-math identity
+                // ceil(a / b) = (a + b − 1) / b for positive a, b
+                // so we never under-estimate the number of missing buckets.
+                // 3. Add one extra “safety” bucket to cover clock skew / network jitter.
+                // 4. Transform the final bucket count back to milliseconds.
+                //
+                // ---------------------------------------------------------------------------
+
                 if (currentMillis > latestTime.get()) {
-                    windowDelayMillis = (long) Math.ceil((currentMillis - latestTime.get()) * TimeSeriesSettings.WINDOW_DELAY_RATIO);
+
+                    // Milliseconds we are behind real time
+                    long gapMs = currentMillis - latestTime.get();
+
+                    // Length of one bucket (config interval)
+                    long bucketMs = config.getIntervalInMilliseconds();
+
+                    /* Missing buckets (ceiling division)
+                        Example: gap = 15 000 ms, bucket = 10 000 ms
+                        bucketsBehind = (15 000 + 10 000 − 1) / 10 000
+                                      = 24 999 / 10 000
+                                      = 2  ← correct (15 000 ms spans 2 full buckets)
+                    */
+                    long bucketsBehind = (gapMs + bucketMs - 1) / bucketMs;
+
+                    // Always keep one extra bucket as a cushion
+                    long safetyBuckets = 1;
+
+                    // Convert back to milliseconds
+                    windowDelayMillis = (bucketsBehind + safetyBuckets) * bucketMs;
                 }
 
                 // in case windowDelayMillis is small, we want at least 1 minute