Implemented back off handling for consecutively failed calls.

2026-09-19 20:25:31 +00:00 · 2021-06-16 18:24:21 +02:00
parent 5b749bd46e
commit 7b45ec066f
2 changed files with 63 additions and 19 deletions
@@ -5,6 +5,7 @@ import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -20,6 +21,7 @@ import org.json.simple.parser.ParseException;

 import com.sap.sailing.domain.windfinder.ReviewedSpotsCollection;
 import com.sap.sailing.domain.windfinder.Spot;
+import com.sap.sse.common.util.BackoffTracker;
 import com.sap.sse.util.HttpUrlConnectionHelper;
 import com.sap.sse.util.ThreadPoolUtil;

@@ -42,18 +44,17 @@ public class ReviewedSpotsCollectionImpl implements ReviewedSpotsCollection {
     * map initialized with the result of calling {@link #loadSpots()}.
     */
    private Future<ConcurrentMap<String, Spot>> spotsByIdCache;
+
+    private BackoffTracker backoffTracker;
    
    public ReviewedSpotsCollectionImpl(String id) {
        this.id = id;
        this.parser = new WindFinderReportParser();
-        this.spotsByIdCache = ThreadPoolUtil.INSTANCE.getDefaultForegroundTaskThreadPoolExecutor().schedule(()->{
+        this.spotsByIdCache = ThreadPoolUtil.INSTANCE.getDefaultForegroundTaskThreadPoolExecutor().schedule(() -> {
+            backoffTracker = new BackoffTracker(TimeUnit.SECONDS.toMillis(5), 2);
            final ConcurrentMap<String, Spot> result = new ConcurrentHashMap<>();
-            try {
-                for (final Spot spot : loadSpots()) {
-                    result.put(spot.getId(), spot);
-                }
-            } catch (Exception e) {
-                logger.log(Level.SEVERE, "Problem loading spots for spot collection "+id, e);
+            for (final Spot spot : loadSpots()) {
+                result.put(spot.getId(), spot);
            }
            return result;
        }, /* delay */ 0, TimeUnit.MILLISECONDS);
@@ -103,19 +104,22 @@ public class ReviewedSpotsCollectionImpl implements ReviewedSpotsCollection {
        return result;
    }
    
-    private Iterable<Spot> loadSpots() throws IOException, ParseException, MalformedURLException {
-        final Iterable<Spot> result;
-        final InputStreamReader in = new InputStreamReader(
-                            (InputStream) HttpUrlConnectionHelper.redirectConnection(
-                                    new URL(Activator.BASE_URL_FOR_JSON_DOCUMENTS+"/"+getId()+SPOT_LIST_DOCUMENT_SUFFIX))
-                            .getContent());
-        try {
-            JSONArray spotsAsJson = (JSONArray) new JSONParser().parse(in);
-            result = parser.parseSpots(spotsAsJson, this);
-            return result;
-        } finally {
-            in.close();
+    private Iterable<Spot> loadSpots() {
+        Iterable<Spot> result = Collections.emptySet();
+        if (!backoffTracker.backOff()) {
+            try (InputStreamReader in = new InputStreamReader((InputStream) HttpUrlConnectionHelper
+                    .redirectConnection(
+                            new URL(Activator.BASE_URL_FOR_JSON_DOCUMENTS + "/" + getId() + SPOT_LIST_DOCUMENT_SUFFIX))
+                    .getContent())) {
+                JSONArray spotsAsJson = (JSONArray) new JSONParser().parse(in);
+                result = parser.parseSpots(spotsAsJson, this);
+                backoffTracker.clear();
+            } catch (Exception e) {
+                logger.log(Level.SEVERE, "Problem loading spots for spot collection " + id, e);
+                backoffTracker.logFailure();
+            }
        }
+        return result;
    }

    @Override
@@ -0,0 +1,40 @@
+package com.sap.sse.common.util;
+
+import java.util.concurrent.TimeUnit;
+
+public class BackoffTracker {
+    private Long backOffUntil;
+    private final int factor;
+    private Long currentTimeoutInMillis;
+    private final Long initialTimeoutInMillis;
+    private static final Long maxTimeout = TimeUnit.MINUTES.toMillis(5);
+    
+    /**
+     * A tracker to handle continous failures of processes. Before every process execution call {@link #backOff()} to query whether there is a timeout.
+     * Every failure should call {@link #logFailure()}, which will increase the time until {@link #backOff()} returns false again.
+     * @param initialTimeoutInMillis
+     * @param backoffMultiplier: The factor by which the timeout will be multiplied on consecutive failures
+     */
+    public BackoffTracker(Long initialTimeoutInMillis, int backoffMultiplier) {
+        this.initialTimeoutInMillis = initialTimeoutInMillis;
+        this.factor = backoffMultiplier;
+    }
+    
+    public void logFailure() {
+        if(currentTimeoutInMillis == null) {
+            currentTimeoutInMillis = initialTimeoutInMillis;
+        }
+        final Long newTimeOut = currentTimeoutInMillis * factor;
+        currentTimeoutInMillis = newTimeOut >= maxTimeout ? maxTimeout : newTimeOut;
+        backOffUntil = System.currentTimeMillis() + currentTimeoutInMillis;
+    }
+    
+    public boolean backOff() {
+        return backOffUntil == null ? false : backOffUntil > System.currentTimeMillis();
+    }
+    
+    public void clear() {
+        currentTimeoutInMillis = null;
+        backOffUntil = null;
+    }
+}