(feeds) Refresh the feed db using the previous db, when it is available.

code/functions/live-capture/java/nu/marginalia/rss/db/FeedDbReader.java

@@ -41,12 +41,16 @@ public class FeedDbReader implements AutoCloseable {
             var rs = stmt.executeQuery("""
                 select
                     json_extract(feed, '$.domain') as domain,
-                    json_extract(feed, '$.feedUrl') as url
+                    json_extract(feed, '$.feedUrl') as url,
+                    json_extract(feed, '$.updated') as updated
                 from feed
                 """);
 
             while (rs.next()) {
-                ret.add(new FeedDefinition(rs.getString("domain"), rs.getString("url")));
+                ret.add(new FeedDefinition(
+                        rs.getString("domain"),
+                        rs.getString("url"),
+                        rs.getString("updated")));
             }
 
         } catch (SQLException e) {

code/functions/live-capture/java/nu/marginalia/rss/db/FeedDbWriter.java

@@ -31,13 +31,6 @@ public class FeedDbWriter implements AutoCloseable {
         connection = DriverManager.getConnection(dbUrl);
 
         try (var stmt = connection.createStatement()) {
-            // Disable synchronous writes for speed.  We don't care about recovery.
-            //
-            // If this operation fails we just retry the entire operation from scratch
-            // with a new db file.
-
-            stmt.execute("PRAGMA synchronous = OFF");
-
             stmt.executeUpdate("CREATE TABLE IF NOT EXISTS feed (domain TEXT PRIMARY KEY, feed JSON)");
         }
 

code/functions/live-capture/java/nu/marginalia/rss/model/FeedDefinition.java

@@ -1,3 +1,28 @@
 package nu.marginalia.rss.model;
 
-public record FeedDefinition(String domain, String feedUrl) { }
+import javax.annotation.Nullable;
+import java.time.Duration;
+import java.time.ZonedDateTime;
+
+public record FeedDefinition(
+        String domain,
+        String feedUrl,
+        @Nullable String updated)
+{
+
+    private static final Duration defaultDuration = Duration.ofDays(30);
+
+    public Duration durationSinceUpdated() {
+        if (updated == null) { // Default to 30 days if no update time is available
+            return defaultDuration;
+        }
+
+        try {
+            return Duration.between(ZonedDateTime.parse(updated), ZonedDateTime.now());
+        }
+        catch (Exception e) {
+            return defaultDuration;
+        }
+    }
+
+}

code/functions/live-capture/java/nu/marginalia/rss/svc/FeedFetcherService.java

@@ -5,6 +5,7 @@ import com.google.inject.Inject;
 import com.opencsv.CSVReader;
 import nu.marginalia.WmsaHome;
 import nu.marginalia.executor.client.ExecutorClient;
+import nu.marginalia.model.EdgeDomain;
 import nu.marginalia.nodecfg.NodeConfigurationService;
 import nu.marginalia.rss.db.FeedDb;
 import nu.marginalia.rss.model.FeedDefinition;
@@ -28,6 +29,7 @@ import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.util.*;
 import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.BiFunction;
@@ -67,11 +69,11 @@ public class FeedFetcherService {
         this.nodeConfigurationService = nodeConfigurationService;
         this.serviceHeartbeat = serviceHeartbeat;
         this.executorClient = executorClient;
+
+        rssReader.addHeader("User-Agent", WmsaHome.getUserAgent().uaIdentifier() + "  RSS Feed Fetcher");
     }
 
     public void updateFeeds() throws IOException {
-        rssReader.addHeader("User-Agent", WmsaHome.getUserAgent().uaIdentifier() + "  RSS Feed Fetcher");
-
         if (updating) // Prevent concurrent updates
         {
             logger.error("Already updating feeds, refusing to start another update");
@@ -82,30 +84,69 @@ public class FeedFetcherService {
             var heartbeat = serviceHeartbeat.createServiceAdHocTaskHeartbeat("Update Rss Feeds")
         ) {
             updating = true;
-            var definitions = readDefinitions();
+
+            // Read the feed definitions from the database, if they are not available, read them from the system's
+            // RSS exports instead
+
+            Collection<FeedDefinition> definitions = feedDb.getAllFeeds();
+            if (definitions == null) {
+                definitions = readDefinitionsFromSystem();
+            }
 
             logger.info("Found {} feed definitions", definitions.size());
 
-            AtomicInteger updated = new AtomicInteger(0);
+            final AtomicInteger definitionsUpdated = new AtomicInteger(0);
+            final int totalDefinitions = definitions.size();
 
             SimpleBlockingThreadPool executor = new SimpleBlockingThreadPool("FeedFetcher", 64, 4);
 
             for (var feed : definitions) {
                 executor.submitQuietly(() -> {
+                    var oldData = feedDb.getFeed(new EdgeDomain(feed.domain()));
+
+                    // If we have existing data, we might skip updating it with a probability that increases with time,
+                    // this is to avoid hammering the feeds that are updated very rarely and save some time and resources
+                    // on our end
+
+                    if (!oldData.isEmpty()) {
+                        Duration duration = feed.durationSinceUpdated();
+                        long daysSinceUpdate = duration.toDays();
+
+
+                        if (daysSinceUpdate > 2 && ThreadLocalRandom.current()
+                                .nextInt(1, 1 + (int) Math.min(10, daysSinceUpdate) / 2) > 1)
+                        {
+                            // Skip updating this feed, just write the old data back instead
+                            writer.saveFeed(oldData);
+                            return;
+                        }
+                    }
+
+
                     var items = fetchFeed(feed);
                     if (!items.isEmpty()) {
                         writer.saveFeed(items);
                     }
 
-                    if ((updated.incrementAndGet() % 10_000) == 0) {
-                        // Update the progress every 10k feeds, to avoid hammering the database and flooding the logs
-                        heartbeat.progress("Updated " + updated + "/" + definitions.size() + " feeds", updated.get(), definitions.size());
+                    if ((definitionsUpdated.incrementAndGet() % 1_000) == 0) {
+                        // Update the progress every 1k feeds, to avoid hammering the database and flooding the logs
+                        heartbeat.progress("Updated " + definitionsUpdated + "/" + totalDefinitions + " feeds", definitionsUpdated.get(), totalDefinitions);
                     }
                 });
             }
 
             executor.shutDown();
-            executor.awaitTermination(1, TimeUnit.DAYS);
+            // Wait for the executor to finish, but give up after 60 minutes to avoid hanging indefinitely
+            for (int waitedMinutes = 0; waitedMinutes < 60; waitedMinutes++) {
+                if (executor.awaitTermination(1, TimeUnit.MINUTES)) break;
+            }
+            executor.shutDownNow();
+
+            // Wait for any in-progress writes to finish before switching the database
+            // in case we ended up murdering the writer with shutDownNow.  It's a very
+            // slim chance but this increases the odds of a clean switch over.
+
+            TimeUnit.SECONDS.sleep(5);
 
             feedDb.switchDb(writer);
 
@@ -117,7 +158,7 @@ public class FeedFetcherService {
         }
     }
 
-    public Collection<FeedDefinition> readDefinitions() throws IOException {
+    public Collection<FeedDefinition> readDefinitionsFromSystem() throws IOException {
         Collection<FileStorage> storages = getLatestFeedStorages();
         List<FeedDefinition> feedDefinitionList = new ArrayList<>();
 
@@ -134,7 +175,7 @@ public class FeedFetcherService {
                     var domain = row[0].trim();
                     var feedUrl = row[2].trim();
 
-                    feedDefinitionList.add(new FeedDefinition(domain, feedUrl));
+                    feedDefinitionList.add(new FeedDefinition(domain, feedUrl, null));
                 }
 
             }