Fix MySQL/MariaDB round-stats SQL (GREATEST vs MAX) and throttle DB failure logging

src/main/java/us/tss3/blockparty/persistence/StatsDatabase.java

@@ -10,7 +10,10 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
+import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 
 /** SQLite- or MySQL-backed statistics storage, selected via storage.type in config.yml.
@@ -18,17 +21,39 @@ import java.util.logging.Level;
  *  them off the main thread (see StatsManager). */
 public class StatsDatabase {
 
+    private static final long ERROR_LOG_INTERVAL_MS = TimeUnit.MINUTES.toMillis(5);
+
     private final Plugin plugin;
     private final StorageSettings settings;
     private final String table;
     private Connection connection;
 
+    /** operation name -> last time we actually logged a failure for it, so a persistently
+     *  broken database (bad SQL, dropped connection, etc.) logs once immediately for
+     *  diagnosis and then at most once every {@link #ERROR_LOG_INTERVAL_MS} after that,
+     *  instead of spamming a full stack trace on every round/query. */
+    private final Map<String, Long> lastLoggedAt = new ConcurrentHashMap<>();
+
     public StatsDatabase(Plugin plugin, StorageSettings settings) {
         this.plugin = plugin;
         this.settings = settings;
         this.table = settings.isMysql() ? settings.tablePrefix() + "player_stats" : "player_stats";
     }
 
+    private void logFailure(String operation, UUID uuid, SQLException ex) {
+        long now = System.currentTimeMillis();
+        Long last = lastLoggedAt.get(operation);
+        if (last == null) {
+            plugin.getLogger().log(Level.WARNING, "Failed to " + operation + " for " + uuid
+                    + " (further repeats of this error are throttled to once per 5 minutes)", ex);
+            lastLoggedAt.put(operation, now);
+        } else if (now - last >= ERROR_LOG_INTERVAL_MS) {
+            plugin.getLogger().warning("Still failing to " + operation + ": "
+                    + ex.getClass().getSimpleName() + ": " + ex.getMessage());
+            lastLoggedAt.put(operation, now);
+        }
+    }
+
     public synchronized void connect() {
         try {
             if (settings.isMysql()) {
@@ -119,7 +144,7 @@ public class StatsDatabase {
                 }
             }
         } catch (SQLException ex) {
-            plugin.getLogger().log(Level.WARNING, "Failed to read stats for " + uuid, ex);
+            logFailure("read stats", uuid, ex);
         }
         return PlayerStats.empty(uuid);
     }
@@ -142,14 +167,17 @@ public class StatsDatabase {
         }
         try {
             ensureRow(uuid.toString());
+            // MySQL/MariaDB's MAX() is aggregate-only; the two-argument "greatest of these
+            // values" form used by SQLite must be GREATEST() on that dialect instead.
+            String greatestFn = settings.isMysql() ? "GREATEST" : "MAX";
             try (PreparedStatement ps = connection.prepareStatement(
-                    "UPDATE " + table + " SET best_round = MAX(best_round, ?), total_rounds_survived = total_rounds_survived + 1 WHERE uuid=?")) {
+                    "UPDATE " + table + " SET best_round = " + greatestFn + "(best_round, ?), total_rounds_survived = total_rounds_survived + 1 WHERE uuid=?")) {
                 ps.setInt(1, round);
                 ps.setString(2, uuid.toString());
                 ps.executeUpdate();
             }
         } catch (SQLException ex) {
-            plugin.getLogger().log(Level.WARNING, "Failed to update round stats for " + uuid, ex);
+            logFailure("update round stats", uuid, ex);
         }
     }
 
@@ -165,7 +193,7 @@ public class StatsDatabase {
                 ps.executeUpdate();
             }
         } catch (SQLException ex) {
-            plugin.getLogger().log(Level.WARNING, "Failed to update stats for " + uuid, ex);
+            logFailure("update stats (" + setClause + ")", uuid, ex);
         }
     }
 }