perf: flush the sales folder's parent only when the folder is new

src/main/java/net/tfminecraft/marketblock/trade/MarketSale.java

@@ -7,7 +7,9 @@
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 import java.util.Properties;
+import java.util.Set;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 import net.tfminecraft.denareconomy.api.Denars;
 import net.tfminecraft.denareconomy.api.Result;
@@ -20,6 +22,9 @@
  * after the payment is applied.
  */
 public final class MarketSale {
+    /** Sale folders whose entry in their parent folder this server run has flushed to disk. */
+    private static final Set<Path> FLUSHED_FOLDERS = ConcurrentHashMap.newKeySet();
+
     private final String opId;
     private final CharacterRef seller;
     private final SaleTake take;
@@ -53,15 +58,26 @@ public Result settle() throws IOException {
         }
         if (result == Result.APPLIED || result == Result.REFUSED) {
             Files.deleteIfExists(intent);
+            // Must stay: an intent that comes back after a crash blocks the seller's next sale (CREATE_NEW).
             syncDirectory();
         }
         return result;
     }
 
     private void record() throws IOException {
-        Files.createDirectories(intent.getParent());
-        try (FileChannel parent = FileChannel.open(intent.getParent().getParent(), StandardOpenOption.READ)) {
-            parent.force(true);
+        Path folder = intent.getParent();
+        Path key = folder.toAbsolutePath().normalize();
+        boolean created = !Files.isDirectory(folder);
+        if (created) {
+            // A recreated folder is a new entry: forget the earlier flush until this one succeeds.
+            FLUSHED_FOLDERS.remove(key);
+            Files.createDirectories(folder);
+        }
+        // A new folder survives a crash only once its parent is flushed. An existing one is flushed once per
+        // run, in case the flush after it was made failed; after that its entry is already on disk.
+        if (created || !FLUSHED_FOLDERS.contains(key)) {
+            force(folder.getParent());
+            FLUSHED_FOLDERS.add(key);
         }
         Properties data = new Properties();
         data.setProperty("operation", opId);
@@ -80,8 +96,12 @@ private void record() throws IOException {
     }
 
     private void syncDirectory() throws IOException {
-        try (FileChannel directory = FileChannel.open(intent.getParent(), StandardOpenOption.READ)) {
-            directory.force(true);
+        force(intent.getParent());
+    }
+
+    static void force(Path directory) throws IOException {
+        try (FileChannel channel = FileChannel.open(directory, StandardOpenOption.READ)) {
+            channel.force(true);
         }
     }
 }

src/test/java/net/tfminecraft/marketblock/trade/MarketSaleTest.java

@@ -117,6 +117,46 @@ void paidRetryUsesStoredResultAfterTaxChangesAndRefusesChangedGoods() throws Exc
     }
 
 
+    @Test
+    void theParentFolderIsFlushedOnlyForANewSaleFolderOrOnceARunForAnExistingOne() throws Exception {
+        var seller = money.play(player);
+        player.getInventory().setItem(0, new ItemStack(Material.CARROT, 14));
+        Path sales = folder.resolve("sales");
+        Path existing = java.nio.file.Files.createDirectories(folder.resolve("existing"));
+        try (var flushes = mockStatic(MarketSale.class, CALLS_REAL_METHODS)) {
+            flushes.when(() -> MarketSale.force(any(Path.class))).thenAnswer(call -> null);
+
+            assertEquals(Result.APPLIED, sell(sales, seller));
+            assertEquals(Result.APPLIED, sell(sales, seller));
+            flushes.verify(() -> MarketSale.force(folder), times(1));
+            // Each sale still flushes its intent being written and being removed.
+            flushes.verify(() -> MarketSale.force(sales), times(4));
+
+            assertEquals(Result.APPLIED, sell(existing, seller));
+            assertEquals(Result.APPLIED, sell(existing, seller));
+            flushes.verify(() -> MarketSale.force(folder), times(2));
+
+            java.nio.file.Files.delete(sales);
+            assertEquals(Result.APPLIED, sell(sales, seller));
+            flushes.verify(() -> MarketSale.force(folder), times(3));
+            assertTrue(java.nio.file.Files.isDirectory(sales));
+
+            // A recreated folder whose flush fails is flushed again by the next sale, before it pays.
+            java.nio.file.Files.delete(sales);
+            flushes.when(() -> MarketSale.force(folder)).thenThrow(new java.io.IOException("simulated parent flush failure"));
+            assertThrows(java.io.IOException.class, () -> sell(sales, seller));
+            flushes.when(() -> MarketSale.force(folder)).thenAnswer(call -> null);
+            assertEquals(Result.APPLIED, sell(sales, seller));
+            flushes.verify(() -> MarketSale.force(folder), times(5));
+        }
+        assertEquals(2, player.getInventory().getItem(0).getAmount());
+        assertEquals(600, Denars.balance(Denars.pouch(seller)));
+    }
+
+    private Result sell(Path sales, net.tfminecraft.tlibs.character.CharacterRef seller) throws Exception {
+        return new MarketSale(sales, seller, InventoryUtils.planTake(player, "v.carrot", 2), 100).settle();
+    }
+
     @Test void waitingForFactionTaxDoesNotCreateAnAmbiguousSale() throws Exception {
         var seller=money.play(player);
         MockBukkit.createMockPlugin("SimpleFactions");