feat: implement lazy auto-commit handling to prevent race conditions during store initialization

Author: anidotnet

nitrite-mvstore-adapter/src/main/java/org/dizitart/no2/mvstore/MVStoreUtils.java

@@ -119,9 +119,10 @@ private static MVStore.Builder createBuilder(MVStoreConfig mvStoreConfig) {
             builder = builder.fileName(mvStoreConfig.filePath());
         }
 
-        if (!mvStoreConfig.autoCommit()) {
-            builder = builder.autoCommitDisabled();
-        }
+        // auto-commit is enabled after the store is fully bootstrapped (see openOrCreate),
+        // to avoid the background writer racing with creation of the very first map/chunk
+        // on a brand new store, which can corrupt the file (github issue: CI flakiness)
+        builder = builder.autoCommitDisabled();
 
         if (mvStoreConfig.autoCommitBufferSize() > 0) {
             builder = builder.autoCommitBufferSize(mvStoreConfig.autoCommitBufferSize());

nitrite-mvstore-adapter/src/main/java/org/dizitart/no2/mvstore/NitriteMVStore.java

@@ -45,6 +45,7 @@ public class NitriteMVStore extends AbstractNitriteStore<MVStoreConfig> {
     private MVStore mvStore;
     private final Map<String, NitriteMap<?, ?>> nitriteMapRegistry;
     private final Map<String, NitriteRTree<?, ?>> nitriteRTreeMapRegistry;
+    private volatile boolean autoCommitPending;
 
     public NitriteMVStore() {
         super();
@@ -54,11 +55,23 @@ public NitriteMVStore() {
 
     @Override
     public void openOrCreate() {
+        // MVStoreUtils always opens with auto-commit disabled; it is enabled lazily
+        // right after the very first map is created (see enableAutoCommitIfPending()),
+        // so the background writer never races with bootstrapping a brand new store
+        this.autoCommitPending = getStoreConfig().autoCommit();
         this.mvStore = MVStoreUtils.openOrCreate(getStoreConfig());
         initEventBus();
         alert(StoreEvents.Opened);
     }
 
+    private void enableAutoCommitIfPending() {
+        if (autoCommitPending) {
+            autoCommitPending = false;
+            mvStore.commit();
+            mvStore.setAutoCommitDelay(1000);
+        }
+    }
+
     @Override
     public boolean isClosed() {
         return mvStore == null || mvStore.isClosed();
@@ -76,7 +89,20 @@ public boolean isReadOnly() {
 
     @Override
     public void commit() {
-        mvStore.commit();
+        // pause the background writer for the duration of this explicit commit;
+        // H2's autocommit thread and an explicit commit() racing on the same store
+        // can trip an internal MVStore assertion (concurrent chunk serialization)
+        int delay = mvStore.getAutoCommitDelay();
+        if (delay > 0) {
+            mvStore.setAutoCommitDelay(0);
+        }
+        try {
+            mvStore.commit();
+        } finally {
+            if (delay > 0) {
+                mvStore.setAutoCommitDelay(delay);
+            }
+        }
         alert(StoreEvents.Commit);
     }
 
@@ -187,7 +213,9 @@ private MVMap openMVMap(String mapName, MVMap.MapBuilder builder) {
 
             while (version >= 0) {
                 try {
-                    return mvStore.openMap(mapName, mapBuilder);
+                    MVMap map = mvStore.openMap(mapName, mapBuilder);
+                    enableAutoCommitIfPending();
+                    return map;
                 } catch (MVStoreException me) {
                     if (version == 0) {
                         throw me;