feat(API): refactor merge rpc

framework/src/main/java/org/tron/core/services/filter/CursorServerInterceptor.java

@@ -0,0 +1,52 @@
+package org.tron.core.services.filter;
+
+import io.grpc.ForwardingServerCallListener.SimpleForwardingServerCallListener;
+import io.grpc.Metadata;
+import io.grpc.ServerCall;
+import io.grpc.ServerCallHandler;
+import io.grpc.ServerInterceptor;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.tron.core.db.Manager;
+import org.tron.core.db2.core.Chainbase;
+
+/**
+ * Switches the current thread's read cursor around the synchronous handler callback and restores it
+ * afterwards, so the handler reads from the snapshot its subclass selects (HEAD / SOLIDITY / PBFT);
+ * the services behind it never touch the cursor.
+ *
+ * <p>Two invariants it relies on:
+ * <ul>
+ * <li>The bracket wraps {@code onHalfClose()} — where gRPC runs the unary handler inline — not
+ * {@code interceptCall}, which may land on another pool thread; the cursor is a
+ * {@link ThreadLocal}, so setting it elsewhere fails silently and the port serves HEAD.
+ * <li>Handlers must be synchronous: the cursor is reset when {@code onHalfClose} returns, so a read
+ * deferred to another thread would read HEAD.
+ * </ul>
+ *
+ * <p>The {@code finally} reset is mandatory: the fixed thread pool is reused, so a leftover cursor
+ * leaks into the next call on that thread.
+ */
+public abstract class CursorServerInterceptor implements ServerInterceptor {
+
+  @Autowired
+  protected Manager dbManager;
+
+  /** Snapshot every call on this server reads from; set by the subclass. */
+  protected Chainbase.Cursor cursor;
+
+  @Override
+  public <Q, A> ServerCall.Listener<Q> interceptCall(
+      ServerCall<Q, A> call, Metadata headers, ServerCallHandler<Q, A> next) {
+    return new SimpleForwardingServerCallListener<Q>(next.startCall(call, headers)) {
+      @Override
+      public void onHalfClose() {
+        try {
+          dbManager.setCursor(cursor);
+          super.onHalfClose();
+        } finally {
+          dbManager.resetCursor();
+        }
+      }
+    };
+  }
+}

framework/src/main/java/org/tron/core/services/filter/PbftCursorInterceptor.java

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+package org.tron.core.services.filter;
+
+import org.springframework.stereotype.Component;
+import org.tron.core.db2.core.Chainbase;
+
+/**
+ * Makes every call on the PBFT gRPC server read the PBFT-confirmed state view.
+ */
+@Component
+public class PbftCursorInterceptor extends CursorServerInterceptor {
+
+  public PbftCursorInterceptor() {
+    this.cursor = Chainbase.Cursor.PBFT;
+  }
+}

framework/src/main/java/org/tron/core/services/filter/SolidityCursorInterceptor.java

@@ -0,0 +1,15 @@
+package org.tron.core.services.filter;
+
+import org.springframework.stereotype.Component;
+import org.tron.core.db2.core.Chainbase;
+
+/**
+ * Makes every call on the Solidity gRPC server read the solidified state view.
+ */
+@Component
+public class SolidityCursorInterceptor extends CursorServerInterceptor {
+
+  public SolidityCursorInterceptor() {
+    this.cursor = Chainbase.Cursor.SOLIDITY;
+  }
+}