rpcdaemon: json streamed request exception handling (#1790)

silkworm/rpc/http/request_handler.cpp

@@ -158,20 +158,27 @@ Task<void> RequestHandler::handle_request(commands::RpcApiTable::HandleMethod ha
 }
 
 Task<void> RequestHandler::handle_request(commands::RpcApiTable::HandleStream handler, const nlohmann::json& request_json) {
-    try {
-        auto io_executor = co_await boost::asio::this_coro::executor;
+    auto io_executor = co_await boost::asio::this_coro::executor;
 
+    try {
         co_await channel_->open_stream();
         ChunkWriter chunk_writer(*channel_);
         json::Stream stream(io_executor, chunk_writer);
 
-        co_await (rpc_api_.*handler)(request_json, stream);
-
+        try {
+            co_await (rpc_api_.*handler)(request_json, stream);
+        } catch (const std::exception& e) {
+            SILK_ERROR << "exception: " << e.what();
+            const auto error = make_json_error(request_json, 100, e.what());
+            stream.write_json(error);
+        } catch (...) {
+            SILK_ERROR << "unexpected exception";
+            const auto error = make_json_error(request_json, 100, "unexpected exception");
+            stream.write_json(error);
+        }
         co_await stream.close();
     } catch (const std::exception& e) {
         SILK_ERROR << "exception: " << e.what();
-    } catch (...) {
-        SILK_ERROR << "unexpected exception";
     }
 
     co_return;