Flutter中使用graphql_flutter遇间歇性Connection closed before full header was received错误

针对这种偶发的连接错误，给你几个可行的解决方向：

• 延长请求超时时间
  默认HttpLink的超时设置可能偏短，遇到网络波动时容易提前断开。初始化HttpLink时可以手动设置更长的连接和闲置超时：

  final httpLink = HttpLink(
    '你的GraphQL端点地址',
    httpClient: IOClient(
      HttpClient()
        ..connectionTimeout = const Duration(seconds: 30)
        ..idleTimeout = const Duration(seconds: 30),
    ),
  );
  

• 给请求加重试机制
  既然是偶发错误，重试能大概率解决问题。用RetryLink包装你的HttpLink，设置重试次数和间隔：

  final retryLink = RetryLink(
    delay: const Duration(milliseconds: 500),
    maxAttempts: 3,
    retryIf: (response) => response == null || response.hasErrors,
  );
  
  final link = retryLink.concat(httpLink);
  

• 排查服务器端配置
  这个错误也可能是服务器端的问题：比如服务器连接超时设置过短，或者负载过高导致主动断开连接。需要确认服务器的连接超时、Keep-Alive参数，以及服务器是否存在过载情况。

• 更换HTTP客户端
  试试替换默认的IOClient，比如用Dio作为底层客户端，有时候不同客户端的连接处理逻辑能规避兼容性问题：

  // 需要先添加dio依赖
  final dio = Dio();
  dio.options.connectTimeout = const Duration(seconds: 30);
  final httpLink = HttpLink(
    '你的GraphQL端点地址',
    httpClient: DioHttpClient(dio),
  );
  

• 检查网络环境
  偶发错误可能和用户的网络波动有关，比如弱网下数据包丢失。可以在应用里加个网络状态检测，网络不稳定时提醒用户或者暂缓请求。

错误日志详情 #

flutter: OperationException(linkException: ServerException(originalException: Connection closed before full header was received, originalStackTrace: #0      IOClient.send (package:http/src/io_client.dart:96:7)
<asynchronous suspension>
#1      HttpLink._executeRequest (package:gql_http_link/src/link.dart:131:24)
<asynchronous suspension>
#2      HttpLink.request (package:gql_http_link/src/link.dart:76:26)
<asynchronous suspension>
#3      _StreamController._add (dart:async/stream_controller.dart:656:3)
<asynchronous suspension>
, parsedResponse: null), graphqlErrors: [])

内容的提问来源于stack exchange，提问作者Mansoor Ali