.NET5环境下Hangfire调用DI注入的WCF客户端代理出现故障态问题

你注册WCF客户端的代码存在本质错误：预先创建了一个CustomerUpdateStarTransportPortTypesClient全局实例，再通过AddTransient返回该固定实例，即使标注了Transient生命周期，实际容器每次返回的都是同一个单例实例。WCF客户端代理不是线程安全的，多线程并发调用或者上一次调用出错进入故障状态后，后续所有调用都会直接报错，这就是你碰到故障状态报错的核心原因。

1. 修正服务注册逻辑 #

要实现真正的Transient生命周期，每次获取客户端都新建实例，把实例创建逻辑放到注册委托内部：

public static IServiceCollection AddCustomerUpdateClient(this IServiceCollection services, IConfigurationRoot config)
{
    ServicePointManager.Expect100Continue = true;
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
            | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
    // 绑定配置是固定的，可以复用不需要每次创建
    BasicHttpsBinding binding = new BasicHttpsBinding()
    {
        SendTimeout = TimeSpan.FromMinutes(1),
        OpenTimeout = TimeSpan.FromMinutes(1),
        CloseTimeout = TimeSpan.FromMinutes(1),
        ReceiveTimeout = TimeSpan.FromMinutes(10),
        
        Namespace = "http://www.starstandards.org/webservices/2005/10/transport",
        TextEncoding = System.Text.Encoding.UTF8,
        UseDefaultWebProxy = true,
        
    };
    binding.MaxReceivedMessageSize = 50000000;
    binding.ReaderQuotas.MaxArrayLength = 50000000;
    binding.ReaderQuotas.MaxStringContentLength = 50000000;
    binding.ReaderQuotas.MaxNameTableCharCount = 50000000;
    var endpointConfig = config.GetSection(nameof(EndPointConfig));
    EndpointAddress endpointAddress = new EndpointAddress($"{endpointConfig[nameof(EndPointConfig.CuUrl)]}");
    
    // 把客户端创建放到委托内，每次请求都新建实例
    services.AddTransient(x => new CustomerUpdateStarTransportPortTypesClient(binding, endpointAddress));
    return services;
}

2. 增加WCF客户端状态校验与异常处理 #

WCF客户端调用前需要判断状态，故障状态直接销毁重建，调用结束后正确释放资源，同时修正OperationContextScope的异步使用问题：
修改CustomerUpdateService代码如下：

public class CustomerUpdateService : StarService, ICustomerUpdateService
{
    private readonly IServiceProvider _serviceProvider;

    // 改为注入IServiceProvider，每次需要客户端时主动获取新实例
    public CustomerUpdateService(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    [OperationContract]
    public async Task<AcknowledgeCustomerInformationPayload> ProcessCustomerUpdateAsync(
        ProcessCustomerInformationPayload customerPayload,
        string siteCode,
        ApplicationSetttings appSettings,
        string token,
        string customerName
        )
    {
        var fordHeader = new FordDealerIdentity()
        {
            SiteCode = siteCode
        };

        DataContractSerializer dcs = new DataContractSerializer(typeof(FordDealerIdentity));
        // 每次调用从容器拿新的客户端实例
        var starClient = _serviceProvider.GetRequiredService<CustomerUpdateStarTransportPortTypesClient>();
        try
        {
            if (starClient.State == CommunicationState.Faulted)
            {
                starClient.Abort();
                // 故障则重新获取实例
                starClient = _serviceProvider.GetRequiredService<CustomerUpdateStarTransportPortTypesClient>();
            }

            using (OperationContextScope scope = new OperationContextScope(starClient.InnerChannel))
            {
                AddHeaders(appSettings, fordHeader, dcs, token);
                var message = new ProcessMessage()
                {
                    payload = customerPayload
                };
                // 把await放到using块内部，避免OperationContext异步丢失
                var result = await starClient.ProcessMessageAsync(null, message);
                return result.ProcessMessageResponse.payload;
            }
        }
        catch (CommunicationException ex)
        {
            starClient.Abort();
            throw;
        }
        finally
        {
            if (starClient.State == CommunicationState.Opened)
            {
                starClient.Close();
            }
            else if (starClient.State == CommunicationState.Faulted)
            {
                starClient.Abort();
            }
        }
    }
}

3. 可选高性能复用方案 #

如果要避免每次调用都新建客户端的性能损耗，可以实现线程安全的WCF代理池服务，每次从池里取可用实例，故障实例直接销毁，使用完成后归还到池。该方案同样完全兼容DI规范，适合调用量较高的场景。

内容的提问来源于stack exchange，提问作者CT1971