小编Sea*_*nOB的帖子

我正在编写一个将csv文件从"queue"文件夹移动到"processing"文件夹的程序,然后以csv文件路径作为参数启动名为import.exe的第三方进程.Import.exe是一个长期运行的任务.

我需要程序继续运行并检查队列中的新文件.出于这个原因,我选择了一个Windows服务应用程序,因为它将长期运行.

我的问题是我对选项不知所措,无法理解我是否应该使用后台线程或并行编程来解决这个问题,或者很可能是两者的结合.

到目前为止,我有这个代码只是同步运行.您很快就会看到,我只是疯狂地解决流程而无需管理或检查完成情况.我已经注释掉了process.WaitForExit(),显然这是一个阻塞调用.

public int maxConcurrentProcesses = 10;
protected override void OnStart(string[] args)
    {
        // Set up a timer to trigger every minute.
        System.Timers.Timer timer = new System.Timers.Timer(60000);            
        timer.Elapsed += new System.Timers.ElapsedEventHandler(this.OnTimer);
        timer.Start();
    }

private void OnTimer(object sender, System.Timers.ElapsedEventArgs args)
    {            
        // How many instances of import.exe are running?
        Process[] importProcesses = Process.GetProcessesByName("import");
        int countRunning = importProcesses.Count();

        // If there are less than maxConcurrentProcesses, create as many as needed to reach maxConcurrentProcesses
        if (countRunning < …

我在 Startup.ConfigureServices 方法中在 HttpClient 上创建了重试策略。另请注意，默认情况下，asp.net core 2.1 为 HttpClient 进行的每个调用记录 4 行 [信息] 行，这些行显示在我的问题末尾的日志中。

services.AddHttpClient("ResilientClient")\n            .AddPolicyHandler(\n                Policy.WrapAsync(\n                    PollyRetryPolicies.TransientErrorRetryPolicy(),\n                    Policy.TimeoutAsync<HttpResponseMessage>(TimeSpan.FromSeconds(60))));\n

该策略定义如下。请注意，我将重试尝试写入日志，因此我会知道是否调用了重试策略。

public static IAsyncPolicy < HttpResponseMessage > TransientErrorRetryPolicy() {\n    return HttpPolicyExtensions\n        .HandleTransientHttpError()\n        .Or < TimeoutRejectedException > ()\n        .WaitAndRetryAsync(sleepDurations: ExponentialBackoffPolicy.DecorrelatedJitter(3, SEED_DELAY, MAX_DELAY),\n            onRetry: (message, timespan, attempt, context) => {\n                context.GetLogger() ? .LogInformation($ "Retrying request to {message?.Result?.RequestMessage?.RequestUri} in {timespan.TotalSeconds} seconds. Retry attempt {attempt}.");\n    });\n}\n

HandleTransientHttpError() 是一个 Polly 扩展，它在注释中指出：

\n

配置要处理的条件是：\n\xe2\x80\xa2 网络故障（如 System.Net.Http.HttpRequestException）

\n

我的httpclient用法是这样的：

using (HttpResponseMessage …

我有一个链接到基于谓词的动作块的转换块。

// Blocks
public TransformBlock<Document, Document> DocumentCreationTransformBlock =
    new TransformBlock<Document, Document>(async document => 
    {          
        return await CreateAsync(document); // REST API call that sets document.NewId
    }, 
    new ExecutionDataflowBlockOptions {
        BoundedCapacity = 100,
        MaxDegreeOfParallelism = 20
    });

public ActionBlock<Document> SplitPipelineActionBlock = 
    new ActionBlock<Document>(async document => 
    { // implementation obfuscated 
    },
    new ExecutionDataflowBlockOptions {
        BoundedCapacity = 100           
    }; 

// Shared block elements      
public DataflowLinkOptions CommonLinkOptions = new DataflowLinkOptions {
    PropagateCompletion = true };

// Link mesh
DocumentCreationTransformBlock.LinkTo(SplitPipelineActionBlock, 
    CommonLinkOptions, 
    document => !string.IsNullOrEmpty(document.NewId));

DocumentCreationTransformBlock.LinkTo(DataflowBlock.NullTarget<Document>(), 
    CommonLinkOptions); …