URL 监视器不断增加内存使用量

Question

我使用 .net 4.0 在 vb 中编写了一个 URL 监控程序。基本上，它设置了一个计时器，每 60 分钟检查一次 url，使用 htpwebreques/httpwebresponse 并在 url 关闭时发送电子邮件。但是，每次检查 url 时，应用程序使用的内存都会不断增加。这显然最终会导致问题，因为该应用程序旨在运行永久监控网站的可用性，并且监控机器最终会运行资源不足。

下面是我的检查URL例程的代码。非常感谢任何建议，提前致谢。

    Private Sub checkURL()
    Timer1.Stop()
    Dim wReq As HttpWebRequest
    Dim wResp As HttpWebResponse ' WebResponse

    wReq = HttpWebRequest.Create(url)
    wReq.Method = "HEAD"
    Try
        wResp = wReq.GetResponse()
        If wResp.StatusCode = 200 Then
                txtResponse.Text = wResp.StatusCode & ": " & wResp.StatusDescription & vbNewLine & "The " & siteName & " is up"

                'Only send success results if specified
                If sendOnFailure = False Then
                    sendResults = True
                End If
            Else txtResponse.Text = "There may be a problem with the " & siteName & vbNewLine & "Please verify manually that it is operational." & vbNewLine & "The response received was:" & vbNewLine & "Status Code: " & wResp.StatusCode & " - " & wResp.StatusDescription
                sendResults = True
            End If

        wResp.Close()
        wResp = Nothing
        wReq = Nothing

    Catch ex As Exception
            txtResponse.Text = "There may be a problem with the " & siteName & vbNewLine & "The error returned was:" & vbNewLine & ex.ToString
            sendResults = True

    End Try

    txtLastCheck.Text = Now.ToString("d MMM yyyy HH:mm")
    setNextCheck()

End Sub

Answer 1

首先，您应该使用 Option Strict On, which will show you where you have variable type mismatches and may even suggest corrections for you, for example, see where the DirectCast 运算符，用于以下代码。

其次，HttpWebResponse has a .Dispose() method, so you should call that when you have finished using it, or, as Zaggler pointed out, you can use Using确保正确清理非托管资源，从而消除您担心的内存泄漏。注意，代码中可能还有其他类似的问题我们看不到。

您应该不将事物设置为 Nothing 以试图摆脱它们 - 这样做会扰乱垃圾收集器并且不会确保它们的清洁处理.

Option Strict On
' ....

Private Sub checkURL()
    timer1.Stop()
    Dim wReq As HttpWebRequest = DirectCast(HttpWebRequest.Create(url), HttpWebRequest)
    wReq.Method = "HEAD"

    Try
        Using wResp As HttpWebResponse = DirectCast(wReq.GetResponse(), HttpWebResponse)

            If wResp.StatusCode = 200 Then
                txtResponse.Text = wResp.StatusCode & ": " & wResp.StatusDescription & vbNewLine & "The " & siteName & " is up"

                'Only send success results if specified
                If sendOnFailure = False Then
                    sendResults = True
                End If
            Else txtResponse.Text = "There may be a problem with the " & siteName & vbNewLine & "Please verify manually that it is operational." & vbNewLine & "The response received was:" & vbNewLine & "Status Code: " & wResp.StatusCode & " - " & wResp.StatusDescription
                sendResults = True
            End If

            wResp.Close()
        End Using

    Catch ex As Exception
        txtResponse.Text = "There may be a problem with the " & siteName & vbNewLine & "The error returned was:" & vbNewLine & ex.ToString
        sendResults = True

    End Try

    txtLastCheck.Text = Now.ToString("d MMM yyyy HH:mm")
    setNextCheck()

End Sub

URL 监视器不断增加内存使用量

URL monitor keeps increasing memory usage

vb.net

.net-4.0