Question

我使用.net 4.0在vb中编写了一个URL监控程序。基本上它设置一个计时器使用htpwebreques / httpwebresponse每隔60分钟检查一次网址，并在网址关闭时发送一封电子邮件。但是，每次检查URL时，应用程序使用的内存都会不断增加。这显然会导致问题，因为应用程序旨在永久监控网站的可用性，监控机器最终会耗尽资源。

下面的CheckURL例程代码。任何建议都非常感谢，提前感谢。

    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，它会向您显示变量类型不匹配的位置，甚至可能会为您建议更正，例如，请参阅以下代码中DirectCast运算符的使用位置

其次，HttpWebResponse有.Dispose()方法，因此您应该在使用完毕后调用它，或者，正如Zaggler指出的那样，您可以使用Using来确保不受管理资源被正确清理，从而消除了您所关心的内存泄漏。请注意，我们无法看到的代码中可能存在其他类似问题。

你应该不将东西设置为Nothing以试图摆脱它们 - 这样做会对垃圾收集器造成混乱，并且无法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

1 个答案: