Some info about Project Velocity CTP-1

Named caches are universal across the cluster.

Regions are local to any cache host.It may limiti the scalibility to the cache cluster.

There are three ports.
1- Cluster Port
2- Aribitration port
3- Cache port

Your application must implement the Cache Aside pattern. i.e. it may support its operation even if data is not available in the cluster or even if any server is not available.It should be able to access data directly from database.

There are two types of clients.
1- Simple:
2- Routing

A simple client has no routing capabilities. It also can not track where each cached object is stored.It can request data from only one cache host. If that host does not hold the data. It gets data from other cache host (if available) and presents it to the client.


Each client also has the option to store cached data locally.This feature is called Local Cache.The type of client is configured in the configuration file.


The configuration in the application, so that clients may access the cluster, is maintained in Application Configuration file (app.config)

The configuration of cluster is maintained in ClusterConfig.xml file. This file presents a single point of failure in Velocity which is not yet taken care of (Till CTP1)


Objects are serialized before they are stored on cache host. Before it is used by the client, it must be deserialized. So it is recommended to have a local cache.

Concurrency Model:
Velocity supports the following concurrency models.
1- Optimistic
2- Pessimistic

Cache Expiration and Eviction:
The expiration is configured on named cache level in ClusterConfig.xml file. A TTL (Time to Live) may be associated with an object at the time of "Put".

Eviction is done by using LRU (Least Recently Used) algorithm.

Sample code for FTP client using System.net (FTPWebRequest)

Imports System.Text
Imports System.Net
Imports System.IO

Public Class FTPClient
    Private UserID As String
    Private Password As String

    Public Sub New(ByVal UserID As String, ByVal Password As String)
        Me.UserID = UserID
        Me.Password = Password
    End Sub

    Public Sub uploadFile(ByVal URI As String, ByVal UploadFileName As
String, ByVal LocalPath As String, ByVal LocalFileName As String, Optional
ByVal FTPUserID As String = "", Optional ByVal FTPPassword As String = "")
        Dim completePath = LocalPath + "/" + LocalFileName
        Dim fileInf As FileInfo = New FileInfo(completePath)

        If UploadFileName = "" Then
            UploadFileName = LocalFileName
        End If

        If FTPUserID = "" Then
            FTPUserID = Me.UserID
        End If

        If FTPPassword = "" Then
            FTPPassword = Me.Password
        End If

        Dim MyURI As String = URI + "/" + UploadFileName



        Dim reqFTP As FtpWebRequest


        Dim buffLength As Integer = 2048
        Dim buff(buffLength) As Byte
        Dim contentLen As Integer

        Dim response As FtpWebResponse = Nothing

        Dim fs As FileStream = fileInf.OpenRead()
        Dim strm As Stream = Nothing

        Try
            reqFTP = CType(FtpWebRequest.Create(New Uri(MyURI)),
FtpWebRequest)
            reqFTP.Credentials = New NetworkCredential(FTPUserID,
FTPPassword)
            reqFTP.KeepAlive = False
            reqFTP.Method = WebRequestMethods.Ftp.UploadFile
            reqFTP.UseBinary = True
            reqFTP.ContentLength = fileInf.Length
            reqFTP.UsePassive = True

            response = CType(reqFTP.GetResponse(), FtpWebResponse)

            strm = reqFTP.GetRequestStream()
            contentLen = fs.Read(buff, 0, buffLength)

            While (contentLen <> 0)
                strm.Write(buff, 0, contentLen)
                contentLen = fs.Read(buff, 0, buffLength)
            End While
        Finally
            strm.Close()
            fs.Close()
            response.Close()
        End Try
    End Sub


    Public Function GetFileList(ByVal URI As String, Optional ByVal
FTPUserID As String = "", Optional ByVal FTPPassword As String = "") As
String()
        Dim downloadFiles() As String
        Dim result As StringBuilder = New StringBuilder()
        Dim reqFTP As FtpWebRequest = Nothing
        Dim response As WebResponse = Nothing
        Dim reader As StreamReader = Nothing

        If FTPUserID = "" Then
            FTPUserID = Me.UserID
        End If

        If FTPPassword = "" Then
            FTPPassword = Me.Password
        End If

        Try
            reqFTP = CType(FtpWebRequest.Create(URI), FtpWebRequest)
            reqFTP.UseBinary = True
            reqFTP.Credentials = New NetworkCredential(FTPUserID,
FTPPassword)
            reqFTP.Method = WebRequestMethods.Ftp.ListDirectory

            response = reqFTP.GetResponse()

            reader = New StreamReader(response.GetResponseStream())

            Dim line As String = reader.ReadLine()

            While Not line Is Nothing
                result.Append(line)
                result.Append("\n")
                line = reader.ReadLine()
            End While

            result.Remove(result.ToString().LastIndexOf("\n"), 1)

            downloadFiles = result.ToString().Split("\n")
        Catch ex As Exception
            downloadFiles = Nothing
        Finally
            reader.Close()
            response.Close()
        End Try

        Return downloadFiles
    End Function


    Public Sub downloadFile(ByVal Uri As String, ByVal ToDownLoadFileName
As String, ByVal LocalPath As String, Optional ByVal LocalFileName As
String = "", Optional ByVal FTPUserID As String = "", Optional ByVal
FTPPassword As String = "")
        Dim result As StringBuilder = New StringBuilder()
        Dim reqFTP As FtpWebRequest = Nothing
        Dim response As FtpWebResponse = Nothing
        Dim reader As StreamReader = Nothing

        Dim ftpStream As Stream = Nothing
        Dim outputStream As FileStream = Nothing

        If FTPUserID = "" Then
            FTPUserID = Me.UserID
        End If

        If FTPPassword = "" Then
            FTPPassword = Me.Password
        End If

        If LocalFileName = "" Then
            LocalFileName = ToDownLoadFileName
        End If

        Try
            outputStream = New FileStream(LocalPath + "\\" + LocalFileName,
FileMode.Create)
            reqFTP = CType(FtpWebRequest.Create(Uri + "/" +
ToDownLoadFileName), FtpWebRequest)
            reqFTP.UseBinary = True
            reqFTP.Credentials = New NetworkCredential(FTPUserID,
FTPPassword)
            reqFTP.Method = WebRequestMethods.Ftp.DownloadFile


            response = CType(reqFTP.GetResponse(), FtpWebResponse)
            ftpStream = response.GetResponseStream()

            Dim cl As Long = response.ContentLength
            Dim bufferSize As Integer = 2048

            Dim readCount As Integer
            Dim buffer(bufferSize) As Byte
            readCount = ftpStream.Read(buffer, 0, bufferSize)

            While readCount > 0
                outputStream.Write(buffer, 0, readCount)
                readCount = ftpStream.Read(buffer, 0, bufferSize)
            End While
        Finally
            ftpStream.Close()
            outputStream.Close()
            response.Close()
        End Try
    End Sub
End Class