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  • How can I solve Windows PPTP VPN issues?

    - by Robin M
    I'm having persistent problems with Windows PPTP VPN connections. The VPN appears up whilst the tunnel won't transfer traffic (ping to a remote IP within the VPN works for a while, and then fails). The client receives routing information via DHCP. When the connection fails, the routing table is still correct so I don't think it's a routing problem. My internet connection is via an ADSL2 line. There's software to deal with PPTP problems, like TunnelRat, but I don't want to install v1.1 of the .NET framework and I'd rather get to the bottom of the problem (I have multiple VPN connections and some are more unreliable than others). What can I do to get to the bottom of this? Alternatively, what can I do to keep the connection alive?

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  • What alternative is there to Nginx that supports http keep-alive between backends ?

    - by felace
    Hi. I recently asked a question about how to keep a backend connection persistent using Nginx, but found out it wasn't possible anyway, It is an HTTP/1.0 proxy without the ability for keep-alive requests yet. (As a result, backend connections are created and destroyed on every request.) It works all fine right now (since the connection between client and Nginx is kept alive and the result is simply the same), but I don't want to establish a new connection every single time a new request is received ,even if it's on a unix domain socket. So, what software (preferably open-source and not too tedious to configure) do you recommend to accomplish that such connections ?

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  • SSH logins failing before success

    - by Vincent
    I am running Ubuntu 12.04 Server, updated, to run a webserver on Tomcat 7. I have about 1000 clients that are very very often using an RSYNC program to sync some file with this server. Those RSync are using SSH with a certain user to open connections on the server. The result is that my server is, as normal, full of connections by the same user. About 5 connections per 1 second every day any time. Then, when I try to open a regular SSH connection with my Putty client, the connection fails before login saying "Server unexpectedly closed network connection", about 6 times for 10 attemps, anbd for 4 attemps out of 10, it works normally and I am able to login as any user. Is there a overload of connections here? The server statistics are very calm saying less then 40% of network usage and less of 2% CPU. How can I improve this? Thank you for any help. V.

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  • I Cannot connect to remote MySQL database using SSH tunnel

    - by Scott
    Brand new server, brand new MySQL 5.5 install on Ubuntu 12.04. I can log in to the database as root from the command line. I can log on via Navicat MySQL or Sequel Pro as root on port 3306 from my Mac. I cannot log in using an SSH tunnel to the server and then to the database as root. I have tried both localhost and 127.0.0.1 as server for the local connection part. My password is fine. root is currently defined at %, 127.0.0.1, and localhost. I have set up this same type of connection at least 30 times before and never had a problem. The SSH connection gets made with no problem, and then it just hangs trying to connect to the DB and finally times out. The only thing I changed in my.cnf was to comment out the bind-address = 127.0.0.1 line. Any help? Any Ideas?

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  • Win xp reinstall now I am unable to connect to broadband what shall I select to do this?

    - by waterfallrain
    Hello, My hardrive was failing so I needed to reinstall win xp. I completed the reinstall and the drivers but now only the wireless connection works. The broadband states connected but does not go out to the interenet. When I click Internet Explorer it says unable to find webpage. I have tried several major sites so I know its not the site but some configuration or something I need to do on my end. When I go to the cmd prompt and renew the ip it refers to my wireless nothing about this broadband connection. What do I type/select to get this to go out to the Internet. The broadband is working for my other laptop so I know the connection is not the issue. Any help would be much appreciated thank you.

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  • openvpn and selective routing

    - by mx2323
    hi everyone, whats the best way to configure openvpn clients to go selectively go about using an openvpn connection? i want to setup a vpn server for friends in china, but i dont want them to use it for everything, just so they can access sites like youtube, facebook, cnn, etc. while they are in china through the vpn (these are blocked). it would be nice if the vpn was a backup, so for instance if they are trying to go to facebook (which is blocked), it would go through the vpn connection once finding that the normal connection does not work. this would save a lot of bandwidth cost actually, and give them a better browsing experience. is this a iptable route thing? or a dns server that i push to my clients?

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  • Windows XP reinstall, now I am unable to connect to broadband what shall I select to do this?

    - by waterfallrain
    My hardrive was failing so I needed to reinstall Windows XP. I completed the reinstall and the drivers but now only the wireless connection works. The broadband states connected but does not go out to the Internet. When I click Internet Explorer it says unable to find webpage. I have tried several major sites so I know it's not the site but some configuration or something I need to do on my end. When I go to the command prompt and renew the IP address it refers to my wireless, nothing about this broadband connection. What do I type/select to get this to go out to the Internet. The broadband is working for my other laptop so I know the connection is not the issue. Any help would be much appreciated.

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  • Opening up a link in a new tab in Firefox doesn't show address

    - by Tim
    Sometimes for some reason, connection to a new link/address takes a long time to establish. In Firefox 11.0, the address bar will keep showing "about:blank". I take this as normal, and let me know if it isn't. If the connection is stopped for some reason, I will not be able to find out the address that I was trying to connect to. I wonder how to find out that address, both before and after the connection is stopped at "about:blank"? Thanks and regards!

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  • exchange server 5.5 stops responding

    - by user57221
    From last couple of weeks I am getting connection problem with my in-house exchange server 5.5 running on windows 2003. It has been working fine from last 5 years. but from few weeks it is loosing connection with other outlook clients. I have to restart my exchange server to make it work. This happens few times in a week. It looses connection somewhere between 7PM to 8AM as when I come in office. I find this problem, while it leave office it works fine. We have not installed any updates or software since last more than 2 years. What could be the reason for stop working?

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  • Allowing ssh in iptables

    - by sat
    I am doing iptables firewall configuration. Actually, I need to allow ssh connection only from particular IP. But, It is blocking the ssh connection. I used the below commands. sat:~# iptables -F sat:~# iptables -A INPUT -p tcp -s src_ip_address -d my_ip_address --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT sat:~# iptables -A INPUT -j DROP sat:~# iptables -nL Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT tcp -- src_ip_address my_ip_address tcp dpt:22 state NEW,ESTABLISHED DROP all -- 0.0.0.0/0 0.0.0.0/0 Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination If I try to connect from src_ip_address to my_ip_address, it is blocking the connection. Even, It is blocking from my_ip_address to src_ip_address . I haven't put any rules for OUTPUT chain. What is wrong with my commands? How to allow ssh in iptables?

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  • Architecture for a business objects / database access layer

    - by gregmac
    For various reasons, we are writing a new business objects/data storage library. One of the requirements of this layer is to separate the logic of the business rules, and the actual data storage layer. It is possible to have multiple data storage layers that implement access to the same object - for example, a main "database" data storage source that implements most objects, and another "ldap" source that implements a User object. In this scenario, User can optionally come from an LDAP source, perhaps with slightly different functionality (eg, not possible to save/update the User object), but otherwise it is used by the application the same way. Another data storage type might be a web service, or an external database. There are two main ways we are looking at implementing this, and me and a co-worker disagree on a fundamental level which is correct. I'd like some advice on which one is the best to use. I'll try to keep my descriptions of each as neutral as possible, as I'm looking for some objective view points here. Business objects are base classes, and data storage objects inherit business objects. Client code deals with data storage objects. In this case, common business rules are inherited by each data storage object, and it is the data storage objects that are directly used by the client code. This has the implication that client code determines which data storage method to use for a given object, because it has to explicitly declare an instance to that type of object. Client code needs to explicitly know connection information for each data storage type it is using. If a data storage layer implements different functionality for a given object, client code explicitly knows about it at compile time because the object looks different. If the data storage method is changed, client code has to be updated. Business objects encapsulate data storage objects. In this case, business objects are directly used by client application. Client application passes along base connection information to business layer. Decision about which data storage method a given object uses is made by business object code. Connection information would be a chunk of data taken from a config file (client app does not really know/care about details of it), which may be a single connection string for a database, or several pieces connection strings for various data storage types. Additional data storage connection types could also be read from another spot - eg, a configuration table in a database that specifies URLs to various web services. The benefit here is that if a new data storage method is added to an existing object, a configuration setting can be set at runtime to determine which method to use, and it is completely transparent to the client applications. Client apps do not need to be modified if data storage method for a given object changes. Business objects are base classes, data source objects inherit from business objects. Client code deals primarily with base classes. This is similar to the first method, but client code declares variables of the base business object types, and Load()/Create()/etc static methods on the business objects return the appropriate data source-typed objects. The architecture of this solution is similar to the first method, but the main difference is the decision about which data storage object to use for a given business object is made by the business layer, not the client code. I know there are already existing ORM libraries that provide some of this functionality, but please discount those for now (there is the possibility that a data storage layer is implemented with one of these ORM libraries) - also note I'm deliberately not telling you what language is being used here, other than that it is strongly typed. I'm looking for some general advice here on which method is better to use (or feel free to suggest something else), and why.

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  • How to make Net::Msmgr run?

    - by codeholic
    There's Net::Msmgr module on CPAN. It's written clean and the code looks trustworthy at the first glance. However this module seems to be beta and there is little documentation and no tests :-/ Has anyone used this module in production? I haven't managed to make it run by now, because it requires all event loop processing to be done in the application and as I've already said there is little documentation and no working examples to study. That's where I've gone so far: #!/usr/bin/perl use strict; use warnings; use Event; use Net::Msmgr::Object; use Net::Msmgr::Session; use Net::Msmgr::User; use constant DEBUG => 511; use constant EVENT_TIMEOUT => 5; # seconds my ($username, $password) = qw/[email protected] my.password/; my $buddy = '[email protected]'; my $user = Net::Msmgr::User->new(user => $username, password => $password); my $session = Net::Msmgr::Session->new; $session->debug(DEBUG); $session->login_handler(\&login_handler); $session->user($user); my $conv; sub login_handler { my $self = shift; print "LOGIN\n"; $self->ui_state_nln; $conv = $session->ui_new_conversation; $conv->invite($buddy); } our %watcher; sub ConnectHandler { my ($connection) = @_; warn "CONNECT\n"; my $socket = $connection->socket; $watcher{$connection} = Event->io(fd => $socket, cb => [ $connection, '_recv_message' ], poll => 're', desc => 'recv_watcher', repeat => 1); } sub DisconnectHandler { my $connection = shift; print "DISCONNECT\n"; $watcher{$connection}->cancel; } $session->connect_handler(\&ConnectHandler); $session->disconnect_handler(\&DisconnectHandler); $session->Login; Event::loop(); That's what it outputs: Dispatch Server connecting to: messenger.hotmail.com:1863 Dispatch Server connected CONNECT Dispatch Server >>>VER 1 MSNP2 CVR0 --> VER 1 MSNP2 CVR0 Dispatch Server >>>USR 2 MD5 I [email protected] --> USR 2 MD5 I [email protected] Dispatch Server <<<VER 1 CVR0 <-- VER 1 CVR0 And that's all, here it hangs. The handler on login is not being triggered. What am I doing wrong?

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  • How to make Net::Msmnr run?

    - by codeholic
    There's Net::Msmgr module on CPAN. It's written clean and the code looks trustworthy at the first glance. However this module seems to be beta and there is little documentation and no tests :-/ Has anyone used this module in production? I haven't managed to make it run by now, because it requires all event loop processing to be done in the application and as I've already said there is little documentation and no working examples to study. That's where I've gone so far: #!/usr/bin/perl use strict; use warnings; use Event; use Net::Msmgr::Object; use Net::Msmgr::Session; use Net::Msmgr::User; use constant DEBUG => 511; use constant EVENT_TIMEOUT => 5; # seconds my ($username, $password) = qw/[email protected] my.password/; my $buddy = '[email protected]'; my $user = Net::Msmgr::User->new(user => $username, password => $password); my $session = Net::Msmgr::Session->new; $session->debug(DEBUG); $session->login_handler(\&login_handler); $session->user($user); my $conv; sub login_handler { my $self = shift; print "LOGIN\n"; $self->ui_state_nln; $conv = $session->ui_new_conversation; $conv->invite($buddy); } our %watcher; sub ConnectHandler { my ($connection) = @_; warn "CONNECT\n"; my $socket = $connection->socket; $watcher{$connection} = Event->io(fd => $socket, cb => [ $connection, '_recv_message' ], poll => 're', desc => 'recv_watcher', repeat => 1); } sub DisconnectHandler { my $connection = shift; print "DISCONNECT\n"; $watcher{$connection}->cancel; } $session->connect_handler(\&ConnectHandler); $session->disconnect_handler(\&DisconnectHandler); $session->Login; Event::loop(); That's what it outputs: Dispatch Server connecting to: messenger.hotmail.com:1863 Dispatch Server connected CONNECT Dispatch Server >>>VER 1 MSNP2 CVR0 --> VER 1 MSNP2 CVR0 Dispatch Server >>>USR 2 MD5 I [email protected] --> USR 2 MD5 I [email protected] Dispatch Server <<<VER 1 CVR0 <-- VER 1 CVR0 And that's all, here it hangs. The handler on login is not being triggered. What am I doing wrong?

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  • Inconsistent accessibility

    - by user1312412
    I am getting the following error Inconsistent accessibility: parameter type 'Db.Form1.ConnectionString' is less accessible than method 'Db.Form1.BuildConnectionString(Db.Form1.ConnectionString)' //Name spaces using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using Microsoft.VisualBasic; using System.Collections; using System.Diagnostics; using System.Data.OleDb; using System.IO; using System.Drawing.Printing; // namespace Db { public partial class Form1 : Form { public Form1() { InitializeComponent(); } public void SetBusy() { this.Cursor = Cursors.WaitCursor; Application.DoEvents(); } public void SetFree() { this.Cursor = Cursors.Default; Application.DoEvents(); } //connection string into parts struct ConnectionString { public string Provider; public string DataSource; public string UserId; public string Password; public string Database; } //Declare public string BuildConnectionString(ConnectionString connStr) ------> getting error here { string[] parts = new string[5]; parts[0] = "Provider=" + connStr.Provider; parts[1] = "Data Source=" + connStr.DataSource; parts[2] = "User Id=" + connStr.UserId; parts[3] = "Password=" + connStr.Password; parts[4] = "Initial Catalog=" + connStr.Database; return string.Join(";", parts); } // settings public bool IsValidConnectionForPrinting() { SetBusy(); ConnectionString connStr = new ConnectionString(); connStr.Provider = cboProvider.Text; connStr.DataSource = cboDataSource.Text; connStr.UserId = txtUserId.Text; connStr.Password = txtPassword.Text; connStr.Database = cboDatabase.Text; //connection string to database string connectionString = BuildConnectionString(connStr); OleDbConnection conn = new OleDbConnection(connectionString); try { conn.Open(); OleDbCommand cmd = conn.CreateCommand; cmd.CommandType = CommandType.TableDirect; cmd.CommandText = "vw_pr_DL"; cmd.ExecuteScalar(); cmd.CommandText = "vw_pr_VR"; cmd.ExecuteScalar(); //cmd.CommandText = "vw_pr_VR" //cmd.ExecuteScalar() conn.Close(); } //Exception messages catch (Exception ex) { SetFree(); if (ex.Message.StartsWith("Invalid object name")) { MessageBox.Show(ex.Message.Replace("Invalid object name", "Table or view not found"), "Connection Test"); } else { MessageBox.Show(ex.GetBaseException().Message, "Connection Test"); } return false; } SetFree(); return true; } // when user click testbutton private void btnConnTest_Click(object sender, EventArgs e) { if (IsValidConnectionForPrinting()) { MessageBox.Show("Connection succeeded", "Connection Test"); } }

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  • Why does Perl's Net::Msmgr hang when I try to authenticate?

    - by codeholic
    There's Net::Msmgr module on CPAN. It's written clean and the code looks trustworthy at the first glance. However this module seems to be beta and there is little documentation and no tests :-/ Has anyone used this module in production? I haven't managed to make it run by now, because it requires all event loop processing to be done in the application and as I've already said there is little documentation and no working examples to study. That's where I've gone so far: #!/usr/bin/perl use strict; use warnings; use Event; use Net::Msmgr::Object; use Net::Msmgr::Session; use Net::Msmgr::User; use constant DEBUG => 511; use constant EVENT_TIMEOUT => 5; # seconds my ($username, $password) = qw/[email protected] my.password/; my $buddy = '[email protected]'; my $user = Net::Msmgr::User->new(user => $username, password => $password); my $session = Net::Msmgr::Session->new; $session->debug(DEBUG); $session->login_handler(\&login_handler); $session->user($user); my $conv; sub login_handler { my $self = shift; print "LOGIN\n"; $self->ui_state_nln; $conv = $session->ui_new_conversation; $conv->invite($buddy); } our %watcher; sub ConnectHandler { my ($connection) = @_; warn "CONNECT\n"; my $socket = $connection->socket; $watcher{$connection} = Event->io(fd => $socket, cb => [ $connection, '_recv_message' ], poll => 're', desc => 'recv_watcher', repeat => 1); } sub DisconnectHandler { my $connection = shift; print "DISCONNECT\n"; $watcher{$connection}->cancel; } $session->connect_handler(\&ConnectHandler); $session->disconnect_handler(\&DisconnectHandler); $session->Login; Event::loop(); That's what it outputs: Dispatch Server connecting to: messenger.hotmail.com:1863 Dispatch Server connected CONNECT Dispatch Server >>>VER 1 MSNP2 CVR0 --> VER 1 MSNP2 CVR0 Dispatch Server >>>USR 2 MD5 I [email protected] --> USR 2 MD5 I [email protected] Dispatch Server <<<VER 1 CVR0 <-- VER 1 CVR0 And that's all, here it hangs. The handler on login is not being triggered. What am I doing wrong?

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  • Magento - Data is not inserted into database, but the id is autoincremented

    - by Joseph
    I am working on a new payment module for Magento and have come across an issue that I cannot explain. The following code that runs after the credit card is verified: $table_prefix = Mage::getConfig()->getTablePrefix(); $tableName = $table_prefix.'authorizecim_magento_id_link'; $resource = Mage::getSingleton('core/resource'); $writeconnection = $resource->getConnection('core_write'); $acPI = $this->_an_customerProfileId; $acAI = $this->_an_customerAddressId; $acPPI = $this->_an_customerPaymentProfileId; $sql = "insert into {$tableName} values ('', '$customerId', '$acPI', '$acPI', '3')"; $writeconnection->query($sql); $sql = "insert into {$tableName} (magCID, anCID, anOID, anObjectType) values ('$customerId', '$acPI', '$acAI', '2')"; $writeconnection->query($sql); $sql = "insert into {$tableName} (magCID, anCID, anOID, anObjectType) values ('$customerId', '$acPI', '$acPPI', '1')"; $writeconnection->query($sql); I have verified using Firebug and FirePHP that the SQL queries are syntactically correct and no errors are returned. The odd thing here is that I have checked the database, and the autoincrement value is incremented on every run of the code. However, no rows are inserted in the database. I have verified this by adding a die(); statement directly after the first write. Any ideas why this would be occuring? The relative portion of the config.xml is this: <config> <global> <models> <authorizecim> <class>CPAP_AuthorizeCim_Model</class> </authorizecim> <authorizecim_mysql4> <class>CPAP_AuthorizeCim_Model_Mysql4</class> <entities> <anlink> <table>authorizecim_magento_id_link</table> </anlink> </entities> <entities> <antypes> <table>authorizecim_magento_types</table> </antypes> </entities> </authorizecim_mysql4> </models> <resources> <authorizecim_setup> <setup> <module>CPAP_AuthorizeCim</module> <class>CPAP_AuthorizeCim_Model_Resource_Mysql4_Setup</class> </setup> <connection> <use>core_setup</use> </connection> </authorizecim_setup> <authorizecim_write> <connection> <use>core_write</use> </connection> </authorizecim_write> <authorizecim_read> <connection> <use>core_read</use> </connection> </authorizecim_read> </resources> </global> </config>

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  • Resumable upload from Java client to Grails web application?

    - by dersteps
    After almost 2 workdays of Googling and trying several different possibilities I found throughout the web, I'm asking this question here, hoping that I might finally get an answer. First of all, here's what I want to do: I'm developing a client and a server application with the purpose of exchanging a lot of large files between multiple clients on a single server. The client is developed in pure Java (JDK 1.6), while the web application is done in Grails (2.0.0). As the purpose of the client is to allow users to exchange a lot of large files (usually about 2GB each), I have to implement it in a way, so that the uploads are resumable, i.e. the users are able to stop and resume uploads at any time. Here's what I did so far: I actually managed to do what I wanted to do and stream large files to the server while still being able to pause and resume uploads using raw sockets. I would send a regular request to the server (using Apache's HttpClient library) to get the server to send me a port that was free for me to use, then open a ServerSocket on the server and connect to that particular socket from the client. Here's the problem with that: Actually, there are at least two problems with that: I open those ports myself, so I have to manage open and used ports myself. This is quite error-prone. I actually circumvent Grails' ability to manage a huge amount of (concurrent) connections. Finally, here's what I'm supposed to do now and the problem: As the problems I mentioned above are unacceptable, I am now supposed to use Java's URLConnection/HttpURLConnection classes, while still sticking to Grails. Connecting to the server and sending simple requests is no problem at all, everything worked fine. The problems started when I tried to use the streams (the connection's OutputStream in the client and the request's InputStream in the server). Opening the client's OutputStream and writing data to it is as easy as it gets. But reading from the request's InputStream seems impossible to me, as that stream is always empty, as it seems. Example Code Here's an example of the server side (Groovy controller): def test() { InputStream inStream = request.inputStream if(inStream != null) { int read = 0; byte[] buffer = new byte[4096]; long total = 0; println "Start reading" while((read = inStream.read(buffer)) != -1) { println "Read " + read + " bytes from input stream buffer" //<-- this is NEVER called } println "Reading finished" println "Read a total of " + total + " bytes" // <-- 'total' will always be 0 (zero) } else { println "Input Stream is null" // <-- This is NEVER called } } This is what I did on the client side (Java class): public void connect() { final URL url = new URL("myserveraddress"); final byte[] message = "someMessage".getBytes(); // Any byte[] - will be a file one day HttpURLConnection connection = url.openConnection(); connection.setRequestMethod("GET"); // other methods - same result // Write message DataOutputStream out = new DataOutputStream(connection.getOutputStream()); out.writeBytes(message); out.flush(); out.close(); // Actually connect connection.connect(); // is this placed correctly? // Get response BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); String line = null; while((line = in.readLine()) != null) { System.out.println(line); // Prints the whole server response as expected } in.close(); } As I mentioned, the problem is that request.inputStream always yields an empty InputStream, so I am never able to read anything from it (of course). But as that is exactly what I'm trying to do (so I can stream the file to be uploaded to the server, read from the InputStream and save it to a file), this is rather disappointing. I tried different HTTP methods, different data payloads, and also rearranged the code over and over again, but did not seem to be able to solve the problem. What I hope to find I hope to find a solution to my problem, of course. Anything is highly appreciated: hints, code snippets, library suggestions and so on. Maybe I'm even having it all wrong and need to go in a totally different direction. So, how can I implement resumable file uploads for rather large (binary) files from a Java client to a Grails web application without manually opening ports on the server side?

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  • JDBC Lock a row using SELECT FOR UPDATE, doesn't work

    - by Rachid
    I am having issues with MySQL's SELECT .. FOR UPDATE, here is the query I am trying to run: SELECT * FROM tableName WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE After this, the concerned thread will do an UPDATE and change the HostName, which is then it should unlock the row. I am running a multi-threaded java application, so 3 threads are running this SQL statement, but when thread 1 runs this, it doesn't lock its results from thread 2 & 3. Therefore threads 2 & 3 are getting the same results and they could update the same row. Also each thread is on its own mysql connection. I'm using Innodb, with transaction-isolation = READ-COMMITTED, and the Autocommit is off before executing the select for update may I miss something? OR perhaps there is a better solution? Thanks a lot. Code : public BasicJDBCDemo() { Le_Thread newThread1=new Le_Thread(); Le_Thread newThread2=new Le_Thread(); newThread1.start(); newThread2.start(); } Thread : class Le_Thread extends Thread { public void run() { tring name = Thread.currentThread().getName(); System.out.println( name+": Debut."); long oid=Util.doSelectLockTest(name); Util.doUpdateTest(oid,name); } } Select : public static long doSelectLockTest(String threadName) { System.out.println("[OUTPUT FROM SELECT Lock ]...threadName="+threadName); PreparedStatement pst = null; ResultSet rs=null; Connection conn=null; long oid=0; try { String query = "SELECT * FROM table WHERE Host=? ORDER BY Timestamp asc limit 1 FOR UPDATE"; conn=getNewConnection(); pst = conn.prepareStatement(query); pst.setString(1, DbProperties.UnknownHost); System.out.println("pst="+threadName+"__"+pst); rs = pst.executeQuery(); if (rs.first()) { String s = rs.getString("HostName"); oid = rs.getLong("OID"); System.out.println("oid_oldest/host/threadName=="+oid+"/"+s+"/"+threadName); } } catch (SQLException ex) { ex.printStackTrace(); } finally { DBUtil.close(pst); DBUtil.close(rs); DBUtil.close(conn); } return oid; } Please help.... : Result : Thread-1: Debut. Thread-2: Debut. [OUTPUT FROM SELECT Lock ]...threadName=Thread-1 New connection.. [OUTPUT FROM SELECT Lock ]...threadName=Thread-2 New connection.. pst=Thread-2: SELECT * FROM b2biCheckPoint WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE pst=Thread-1: SELECT * FROM b2biCheckPoint WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE oid_oldest/host/threadName==1/UnknownHost/Thread-2 oid_oldest/host/threadName==1/UnknownHost/Thread-1 [Performing UPDATE] ... oid = 1, thread=Thread-2 New connection.. [Performing UPDATE] ... oid = 1, thread=Thread-1 pst_threadname=Thread-2: UPDATE b2bicheckpoint SET HostName='1_host_Thread-2',UpdateTimestamp=1294940161838 where OID = 1 New connection.. pst_threadname=Thread-1: UPDATE b2bicheckpoint SET HostName='1_host_Thread-1',UpdateTimestamp=1294940161853 where OID = 1

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  • "FOR UPDATE" v/s "LOCK IN SHARE MODE" : Allow concurrent threads to read updated "state" value of locked row

    - by shadesco
    I have the following scenario: User X logs in to the application from location lc1: call it Ulc1 User X (has been hacked, or some friend of his knows his login credential, or he just logs in from a different browser on his machine,etc.. u got the point) logs in at the same time from location lc2: call it Ulc2 I am using a main servlet which : - gets a connection from database pooling - sets autocommit to false - executes a command that goes through app layers: if all successful, set autocommit to true in a "finally" statement, and closes connection. Else if an exception happens, rollback(). In my database (mysql/innoDb) i have a "history" table, with row columns: id(primary key) |username | date | topic | locked The column "locked" has by default value "false" and it serves as a flag that marks if a specific row is locked or not. Each row is specific to a user (as u can see from the username column) So back to the scenario: --Ulc1 sends the command to update his history from the db for date "D" and topic "T". --Ulc2 sends the same command to update history from the db for the same date "D" and same topic "T" at the exact same time. I want to implement an mysql/innoDB locking system that will enable whichever thread arriving to do the following check: Is column "locked" for this row true or not? if true, return a message to the user that " he is already updating the same data from another location" if not true (ie not locked) : flag it as locked and update then reset locked to false once finished. Which of these two mysql locking techniques, will actually allow the 2nd arriving thread from reading the "updated" value of the locked column to decide wt action to take?Should i use "FOR UPDATE" or "LOCK IN SHARE MODE"? This scenario explains what i want to accomplish: - Ulc1 thread arrives first: column "locked" is false, set it to true and continue updating process - Ulc2 thread arrives while Ulc1's transaction is still in process, and even though the row is locked through innoDb functionalities, it doesn't have to wait but in fact reads the "new" value of column locked which is "true", and so doesn't in fact have to wait till Ulc1 transaction commits to read the value of the "locked" column(anyway by that time the value of this column will already have been reset to false). I am not very experienced with the 2 types of locking mechanisms, what i understand so far is that LOCK IN SHARE MODE allow other transaction to read the locked row while FOR UPDATE doesn't even allow reading. But does this read gets on the updated value? or the 2nd arriving thread has to wait the first thread to commit to then read the value? Any recommendations about which locking mechanism to use for this scenario is appreciated. Also if there's a better way to "check" if the row has been locked (other than using a true/false column flag) please let me know about it. thank you SOLUTION (Jdbc pseudocode example based on @Darhazer's answer) Table : [ id(primary key) |username | date | topic | locked ] connection.setautocommit(false); //transaction-1 PreparedStatement ps1 = "Select locked from tableName for update where id="key" and locked=false); ps1.executeQuery(); //transaction 2 PreparedStatement ps2 = "Update tableName set locked=true where id="key"; ps2.executeUpdate(); connection.setautocommit(true);// here we allow other transactions threads to see the new value connection.setautocommit(false); //transaction 3 PreparedStatement ps3 = "Update tableName set aField="Sthg" where id="key" And date="D" and topic="T"; ps3.executeUpdate(); // reset locked to false PreparedStatement ps4 = "Update tableName set locked=false where id="key"; ps4.executeUpdate(); //commit connection.setautocommit(true);

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  • Update transaction in SQL Server 2008 R2 from ASP.Net not working

    - by Amarus
    Hello! Even though I've been a stalker here for ages, this is the first post I'm making. Hopefully, it won't end here and more optimistically future posts might actually be me trying to give a hand to someone else, I do owe this community that much and more. Now, what I'm trying to do is simple and most probably the reason behind it not working is my own stupidity. However, I'm stumped here. I'm working on an ASP.Net website that interacts with an SQL Server 2008 R2 database. So far everything has been going okay but updating a row (or more) just won't work. I even tried copying and pasting code from this site and others but it's always the same thing. In short: No exception or errors are shown when the update command executes (it even gives the correct count of affected rows) but no changes are actually made on the database. Here's a simplified version of my code (the original had more commands and tons of parameters each, but even when it's like this it doesn't work): protected void btSubmit_Click(object sender, EventArgs e) { using (SqlConnection connection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString)) { string commandString = "UPDATE [impoundLotAlpha].[dbo].[Vehicle]" + "SET [VehicleMake] = @VehicleMake" + " WHERE [ComplaintID] = @ComplaintID"; using (SqlCommand command = new SqlCommand(commandString, connection)) { SqlTransaction transaction = null; try { command.Connection.Open(); transaction = connection.BeginTransaction(IsolationLevel.Serializable); command.Transaction = transaction; SqlParameter complaintID = new SqlParameter("@complaintID", SqlDbType.Int); complaintID.Value = HttpContext.Current.Request.QueryString["complaintID"]; command.Parameters.Add(complaintID); SqlParameter VehicleMake = new SqlParameter("@VehicleMake", SqlDbType.VarChar, 20); VehicleMake.Value = tbVehicleMake.Text; command.Parameters.Add(VehicleMake); command.ExecuteNonQuery(); transaction.Commit(); } catch { transaction.Rollback(); throw; } finally { connection.Close(); } } } } I've tried this with the "SqlTransaction" stuff and without it and nothing changes. Also, since I'm doing multiple updates at once, I want to have them act as a single transaction. I've found that it can be either done like this or by use of the classes included in the System.Transactions namespace (CommittableTransaction, TransactionScope...). I tried all I could find but didn't get any different results. The connection string in web.config is as follows: <connectionStrings> <add name="ApplicationServices" connectionString="Data Source=localhost;Initial Catalog=ImpoundLotAlpha;Integrated Security=True" providerName="System.Data.SqlClient"/> </connectionStrings> So, tldr; version: What is the mistake that I did with that record update attempt? (Figured it out, check below if you're having a similar issue.) What is the best method to gather multiple update commands as a single transaction? Thanks in advance for any kind of help and/or suggestions! Edit: It seems that I was lacking some sleep yesterday cause this time it only took me 5 minutes to figure out my mistake. Apparently the update was working properly but I failed to notice that the textbox values were being overwritten in Page_Load. For some reason I had this part commented: if (IsPostBack) return; The second part of the question still stands. But should I post this as an answer to my own question or keep it like this?

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  • nth ugly number

    - by Anil Katti
    Numbers whose only prime factors are 2, 3 or 5 are called ugly numbers. Example: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, ... 1 can be considered as 2^0. I am working on finding nth ugly number. Note that these numbers are extremely sparsely distributed as n gets large. I wrote a trivial program that computes if a given number is ugly or not. For n 500 - it became super slow. I tried using memoization - observation: ugly_number * 2, ugly_number * 3, ugly_number * 5 are all ugly. Even with that it is slow. I tried using some properties of log - since that will reduce this problem from multiplication to addition - but, not much luck yet. Thought of sharing this with you all. Any interesting ideas? Using a concept similar to "Sieve of Eratosthenes" (thanks Anon) for (int i(2), uglyCount(0); ; i++) { if (i % 2 == 0) continue; if (i % 3 == 0) continue; if (i % 5 == 0) continue; uglyCount++; if (uglyCount == n - 1) break; } i is the nth ugly number. Even this is pretty slow. I am trying to find 1500th ugly number.

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  • Force creation of query execution plan

    - by Marc
    I have the following situation: .net 3.5 WinForm client app accessing SQL Server 2008 Some queries returning relatively big amount of data are used quite often by a form Users are using local SQL Express and restarting their machines at least daily Other users are working remotely over slow network connections The problem is that after a restart, the first time users open this form the queries are extremely slow and take more or less 15s on a fast machine to execute. Afterwards the same queries take only 3s. Of course this comes from the fact that no data is cached and must be loaded from disk first. My question: Would it be possible to force the loading of the required data in advance into SQL Server cache? Note My first idea was to execute the queries in a background worker when the application starts, so that when the user starts the form the queries will already be cached and execute fast directly. I however don't want to load the result of the queries over to the client as some users are working remotely or have otherwise slow networks. So I thought just executing the queries from a stored procedure and putting the results into temporary tables so that nothing would be returned. Turned out that some of the result sets are using dynamic columns so I couldn't create the corresponding temp tables and thus this isn't a solution. Do you happen to have any other idea?

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  • Big-O of PHP functions?

    - by Kendall Hopkins
    After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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  • .post inside jQuery.validator.addMethod always returns false :(

    - by abdullah kahraman
    Hello! I am very new to jQuery and javascript programming. I have a program below that checks whether username is taken or not. For now, the PHP script always returns if(isset($_POST["username"]) )//&& isset($_POST["checking"])) { $xml="<register><message>Available</message></register>"; echo $xml; } Login function works, but username checking doesn't. Any ideas? Here is all of my code: $(document).ready(function() { jQuery.validator.addMethod("checkAvailability",function(value,element){ $.post( "login.php" , {username:"test", checking:"yes"}, function(xml){ if($("message", xml).text() == "Available") return true; else return false; }); },"Sorry, this user name is not available"); $("#loginForm").validate({ rules: { username: { required: true, minlength: 4, checkAvailability: true }, password:{ required: true, minlength: 5 } }, messages: { username:{ required: "You need to enter a username." , minlength: jQuery.format("Your username should be at least {0} characters long.") } }, highlight: function(element, errorClass) { $(element).fadeOut("fast",function() { $(element).fadeIn("slow"); }) }, success: function(x){ x.text("OK!") }, submitHandler: function(form){send()} }); function send(){ $("#message").hide("fast"); $.post( "login.php" , {username:$("#username").val(), password:$("#password").val()}, function(xml){ $("#message").html( $("message", xml).text() ); if($("message", xml).text() == "You are successfully logged in.") { $("#message").css({ "color": "green" }); $("#message").fadeIn("slow", function(){location.reload(true);}); } else { $("#message").css({ "color": "red" }); $("#message").fadeIn("slow"); } }); } $("#newUser").click(function(){ return false; }); });

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  • Trouble with jquery email form submitHandler

    - by Robert
    Here is the code I'm using for the submitHandler: submitHandler: function() { $('.holder').fadeOut('slow'); $('#loading').fadeIn('slow'); $.post('email.php',{name:$('#em_name').val(), email:$('#em_email').val(), message:$('#em_message').val()}, function(data){ $('#loading').css({display:'none'}); if( data == 'success') { $('#callback').show().append('Message delivered successfully'); $('#emailform').slideUp('slow'); } else { $('#callback').show().append('Sorry but your message could not be sent, try again later'); } }); } This isn't working when used in conjunction with this php: <?php $name = stripcslashes($_POST['name']); $emailAddr = stripcslashes($_POST['email']); $message = stripcslashes($_POST['message']); $email = "Message: $message \r \n From: $name \r \n Reply to: $emailAddr"; $to = '[email protected]'; $subject = 'Message from example'; //validate the email address on the server side if(eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $emailAddr) ) { //if successful lets send the message mail($to, $subject, $email); echo('success'); //return success callback } else { echo('An invalid email address was entered'); //email was not valid } ?> Does anyone have any suggestions as to why this isn't working like it should. It seems to just lock up when I submit. Any help would be appreciated. Thanks!

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