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• How to measure the time HTTP requests spend sitting in the accept-queue?

  - by David Jones

  I am using Apache2 on Ubuntu 9.10, and I am trying to tune my configuration for a web application to reduce latency of responses to HTTP requests. During a moderately heavy load on my small server, there are 24 apache2 processes handling requests. Additional requests get queued. Using "netstat", I see 24 connections are ESTABLISHED and 125 connections are TIME_WAIT. I am trying to figure out if that is considered a reasonable backlog. Most requests get serviced in a fraction of a second, so I am assuming requests move through the accept-queue fairly quickly, probably within 1 or 2 seconds, but I would like to be more certain. Can anyone recommend an easy way to measure the time an HTTP request sits in the accept-queue? The suggestions I have come across so far seem to start the clock after the apache2 worker accepts the connection. I'm trying to quantify the accept-queue delay before that. thanks in advance, David Jones

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• BindException/Too many file open while using HttpClient under load

  - by Langali

  I have got 1000 dedicated Java threads where each thread polls a corresponding url every one second. public class Poller { public static Node poll(Node node) { GetMethod method = null; try { HttpClient client = new HttpClient(new SimpleHttpConnectionManager(true)); ...... } catch (IOException ex) { ex.printStackTrace(); } finally { method.releaseConnection(); } } } The threads are run every one second: for (int i=0; i <1000; i++) { MyThread thread = threads.get(i) // threads is a static field if(thread.isAlive()) { // If the previous thread is still running, let it run. } else { thread.start(); } } The problem is if I run the job every one second I get random exceptions like these: java.net.BindException: Address already in use INFO httpclient.HttpMethodDirector: I/O exception (java.net.BindException) caught when processing request: Address already in use INFO httpclient.HttpMethodDirector: Retrying request But if I run the job every 2 seconds or more, everything runs fine. I even tried shutting down the instance of SimpleHttpConnectionManager() using shutDown() with no effect. If I do netstat, I see thousands of TCP connections in TIME_WAIT state, which means they are have been closed and are clearing up. So to limit the no of connections, I tried using a single instance of HttpClient and use it like this: public class MyHttpClientFactory { private static MyHttpClientFactory instance = new HttpClientFactory(); private MultiThreadedHttpConnectionManager connectionManager; private HttpClient client; private HttpClientFactory() { init(); } public static HttpClientFactory getInstance() { return instance; } public void init() { connectionManager = new MultiThreadedHttpConnectionManager(); HttpConnectionManagerParams managerParams = new HttpConnectionManagerParams(); managerParams.setMaxTotalConnections(1000); connectionManager.setParams(managerParams); client = new HttpClient(connectionManager); } public HttpClient getHttpClient() { if (client != null) { return client; } else { init(); return client; } } } However after running for exactly 2 hours, it starts throwing 'too many open files' and eventually cannot do anything at all. ERROR java.net.SocketException: Too many open files INFO httpclient.HttpMethodDirector: I/O exception (java.net.SocketException) caught when processing request: Too many open files INFO httpclient.HttpMethodDirector: Retrying request I should be able to increase the no of connections allowed and make it work, but I would just be prolonging the evil. Any idea what is the best practise to use HttpClient in a situation like above? Btw, I am still on HttpClient3.1.

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• Multiple complete HTTP requests stuck in TCP CLOSE_WAIT state

  - by Sean Owen

  I have a Java and Tomcat-based server application which initiates many outbound HTTP requests to other web sites. We use Jakarta's HTTP Core/Client libraries, very latest versions. The server locks up at some point since all its worker threads are stuck trying to close completed HTTP connections. Using 'lsof' reveals a bunch of sockets stuck in TCP CLOSE_WAIT state. This doesn't happen for all, or even most connections. In fact, I saw it before and resolved it by making sure to set the Connection: Close response header. So that makes me think it may be bad behavior of remote servers. It may have come up again since I moved the app to a totally new service provider -- different OS, network situation. But, I am still at a loss as to what I could do, if anything, to work around this. Some poking around on the internet didn't turn up anything I'm not already doing. Just thought I'd ask if anyone has seen and solved this?

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• DriverManager always returns my custom driver regardless of the connection URL

  - by JGB146

  I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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• Async Socket Listener on separate thread - VB.net

  - by TheHockeyGeek

  I am trying to use the code from Microsoft for an Async Socket connection. It appears the listener runs in the main thread locking the GUI. I am new at both socket connections and multi-threading all at the same time. Having a hard time getting my mind wrapped around this all at once. The code used is at http://msdn.microsoft.com/en-us/library/fx6588te.aspx Using this example, how can I move the listener to its own thread? Public Shared Sub Main() ' Data buffer for incoming data. Dim bytes() As Byte = New [Byte](1023) {} ' Establish the local endpoint for the socket. Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName()) Dim ipAddress As IPAddress = ipHostInfo.AddressList(1) Dim localEndPoint As New IPEndPoint(ipAddress, 11000) ' Create a TCP/IP socket. Dim listener As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) ' Bind the socket to the local endpoint and listen for incoming connections. listener.Bind(localEndPoint) listener.Listen(100)

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• Matlab: Adding symbols to figure

  - by niko

  Hi, Below is the user interface I have created to simulate LDPC coding and decoding The code sequence is decoded iteratively by passing values between the left and right nodes through the connections. The first thing it would be good to add in order to improve visualization is to add arrows to the connections in the direction of passing values. The alternative is to draw a bigger arrow at the top of the connection showing the direction. Another thing I would like to do is displaying the current mathematical operation below the connection (in this example c * H'). What I don't know how to do is displaying special characters and mathematical symbols and other kinds of text such as subscript and superscript in the figure (for example sum sign and subscript "T" instead of sign ="'" to indicate transposed matrix). I would be very thankful if anyone could point to any useful resources for the questions above or show the solution. Thank you.

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• Ruby Rack: startup and teardown operations (Tokyo Cabinet connection)

  - by clint.tseng

  I have built a pretty simple REST service in Sinatra, on Rack. It's backed by 3 Tokyo Cabinet/Table datastores, which have connections that need to be opened and closed. I have two model classes written in straight Ruby that currently simply connect, get or put what they need, and then disconnect. Obviously, this isn't going to work long-term. I also have some Rack middleware like Warden that rely on these model classes. What's the best way to manage opening and closing the connections? Rack doesn't provide startup/shutdown hooks as I'm aware. I thought about inserting a piece of middleware that provides reference to the TC/TT object in env, but then I'd have to pipe that through Sinatra to the models, which doesn't seem efficient either; and that would only get be a per-request connection to TC. I'd imagine that per-server-instance-lifecycle would be a more appropriate lifespan. Thanks!

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• ODBC Connection Pooling

  - by beansy

  I have inherited a suite of .Net c# applications from a developer which talk to an Informix database on a unix server. Instead of using the usual practices for managing the database connections (disposable pattern / "open late / close early"), the code seems to open one ODBC connection when each app loads and doesn't close it. Connection pooling is turned via the ODBC administrator. Is there any way of seeing how many ODBC connections are open? What is the effect of turning off connection pooling? Am I right in thinking the .NET framework will use connection pooling anyway?

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• Handle mysql restart in SQLAlchemy

  - by wRAR

  My Pylons app uses local MySQL server via SQLAlchemy and python-MySQLdb. When the server is restarted, open pooled connections are apparently closed, but the application doesn't know about this and apparently when it tries to use such connection it receives "MySQL server has gone away": File '/usr/lib/pymodules/python2.6/sqlalchemy/engine/default.py', line 277 in do_execute cursor.execute(statement, parameters) File '/usr/lib/pymodules/python2.6/MySQLdb/cursors.py', line 166 in execute self.errorhandler(self, exc, value) File '/usr/lib/pymodules/python2.6/MySQLdb/connections.py', line 35 in defaulterrorhandler raise errorclass, errorvalue OperationalError: (OperationalError) (2006, 'MySQL server has gone away') This exception is not caught anywhere so it bubbles up to the user. If I should handle this exception somewhere in my code, please show the place for such code in a Pylons WSGI app. Or maybe there is a solution in SA itself?

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• Permissions denied on apache rewrite module virtual host configuration

  - by sina

  All of a sudden I keep getting "Permissions denied" on apache 2 virtualhost once we moved it to its own conf file. I have tried all the suggestions I have found here but none work. Please can someone tell me what I am doing wrong? Thanks! <VirtualHost *:80> DocumentRoot "/var/www/mm" <Directory "/var/www/mm"> Options +Indexes +MultiViews +FollowSymLinks AllowOverride all Order deny,allow Allow from all AddType text/vnd.sun.j2me.app-descriptor .jad AddType application/vnd.rim.cod .cod </Directory> Alias /holdspace "/var/www/mm/holdspace" RewriteLogLevel 9 RewriteLog "/var/log/httpd/rewrite.log" RewriteEngine on # 91xx RewriteCond %{HTTP_USER_AGENT} BlackBerry.9105 RewriteRule ^/download/(.*) /holdspace/bb6-360x480/$1 [L] # 92xx RewriteCond %{HTTP_USER_AGENT} BlackBerry.9220 RewriteRule ^/download/(.*) /holdspace/bb5-320x240/$1 [L] Errors in error.log: [Wed May 28 12:44:58 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /download/eazymoney.jad denied [Wed May 28 12:44:58 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /error/HTTP_FORBIDDEN.html.var denied [Wed May 28 12:44:59 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /favicon.ico denied [Wed May 28 12:44:59 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /error/HTTP_FORBIDDEN.html.var denied [Wed May 28 12:44:59 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /favicon.ico denied [Wed May 28 12:44:59 2014] [error] [client 197.255.173.95] (13)Permission denied: access to /error/HTTP_FORBIDDEN.html.var denied Errors in rewrite.log: 197.255.173.95 - - [28/May/2014:12:46:01 +0100] [41.203.113.103/sid#7fe41704ca28][rid#7fe417123378/initial/redir#1] (3) applying pattern '^/download/(.*)' to uri '/error/HTTP_FORBIDDEN.html.var' 197.255.173.95 - - [28/May/2014:12:46:01 +0100] [41.203.113.103/sid#7fe41704ca28][rid#7fe417123378/initial/redir#1] (3) applying pattern '^/download/(.*)' to uri '/error/HTTP_FORBIDDEN.html.var' Apache Configuration file: ServerTokens Prod ServerRoot "/etc/httpd" PidFile run/httpd.pid Timeout 60 KeepAlive Off MaxKeepAliveRequests 100 KeepAliveTimeout 15 <IfModule prefork.c> StartServers 8 MinSpareServers 5 MaxSpareServers 20 ServerLimit 256 MaxClients 256 MaxRequestsPerChild 4000 </IfModule> <IfModule worker.c> StartServers 4 MaxClients 300 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> Listen 80 LoadModule auth_basic_module modules/mod_auth_basic.so LoadModule auth_digest_module modules/mod_auth_digest.so LoadModule authn_file_module modules/mod_authn_file.so LoadModule authn_alias_module modules/mod_authn_alias.so LoadModule authn_anon_module modules/mod_authn_anon.so LoadModule authn_dbm_module modules/mod_authn_dbm.so LoadModule authn_default_module modules/mod_authn_default.so LoadModule authz_host_module modules/mod_authz_host.so LoadModule authz_user_module modules/mod_authz_user.so LoadModule authz_owner_module modules/mod_authz_owner.so LoadModule authz_groupfile_module modules/mod_authz_groupfile.so LoadModule authz_dbm_module modules/mod_authz_dbm.so LoadModule authz_default_module modules/mod_authz_default.so LoadModule ldap_module modules/mod_ldap.so LoadModule authnz_ldap_module modules/mod_authnz_ldap.so LoadModule include_module modules/mod_include.so LoadModule log_config_module modules/mod_log_config.so LoadModule logio_module modules/mod_logio.so LoadModule env_module modules/mod_env.so LoadModule ext_filter_module modules/mod_ext_filter.so LoadModule mime_magic_module modules/mod_mime_magic.so LoadModule expires_module modules/mod_expires.so LoadModule deflate_module modules/mod_deflate.so LoadModule headers_module modules/mod_headers.so LoadModule usertrack_module modules/mod_usertrack.so LoadModule setenvif_module modules/mod_setenvif.so LoadModule mime_module modules/mod_mime.so LoadModule dav_module modules/mod_dav.so LoadModule status_module modules/mod_status.so LoadModule autoindex_module modules/mod_autoindex.so LoadModule info_module modules/mod_info.so LoadModule dav_fs_module modules/mod_dav_fs.so LoadModule vhost_alias_module modules/mod_vhost_alias.so LoadModule negotiation_module modules/mod_negotiation.so LoadModule dir_module modules/mod_dir.so LoadModule actions_module modules/mod_actions.so LoadModule speling_module modules/mod_speling.so LoadModule userdir_module modules/mod_userdir.so LoadModule alias_module modules/mod_alias.so LoadModule substitute_module modules/mod_substitute.so LoadModule rewrite_module modules/mod_rewrite.so LoadModule proxy_module modules/mod_proxy.so LoadModule proxy_ftp_module modules/mod_proxy_ftp.so LoadModule proxy_http_module modules/mod_proxy_http.so LoadModule proxy_ajp_module modules/mod_proxy_ajp.so LoadModule proxy_connect_module modules/mod_proxy_connect.so LoadModule cache_module modules/mod_cache.so LoadModule suexec_module modules/mod_suexec.so LoadModule disk_cache_module modules/mod_disk_cache.so LoadModule cgi_module modules/mod_cgi.so LoadModule version_module modules/mod_version.so Include conf.d/*.conf User apache Group apache ServerAdmin root@localhost ServerName sv001zma002.africa.int.myorg.com UseCanonicalName Off DocumentRoot "/var/www/html" <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory "/var/www/html"> Options FollowSymLinks AllowOverride None Order allow,deny Allow from all </Directory> <IfModule mod_userdir.c> UserDir disabled </IfModule> DirectoryIndex index.html index.html.var AccessFileName .htaccess <Files ~ "^\.ht"> Order allow,deny Deny from all Satisfy All </Files> TypesConfig /etc/mime.types DefaultType text/plain <IfModule mod_mime_magic.c> MIMEMagicFile conf/magic </IfModule> HostnameLookups Off ErrorLog logs/error_log LogLevel warn LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %b" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent CustomLog logs/access_log combined ServerSignature Off TraceEnable Off Alias /icons/ "/var/www/icons/" <Directory "/var/www/icons"> Options MultiViews FollowSymLinks AllowOverride None Order allow,deny Allow from all </Directory> <IfModule mod_dav_fs.c> DAVLockDB /var/lib/dav/lockdb </IfModule> ScriptAlias /cgi-bin/ "/var/www/cgi-bin/" <Directory "/var/www/cgi-bin"> AllowOverride None Options None Order allow,deny Allow from all </Directory> IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable Charset=UTF-8 AddIconByEncoding (CMP,/icons/compressed.gif) x-compress x-gzip AddIconByType (TXT,/icons/text.gif) text/* AddIconByType (IMG,/icons/image2.gif) image/* AddIconByType (SND,/icons/sound2.gif) audio/* AddIconByType (VID,/icons/movie.gif) video/* AddIcon /icons/binary.gif .bin .exe AddIcon /icons/binhex.gif .hqx AddIcon /icons/tar.gif .tar AddIcon /icons/world2.gif .wrl .wrl.gz .vrml .vrm .iv AddIcon /icons/compressed.gif .Z .z .tgz .gz .zip AddIcon /icons/a.gif .ps .ai .eps AddIcon /icons/layout.gif .html .shtml .htm .pdf AddIcon /icons/text.gif .txt AddIcon /icons/c.gif .c AddIcon /icons/p.gif .pl .py AddIcon /icons/f.gif .for AddIcon /icons/dvi.gif .dvi AddIcon /icons/uuencoded.gif .uu AddIcon /icons/script.gif .conf .sh .shar .csh .ksh .tcl AddIcon /icons/tex.gif .tex AddIcon /icons/bomb.gif core AddIcon /icons/back.gif .. AddIcon /icons/hand.right.gif README AddIcon /icons/folder.gif ^^DIRECTORY^^ AddIcon /icons/blank.gif ^^BLANKICON^^ DefaultIcon /icons/unknown.gif ReadmeName README.html HeaderName HEADER.html IndexIgnore .??* *~ *# HEADER* README* RCS CVS *,v *,t AddLanguage ca .ca AddLanguage cs .cz .cs AddLanguage da .dk AddLanguage de .de AddLanguage el .el AddLanguage en .en AddLanguage eo .eo AddLanguage es .es AddLanguage et .et AddLanguage fr .fr AddLanguage he .he AddLanguage hr .hr AddLanguage it .it AddLanguage ja .ja AddLanguage ko .ko AddLanguage ltz .ltz AddLanguage nl .nl AddLanguage nn .nn AddLanguage no .no AddLanguage pl .po AddLanguage pt .pt AddLanguage pt-BR .pt-br AddLanguage ru .ru AddLanguage sv .sv AddLanguage zh-CN .zh-cn AddLanguage zh-TW .zh-tw LanguagePriority en ca cs da de el eo es et fr he hr it ja ko ltz nl nn no pl pt pt-BR ru sv zh-CN zh-TW ForceLanguagePriority Prefer Fallback AddDefaultCharset UTF-8 AddType application/x-compress .Z AddType application/x-gzip .gz .tgz AddType application/x-x509-ca-cert .crt AddType application/x-pkcs7-crl .crl AddHandler type-map var AddType text/html .shtml AddOutputFilter INCLUDES .shtml ProxyErrorOverride On Alias /error/ "/var/www/error/" <IfModule mod_negotiation.c> <IfModule mod_include.c> <Directory "/var/www/error"> AllowOverride None Options IncludesNoExec AddOutputFilter Includes html AddHandler type-map var Order allow,deny Allow from all LanguagePriority en es de fr ForceLanguagePriority Prefer Fallback </Directory> ErrorDocument 400 /error/HTTP_BAD_REQUEST.html.var ErrorDocument 401 /error/HTTP_UNAUTHORIZED.html.var ErrorDocument 403 /error/HTTP_FORBIDDEN.html.var ErrorDocument 404 /error/HTTP_NOT_FOUND.html.var </IfModule> </IfModule> BrowserMatch "Mozilla/2" nokeepalive BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0 BrowserMatch "RealPlayer 4\.0" force-response-1.0 BrowserMatch "Java/1\.0" force-response-1.0 BrowserMatch "JDK/1\.0" force-response-1.0 BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-carefully BrowserMatch "MS FrontPage" redirect-carefully BrowserMatch "^WebDrive" redirect-carefully BrowserMatch "^WebDAVFS/1.[0123]" redirect-carefully BrowserMatch "^gnome-vfs/1.0" redirect-carefully BrowserMatch "^XML Spy" redirect-carefully BrowserMatch "^Dreamweaver-WebDAV-SCM1" redirect-carefully ErrorDocument 400 "Bad Request"

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• How should I move my code from dev to production?

  - by Teddy

  I have created a PHP web-application. I have 3 environments: DEV, TEST, PROD. What's a good tool / business practice for me to move my PHP web-application code from DEV to TEST to the PROD environment? Realizing that my TEST environment still only connects to my TEST database; whereas, I need to PROD environment to connect to my PROD database. So the code is mostly the same, except that I need to change my TEST code once moved into PROD to connect to the PROD database and not TEST database. I've heard of people taking down Apache in such away that it doesn't allow new connections and once all the existing connections are idle it simply brings down the web server. Then people manually copy the code and then manually update the config files of the PHP application to also point to the PROD instance. That seems terribly dangerous. Does a best practice exists?

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• Searching for patterns to create a TCP Connection Pool for high performance messaging

  - by JoeGeeky

  I'm creating a new Client / Server application in C# and expect to have a fairly high rate of connections. That made me think of database connection pools which help mitigate the expense of creating and disposing connections between the client and database. I would like to create a similar capability for my application and haven't been able to find any good examples of how to apply this pattern. Do I really need to spin up an instance of a TcpClient every time I want to send a message to the server and receive a receipt message? Each connection is expected to transport between 1-5KB with each receiving a 1KB response message. I realize this question is somewhat vague, but I am starting from scratch so I am open to suggestions. Even if that means my suppositions are all wrong.

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• PHP: How should I move my code from dev to production?

  - by Teddy

  I have created a PHP web-application. I have 3 environments: DEV, TEST, PROD. What's a good tool / business practice for me to move my PHP web-application code from DEV to TEST to the PROD environment? Realizing that my TEST environment still only connects to my TEST database; whereas, I need to PROD environment to connect to my PROD database. So the code is mostly the same, except that I need to change my TEST code once moved into PROD to connect to the PROD database and not TEST database. I've heard of people taking down Apache in such away that it doesn't allow new connections and once all the existing connections are idle it simply brings down the web server. Then people manually copy the code and then manually update the config files of the PHP application to also point to the PROD instance. That seems terribly dangerous. Does a best practice exists?

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• DataSource or ConnectionPoolDataSource for Application Server JDBC resources

  - by Vinnie

  When creating JNDI JDBC connection pools in an application server, I always specified the type as javax.sql.ConnectionPoolDataSource. I never really gave it too much thought as it always seemed natural to prefer pooled connections over non-pooled. However, in looking at some examples (specifically for Tomcat) I noticed that they specify javax.sql.DataSource. Further, it seems there are settings for maxIdle and maxWait giving the impression that these connections are pooled as well. Glassfish also allows these parameters regardless of the type of data source selected. Are javax.sql.DataSource pooled in an application server (or servlet container)? What (if any) advantages are there for choosing javax.sql.ConnectionPoolDataSource over javax.sql.DataSource (or vice versa)?

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• How to check connection leak using regular expression ?

  - by gauravkarnatak

  I have to check connection leak in my application i.e. open connections which have not been closed. After searching, after I found out that a thousands times connections have been opened but I can't manually go to each and every code fragment and check for connection close thing. I think, it could be possible using a regular expression but the fact is, I am not that well versed with regex that I could write one. Please suggest a regular expression for checking in a no of java files that a opened connection has been closed or not. My code pattern is something like this. try { /* Some code goes here */ con = EJBUtil.getConnection(JNDI_NAME); /* Some code goes here */ } finally { /* Some code goes here */ DBUtil.close(con); or closeConnection.close(con); /* Some code goes here */ }

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• Cannot connect to sql server

  - by Tony

  Hi I cannot connect to Sql server remotely from management studio , It is corrrect User name and password, but how to enable remote connections to a sql server? what is other chances? Cannot connect to xxxx.xxxx.xxxx.xxxx =================================== A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (.Net SqlClient Data Provider) thanks

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• An Actor "queue" ?

  - by synic

  In Java, to write a library that makes requests to a server, I usually implement some sort of dispatcher (not unlike the one found here in the Twitter4J library: http://github.com/yusuke/twitter4j/blob/master/twitter4j-core/src/main/java/twitter4j/internal/async/DispatcherImpl.java) to limit the number of connections, to perform asynchronous tasks, etc. The idea is that N number of threads are created. A "Task" is queued and all threads are notified, and one of the threads, when it's ready, will pop an item from the queue, do the work, and then return to a waiting state. If all the threads are busy working on a Task, then the Task is just queued, and the next available thread will take it. This keeps the max number of connections to N, and allows at most N Tasks to be operating at the same time. I'm wondering what kind of system I can create with Actors that will accomplish the same thing? Is there a way to have N number of Actors, and when a new message is ready, pass it off to an Actor to handle it - and if all Actors are busy, just queue the message?

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• PostgreSQL pgdb driver raises "can't rollback" exception

  - by David Parunakian

  Hello, for some reason I'm experiencing the Operational Error with "can't rollback" message when I attempt to roll back my transaction in the following context: try: cursors[instance].execute("lock revision, app, timeout IN SHARE MODE") cursors[instance].execute("insert into app (type, active, active_revision, contents, z) values ('session', true, %s, %s, 0) returning id", (cRevision, sessionId)) sAppId = cursors[instance].fetchone()[0] cursors[instance].execute("insert into revision (app_id, type) values (%s, 'active')", (sAppId,)) cursors[instance].execute("insert into timeout (app_id, last_seen) values (%s, now())", (sAppId,)) connections[instance].commit() except pgdb.DatabaseError, e: connections[instance].rollback() return "{status: 'error', errno:4, errmsg: \"%s\"}"%(str(e).replace('\"', '\\"').replace('\n', '\\n').replace('\r', '\\r')) The driver in use is PGDB. What is fundamentally wrong here?

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• can you use proxies to do load/stress testing on a server, with proxy serving as a sort of mirror?

  - by EndangeringSpecies

  suppose I want to test a server's and its web application's ability to handle many simultaneous connections well and show decent latency. So ideally I would want a thousand machines to bombard it with usage requests, but that's not practicable. So instead, can I just make a testing script with a thousand threads to run on the same server and have them perform the testing, connecting to the server via a geographically far-away proxy? My reasoning here is that the signal will have to travel realistically big distances to the proxy and back, so that sort of emulates the reality of real clients accessing the server. Then again, to take this one step further, are there prepackaged emulators/frameworks that could perform a similar test without using internet at all, just simulating the latency of the network, realistically creating all the socket connections and other resource intensive stuff etc?

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• Library Recommendation: C++ HTML Parser

  - by Zombies

  Preferably a light weight HTML parser, not exactly creating a browser or looking to modulate JS or any http connections.

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• Mixing .NET versions between website and virtual directories and the "server application unavailable" error Message

  - by Doug Chamberlain

  Backstory Last month our development team created a new asp.net 3.5 application to place out on our production website. Once we had the work completed, we requested from the group that manages are server to copy the app out to our production site, and configure the virtual directory as a new application. On 12/27/2010, two public 'Gineau Pigs' were selected to use the app, and it worked great. On 12/30/2010, We received notification by internal staff, that when that staff member tried to access the application (this was the Business Process Owner) they recieved the 'Server Application Unavailable' message. When I called the group that does our server support, I was told that it probably failed, because I didn't close the connections in my code. However, the same group went in and then created a separate app pool for this Extension Request application. It has had no issues since. I did a little googling, since I do not like being blamed for things. I found that the 'Server Application Unavailable' message will also appear when you have multiple applications using different frameworks and you do not put them in different application pools. Technical Details - Tree of our website structure Main Website <-- ASP Classic +-Virtual Directory(ExtensionRequest) <-- ASP 3.5 From our server support group: 'Reviewed server logs and website setup in IIS. Had to reset the application pool as it was not working properly. This corrected the website and it is now back online. We went ahead and created a application pool for the extension web so it is isolated from the main site pool. In the past we have seen other application do this when there is a connection being left open and the pool fills up. Would recommend reviewing site code to make sure no connections are being left open.' The Real Question: What really caused the failure? Isn't the connection being left open issue an ASP Classic issue? Wouldn't the ExtensionRequest application have to be used (more than twice) in the first place to have the connections left open? Is it more likely the failure is caused by them not bothering to setup the new Application in it's own App Pool in the first place? Sorry for the long windedness

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• More memory usage for IIS 6 asp.net 2.0 on webserver 2003

  - by Alan King

  Running a webserver 2003 SP2 (x86) with IIS 6 and asp.net 2. The box is running mostly dynamic asp pages connecting to a sql 2008 server. At any given time there is over 1 gig of memory available out of the 2 gig in the box. It seems like there would be a way for it to make better use of the free memory. It is using a default machine.config file and default http.sys. I would like to maximize incoming internet connections and database connections. Is there something I can do to make better use of the available memory?

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• Handling Incoming Data from Multiple Sockets in Python

  - by user859434

  Background: I have a current implementation that receives data from about 120 different socket connections in python. In my current implementation, I handle each of these separate socket connections with a dedicated thread for each. Each of these threads parse the data and eventually store it within a shared locked dictionary. These sockets DO NOT have uniform data rates, some sockets get more data than others. Question: Is this the best way to handle incoming data in python, or does python have a better way on handling multiple sockets per thread?

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• Integrating WebSockets with Rails using Rack and Event Machine

  - by Toby Hede

  I have created an Asynchronous version of Rails 3 that I would like to integrate with a WebSocket implementation. I am using EventMachine, Ruby 1.9, Fibers and various em-flavoured libraries as documented by the wickedly good Ilya Grigorik. I have been looking at em-websocket as the handler for WebSocket connections but unsure of the best approach for hooking this into a Rails app. Ideally, this would work in a similar fashion to node.js with Express and Socket.io - incoming connections should be detected and dispatched to the WebSocket handler or the regular rails stack as indicated by the HTTP headers & etc. TL;DR WebSocket handler that plugs into an existing Rails application Transparently dispatch incoming WebSocket requests to endpoints in the app

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• Java DriverManager Always Assigns My Driver

  - by JGB146

  I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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