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  • Ubuntu Server, 2 Ethernet Devices, Same Gateway - Want to force internet traffic through 1 device (or at least allow it to work!)

    - by Chris Drumgoole
    I have a Ubuntu 10.04 Server with 2 ethernet devices, eth0 and eth1. eth0 has a static IP of 192.168.1.210 eth1 has a static IP if 192.168.1.211 The DHCP server (which also serves as the internet gateway) sits at 192.168.1.1. The issue I have right now is when I have both plugged in, I can connect to both IPs over SSH internally, but I can't connect to the internet from the server. If I unplug one of the devices (e.g. eth1), then it works, no problem. (Also, I get the same result when I run sudo ifconfig eth1 down). Question, how can I configure it so that I can have both devices eth0 and eth1 play nice on the same network, but allow internet access as well? (I am open to either enforcing all inet traffic going through a single device, or through both, I'm flexible). From my google searching, it seems I could have a unique (or not popular) problem, so haven't been able to find a solution. Is this something that people generally don't do? The reason I want to make use of both ethernet devices is because I want to run different local traffic services on on both to split the load, so to speak... Thanks in advance. UPDATE Contents of /etc/network/interfaces: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp # The secondary network interface #auto eth1 #iface eth1 inet dhcp (Note: above, I commented out the last 2 lines because I thought that was causing issues... but it didn't solve it) netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 192.168.1.1 255.255.255.0 UG 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 UPDATE 2 I made a change to the /etc/network/interfaces file as suggested by Kevin. Before I display the file contents and the route table, when I am logged into the server (through SSH), I can not ping an external server, so this is the same issue I was experiencing that led to me posting this question. I ran a /etc/init.d/networking restart after making the file changes. Contents of /etc/network/interfaces: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp address 192.168.1.210 netmask 255.255.255.0 gateway 192.168.1.1 # The secondary network interface auto eth1 iface eth1 inet dhcp address 192.168.1.211 netmask 255.255.255.0 ifconfig output eth0 Link encap:Ethernet HWaddr 78:2b:cb:4c:02:7f inet addr:192.168.1.210 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::7a2b:cbff:fe4c:27f/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6397 errors:0 dropped:0 overruns:0 frame:0 TX packets:683 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:538881 (538.8 KB) TX bytes:85597 (85.5 KB) Interrupt:36 Memory:da000000-da012800 eth1 Link encap:Ethernet HWaddr 78:2b:cb:4c:02:80 inet addr:192.168.1.211 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::7a2b:cbff:fe4c:280/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5799 errors:0 dropped:0 overruns:0 frame:0 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:484436 (484.4 KB) TX bytes:1184 (1.1 KB) Interrupt:48 Memory:dc000000-dc012800 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:635 errors:0 dropped:0 overruns:0 frame:0 TX packets:635 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:38154 (38.1 KB) TX bytes:38154 (38.1 KB) netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

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  • Set source address to use tun device does not work (Debian Squeeze)

    - by A. Donda
    there have been similar questions on StackExchange but none of the answers helped me, so I'll try a question of my own. I have a VPN connection via OpenVPN. By default, all traffic is redirected through the tunnel using OpenVPN's "two more specific routes" trick, but I disabled that. My routing table is like this: 198.144.156.141 192.168.2.1 255.255.255.255 UGH 0 0 0 eth0 10.30.92.5 0.0.0.0 255.255.255.255 UH 0 0 0 tun1 10.30.92.1 10.30.92.5 255.255.255.255 UGH 0 0 0 tun1 192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 10.30.92.5 0.0.0.0 UG 0 0 0 tun1 0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 eth0 And the interface configuration is like this: # ifconfig eth0 Link encap:Ethernet HWaddr XX-XX- inet addr:192.168.2.100 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::211:9ff:fe8d:acbd/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:394869 errors:0 dropped:0 overruns:0 frame:0 TX packets:293489 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:388519578 (370.5 MiB) TX bytes:148817487 (141.9 MiB) Interrupt:20 Base address:0x6f00 tun1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.30.92.6 P-t-P:10.30.92.5 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:64 errors:0 dropped:0 overruns:0 frame:0 TX packets:67 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:9885 (9.6 KiB) TX bytes:4380 (4.2 KiB) plus the lo device. The routing table has two default routes, one via eth0 through my local network router (DSL modem) at 192.168.2.1, and another via tun1 through the VPN's gateway. With this configuration, if I connect to a site, the route chosen is the direct one (because it has less hops?): # traceroute 8.8.8.8 -n traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets 1 192.168.2.1 0.427 ms 0.491 ms 0.610 ms 2 213.191.89.13 17.981 ms 20.137 ms 22.141 ms 3 62.109.108.48 23.681 ms 25.009 ms 26.401 ms ... This is fine, because my goal is to send only traffic from specific applications through the tunnel (esp. transmission, using its -i / bind-address-ipv4 option). To test whether this can work at all, I check it first with traceroute's -s option: # traceroute 8.8.8.8 -n -s 10.30.92.6 traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets 1 * * * 2 * * * 3 * * * ... This I take to mean that connection using the tunnel's local address as source is not possible. What is possible (though only as root) is to specify the source interface: # traceroute 8.8.8.8 -n -i tun1 traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets 1 10.30.92.1 129.337 ms 297.758 ms 297.725 ms 2 * * * 3 198.144.152.17 297.653 ms 297.652 ms 297.650 ms ... So apparently the tun1 interface is working and it is possible to send packets through it. But selecting the source interface is not implemented in my actual target application (transmission), so I would like to get source address selection to work. What am I doing wrong?

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  • Fixed ruby/mysql connection with new libmysql.dll, and broke Apache in the process

    - by jmtoporek
    Ok so bit of background - all my development has been on a local Windows 7 machine. I had Apache with PHP/MySQL running with no issues. Been using ruby (1.9.3 and latest rails release 3.2.9) with built in webrick server, but had a devil of a time connecting to mysql. Did some research, updated my libmysql.dll file in c:/ruby/bin and it worked! Very happy... except now Apache stopped working. In my attempt to resolve the issue I found an older copy of libmysql.dll, renamed the new file, copied the old file back to c:ruby/bin and apache works, ruby does not. So I can take this ass backwards approach but obviously this seems pretty stupid. I was surprised that Apache was using the dll file in ruby/bin folder. I presume this is related to path variables perhaps? I guess I was hoping someone could direct me as to how I can use one dll file for apache and another for ruby. Or if you have some other smarter approach - I've smart enough to follow directions to install apache from scratch and enable php on windows as well as ubuntu, but I'm not much of a sys admin, just a semi competent web developer.

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  • HAProxy, health checking multiple servers with different host names

    - by Marco Bettiolo
    I need to load balance between multiple running servers with different host names. I cannot set-up the same virtual host on each one. Is it possible to have only one listen configuration with multiple server and make the Health Checks apply the http-send-name-header Host directive? I am using HAProxy 1.5. I came up with this working haproxy.cfg, as you can see, I had to set a different hostname for each health check as the health check ignores the http-send-name-header Host. I would have preferred to use variables or other methods and keep things more concise. global log 127.0.0.1 local0 notice maxconn 2000 user haproxy group haproxy defaults log global mode http option httplog option dontlognull retries 3 option redispatch timeout connect 5000 timeout client 10000 timeout server 10000 stats enable stats uri /haproxy?stats stats refresh 5s balance roundrobin option httpclose listen inbound :80 option httpchk HEAD / HTTP/1.1\r\n server instance1 127.0.0.101 check inter 3000 fall 1 rise 1 server instance2 127.0.0.102 check inter 3000 fall 1 rise 1 listen instance1 127.0.0.101:80 option forwardfor http-send-name-header Host option httpchk HEAD / HTTP/1.1\r\nHost:\ www.example.com server www.example.com www.example.com:80 check inter 5000 fall 3 rise 2 listen instance2 127.0.0.102:80 option forwardfor http-send-name-header Host option httpchk HEAD / HTTP/1.1\r\nHost:\ www.bing.com server www.bing.com www.bing.com:80 check inter 5000 fall 3 rise 2

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  • redirecting output from telnet / nc to file in script fails when cron'd

    - by qhartman
    So, I have device on my network which sits there listening on a port for a connection, and when a connection is made it dumps ascii data out. I need to capture that data to a file. I wrote a dead simple shell script that does this: #!/bin/bash #Config Variables. Age is in Days. DATA_ROOT=/root/data FILENAME=data_`date +%F`.dat HOST=device COMPRESS_AGE=3 #Sanity Checks if [ ! -e $DATA_ROOT ] then echo "The directory $DATA_ROOT seems to not exist. Please create it." exit 1 fi if [ -e $DATA_ROOT/$FILENAME ] then echo "You seem to have extracted data already today. Aborting" exit 1 fi #Get Data nc $HOST 2202 > $DATA_ROOT/$FILENAME #Compress old Data find $DATA_ROOT -type f -mtime +$COMPRESS_AGE -exec gzip {} \; exit 0 It works great when I run it by hand, but when I run it from cron, it doesn't capture any of the output. If I replace nc with telnet I see the initial telnet headers about escape sequences and whatnot, but not the data. Ideas? I've tried forcing bash to act like an interactive shell with -i. I've tried redirecting both stderr and stdout. I know it's got to be some silly simple thing, but I'm utterly failing. This is driving me nuts... EDIT I also just noticed that the nc processes from all my previous attempts at this have been siting sleeping, and when I killed them, cron sent me a bunch of non-sensical error messages. At least now I have something to dig into!

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  • LighTPD and PHP not working if outside of LightTPD folder

    - by Marco83
    I need to set up a simple web server with PHP on Windows XP that a number of different people will use for local testing. I'm using LightTPD 1.4.30-4-IPv6-Win32-SSL and PHP 5.2. So far I've created this folder structure: tools/ LightTPD/ htdocs/ PHP/ I set up PHP as CGI and the document root as server_root + "/htdocs". It works fine (well, it's slow but I don't want to bother with FastCGI for now :) ). My problem is when I try to put the htdocs outside of LightTPD folder, like this: htdocs/ tools/ LightTPD/ PHP/ I update the document root to server_root + "/../../htdocs" and while static HTML pages work fine, PHP pages stop working (they return a "No input file specified"). I literally just change the document root, I didn't change anything in the php.ini or anywhere else. Please also note that I left all doc_root, user_dir and cgi.force_redirect to the default values in php.ini, and it works when htdocs is inside LightTPD, but not when I move it ouside. Any idea of why it's breaking?? Here's my lightTPD.conf: server.modules = ( "mod_access", "mod_accesslog", "mod_alias", "mod_cgi", "mod_status", ) include "variables.conf" include "mimetype.conf" # THIS WORKS server.document-root = server_root + "/htdocs" # THIS DOESN'T #server.document-root = server_root + "/../../htdocs" server.upload-dirs = ( temp_dir ) index-file.names = ( "index.php", "index.pl", "index.cgi", "index.cml", "index.html", "index.htm", "default.htm" ) server.event-handler = "libev" url.access-deny = ( "~", ".inc" ) $HTTP["url"] =~ "\.pdf$" { server.range-requests = "disable" } static-file.exclude-extensions = ( ".php", ".pl", ".cgi" ) server.errorlog = server_root + "/logs/error.log" ######### Options that are good to be but not neccesary to be changed ####### dir-listing.activate = "enable" #### CGI module cgi.assign = ( ".php" => server_root + "/../PHP/php-cgi.exe" ) status.status-url = "/server-status" status.config-url = "/server-config"

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  • I can't connect to internet via lan cable because 2032 battery died and my bios bios info is now empty [closed]

    - by Rand Om Guy
    I have a compaq CQ61-112SL from about 5 years now... the main battery is almost dead, doesn't keep more then 10 minutes. anyway my problem is that my motherboard battery didn't have any more energy left a few days ago and since then I can't access internet through lan cable but only via wifi. I need cable though. I saw that on my BIOS setup page there were a bunch of parameters missing like serial number, UUID, product number and stuff like that. Also when I start the notebook it prints something like : No serial found. or something like that. I don't really know if the reason why my lan cable doesn't work is the empty BIOS but i assume that's it. If it's not please enlighten me. Or anyway tell me how to update the serial number and product number to the real ones (instead of the 0000000000000 that is now in my bios). I downloaded HP DMI which should make it possible to set these variables on the BIOS but i'm on Windows 8 64bit and the executable file that I need to open for my laptop model says it can't run on 64 bit.

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  • Log transport and aggregation at scale

    - by markdrayton
    How're you analysing log files from UNIX/Linux machines? We run several hundred servers which all generate their own log files, either directly or through syslog. I'm looking for a decent solution to aggregate these and pick out important events. This problem breaks down into 3 components: 1) Message transport The classic way is to use syslog to log messages to a remote host. This works fine for applications that log into syslog but less useful for apps that write to a local file. Solutions for this might include having the application log into a FIFO connected to a program to send the message using syslog, or by writing something that will grep the local files and send the output to the central syslog host. However, if we go to the trouble of writing tools to get messages into syslog would we be better replacing the whole lot with something like Facebook's Scribe which offers more flexibility and reliability than syslog? 2) Message aggregation Log entries seem to fall into one of two types: per-host and per-service. Per-host messages are those which occur on one machine; think disk failures or suspicious logins. Per-service messages occur on most or all of the hosts running a service. For instance, we want to know when Apache finds an SSI error but we don't want the same error from 100 machines. In all cases we only want to see one of each type of message: we don't want 10 messages saying the same disk has failed, and we don't want a message each time a broken SSI is hit. One approach to solving this is to aggregate multiple messages of the same type into one on each host, send the messages to a central server and then aggregate messages of the same kind into one overall event. SER can do this but it's awkward to use. Even after a couple of days of fiddling I had only rudimentary aggregations working and had to constantly look up the logic SER uses to correlate events. It's powerful but tricky stuff: I need something which my colleagues can pick up and use in the shortest possible time. SER rules don't meet that requirement. 3) Generating alerts How do we tell our admins when something interesting happens? Mail the group inbox? Inject into Nagios? So, how're you solving this problem? I don't expect an answer on a plate; I can work out the details myself but some high-level discussion on what is surely a common problem would be great. At the moment we're using a mishmash of cron jobs, syslog and who knows what else to find events. This isn't extensible, maintainable or flexible and as such we miss a lot of stuff we shouldn't. Updated: we're already using Nagios for monitoring which is great for detected down hosts/testing services/etc but less useful for scraping log files. I know there are log plugins for Nagios but I'm interested in something more scalable and hierarchical than per-host alerts.

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  • Apache APC (Windows) Can I optimize these APC settings more?

    - by ar099968
    I would like to optimize APC some more but I am not sure where I could do something. First here is the stats after 1 week of running with the current configuration: General Cache Information APC Version 3.1.9 PHP Version 5.4.4 APC Host XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Server Software Apache Shared Memory 1 Segment(s) with 128.0 MBytes (IPC shared memory, Windows Slim RWLOCK (native) locking) Start Time 2014/06/08 05:00:00 Uptime 6 days, 11 hours and 55 minutes File Upload Support 1 Host Status Diagrams Memory Usage Free: 99.7 MBytes (77.9%) Used: 28.3 MBytes (22.1%) Hits & Misses Hits: 510818 (99.9%) Misses: 608 (0.1%) Detailed Memory Usage and Fragmentation Fragmentation: 0.60% (609.8 KBytes out of 99.7 MBytes in 83 fragments) File Cache Information Cached Files 693 ( 35.4 MBytes) Hits 5143359 Misses 1087 Request Rate (hits, misses) 13.24 cache requests/second Hit Rate 13.24 cache requests/second Miss Rate 0.00 cache requests/second Insert Rate 0.01 cache requests/second Cache full count 0 User Cache Information Cached Variables 0 ( 0.0 Bytes) Hits 0 Misses 0 Request Rate (hits, misses) 0.00 cache requests/second Hit Rate 0.00 cache requests/second Miss Rate 0.00 cache requests/second Insert Rate 0.00 cache requests/second Cache full count 0 Runtime Settings apc.cache_by_default 1 apc.canonicalize 1 apc.coredump_unmap 0 apc.enable_cli 0 apc.enabled 1 apc.file_md5 0 apc.file_update_protection 2 apc.filters -/apc.php$, -/apc_clean.php$, -.tpl.cache.php$, -.tpl.php$, -.string.cache.php$, -.string.php$ apc.gc_ttl 3600 apc.include_once_override 0 apc.lazy_classes 0 apc.lazy_functions 0 apc.max_file_size 2M apc.num_files_hint 7000 apc.preload_path apc.report_autofilter 0 apc.rfc1867 0 apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.serializer default apc.shm_segments 1 apc.shm_size 128M apc.shm_strings_buffer 4M apc.slam_defense 0 apc.stat 1 apc.stat_ctime 0 apc.ttl 7200 apc.use_request_time 1 apc.user_entries_hint 4096 apc.user_ttl 7200 apc.write_lock 1

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  • Find which files an apache process is writing to?

    - by Haluk
    We have this apache process which becomes io-bound time to time. Using atop, we can see it is a write operation. Using lsof -p <PID> we can see a list of files open by the httpd process. First we thought "log" files must be the problem. So we turned them off just to test. However write operations still continues. We will continue testing a few other things. For instance we use php session variables a lot. Maybe php session files are getting all the writing. But is there a way to quickly identify files which get written to by the httpd process? This way we can focus our efforts on those files. UPDATE: We used the strace command as suggested. Here are two lines from the output. write(23, "\27\0\0\0\3SET CHARACTER SET utf8", 27) = 27 write(23, "\17\0\0\0\3SET NAMES utf8", 19) = 19 We do not have a mysql process on this server. So is strace also showing what is being written to an ethernet port? UPDATE2: During high io load, the process which consumes most of the write resources gives the following output to strace -e trace=write -p <PID>: --- SIGCHLD (Child exited) @ 0 (0) --- write(9, "!", 1) = 1 write(19, "OPTIONS * HTTP/1.0\r\nUser-Agent: Apache (internal dummy connection)\r\n\r\n", 70) = 70 However I cannot figure out where these are being written to.

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  • vSphere education - What are the downsides of configuring virtual machines with *too* much RAM?

    - by ewwhite
    VMware memory management seems to be a tricky balancing act. With cluster RAM, Resource Pools, VMware's management techniques (TPS, ballooning, host swapping), in-guest RAM utilization, swapping, reservations, shares and limits, there are a lot of variables. I'm in a situation where clients are using dedicated vSphere cluster resources. However, they are configuring the virtual machines as though they were on physical hardware. In turn, this means a standard VM build may have 4 vCPUs and 16GB or more of RAM. I come from the school of starting small (1 vCPU, minimal RAM), checking real-world use and adjusting up as necessary. Some examples from a "problem" cluster. Resource pool summary - Looks almost 4:1 overcommitted. Note the high amount of ballooned RAM. Resource allocation - The Worst Case Allocation column shows that these VMs would have access to less than 50% of their configured RAM under constrained conditions. The real-time memory utilization graph of the top VM in the listing above. 4 vCPU and 64GB RAM allocated. It averages under 9GB use. Summary of the same VM What are the downsides of overcommitting and overconfiguring resources (specifically RAM) in vSphere environments? Assuming that the VMs can run in less RAM, is it fair to say that there's overhead to configuring virtual machines with more RAM than they need? What is the counter-argument to: "if a VM has 16GB of RAM allocated, but only uses 4GB, what's the problem??"? E.g. do customers need to be educated? What specific metric should be used to meter RAM usage. Tracking the peaks of "Active" versus time?

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  • Lenovo System Update Breaks Windows Live

    - by wolfvilleian
    Hey everyone, I've been racking my brain (and fingers from typing) trying to solve this issue to no avail. I have a Lenovo computer and I install their system update tool to install all my missing drivers. However after this tool is installed Windows Live 2011 breaks, it will no longer sign in giving error number 8e5e0247 all the solutions online haven't helped. It appears that a language setting somewhere gets set to en_ms, and I'm en_ca. My computer is running Windows 7 x64. When i try to sign onto messenger it gives an error that (with some research) means your locale or language is not supported, I've searched my computer for any reference to en_ms but find none. Also a few other things seem to have broken, When a UAC box comes up it is no longer able to identify the publisher of anything, and also the indexing service does not work (I'm not sure if the indexing issue is related, but the UAC issue happened right after installation), I had this issue before but I don't remember how I fixed it, I believe it had something to do with environmental variables. When it goes to sign in it gets as far as the "Loading contacts" then stops and goes back to the sign in screen. Has anyone seen this before? Thanks

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  • What needs to be considered when setting up for Linux Development? [closed]

    - by user123586
    I want to set up a box for Linux development. I have a working linux install with the usual toolchain and an IDE. I'm looking for advice on how to approach structuring accounts and folders for development. As the Perl folks say "There's always more than one way to do it." Left to my own devices, I'll come up with several unproductive ways of doing it before figuring out what an experienced Linux programmer would think obvious. I'm not looking for instructions to follow for a specific set of tools or a specific software package. Instead, I'm looking for insight into what decisions need to be made and how to make them, with understanding of the advantages and disadvantages of each individual choice. These are some of the questions that come up: Where to put sources Where to put built object files and libraries where to install what to set in environment variables what compiler flags matter and how do you manage them across several types of builds what configuration entries to make in an IDE how to manage libraries to support multiple environments how to handle different build versions such as debug vs release, or cross platform builds If you are an experienced Linux developer, the answers to these questions may seem trivial and obvious. I'd like to learn to make decisions about these questions that result in as little manual configuration as possible, given some existing sources, a particular IDE, or no IDE at all, a paticular set of development libraries etc. At this point you're probably thinking: Can you be more specific? Sure. But remember that I'm trying to learn how to think about this stuff, not just follow a recipie for a specific set of results. Example: Setup a project that uses CMake for some of its components, autogen.sh followed by configure for others and just configure for a few more: debug builds without an IDE debug builds in NetBeans debug builds in Eclipse debug build in Visual Studio all of the above with release builds for Linux, Mac and Windows. So... **What are your thoughts on an approach that works for all four? Do you have any advice on what to read?**

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  • mysqldump isn't able to export a specific database, phpMyAdmin crashes

    - by Devils Child
    I'm experiencing problems with a database on my server (Note: All other databases work fine). Once I try to export it with mysqldump I get this error: # mysqldump -u root -pXXXXXXXXX databasename > /root/databasename.sql mysqldump: Couldn't execute 'show table status like 'apps'': Lost connection to MySQL server during query (2013) Also, phpMyAdmin throws an error when selecting this database and immediately logs out. However, the web site which uses this database works fine. I can also execute SELECT statements on the table named "apps" from the MySQL shell. I tried restarting the MySQL daemon as well as REPAIR DATABASE and REPAIR TABLE but the problem still persists. I had this problem before, then it disappeared somehow without me doing anything to resolve the issue. Now, the problem is back and I'm simply unable to create a backup of this database. Used software Debian 6.0.7 x64 MySQL 5.1.66-0 MySQL Version: mysql> SHOW VARIABLES LIKE "%version%"; +-------------------------+-------------------+ | Variable_name | Value | +-------------------------+-------------------+ | protocol_version | 10 | | version | 5.1.66-0+squeeze1 | | version_comment | (Debian) | | version_compile_machine | x86_64 | | version_compile_os | debian-linux-gnu | +-------------------------+-------------------+

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  • Wildcard subdomain setup ... want to change host IP throws off client A records... what to do...

    - by Joe
    Here is the current set up (in a nutshell). The site is set up with a wildcard subdomain, so *.website.com is accessible. Clients can then domain map their own domains with an A record to the server IP address and it will translate the to appropriate *.website.com with re directions and env variables in htaccess. Everything is working perfect... but now comes the problem. The site has grown larger than a single DQC Xeon server can handle at peak times. Looking at cloud options seems tempting, but clients are pointing their domains to a single IP address with the A record (our server). Now, this was probably bad planing from the start, but the question is, if this was to be done today, how would we set it up so that clients use a CNAME perhaps to point their domains to our server rather than an A record. And, if that is not possible for the root domain, how can we then use multiple IP addresses on our side to translate the incoming http request? Complex enough? Hope I've explained it well!

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  • How broken is routing strategy that causes a martian packet (so far only) during tracepath?

    - by lkraav
    I believe I've achieved a table that routes packets from and to eth1/192.168.3.x through 192.168.3.1, and packets from and to eth0/192.168.1.x through 192.168.1.1 (helpful source). Question: when doing tracepath from 192.168.3.20 (from within vserver), I'm getting kernel: [318535.927489] martian source 192.168.3.20 from 212.47.223.33, on dev eth0 at or near the target IP, while intermediary hops go without (log below). I don't understand why this packet is arriving on eth0, instead of eth1, even after reading this: Note that you may see packets from non-routable IP addresses when running the traceroute or tracepath commands. While packets cannot be routed to these routers, packets sent between 2 routers only need to know the address of the next hop within the local networks, which could be a non-routable address. Can someone explain that paragraph in human language? Based on short initial trials so far, everything else seems to work without causing martians. Is this contained to the nature of tracepath operation or do I have some other bigger routing problem that will cause work traffic breakage? Side note: is it possible to inspect martian packet with tcpdump or wireshark or anything of the sort? I'm have not been able to get it to show up on my own. vserver-20 / # tracepath -n 212.47.223.33 1: 192.168.3.2 0.064ms pmtu 1500 1: 192.168.3.1 1.076ms 1: 192.168.3.1 1.259ms 2: 90.191.8.2 1.908ms 3: 90.190.134.194 2.595ms 4: 194.126.123.94 2.136ms asymm 5 5: 195.250.170.22 2.266ms asymm 6 6: 212.47.201.86 2.390ms asymm 7 7: no reply 8: no reply 9: no reply ^C Host routing: $ sudo ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo 2: sit0: <NOARP> mtu 1480 qdisc noop state DOWN link/sit 0.0.0.0 brd 0.0.0.0 3: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:24:1d:de:b3:5d brd ff:ff:ff:ff:ff:ff inet 192.168.1.2/24 scope global eth0 4: eth1: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:46:46:a3:6a brd ff:ff:ff:ff:ff:ff inet 192.168.3.2/27 scope global eth1 inet 192.168.3.20/27 brd 192.168.3.31 scope global secondary eth1 # linux-vserver instance $ sudo ip route default via 192.168.1.1 dev eth0 metric 3 unreachable 127.0.0.0/8 scope host 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.2 192.168.3.0/27 dev eth1 proto kernel scope link src 192.168.3.2 $ sudo ip rule 0: from all lookup local 32764: from all to 192.168.3.0/27 lookup dmz 32765: from 192.168.3.0/27 lookup dmz 32766: from all lookup main 32767: from all lookup default $ sudo ip route show table dmz default via 192.168.3.1 dev eth1 metric 4 192.168.3.0/27 dev eth1 scope link metric 4 Gateway routing # ip route 10.24.0.2 dev tun0 proto kernel scope link src 10.24.0.1 10.24.0.0/24 via 10.24.0.2 dev tun0 192.168.3.0/24 dev br-dmz proto kernel scope link src 192.168.3.1 192.168.1.0/24 dev br-lan proto kernel scope link src 192.168.1.1 $ISP_NET/23 dev eth0.1 proto kernel scope link src $WAN_IP default via $ISP_GW dev eth0.1 Additional background Options for non-virtualized network interface isolation?

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  • locale: What is the LANGUAGE variable used for? (and when?)

    - by seya
    I am trying to understand the locales used in Linux. On my Ubuntu 11.10 system locale puts out the following: LANG=en_DK.UTF-8 LANGUAGE=en_GB:en LC_CTYPE=en_GB.UTF-8 LC_NUMERIC="en_DK.UTF-8" LC_TIME="en_DK.UTF-8" LC_COLLATE=en_GB.UTF-8 LC_MONETARY="en_DK.UTF-8" LC_MESSAGES=en_GB.UTF-8 LC_PAPER="en_DK.UTF-8" LC_NAME="en_DK.UTF-8" LC_ADDRESS="en_DK.UTF-8" LC_TELEPHONE="en_DK.UTF-8" LC_MEASUREMENT="en_DK.UTF-8" LC_IDENTIFICATION="en_DK.UTF-8" LC_ALL= (en_dk is for using international day format, continental European number formatting (1.234,56) etc.) I think I understand what the LC_* family does, that LANG is the fallback if one of them is not set and that LC_ALL sets all of the LC_* variables to its value. What I don't know yet, is what LANGUAGE is used for. The notation en_GB:en reminds me of the Accept-Language HTTP header. With the settings above it would mean, British English is used, if a translation for it exists. Otherwise any existing English translation (en_US, en_AU, ..., whatever) would be used. Am I right so far? Also what programs actually obey the LANGUAGE setting? In how far is it different from LC_MESSAGES? Unfortunately, man locale only documents the LC_* family. And searching the web for 'linux locale LANGUAGE' or similar is a mute point. (Of course language is a word often used when talking about locales, and it may also be shown just in the output of locale without being discussed). Does anybody of you can help me out there?

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  • Getting Run time 1004 error in code

    - by krishna123
    I tried the code provided by vba express for combining sheet, while execution it is displaying Run Time error 1004: Application Defined or Object Defined Error: My Scenario is: I have a Excel, in that I have first sheet "Connection" and after it I have Sheet1, Sheet2 and so on. I am combining all sheets except Sheet"Conection" by saying start with sheet2. I tried following line of code to exclude "Connection" sheet: If Not Sheet.Name = "Connection" then but it did not work. Whatever the sheets I have in some of them I have large data in some cells. Here is the code which I am using: I have highlighted the line Sub CopyFromWorksheets() Dim wrk As Workbook 'Workbook object - Always good to work with object variables Dim sht As Worksheet 'Object for handling worksheets in loop Dim trg As Worksheet 'Master Worksheet Dim rng As Range 'Range object Dim colCount As Integer 'Column count in tables in the worksheets Set wrk = ActiveWorkbook 'Working in active workbook For Each sht In wrk.Worksheets If sht.Name = "Master" Then sht.Delete Exit Sub End If Next sht 'We don't want screen updating Application.ScreenUpdating = False 'trg.SaveAs "C:\temp\CPReport1.xls" 'Add new worksheet as the last worksheet Set trg = wrk.Worksheets.Add(After:=wrk.Worksheets(wrk.Worksheets.Count)) 'Rename the new worksheet trg.Name = "Master" 'Get column headers from the first worksheet 'Column count first Set sht = wrk.Worksheets(2) colCount = sht.Cells(1, 255).End(xlToLeft).Column 'Now retrieve headers, no copy&paste needed With trg.Cells(1, 1).Resize(1, colCount) .Value = sht.Cells(1, 1).Resize(1, colCount).Value 'Set font as bold .Font.Bold = True End With trg.SaveAs "C:\temp\CPReport1.xls" 'We can start loop 'Skip Sheet - Connection If Not sht.Name = "Connection" Then For Each sht In wrk.Worksheets 'If worksheet in loop is the last one, stop execution (it is Master worksheet) If sht.Index = wrk.Worksheets.Count Then Exit For End If 'Data range in worksheet - starts from second row as first rows are the header rows in all worksheets Set rng = sht.Range(sht.Cells(2, 1), sht.Cells(65536, 1).End(xlUp).Resize(, colCount)) 'Put data into the Master worksheet '----------------- Error in below line -------------------------------------------------- trg.Cells(65536, 1).End(xlUp).Offset(1).Resize(rng.Rows.Count, rng.Columns.Count).Value = rng.Value '---------------------------------------------------------------------------------------- Next sht End If 'Fit the columns in Master worksheet trg.Columns.AutoFit 'Dim dest, destyfile 'dest = "E:\Test_Merge\" 'destyfile = dest & "_" & trg.Name 'trg.SaveAs (destyfile) 'Screen updating should be activated Application.ScreenUpdating = True End Sub

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  • Odd one: IE6 showing the "view source" command enabled when I was expecting it to be disabled.

    - by caerphilly
    Hi, OK, I admit this problem is odd. I'm just trying to understand why IE is behaving the way it is. I realise that logic may not apply here :) I have Internet Explorer 6 (Sp1) running on Windows 2000. The IE option "Do not store encrypted pages to disk" is checked (enabled). The temporary internet files folder is empty. TEMP and TMP environment variables are set to valid folders. I'm connected to a web server over SSL. The web server is serving a page over SSL with the HTTP cache-control header set to "no-cache, no-store". I was expecting the "view source" command to be greyed out in this circumstance (as it is on another machine). But it works. When I "view source", I get an entry in the Temporary Internet Files folder with an "internet address" property of "view-source:https://myserver/...." and the content of the page. I wasn't expecting that. I can't understand why one machine is different to another in this regard. Obviously there is some environment/setup difference, but I can't track it down. Anyone have any bright ideas?

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  • SQL Server 2012 memory usage steadily growing

    - by pgmo
    I am very worried about the SQL Server 2012 Express instance on which my database is running: the SQL Server process memory usage is growing steadily (1.5GB after only 2 days working). The database is made of seven tables, each having a bigint primary key (Identity) and at least one non-unique index with some included columns to serve the majority of incoming queries. An external application is calling via Microsoft OLE DB some stored procedures, each of which do some calculations using intermediate temporary tables and/or table variables and finally do an upsert (UPDATE....IF @@ROWCOUNT=0 INSERT.....) - I never DROP those temporary tables explicitly: the frequency of those calls is about 100 calls every 5 seconds (I saw that the DLL used by the external application open a connection to SQL Server, do the call and then close the connection for each and every call). The database files are organized in only one filgegroup, recovery type is set to simple. Some questions to diagnose the problem: is that steadily growing memory normal? did I do any mistake in database design which probably lead to this behaviour? (no explicit temp-table drop, filegroup organization, etc) can SQL Server manage such a stored procedure call rate (100 calls every 5 seconds, i.e. 100 upsert every 5 seconds, beyond intermediate calculations)? do the continuous "open connection/do sp call/close connection" pattern disturb SQL Server? is it possible to diagnose what is causing such a memory usage? Perhaps queues of wating requests? (I ran sp_who2, but I didn't see a big amount of orphan connections from the external application) if I restrict the amount of memory which SQL Server is allowed to use, may I sooner or later get into trouble?

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  • What's the proper way to prepare chroot to recover a broken Linux installation?

    - by ~quack
    This question relates to questions that are asked often. The procedure is frequently mentioned or linked to offsite, but is not often clearly and correctly stated. In an objective to concentrate useful information in one place, this question seeks to provide a clear, correct reference for this procedure. What are the proper steps to prepare a chroot environment for a recovery procedure? In many situations, repairing a broken Linux installation is best done from within the installation. But if the system won't boot, how do you fix it from within? Let's assume you manage to boot into an alternate system. Once there, you need to access your broken installation in order to fix it. Many recovery How-Tos recommend using chroot in order to run programs as if you are actually booted into the broken installation. What is the basic procedure? Are there accepted best-practices to follow? What variables need to be considered in order to adapt the basic preparation steps to a particular recovery task? As this is Community Wiki, feel free to edit this question to improve it as well.

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  • Using iptables to make a VPN router

    - by lost_in_the_sauce
    I am attempting to make a VPN connection to a third party VPN site, then forward traffic from my internal computers (ssh and ping for now) out to the VPN site using IPTables. 3rd Party <- (tun0/eth0)Linux VPN Box(eth1) <- Windows7TestBox I am running on CentOS 6.3 Linux and have two network connections eth0-public eth1-private. I am running vpnc-0.5.3-4 which is currently connecting to my destination. When I connect I am able to ping the destination IPAddresses but that is as far as I can get. ping -I tun0 10.1.33.26 success ping -I eth0 10.1.33.26 fail ping -I eth1 10.1.33.26 fail I have my private network Windows 7 test box set up to have the eth1 (private) network of my VPN Server as its gateway and can ping him fine. I need IPTables to send the Windows 7 traffic out the VPN tunnel. I have tried for a few days many different IPTables configurations from this site and others, either the other examples are too simple or overly complicated. The only thing this server is doing is connecting to the VPN and forwarding all traffic. So we can "flush" everything and start from scratch here. It is a blank slate. #!/bin/bash echo "Define variables" ipt="/sbin/iptables" echo "Zero out all counters" $ipt -Z $ipt -t nat -Z $ipt -t mangle -Z echo "Flush all active rules, delete all chains" $ipt -F $ipt -X $ipt -t nat -F $ipt -t nat -X $ipt -t mangle -F $ipt -t mangle -X $ipt -P INPUT ACCEPT $ipt -P FORWARD ACCEPT $ipt -P OUTPUT ACCEPT $ipt -t nat -A POSTROUTING -o tun0 -j MASQUERADE $ipt -A FORWARD -i eth1 -o eth0 -j ACCEPT $ipt -A FORWARD -i eth0 -o eth1 -j ACCEPT $ipt -A FORWARD -i eth0 -o tun0 -j ACCEPT $ipt -A FORWARD -i tun0 -o eth0 -j ACCEPT Again I have done many variations of the above and many other rules from other posts but haven't been able to move forward. It seems like such a simple task, and yet....

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  • Discover intended Foreign Keys from JOINS in scripts

    - by Jason
    I'm inheriting a database that has 400 tables and only 150 foreign key constraints registered. Knowing what I do about the application and looking at the table columns, it's easy to say that there ought to be a lot more. I'm afraid that the current application software will break if I started adding the missing FKs because the developers have probably come to rely on this "freedom", but step one in fixing the problem is to come up with the list of missing FKs so we can evaluate them as a team. To make matters worse, the referencing columns don't share a naming convention. The relationships ARE coded informally into the hundreds of ad-hoc queries and stored procedures, so my hope is to parse these files programmatically looking for JOINS between actual tables (but not table variables, etc). Challenges I foresee in this approach are: newlines, optional aliases and table hints, alias resolution. Any better ideas? (Besides quitting) Are there any pre-built tools that can solve this? I don't think regex can handle this. Do you disagree? SQL Parsers? I tried using Microsoft.SqlServer.Management.SqlParser.Parser but all that is exposed is the lexer - can't get an AST out of it - all that stuff is internal.

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  • The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

    - by Rick Strahl
    I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot easier with the introduction of dynamic type support in .NET. One of the biggest problems with COM interop has been that it’s been really difficult to pass dynamic objects from FoxPro to .NET and get them properly typed. The only way that any strong typing can occur in .NET for FoxPro components is via COM type library exports of Visual FoxPro components. Due to limitations in Visual FoxPro’s type library support as well as the dynamic nature of the Visual FoxPro language where few things are or can be described in the form of a COM type library, a lot of useful interaction between FoxPro and .NET required the use of messy Reflection code in .NET. Reflection is .NET’s base interface to runtime type discovery and dynamic execution of code without requiring strong typing. In FoxPro terms it’s similar to EVALUATE() functionality albeit with a much more complex API and corresponiding syntax. The Reflection APIs are fairly powerful, but they are rather awkward to use and require a lot of code. Even with the creation of wrapper utility classes for common EVAL() style Reflection functionality dynamically access COM objects passed to .NET often is pretty tedious and ugly. Let’s look at a simple example. In the following code I use some FoxPro code to dynamically create an object in code and then pass this object to .NET. An alternative to this might also be to create a new object on the fly by using SCATTER NAME on a database record. How the object is created is inconsequential, other than the fact that it’s not defined as a COM object – it’s a pure FoxPro object that is passed to .NET. Here’s the code: *** Create .NET COM InstanceloNet = CREATEOBJECT('DotNetCom.DotNetComPublisher') *** Create a Customer Object Instance (factory method) loCustomer = GetCustomer() loCustomer.Name = "Rick Strahl" loCustomer.Company = "West Wind Technologies" loCustomer.creditLimit = 9999999999.99 loCustomer.Address.StreetAddress = "32 Kaiea Place" loCustomer.Address.Phone = "808 579-8342" loCustomer.Address.Email = "[email protected]" *** Pass Fox Object and echo back values ? loNet.PassRecordObject(loObject) RETURN FUNCTION GetCustomer LOCAL loCustomer, loAddress loCustomer = CREATEOBJECT("EMPTY") ADDPROPERTY(loCustomer,"Name","") ADDPROPERTY(loCustomer,"Company","") ADDPROPERTY(loCUstomer,"CreditLimit",0.00) ADDPROPERTY(loCustomer,"Entered",DATETIME()) loAddress = CREATEOBJECT("Empty") ADDPROPERTY(loAddress,"StreetAddress","") ADDPROPERTY(loAddress,"Phone","") ADDPROPERTY(loAddress,"Email","") ADDPROPERTY(loCustomer,"Address",loAddress) RETURN loCustomer ENDFUNC Now prior to .NET 4.0 you’d have to access this object passed to .NET via Reflection and the method code to do this would looks something like this in the .NET component: public string PassRecordObject(object FoxObject) { // *** using raw Reflection string Company = (string) FoxObject.GetType().InvokeMember( "Company", BindingFlags.GetProperty,null, FoxObject,null); // using the easier ComUtils wrappers string Name = (string) ComUtils.GetProperty(FoxObject,"Name"); // Getting Address object – then getting child properties object Address = ComUtils.GetProperty(FoxObject,"Address");    string Street = (string) ComUtils.GetProperty(FoxObject,"StreetAddress"); // using ComUtils 'Ex' functions you can use . Syntax     string StreetAddress = (string) ComUtils.GetPropertyEx(FoxObject,"AddressStreetAddress"); return Name + Environment.NewLine + Company + Environment.NewLine + StreetAddress + Environment.NewLine + " FOX"; } Note that the FoxObject is passed in as type object which has no specific type. Since the object doesn’t exist in .NET as a type signature the object is passed without any specific type information as plain non-descript object. To retrieve a property the Reflection APIs like Type.InvokeMember or Type.GetProperty().GetValue() etc. need to be used. I made this code a little simpler by using the Reflection Wrappers I mentioned earlier but even with those ComUtils calls the code is pretty ugly requiring passing the objects for each call and casting each element. Using .NET 4.0 Dynamic Typing makes this Code a lot cleaner Enter .NET 4.0 and the dynamic type. Replacing the input parameter to the .NET method from type object to dynamic makes the code to access the FoxPro component inside of .NET much more natural: public string PassRecordObjectDynamic(dynamic FoxObject) { // *** using raw Reflection string Company = FoxObject.Company; // *** using the easier ComUtils class string Name = FoxObject.Name; // *** using ComUtils 'ex' functions to use . Syntax string Address = FoxObject.Address.StreetAddress; return Name + Environment.NewLine + Company + Environment.NewLine + Address + Environment.NewLine + " FOX"; } As you can see the parameter is of type dynamic which as the name implies performs Reflection lookups and evaluation on the fly so all the Reflection code in the last example goes away. The code can use regular object ‘.’ syntax to reference each of the members of the object. You can access properties and call methods this way using natural object language. Also note that all the type casts that were required in the Reflection code go away – dynamic types like var can infer the type to cast to based on the target assignment. As long as the type can be inferred by the compiler at compile time (ie. the left side of the expression is strongly typed) no explicit casts are required. Note that although you get to use plain object syntax in the code above you don’t get Intellisense in Visual Studio because the type is dynamic and thus has no hard type definition in .NET . The above example calls a .NET Component from VFP, but it also works the other way around. Another frequent scenario is an .NET code calling into a FoxPro COM object that returns a dynamic result. Assume you have a FoxPro COM object returns a FoxPro Cursor Record as an object: DEFINE CLASS FoxData AS SESSION OlePublic cAppStartPath = "" FUNCTION INIT THIS.cAppStartPath = ADDBS( JustPath(Application.ServerName) ) SET PATH TO ( THIS.cAppStartpath ) ENDFUNC FUNCTION GetRecord(lnPk) LOCAL loCustomer SELECT * FROM tt_Cust WHERE pk = lnPk ; INTO CURSOR TCustomer IF _TALLY < 1 RETURN NULL ENDIF SCATTER NAME loCustomer MEMO RETURN loCustomer ENDFUNC ENDDEFINE If you call this from a .NET application you can now retrieve this data via COM Interop and cast the result as dynamic to simplify the data access of the dynamic FoxPro type that was created on the fly: int pk = 0; int.TryParse(Request.QueryString["id"],out pk); // Create Fox COM Object with Com Callable Wrapper FoxData foxData = new FoxData(); dynamic foxRecord = foxData.GetRecord(pk); string company = foxRecord.Company; DateTime entered = foxRecord.Entered; This code looks simple and natural as it should be – heck you could write code like this in days long gone by in scripting languages like ASP classic for example. Compared to the Reflection code that previously was necessary to run similar code this is much easier to write, understand and maintain. For COM interop and Visual FoxPro operation dynamic type support in .NET 4.0 is a huge improvement and certainly makes it much easier to deal with FoxPro code that calls into .NET. Regardless of whether you’re using COM for calling Visual FoxPro objects from .NET (ASP.NET calling a COM component and getting a dynamic result returned) or whether FoxPro code is calling into a .NET COM component from a FoxPro desktop application. At one point or another FoxPro likely ends up passing complex dynamic data to .NET and for this the dynamic typing makes coding much cleaner and more readable without having to create custom Reflection wrappers. As a bonus the dynamic runtime that underlies the dynamic type is fairly efficient in terms of making Reflection calls especially if members are repeatedly accessed. © Rick Strahl, West Wind Technologies, 2005-2010Posted in COM  FoxPro  .NET  CSharp  

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  • New features of C# 4.0

    This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. Dynamic import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

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