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  • Can't connect to STunnel when it's running as a service

    - by John Francis
    I've got STunnel configured to proxy non SSL POP3 requests to GMail on port 111. This is working fine when STunnel is running as a desktop app, but when I run the STunnel service, I can't connect to port 111 on the machine (using Outlook Express for example). The Stunnel log file shows the port binding is succeeding, but it never sees a connection. There's something preventing the connection to that port when STunnel is running as a service? Here's stunnel.conf cert = stunnel.pem ; Some performance tunings socket = l:TCP_NODELAY=1 socket = r:TCP_NODELAY=1 ; Some debugging stuff useful for troubleshooting debug = 7 output = stunnel.log ; Use it for client mode client = yes ; Service-level configuration [gmail] accept = 127.0.0.1:111 connect = pop.gmail.com:995 stunnel.log from service 2010.10.07 12:14:22 LOG5[80444:72984]: Reading configuration from file stunnel.conf 2010.10.07 12:14:22 LOG7[80444:72984]: Snagged 64 random bytes from C:/.rnd 2010.10.07 12:14:23 LOG7[80444:72984]: Wrote 1024 new random bytes to C:/.rnd 2010.10.07 12:14:23 LOG7[80444:72984]: PRNG seeded successfully 2010.10.07 12:14:23 LOG7[80444:72984]: Certificate: stunnel.pem 2010.10.07 12:14:23 LOG7[80444:72984]: Certificate loaded 2010.10.07 12:14:23 LOG7[80444:72984]: Key file: stunnel.pem 2010.10.07 12:14:23 LOG7[80444:72984]: Private key loaded 2010.10.07 12:14:23 LOG7[80444:72984]: SSL context initialized for service gmail 2010.10.07 12:14:23 LOG5[80444:72984]: Configuration successful 2010.10.07 12:14:23 LOG5[80444:72984]: No limit detected for the number of clients 2010.10.07 12:14:23 LOG7[80444:72984]: FD=156 in non-blocking mode 2010.10.07 12:14:23 LOG7[80444:72984]: Option SO_REUSEADDR set on accept socket 2010.10.07 12:14:23 LOG7[80444:72984]: Service gmail bound to 0.0.0.0:111 2010.10.07 12:14:23 LOG7[80444:72984]: Service gmail opened FD=156 2010.10.07 12:14:23 LOG5[80444:72984]: stunnel 4.34 on x86-pc-mingw32-gnu with OpenSSL 1.0.0a 1 Jun 2010 2010.10.07 12:14:23 LOG5[80444:72984]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 stunnel.log from desktop (working) process 2010.10.07 12:10:31 LOG5[80824:81200]: Reading configuration from file stunnel.conf 2010.10.07 12:10:31 LOG7[80824:81200]: Snagged 64 random bytes from C:/.rnd 2010.10.07 12:10:32 LOG7[80824:81200]: Wrote 1024 new random bytes to C:/.rnd 2010.10.07 12:10:32 LOG7[80824:81200]: PRNG seeded successfully 2010.10.07 12:10:32 LOG7[80824:81200]: Certificate: stunnel.pem 2010.10.07 12:10:32 LOG7[80824:81200]: Certificate loaded 2010.10.07 12:10:32 LOG7[80824:81200]: Key file: stunnel.pem 2010.10.07 12:10:32 LOG7[80824:81200]: Private key loaded 2010.10.07 12:10:32 LOG7[80824:81200]: SSL context initialized for service gmail 2010.10.07 12:10:32 LOG5[80824:81200]: Configuration successful 2010.10.07 12:10:32 LOG5[80824:81200]: No limit detected for the number of clients 2010.10.07 12:10:32 LOG7[80824:81200]: FD=156 in non-blocking mode 2010.10.07 12:10:32 LOG7[80824:81200]: Option SO_REUSEADDR set on accept socket 2010.10.07 12:10:32 LOG7[80824:81200]: Service gmail bound to 0.0.0.0:111 2010.10.07 12:10:32 LOG7[80824:81200]: Service gmail opened FD=156 2010.10.07 12:10:33 LOG5[80824:81200]: stunnel 4.34 on x86-pc-mingw32-gnu with OpenSSL 1.0.0a 1 Jun 2010 2010.10.07 12:10:33 LOG5[80824:81200]: Threading:WIN32 SSL:ENGINE Sockets:SELECT,IPv6 2010.10.07 12:10:33 LOG7[80824:81844]: Service gmail accepted FD=188 from 127.0.0.1:24813 2010.10.07 12:10:33 LOG7[80824:81844]: Creating a new thread 2010.10.07 12:10:33 LOG7[80824:81844]: New thread created 2010.10.07 12:10:33 LOG7[80824:25144]: Service gmail started 2010.10.07 12:10:33 LOG7[80824:25144]: FD=188 in non-blocking mode 2010.10.07 12:10:33 LOG7[80824:25144]: Option TCP_NODELAY set on local socket 2010.10.07 12:10:33 LOG5[80824:25144]: Service gmail accepted connection from 127.0.0.1:24813 2010.10.07 12:10:33 LOG7[80824:25144]: FD=212 in non-blocking mode 2010.10.07 12:10:33 LOG6[80824:25144]: connect_blocking: connecting 209.85.227.109:995 2010.10.07 12:10:33 LOG7[80824:25144]: connect_blocking: s_poll_wait 209.85.227.109:995: waiting 10 seconds 2010.10.07 12:10:33 LOG5[80824:25144]: connect_blocking: connected 209.85.227.109:995 2010.10.07 12:10:33 LOG5[80824:25144]: Service gmail connected remote server from 192.168.1.9:24814 2010.10.07 12:10:33 LOG7[80824:25144]: Remote FD=212 initialized 2010.10.07 12:10:33 LOG7[80824:25144]: Option TCP_NODELAY set on remote socket 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): before/connect initialization 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 write client hello A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 read server hello A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 read server certificate A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 read server done A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 write client key exchange A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 write change cipher spec A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 write finished A 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 flush data 2010.10.07 12:10:33 LOG7[80824:25144]: SSL state (connect): SSLv3 read finished A 2010.10.07 12:10:33 LOG7[80824:25144]: 1 items in the session cache 2010.10.07 12:10:33 LOG7[80824:25144]: 1 client connects (SSL_connect()) 2010.10.07 12:10:33 LOG7[80824:25144]: 1 client connects that finished 2010.10.07 12:10:33 LOG7[80824:25144]: 0 client renegotiations requested 2010.10.07 12:10:33 LOG7[80824:25144]: 0 server connects (SSL_accept()) 2010.10.07 12:10:33 LOG7[80824:25144]: 0 server connects that finished 2010.10.07 12:10:33 LOG7[80824:25144]: 0 server renegotiations requested 2010.10.07 12:10:33 LOG7[80824:25144]: 0 session cache hits 2010.10.07 12:10:33 LOG7[80824:25144]: 0 external session cache hits 2010.10.07 12:10:33 LOG7[80824:25144]: 0 session cache misses 2010.10.07 12:10:33 LOG7[80824:25144]: 0 session cache timeouts 2010.10.07 12:10:33 LOG6[80824:25144]: SSL connected: new session negotiated 2010.10.07 12:10:33 LOG6[80824:25144]: Negotiated ciphers: RC4-MD5 SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=MD5 2010.10.07 12:10:34 LOG7[80824:25144]: SSL socket closed on SSL_read 2010.10.07 12:10:34 LOG7[80824:25144]: Sending socket write shutdown 2010.10.07 12:10:34 LOG5[80824:25144]: Connection closed: 53 bytes sent to SSL, 118 bytes sent to socket 2010.10.07 12:10:34 LOG7[80824:25144]: Service gmail finished (0 left)

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  • How to gain admin privileges on D-Link router if my isp is not allowing me to do so?

    - by Fischer
    So I switched to new ISP yesterday, they gave me a D-Link router, can't use my old router. I want to change the wireless password, went to 192.168.1.1, I can login with the the username and password user user, but not as admin. On the catalog it says that the default username and password are admin admin, tried that didn't work. Tried admin and no pass, tried many combinations, none worked. I asked some other users and they said that the isp is blocking the users from logging in as admins, and blocking the reset button, and said that there's a hack where you do something like: cmd telnet "router ip" and do something like dumpcfg. Could you please give a better explanation on how to gain admin privileges on your own router if your isp is not letting you do so by default?

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  • Plesk 9 VPS - Doesn't reply to NameServer requests (nslookup, etc)

    - by Ben
    Hi, I'm trying to troubleshoot a problem with a new VPS i'm setting up. The VPS is running Plesk 9 on a CentOS 5 system. Everything works fine, except it doesn't serve dns requests. If I try something like nslookup [somedomain.com] the.ser.ver.ip to test a DNS query, i get the following error ;; connection timed out; no servers could be reached I can't telnet to it on port 42 either.. I'm guessing something is blocking the requests.. firewall maybe? the plesk firewall module is installed and the nameservers entry is green. Any other way I can check what's blocking it on the server? Any help/tip greatly appreciated. Note: http works, i can telnet to the server on port 80 and i can also ping the server Thanks

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  • i am not able to connect to the application hosted on port 80

    - by shiva
    I am trying to access an application that is hosted on port 80. When i try the url from my personal computer , the site is not reachable but the same url on the server( which hosts the application) i am able to access the site. When i disable the firewall then i am able to access the site from my pc. So there is some rule which is blocking this port. How do i determine what windows firewall rule is blocking this port. I have disables IIS as well. Kindly point me in the right direction

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  • Restrict a port to a single app

    - by viraptor
    I'd like to restrict a range of udp ports to a single application (or a user). What I'd like to achieve is not simply blocking a bind() from other uids, but also remove the range from a pool that can be auto-assigned. For example, if someone tries to explicitly bind 12345, but doesn't run the specified app, they should get EPERM. If someone tries to bind an unspecified port, they should never try to bind 12345 at random. Is there any system that can help here? I tried browsing apparmor / selinux docs, but they seem to do the blocking part only.

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  • Best way to block a country by IP address?

    - by George Edison
    I have a website that needs to block a particular country based on IP address. I am more than aware that IP-based blocking is not a foolproof method for blocking visitors, but it is a necessary step in the right direction. Since I'm using PHP, what I would do is use a GeoIP database like geoplugin.net. However, I'm curious to know if there's a better way of doing this. The website is on a shared webserver (I don't have root access) and it is running Apache on centOS. I guess my question is "can an .htaccess file be configured to block by IP using an external source to lookup IP addresses."

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  • What's the best Flash Blocker for the Chrome Browser on a Mac?

    - by Bryan Schuetz
    Looking at the extensions gallery for Chromium there seems to be a number fo flash-blocking extensions available: A couple with very similar names even. I've been using ClicktoFlash in Safari and am used to it just flat out working everywhere. Unfortunately after using FlashBlock by Ruzanow for a bit I've noticed it gets a bit "Hinky" at times (blocking the flash by collapsing the div so you can't click to enable it, etc.) I have a feeling there may be some other extensions/scripts out there not listed above that are better. Ultimately I'd like to find a flash blocker that works as well as ClickToFlash does in Safari.

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  • No blocked ports on internal interface of ASA

    - by blsub6
    I have a cisco ASA 5505 with three interfaces: Internal (100), DMZ (50) and External (0). The internal has a IPSEC VPN tunnel to my internal network I couldn't log in to my domain because of all of the port restrictions and such. I tried monitoring the traffic through the interface, seeing what it's blocking and then unblocking those ports but even then it didn't work completely correctly I finally just added a rule to permit any ip traffic from any network to any network on the internal interface and, of course, it worked fine But is that good security practice? Should I be blocking ports on an interface that's internal and over a VPN with the highest security level?

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  • Firefox: how to block cookies by name, not by site?

    - by deepc
    Firefox allows to block all cookies on a site-by-site level. This is ok for the most part. However, it does not help with blocking only Google Analytics cookies. The GA cookie names start with __ut. Is there a Firefox add-on which can block all __ut* cookies? I know there are many cookie related add-ons for Firefox - but apparently all of them simply fine tune cookie site-by-site blocking, according to their descriptions. Hopefully I missed the one who can do this... I also know about Google's plugin to opt out of analytics. Installing a specific plug-in for that purpose (as opposed to an add-on) seems a bit overdone. Plus, I would have to trust Google with that and that is exactly what I don't.

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  • Use a Free Tool to Edit, Delete, or Restore the Default Hosts File in Windows

    - by Lori Kaufman
    The hosts file in Windows contains mappings of IP addresses to host names, like an address book for your computer. Your PC uses IP addresses to find websites, so it needs to translate the host names into IP addresses to access websites. When you enter a host name in a browser to visit a website, that host name is looked up in DNS servers to find the IP address. If you enter IP addresses and host names for websites you visit often, these websites will load faster, because the hosts file is loaded into memory when Windows start and overrides DNS server queries, creating a shortcut to the sites. Because the hosts file is checked first, you can also use it to block websites from tracking your activities on the internet, as well as block ads, banners, third-party cookies, and other intrusive elements on webpages. Your computer has its own host address, known as its “localhost” address. The IP address for localhost is 127.0.0.1. To block sites and website elements, you can enter the host name for the unwanted site in the hosts file and associate it with the localhost address. Blocking ads and other undesirable webpage elements, can also speed up the loading of websites. You don’t have to wait for all those items to load. The default hosts file that comes with Windows does not contain any host name/IP address mappings. You can add mappings manually, such as the IP address 74.125.224.72 for www.google.com. As an example of blocking an ad server website, you can enter the following line in your hosts file to block doubleclick.net from serving you ads. How To Use USB Drives With the Nexus 7 and Other Android Devices Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder? Why Your Android Phone Isn’t Getting Operating System Updates and What You Can Do About It

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  • Recommended main loop style

    - by Frootmig-H
    I've just begun attempting an FPS with JMonkeyEngine, but I'm currently stuck as to the best way to implement the main loop - especially with regards to non-instantaneous user actions. By that, I mean things like reloading a weapon. The user starts the action, and it continues for a while with an animation and some sound, and when it completes, game state updates. (I should mention that it's not technically a loop, it's an update method, called as often as possible. Is that different? Me no understand terminology). So, far I've considered : Animation driven Player presses reload Start reload animation If user stars another action, abort animation, start new action. When the animation_complete event is received (JMonkeyEngine provides this), update ammo counters. Event driven Player presses reload Start reload animation Queue up a out-of-thread method to be called at time t + (duration of reload animation) If user starts another action, cancel both animation and queued method. When queued method executes, update ammo. This avoids relying on the animation event (JMonkeyEngine has a particular quirk), but brings in the possibility of thread problems. 'Blocking' (not sure of the correct term) Player presses reload Start reloading animation reloading = true reloadedStartTime = now while (reloading && ((now - reloadingStartTime) < reloadingDuration)) { If user starts another action, break and cancel reloading. } Update ammo counters reloading = false My main concern is that actions can interrupt each other. Reloading can be interrupted by firing, or by dropping or changing weapon, crouching can be interrupted by running, etc. What's the recommended way to handle this? What are the advantages and disadvantages of each method? I'm leaning towards event-driven, even though it requires more care; failing that, blocking.

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  • Distributed transactions and queues, ruby, erlang

    - by chrispanda
    I have a problem that involves several machines, message queues, and transactions. So for example a user clicks on a web page, the click sends a message to another machine which adds a payment to the user's account. There may be many thousands of clicks per second. All aspects of the transaction should be fault tolerant. I've never had to deal with anything like this before, but a bit of reading suggests this is a well known problem. So to my questions. Am I correct in assuming that secure way of doing this is with a two phase commit, but the protocol is blocking and so I won't get the required performance? It appears that DBs like redis and message queuing system like Rescue, RabbitMQ etc don't really help me a lot - even if I implement some sort of two phase commit, the data will be lost if redis crashes because it is essentially memory-only. All of this has led me to look at erlang - but before I wade in and start learning a new language, I would really like to understand better if this is worth the effort. Specifically, am I right in thinking that because of its parallel processing capabilities, erlang is a better choice for implementing a blocking protocol like two phase commit, or am I confused?

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  • CEO Taken Captive in His Own Factory?

    - by Stephen Slade
    Last Friday was no ordinary day for Chip Starnes, the 42 year old factory owner of Specialty Medical Supplies in China. He recently announced movement of some of the production of their diabetes testing equipment from Beijing to Mumbai India.  Of the 110 employees at the facility, about 80 protested by blocking the doors and refusing to let Chip Starnes out of the facility.  He has been trapped in his office several days now.  The employees think the factory was closing but Mr. Starnes said it was not. Mis-information? Poor communications? Work-stoppage. This is a good example of supply chain disruption. Parked cars are blocking the entrance to the facility, front gates are chained close, the CEO a prisoner in his own factory. Chip Starnes was presented with documents to sign in Chinese indicating he would pay severance and other demands he did not understand, possibly bankrupting the company.    If you depend on supply from China and other foreign suppliers, how reliable are your sources? For example how are the shopfloor employee relations? Is it possible to predict these types of HR risks and plan around them? What are your contingencies? It's important to ask the right questions and hear good answers. Having tools in place to rapidly evaluate, assess and react to these disruptions are the keys to survival. Hear how leading organizations are reinforcing their supply chains and mitigating risk through technology with Oracle's latest release of Oracle Supply Chain Management. Source: WSJ pg.B1, June 25, 2013

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  • New "delay" keyword for JavaScript

    - by Van Coding
    I had a great idea for a new javascript keyword "delay", but I don't know what I can do to bring it to the new specification. Also I want to know what you guys think about it and if it's even realistic. What does the delay keyword ? The delay keyword does nothing more than stop the execution of the current stack and immediately continues to the next "job" in the queue. But that's not all! Instead of discarding the stack, it adds it to the end of the queue. After all "jobs" before it are done, the stack continues to execute. What is it good for? delay could help make blocking code non-blocking while it still looks like synchronous code. A short example: setTimeout(function(){ console.log("two"); },0); console.log("one"); delay; //since there is currently another task in the queue, do this task first before continuing console.log("three"); //Outputs: one, two, three This simple keyword would allow us to create a synchronous-looking code wich is asynchronous behind the scenes. Using node.js modules, for example, would no longer be impossible to use in the browser without trickery. There would be so many possibilites with such a keyword! Is this pattern useful? What can I do to bring this into the new ECMAscript specification? Note: I asked this previously on Stack Overflow, where it was closed.

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  • JavaScript and callback nesting

    - by Jake King
    A lot of JavaScript libraries (notably jQuery) use chaining, which allows the reduction of this: var foo = $(".foo"); foo.stop(); foo.show(); foo.animate({ top: 0 }); to this: $(".foo").stop().show().animate({ top: 0 }); With proper formatting, I think this is quite a nice syntactic capability. However, I often see a pattern which I don't particularly like, but appears to be a necessary evil in non-blocking models. This is the ever-present nesting of callback functions: $(".foo").animate({ top: 0, }, { callback: function () { $.ajax({ url: 'ajax.php', }, { callback: function () { ... } }); } }); And it never ends. Even though I love the ease non-blocking models provide, I hate the odd nesting of function literals it forces upon the programmer. I'm interesting in writing a small JS library as an exercise, and I'd love to find a better way to do this, but I don't know how it could be done without feeling hacky. Are there any projects out there that have resolved this problem before? And if not, what are the alternatives to this ugly, meaningless code structure?

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  • Incremental search in Visual Studio

    - by Jalpesh P. Vadgama
    Visual studio is a Great IDE and there are still lots of feature that not known to developers. Incremental search is one of them. This is a amazing feature to find code in particular document and its available from Visual Studio 2010 and carried over in Visual Studio 2012. Incremental search allows developers to search in document without blocking UI and allow to search as they type. Interesting!! right.. So let’s open visual studio and see how it works. Once you open Visual Studio and press Ctrl + I and type something it will find the string without blocking your visual studio UI. Just like following. In the above code you can see that, I have typed Cons and You can see that whole console word is highlighted. Even you can see that find dialog box on top right corner of visual studio 2012 like following. Same way if you see the footer in visual studio where it is finding cons in current document like following. Isn’t that great now we find things very easily and we don’t have to remember whole word like Console. Hope you like it. Stay tuned for more updates.

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  • Kaiden and the Arachnoid Cyst

    - by Martin Hinshelwood
    Some of you may remember when my son Kaiden was born I posted pictures of him and his sister. Kaiden is now 15 months old and is progressing perfectly in every area except that and we had been worried that he was not walking yet. We were only really concerned as his sister was walking at 8 months. Figure: Kai as his usual self   Jadie and I were concerned over that and that he had a rather large head (noggin) so we talked to various GP’s and our health visitor who immediately dismissed our concerns every time. That was until about two months ago when we happened to get a GP whose daughter had Hyper Mobility and she recognised the symptoms immediately. We were referred to the Southbank clinic who were lovely and the paediatrician confirmed that he had Hyper Mobility after testing all of his faculties. This just means that his joints are overly mobile and would need a little physiotherapy to help him out. At the end the paediatrician remarked offhand that he has a rather large head and wanted to measure it. Sure enough he was a good margin above the highest percentile mark for his height and weight. The paediatrician showed the measurements to a paediatric consultant who, as a precautionary measure, referred us for an MRI at Yorkhill Children's hospital. Now, Yorkhill has always been fantastic to us, and this was no exception. You know we have NEVER had a correct diagnosis for the kids (with the exception of the above) from a GP and indeed twice have been proscribed incorrect medication that made the kids sicker! We now always go strait to Yorkhill to save them having to fix GP mistakes as well. Monday 24th May, 7pm The scan went fantastically, with Kaiden sleeping in the MRI machine for all but 5 minutes at the end where he waited patiently for it to finish. We were not expecting anything to be wrong as this was just a precautionary scan to make sure that nothing in his head was affecting his gross motor skills. After the scan we were told to expect a call towards the end of the week… Tuesday 25th May, 12pm The very next day we got a call from Southbank who said that they has found an Arachnoid Cyst and could we come in the next day to see a Consultant and that Kai would need an operation. Wednesday 26th May, 12:30pm We went into the Southbank clinic and spoke to the paediatric consultant who assured us that it was operable but that it was taking up considerable space in Kai’s head. Cerebrospinal fluid is building up as a cyst is blocking the channels it uses to drain. Thankfully they told us that prospects were good and that Kai would expect to make a full recovery before showing us the MRI pictures. Figure: Normal brain MRI cross section. This normal scan shows the spaces in the middle of the brain that contain and produce the Cerebrospinal fluid. Figure: Normal Cerebrospinal Flow This fluid is needed by the brain but is drained in the middle down the spinal column. Figure: Kai’s cyst blocking the four channels. I do not think that I need to explain the difference between the healthy picture and Kai’s picture. However you can see in this first picture the faint outline of the cyst in the middle that is blocking the four channels from draining. After seeing the scans a Neurosurgeon has decided that he is not acute, but needs an operation to unblock the flow. Figure: OMFG! You can see in the second picture the effect of the build up of fluid. If I was not horrified by the first picture I was seriously horrified by this one. What next? Kai is not presenting the symptoms of vomiting or listlessness that would show an immediate problem and as such we will get an appointment to see the Paediatric Neurosurgeon at the Southern General hospital in about 4 weeks. This timescale is based on the Neurosurgeon seeing the scans. After that Kai will need an operation to release the pressure and either remove the cyst completely or put in a permanent shunt (tube from brain to stomach) to bypass the blockage. We have updated his notes for the referral with additional recent information on top of the scan that the consultant things will help improve the timescales, but that is just a guess.   All we can do now is wait and see, and be watchful for tell tail signs of listlessness, eye problems and vomiting that would signify a worsening of his condition.   Technorati Tags: Personal

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  • SQL SERVER – LCK_M_XXX – Wait Type – Day 15 of 28

    - by pinaldave
    Locking is a mechanism used by the SQL Server Database Engine to synchronize access by multiple users to the same piece of data, at the same time. In simpler words, it maintains the integrity of data by protecting (or preventing) access to the database object. From Book On-Line: LCK_M_BU Occurs when a task is waiting to acquire a Bulk Update (BU) lock. LCK_M_IS Occurs when a task is waiting to acquire an Intent Shared (IS) lock. LCK_M_IU Occurs when a task is waiting to acquire an Intent Update (IU) lock. LCK_M_IX Occurs when a task is waiting to acquire an Intent Exclusive (IX) lock. LCK_M_S Occurs when a task is waiting to acquire a Shared lock. LCK_M_SCH_M Occurs when a task is waiting to acquire a Schema Modify lock. LCK_M_SCH_S Occurs when a task is waiting to acquire a Schema Share lock. LCK_M_SIU Occurs when a task is waiting to acquire a Shared With Intent Update lock. LCK_M_SIX Occurs when a task is waiting to acquire a Shared With Intent Exclusive lock. LCK_M_U Occurs when a task is waiting to acquire an Update lock. LCK_M_UIX Occurs when a task is waiting to acquire an Update With Intent Exclusive lock. LCK_M_X Occurs when a task is waiting to acquire an Exclusive lock. LCK_M_XXX Explanation: I think the explanation of this wait type is the simplest. When any task is waiting to acquire lock on any resource, this particular wait type occurs. The common reason for the task to be waiting to put lock on the resource is that the resource is already locked and some other operations may be going on within it. This wait also indicates that resources are not available or are occupied at the moment due to some reasons. There is a good chance that the waiting queries start to time out if this wait type is very high. Client application may degrade the performance as well. You can use various methods to find blocking queries: EXEC sp_who2 SQL SERVER – Quickest Way to Identify Blocking Query and Resolution – Dirty Solution DMV – sys.dm_tran_locks DMV – sys.dm_os_waiting_tasks Reducing LCK_M_XXX wait: Check the Explicit Transactions. If transactions are very long, this wait type can start building up because of other waiting transactions. Keep the transactions small. Serialization Isolation can build up this wait type. If that is an acceptable isolation for your business, this wait type may be natural. The default isolation of SQL Server is ‘Read Committed’. One of my clients has changed their isolation to “Read Uncommitted”. I strongly discourage the use of this because this will probably lead to having lots of dirty data in the database. Identify blocking queries mentioned using various methods described above, and then optimize them. Partition can be one of the options to consider because this will allow transactions to execute concurrently on different partitions. If there are runaway queries, use timeout. (Please discuss this solution with your database architect first as timeout can work against you). Check if there is no memory and IO-related issue using the following counters: Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • PASS Summit 2011 &ndash; Part III

    - by Tara Kizer
    Well we’re about a month past PASS Summit 2011, and yet I haven’t finished blogging my notes! Between work and home life, I haven’t been able to come up for air in a bit.  Now on to my notes… On Thursday of the PASS Summit 2011, I attended Klaus Aschenbrenner’s (blog|twitter) “Advanced SQL Server 2008 Troubleshooting”, Joe Webb’s (blog|twitter) “SQL Server Locking & Blocking Made Simple”, Kalen Delaney’s (blog|twitter) “What Happened? Exploring the Plan Cache”, and Paul Randal’s (blog|twitter) “More DBA Mythbusters”.  I think my head grew two times in size from the Thursday sessions.  Just WOW! I took a ton of notes in Klaus' session.  He took a deep dive into how to troubleshoot performance problems.  Here is how he goes about solving a performance problem: Start by checking the wait stats DMV System health Memory issues I/O issues I normally start with blocking and then hit the wait stats.  Here’s the wait stat query (Paul Randal’s) that I use when working on a performance problem.  He highlighted a few waits to be aware of such as WRITELOG (indicates IO subsystem problem), SOS_SCHEDULER_YIELD (indicates CPU problem), and PAGEIOLATCH_XX (indicates an IO subsystem problem or a buffer pool problem).  Regarding memory issues, Klaus recommended that as a bare minimum, one should set the “max server memory (MB)” in sp_configure to 2GB or 10% reserved for the OS (whichever comes first).  This is just a starting point though! Regarding I/O issues, Klaus talked about disk partition alignment, which can improve SQL I/O performance by up to 100%.  You should use 64kb for NTFS cluster, and it’s automatic in Windows 2008 R2. Joe’s locking and blocking presentation was a good session to really clear up the fog in my mind about locking.  One takeaway that I had no idea could be done was that you can set a timeout in T-SQL code view LOCK_TIMEOUT.  If you do this via the application, you should trap error 1222. Kalen’s session went into execution plans.  The minimum size of a plan is 24k.  This adds up fast especially if you have a lot of plans that don’t get reused much.  You can use sys.dm_exec_cached_plans to check how often a plan is being reused by checking the usecounts column.  She said that we can use DBCC FLUSHPROCINDB to clear out the stored procedure cache for a specific database.  I didn’t know we had this available, so this was great to hear.  This will be less intrusive when an emergency comes up where I’ve needed to run DBCC FREEPROCCACHE. Kalen said one should enable “optimize for ad hoc workloads” if you have an adhoc loc.  This stores only a 300-byte stub of the first plan, and if it gets run again, it’ll store the whole thing.  This helps with plan cache bloat.  I have a lot of systems that use prepared statements, and Kalen says we simulate those calls by using sp_executesql.  Cool! Paul did a series of posts last year to debunk various myths and misconceptions around SQL Server.  He continues to debunk things via “DBA Mythbusters”.  You can get a PDF of a bunch of these here.  One of the myths he went over is the number of tempdb data files that you should have.  Back in 2000, the recommendation was to have as many tempdb data files as there are CPU cores on your server.  This no longer holds true due to the numerous cores we have on our servers.  Paul says you should start out with 1/4 to 1/2 the number of cores and work your way up from there.  BUT!  Paul likes what Bob Ward (twitter) says on this topic: 8 or less cores –> set number of files equal to the number of cores Greater than 8 cores –> start with 8 files and increase in blocks of 4 One common myth out there is to set your MAXDOP to 1 for an OLTP workload with high CXPACKET waits.  Instead of that, dig deeper first.  Look for missing indexes, out-of-date statistics, increase the “cost threshold for parallelism” setting, and perhaps set MAXDOP at the query level.  Paul stressed that you should not plan a backup strategy but instead plan a restore strategy.  What are your recoverability requirements?  Once you know that, now plan out your backups. As Paul always does, he talked about DBCC CHECKDB.  He said how fabulous it is.  I didn’t want to interrupt the presentation, so after his session had ended, I asked Paul about the need to run DBCC CHECKDB on your mirror systems.  You could have data corruption occur at the mirror and not at the principal server.  If you aren’t checking for data corruption on your mirror systems, you could be failing over to a corrupt database in the case of a disaster or even a planned failover.  You can’t run DBCC CHECKDB against the mirrored database, but you can run it against a snapshot off the mirrored database.

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  • C#/.NET Little Wonders: ConcurrentBag and BlockingCollection

    - by James Michael Hare
    In the first week of concurrent collections, began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  The last post discussed the ConcurrentDictionary<T> .  Finally this week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see C#/.NET Little Wonders: A Redux. Recap As you'll recall from the previous posts, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  With .NET 4.0, a new breed of collections was born in the System.Collections.Concurrent namespace.  Of these, the final concurrent collection we will examine is the ConcurrentBag and a very useful wrapper class called the BlockingCollection. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this informative whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentBag<T> – Thread-safe unordered collection. Unlike the other concurrent collections, the ConcurrentBag<T> has no non-concurrent counterpart in the .NET collections libraries.  Items can be added and removed from a bag just like any other collection, but unlike the other collections, the items are not maintained in any order.  This makes the bag handy for those cases when all you care about is that the data be consumed eventually, without regard for order of consumption or even fairness – that is, it’s possible new items could be consumed before older items given the right circumstances for a period of time. So why would you ever want a container that can be unfair?  Well, to look at it another way, you can use a ConcurrentQueue and get the fairness, but it comes at a cost in that the ordering rules and synchronization required to maintain that ordering can affect scalability a bit.  Thus sometimes the bag is great when you want the fastest way to get the next item to process, and don’t care what item it is or how long its been waiting. The way that the ConcurrentBag works is to take advantage of the new ThreadLocal<T> type (new in System.Threading for .NET 4.0) so that each thread using the bag has a list local to just that thread.  This means that adding or removing to a thread-local list requires very low synchronization.  The problem comes in where a thread goes to consume an item but it’s local list is empty.  In this case the bag performs “work-stealing” where it will rob an item from another thread that has items in its list.  This requires a higher level of synchronization which adds a bit of overhead to the take operation. So, as you can imagine, this makes the ConcurrentBag good for situations where each thread both produces and consumes items from the bag, but it would be less-than-idea in situations where some threads are dedicated producers and the other threads are dedicated consumers because the work-stealing synchronization would outweigh the thread-local optimization for a thread taking its own items. Like the other concurrent collections, there are some curiosities to keep in mind: IsEmpty(), Count, ToArray(), and GetEnumerator() lock collection Each of these needs to take a snapshot of whole bag to determine if empty, thus they tend to be more expensive and cause Add() and Take() operations to block. ToArray() and GetEnumerator() are static snapshots Because it is based on a snapshot, will not show subsequent updates after snapshot. Add() is lightweight Since adding to the thread-local list, there is very little overhead on Add. TryTake() is lightweight if items in thread-local list As long as items are in the thread-local list, TryTake() is very lightweight, much more so than ConcurrentStack() and ConcurrentQueue(), however if the local thread list is empty, it must steal work from another thread, which is more expensive. Remember, a bag is not ideal for all situations, it is mainly ideal for situations where a process consumes an item and either decomposes it into more items to be processed, or handles the item partially and places it back to be processed again until some point when it will complete.  The main point is that the bag works best when each thread both takes and adds items. For example, we could create a totally contrived example where perhaps we want to see the largest power of a number before it crosses a certain threshold.  Yes, obviously we could easily do this with a log function, but bare with me while I use this contrived example for simplicity. So let’s say we have a work function that will take a Tuple out of a bag, this Tuple will contain two ints.  The first int is the original number, and the second int is the last multiple of that number.  So we could load our bag with the initial values (let’s say we want to know the last multiple of each of 2, 3, 5, and 7 under 100. 1: var bag = new ConcurrentBag<Tuple<int, int>> 2: { 3: Tuple.Create(2, 1), 4: Tuple.Create(3, 1), 5: Tuple.Create(5, 1), 6: Tuple.Create(7, 1) 7: }; Then we can create a method that given the bag, will take out an item, apply the multiplier again, 1: public static void FindHighestPowerUnder(ConcurrentBag<Tuple<int,int>> bag, int threshold) 2: { 3: Tuple<int,int> pair; 4:  5: // while there are items to take, this will prefer local first, then steal if no local 6: while (bag.TryTake(out pair)) 7: { 8: // look at next power 9: var result = Math.Pow(pair.Item1, pair.Item2 + 1); 10:  11: if (result < threshold) 12: { 13: // if smaller than threshold bump power by 1 14: bag.Add(Tuple.Create(pair.Item1, pair.Item2 + 1)); 15: } 16: else 17: { 18: // otherwise, we're done 19: Console.WriteLine("Highest power of {0} under {3} is {0}^{1} = {2}.", 20: pair.Item1, pair.Item2, Math.Pow(pair.Item1, pair.Item2), threshold); 21: } 22: } 23: } Now that we have this, we can load up this method as an Action into our Tasks and run it: 1: // create array of tasks, start all, wait for all 2: var tasks = new[] 3: { 4: new Task(() => FindHighestPowerUnder(bag, 100)), 5: new Task(() => FindHighestPowerUnder(bag, 100)), 6: }; 7:  8: Array.ForEach(tasks, t => t.Start()); 9:  10: Task.WaitAll(tasks); Totally contrived, I know, but keep in mind the main point!  When you have a thread or task that operates on an item, and then puts it back for further consumption – or decomposes an item into further sub-items to be processed – you should consider a ConcurrentBag as the thread-local lists will allow for quick processing.  However, if you need ordering or if your processes are dedicated producers or consumers, this collection is not ideal.  As with anything, you should performance test as your mileage will vary depending on your situation! BlockingCollection<T> – A producers & consumers pattern collection The BlockingCollection<T> can be treated like a collection in its own right, but in reality it adds a producers and consumers paradigm to any collection that implements the interface IProducerConsumerCollection<T>.  If you don’t specify one at the time of construction, it will use a ConcurrentQueue<T> as its underlying store. If you don’t want to use the ConcurrentQueue, the ConcurrentStack and ConcurrentBag also implement the interface (though ConcurrentDictionary does not).  In addition, you are of course free to create your own implementation of the interface. So, for those who don’t remember the producers and consumers classical computer-science problem, the gist of it is that you have one (or more) processes that are creating items (producers) and one (or more) processes that are consuming these items (consumers).  Now, the crux of the problem is that there is a bin (queue) where the produced items are placed, and typically that bin has a limited size.  Thus if a producer creates an item, but there is no space to store it, it must wait until an item is consumed.  Also if a consumer goes to consume an item and none exists, it must wait until an item is produced. The BlockingCollection makes it trivial to implement any standard producers/consumers process set by providing that “bin” where the items can be produced into and consumed from with the appropriate blocking operations.  In addition, you can specify whether the bin should have a limited size or can be (theoretically) unbounded, and you can specify timeouts on the blocking operations. As far as your choice of “bin”, for the most part the ConcurrentQueue is the right choice because it is fairly light and maximizes fairness by ordering items so that they are consumed in the same order they are produced.  You can use the concurrent bag or stack, of course, but your ordering would be random-ish in the case of the former and LIFO in the case of the latter. So let’s look at some of the methods of note in BlockingCollection: BoundedCapacity returns capacity of the “bin” If the bin is unbounded, the capacity is int.MaxValue. Count returns an internally-kept count of items This makes it O(1), but if you modify underlying collection directly (not recommended) it is unreliable. CompleteAdding() is used to cut off further adds. This sets IsAddingCompleted and begins to wind down consumers once empty. IsAddingCompleted is true when producers are “done”. Once you are done producing, should complete the add process to alert consumers. IsCompleted is true when producers are “done” and “bin” is empty. Once you mark the producers done, and all items removed, this will be true. Add() is a blocking add to collection. If bin is full, will wait till space frees up Take() is a blocking remove from collection. If bin is empty, will wait until item is produced or adding is completed. GetConsumingEnumerable() is used to iterate and consume items. Unlike the standard enumerator, this one consumes the items instead of iteration. TryAdd() attempts add but does not block completely If adding would block, returns false instead, can specify TimeSpan to wait before stopping. TryTake() attempts to take but does not block completely Like TryAdd(), if taking would block, returns false instead, can specify TimeSpan to wait. Note the use of CompleteAdding() to signal the BlockingCollection that nothing else should be added.  This means that any attempts to TryAdd() or Add() after marked completed will throw an InvalidOperationException.  In addition, once adding is complete you can still continue to TryTake() and Take() until the bin is empty, and then Take() will throw the InvalidOperationException and TryTake() will return false. So let’s create a simple program to try this out.  Let’s say that you have one process that will be producing items, but a slower consumer process that handles them.  This gives us a chance to peek inside what happens when the bin is bounded (by default, the bin is NOT bounded). 1: var bin = new BlockingCollection<int>(5); Now, we create a method to produce items: 1: public static void ProduceItems(BlockingCollection<int> bin, int numToProduce) 2: { 3: for (int i = 0; i < numToProduce; i++) 4: { 5: // try for 10 ms to add an item 6: while (!bin.TryAdd(i, TimeSpan.FromMilliseconds(10))) 7: { 8: Console.WriteLine("Bin is full, retrying..."); 9: } 10: } 11:  12: // once done producing, call CompleteAdding() 13: Console.WriteLine("Adding is completed."); 14: bin.CompleteAdding(); 15: } And one to consume them: 1: public static void ConsumeItems(BlockingCollection<int> bin) 2: { 3: // This will only be true if CompleteAdding() was called AND the bin is empty. 4: while (!bin.IsCompleted) 5: { 6: int item; 7:  8: if (!bin.TryTake(out item, TimeSpan.FromMilliseconds(10))) 9: { 10: Console.WriteLine("Bin is empty, retrying..."); 11: } 12: else 13: { 14: Console.WriteLine("Consuming item {0}.", item); 15: Thread.Sleep(TimeSpan.FromMilliseconds(20)); 16: } 17: } 18: } Then we can fire them off: 1: // create one producer and two consumers 2: var tasks = new[] 3: { 4: new Task(() => ProduceItems(bin, 20)), 5: new Task(() => ConsumeItems(bin)), 6: new Task(() => ConsumeItems(bin)), 7: }; 8:  9: Array.ForEach(tasks, t => t.Start()); 10:  11: Task.WaitAll(tasks); Notice that the producer is faster than the consumer, thus it should be hitting a full bin often and displaying the message after it times out on TryAdd(). 1: Consuming item 0. 2: Consuming item 1. 3: Bin is full, retrying... 4: Bin is full, retrying... 5: Consuming item 3. 6: Consuming item 2. 7: Bin is full, retrying... 8: Consuming item 4. 9: Consuming item 5. 10: Bin is full, retrying... 11: Consuming item 6. 12: Consuming item 7. 13: Bin is full, retrying... 14: Consuming item 8. 15: Consuming item 9. 16: Bin is full, retrying... 17: Consuming item 10. 18: Consuming item 11. 19: Bin is full, retrying... 20: Consuming item 12. 21: Consuming item 13. 22: Bin is full, retrying... 23: Bin is full, retrying... 24: Consuming item 14. 25: Adding is completed. 26: Consuming item 15. 27: Consuming item 16. 28: Consuming item 17. 29: Consuming item 19. 30: Consuming item 18. Also notice that once CompleteAdding() is called and the bin is empty, the IsCompleted property returns true, and the consumers will exit. Summary The ConcurrentBag is an interesting collection that can be used to optimize concurrency scenarios where tasks or threads both produce and consume items.  In this way, it will choose to consume its own work if available, and then steal if not.  However, in situations where you want fair consumption or ordering, or in situations where the producers and consumers are distinct processes, the bag is not optimal. The BlockingCollection is a great wrapper around all of the concurrent queue, stack, and bag that allows you to add producer and consumer semantics easily including waiting when the bin is full or empty. That’s the end of my dive into the concurrent collections.  I’d also strongly recommend, once again, you read this excellent Microsoft white paper that goes into much greater detail on the efficiencies you can gain using these collections judiciously (here). Tweet Technorati Tags: C#,.NET,Concurrent Collections,Little Wonders

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  • Windows LiveID "Couldn't sign you out" error at sign-out

    - by Jason
    I'm implementing LiveID authentication on my website. I've done it before, but not on this particular platform, MojoPortal. The sign-in works properly, but when I attempt to sign-out, I get the error message quoted below. My browser is not blocking cookies. I get the same message when logging in to and out of, say, MSDN with a LiveID too now. I can't figure out if there's something about my site's programming that is interfering with the sign-out process of LiveID (since I believe that all (recent?) websites get sent a sign-out command) OR if live.com is just having issues lately and this is a coincidence. Couldn't sign you out We couldn't sign you out because your browser is blocking cookies. To sign out, close all of your browser windows. To keep this from happening again, change your browser's settings to allow cookies. If you don't know how to do that, see your browser's help.

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  • Locking Cache Key without Locking the entire Cache

    - by Gandalf
    I have servlets that caches user information rather then retrieving it from the user store on every request (shared Ehcache). The issue I have is that if a client is multi-threaded and they make more then one simultaneous request, before they have been authenticated, then I get this in my log: Retrieving User [Bob] Retrieving User [Bob] Retrieving User [Bob] Returned [Bob] ...caching Returned [Bob] ...caching Returned [Bob] ...caching What I would want is that the first request would call the user service, while the other two requests get blocked - and when the first request returns, and then caches the object, the other two requests go through: Retrieving User [Bob] blocking... blocking... Returned [Bob] ...caching [Bob] found in cache [Bob] found in cache I've thought about locking on the String "Bob" (because due to interning it's always the same object right?). Would that work? And if so how do I keep track of the keys that actually exist in the cache and build a locking mechanism around them that would then return the valid object once it's retrieved. Thanks.

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  • How to sketch out an event-driven system?

    - by Jordan
    I'm trying to design a system in Node.js (an attempt at solving one of my earlier problems, using Node's concurrency) but I'm running into trouble figuring out how to draw a plan of how the thing should operate. I'm getting very tripped up thinking in terms of callbacks instead of returned values. The flow isn't linear, and it's really boggling my ability to draft it. How does one draw out an operational flow for an event-driven system? I need something I can look at and say "Ok, yes, that's how it will work. I'll start it over here, and it will give me back these results over here." Pictures would be very helpful for this one. Thanks. Edit: I'm looking for something more granular than UML, specifically, something that will help me transition from a blocking and object-oriented programming structure, where I'm comfortable, to a non-blocking and event driven structure, where I'm unfamiliar.

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