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  • Varnish does not start properly (crashes after startup) with no error messages

    - by Matthew Savage
    I am running Varnish (2.0.4 from the Ubuntu unstable apt repository, though I have also used the standard repository) in a test environment (Virtual Machines) on Ubuntu 9.10, soon to be 10.04. When I have a working configuration and the server starts successfully it seems like everything is fine, however if, for whatever reason, I stop and then restart the varnish daemon it doesn't always startup properly, and there are no errors going into syslog or messages to indicate what might be wrong. If I run varnish in debug mode (-d) and issue start when prompted then 7 times out of time it will run, but occasionally it will just shut down 'silently'. My startup command is (the $1 allows for me to pass -d to the script this lives in): varnishd -a :80 $1 \ -T 127.0.0.1:6082 \ -s malloc,1GB \ -f /home/deploy/mysite.vcl \ -u deploy \ -g deploy \ -p obj_workspace=4096 \ -p sess_workspace=262144 \ -p listen_depth=2048 \ -p overflow_max=2000 \ -p ping_interval=2 \ -p log_hashstring=off \ -h classic,5000009 \ -p thread_pool_max=1000 \ -p lru_interval=60 \ -p esi_syntax=0x00000003 \ -p sess_timeout=10 \ -p thread_pools=1 \ -p thread_pool_min=100 \ -p shm_workspace=32768 \ -p thread_pool_add_delay=1 and the VCL looks like this: # nginx/passenger server, HTTP:81 backend default { .host = "127.0.0.1"; .port = "81"; } sub vcl_recv { # Don't cache the /useradmin or /admin path if (req.url ~ "^/(useradmin|admin|session|sessions|login|members|logout|forgot_password)") { pipe; } # If cache is 'regenerating' then allow for old cache to be served set req.grace = 2m; # Forward to cache lookup lookup; } # This should be obvious sub vcl_hit { deliver; } sub vcl_fetch { # See link #16, allow for old cache serving set obj.grace = 2m; if (req.url ~ "\.(png|gif|jpg|swf|css|js)$") { deliver; } remove obj.http.Set-Cookie; remove obj.http.Etag; set obj.http.Cache-Control = "no-cache"; set obj.ttl = 7d; deliver; } Any suggestions would be greatly appreciated, this is driving me absolutely crazy, especially because its such an inconsistent behaviour.

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  • e2fsck extremly slow, although enough memory exists

    - by kaefert
    I've got this external USB-Disk: kaefert@blechmobil:~$ lsusb -s 2:3 Bus 002 Device 003: ID 0bc2:3320 Seagate RSS LLC As can be seen in this dmesg output, there are some problems that prevents that disk from beeing mounted: kaefert@blechmobil:~$ dmesg | grep sdb [ 114.474342] sd 5:0:0:0: [sdb] 732566645 4096-byte logical blocks: (3.00 TB/2.72 TiB) [ 114.475089] sd 5:0:0:0: [sdb] Write Protect is off [ 114.475092] sd 5:0:0:0: [sdb] Mode Sense: 43 00 00 00 [ 114.475959] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 114.477093] sd 5:0:0:0: [sdb] 732566645 4096-byte logical blocks: (3.00 TB/2.72 TiB) [ 114.501649] sdb: sdb1 [ 114.502717] sd 5:0:0:0: [sdb] 732566645 4096-byte logical blocks: (3.00 TB/2.72 TiB) [ 114.504354] sd 5:0:0:0: [sdb] Attached SCSI disk [ 116.804408] EXT4-fs (sdb1): ext4_check_descriptors: Checksum for group 3976 failed (47397!=61519) [ 116.804413] EXT4-fs (sdb1): group descriptors corrupted! So I went and fired up my favorite partition manager - gparted, and told it to verify and repair the partition sdb1. This made gparted call e2fsck (version 1.42.4 (12-Jun-2012)) e2fsck -f -y -v /dev/sdb1 Although gparted called e2fsck with the "-v" option, sadly it doesn't show me the output of my e2fsck process (bugreport https://bugzilla.gnome.org/show_bug.cgi?id=467925 ) I started this whole thing on Sunday (2012-11-04_2200) evening, so about 48 hours ago, this is what htop says about it now (2012-11-06-1900): PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command 3704 root 39 19 1560M 1166M 768 R 98.0 19.5 42h56:43 e2fsck -f -y -v /dev/sdb1 Now I found a few posts on the internet that discuss e2fsck running slow, for example: http://gparted-forum.surf4.info/viewtopic.php?id=13613 where they write that its a good idea to see if the disk is just that slow because maybe its damaged, and I think these outputs tell me that this is not the case in my case: kaefert@blechmobil:~$ sudo hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 3562 MB in 2.00 seconds = 1783.29 MB/sec Timing buffered disk reads: 82 MB in 3.01 seconds = 27.26 MB/sec kaefert@blechmobil:~$ sudo hdparm /dev/sdb /dev/sdb: multcount = 0 (off) readonly = 0 (off) readahead = 256 (on) geometry = 364801/255/63, sectors = 5860533160, start = 0 However, although I can read quickly from that disk, this disk speed doesn't seem to be used by e2fsck, considering tools like gkrellm or iotop or this: kaefert@blechmobil:~$ iostat -x Linux 3.2.0-2-amd64 (blechmobil) 2012-11-06 _x86_64_ (2 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 14,24 47,81 14,63 0,95 0,00 22,37 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util sda 0,59 8,29 2,42 5,14 43,17 160,17 53,75 0,30 39,80 8,72 54,42 3,95 2,99 sdb 137,54 5,48 9,23 0,20 587,07 22,73 129,35 0,07 7,70 7,51 16,18 2,17 2,04 Now I researched a little bit on how to find out what e2fsck is doing with all that processor time, and I found the tool strace, which gives me this: kaefert@blechmobil:~$ sudo strace -p3704 lseek(4, 41026998272, SEEK_SET) = 41026998272 write(4, "\212\354K[_\361\3nl\212\245\352\255jR\303\354\312Yv\334p\253r\217\265\3567\325\257\3766"..., 4096) = 4096 lseek(4, 48404766720, SEEK_SET) = 48404766720 read(4, "\7t\260\366\346\337\304\210\33\267j\35\377'\31f\372\252\ffU\317.y\211\360\36\240c\30`\34"..., 4096) = 4096 lseek(4, 41027002368, SEEK_SET) = 41027002368 write(4, "\232]7Ws\321\352\t\1@[+5\263\334\276{\343zZx\352\21\316`1\271[\202\350R`"..., 4096) = 4096 lseek(4, 48404770816, SEEK_SET) = 48404770816 read(4, "\17\362r\230\327\25\346//\210H\v\311\3237\323K\304\306\361a\223\311\324\272?\213\tq \370\24"..., 4096) = 4096 lseek(4, 41027006464, SEEK_SET) = 41027006464 write(4, "\367yy>x\216?=\324Z\305\351\376&\25\244\210\271\22\306}\276\237\370(\214\205G\262\360\257#"..., 4096) = 4096 lseek(4, 48404774912, SEEK_SET) = 48404774912 read(4, "\365\25\0\21|T\0\21}3t_\272\373\222k\r\177\303\1\201\261\221$\261B\232\3142\21U\316"..., 4096) = 4096 ^CProcess 3704 detached around 16 of these lines every second, so 4 read and 4 write operations every second, which I don't consider to be a lot.. And finally, my question: Will this process ever finish? If those numbers from fseek (48404774912) represent bytes, that would be something like 45 gigabytes, with this beeing a 3 terrabyte disk, which would give me 134 days to go, if the speed stays constant, and he scans the disk like this completly and only once. Do you have some advice for me? I have most of the data on that disk elsewhere, but I've put a lot of hours into sorting and merging it to this disk, so I would prefer to getting this disk up and running again, without formatting it anew. I don't think that the hardware is damaged since the disk is only a few months and since I can't see any I/O errors in the dmesg output. UPDATE: I just looked at the strace output again (2012-11-06_2300), now it looks like this: lseek(4, 1419860611072, SEEK_SET) = 1419860611072 read(4, "3#\f\2447\335\0\22A\355\374\276j\204'\207|\217V|\23\245[\7VP\251\242\276\207\317:"..., 4096) = 4096 lseek(4, 43018145792, SEEK_SET) = 43018145792 write(4, "]\206\231\342Y\204-2I\362\242\344\6R\205\361\324\177\265\317C\334V\324\260\334\275t=\10F."..., 4096) = 4096 lseek(4, 1419860615168, SEEK_SET) = 1419860615168 read(4, "\262\305\314Y\367\37x\326\245\226\226\320N\333$s\34\204\311\222\7\315\236\336\300TK\337\264\236\211n"..., 4096) = 4096 lseek(4, 43018149888, SEEK_SET) = 43018149888 write(4, "\271\224m\311\224\25!I\376\16;\377\0\223H\25Yd\201Y\342\r\203\271\24eG<\202{\373V"..., 4096) = 4096 lseek(4, 1419860619264, SEEK_SET) = 1419860619264 read(4, ";d\360\177\n\346\253\210\222|\250\352T\335M\33\260\320\261\7g\222P\344H?t\240\20\2548\310"..., 4096) = 4096 lseek(4, 43018153984, SEEK_SET) = 43018153984 write(4, "\360\252j\317\310\251G\227\335{\214`\341\267\31Y\202\360\v\374\307oq\3063\217Z\223\313\36D\211"..., 4096) = 4096 So this number of the lseeks before the reads, like 1419860619264 are already a lot bigger, standing for 1.29 terabytes if the numbers are bytes, so it doesn't seem to be a linear progress on a big scale, maybe there are only some areas that need work, that have big gaps in between them. (times are in CET)

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  • ASP.NET, IS7 and IE8 caching?

    - by jdege
    We're suddenly having problems with some of our sites having old versions of .css and .js files show up in the browser. Generally, these problems go away, when the user clears cache in the browser. Is there something we can do either in the code or in IIS7, to convince the browser to not used the cached files? In our weirdest case, we have one customer whose users hit our site, and get an old version of a js file. They clear cache, load the page, get the current version, and the page runs fine. Then they load the file again, and suddenly have the old version, again. Any ideas as to how that might be happening? I can think of three: The browser is somehow holding on to the old version, when we clear cache, and is putting it back in the cache, before the second page load. One of our servers has an old version of the file, and while the first page load after a clear cache pulls it from one of the servers with the current version, second and subsequent page loads pull it from the server that has the old version. The first load after a clear cache goes straight to our servers, while subsequent loads pull the file from the cache on the customer's web proxy. I have to say, all three of those scenarios seem outlandishly unlikely, but it's a repeatable behavior. Any ideas?

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  • Using Node.js as an accelerator for WCF REST services

    - by Elton Stoneman
    Node.js is a server-side JavaScript platform "for easily building fast, scalable network applications". It's built on Google's V8 JavaScript engine and uses an (almost) entirely async event-driven processing model, running in a single thread. If you're new to Node and your reaction is "why would I want to run JavaScript on the server side?", this is the headline answer: in 150 lines of JavaScript you can build a Node.js app which works as an accelerator for WCF REST services*. It can double your messages-per-second throughput, halve your CPU workload and use one-fifth of the memory footprint, compared to the WCF services direct.   Well, it can if: 1) your WCF services are first-class HTTP citizens, honouring client cache ETag headers in request and response; 2) your services do a reasonable amount of work to build a response; 3) your data is read more often than it's written. In one of my projects I have a set of REST services in WCF which deal with data that only gets updated weekly, but which can be read hundreds of times an hour. The services issue ETags and will return a 304 if the client sends a request with the current ETag, which means in the most common scenario the client uses its local cached copy. But when the weekly update happens, then all the client caches are invalidated and they all need the same new data. Then the service will get hundreds of requests with old ETags, and they go through the full service stack to build the same response for each, taking up threads and processing time. Part of that processing means going off to a database on a separate cloud, which introduces more latency and downtime potential.   We can use ASP.NET output caching with WCF to solve the repeated processing problem, but the server will still be thread-bound on incoming requests, and to get the current ETags reliably needs a database call per request. The accelerator solves that by running as a proxy - all client calls come into the proxy, and the proxy routes calls to the underlying REST service. We could use Node as a straight passthrough proxy and expect some benefit, as the server would be less thread-bound, but we would still have one WCF and one database call per proxy call. But add some smart caching logic to the proxy, and share ETags between Node and WCF (so the proxy doesn't even need to call the servcie to get the current ETag), and the underlying service will only be invoked when data has changed, and then only once - all subsequent client requests will be served from the proxy cache.   I've built this as a sample up on GitHub: NodeWcfAccelerator on sixeyed.codegallery. Here's how the architecture looks:     The code is very simple. The Node proxy runs on port 8010 and all client requests target the proxy. If the client request has an ETag header then the proxy looks up the ETag in the tag cache to see if it is current - the sample uses memcached to share ETags between .NET and Node. If the ETag from the client matches the current server tag, the proxy sends a 304 response with an empty body to the client, telling it to use its own cached version of the data. If the ETag from the client is stale, the proxy looks for a local cached version of the response, checking for a file named after the current ETag. If that file exists, its contents are returned to the client as the body in a 200 response, which includes the current ETag in the header. If the proxy does not have a local cached file for the service response, it calls the service, and writes the WCF response to the local cache file, and to the body of a 200 response for the client. So the WCF service is only troubled if both client and proxy have stale (or no) caches.   The only (vaguely) clever bit in the sample is using the ETag cache, so the proxy can serve cached requests without any communication with the underlying service, which it does completely generically, so the proxy has no notion of what it is serving or what the services it proxies are doing. The relative path from the URL is used as the lookup key, so there's no shared key-generation logic between .NET and Node, and when WCF stores a tag it also stores the "read" URL against the ETag so it can be used for a reverse lookup, e.g:   Key Value /WcfSampleService/PersonService.svc/rest/fetch/3 "28cd4796-76b8-451b-adfd-75cb50a50fa6" "28cd4796-76b8-451b-adfd-75cb50a50fa6" /WcfSampleService/PersonService.svc/rest/fetch/3    In Node we read the cache using the incoming URL path as the key and we know that "28cd4796-76b8-451b-adfd-75cb50a50fa6" is the current ETag; we look for a local cached response in /caches/28cd4796-76b8-451b-adfd-75cb50a50fa6.body (and the corresponding .header file which contains the original service response headers, so the proxy response is exactly the same as the underlying service). When the data is updated, we need to invalidate the ETag cache – which is why we need the reverse lookup in the cache. In the WCF update service, we don't need to know the URL of the related read service - we fetch the entity from the database, do a reverse lookup on the tag cache using the old ETag to get the read URL, update the new ETag against the URL, store the new reverse lookup and delete the old one.   Running Apache Bench against the two endpoints gives the headline performance comparison. Making 1000 requests with concurrency of 100, and not sending any ETag headers in the requests, with the Node proxy I get 102 requests handled per second, average response time of 975 milliseconds with 90% of responses served within 850 milliseconds; going direct to WCF with the same parameters, I get 53 requests handled per second, mean response time of 1853 milliseconds, with 90% of response served within 3260 milliseconds. Informally monitoring server usage during the tests, Node maxed at 20% CPU and 20Mb memory; IIS maxed at 60% CPU and 100Mb memory.   Note that the sample WCF service does a database read and sleeps for 250 milliseconds to simulate a moderate processing load, so this is *not* a baseline Node-vs-WCF comparison, but for similar scenarios where the  service call is expensive but applicable to numerous clients for a long timespan, the performance boost from the accelerator is considerable.     * - actually, the accelerator will work nicely for any HTTP request, where the URL (path + querystring) uniquely identifies a resource. In the sample, there is an assumption that the ETag is a GUID wrapped in double-quotes (e.g. "28cd4796-76b8-451b-adfd-75cb50a50fa6") – which is the default for WCF services. I use that assumption to name the cache files uniquely, but it is a trivial change to adapt to other ETag formats.

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  • Why Are Minimized Programs Often Slow to Open Again?

    - by Jason Fitzpatrick
    It seems particularly counterintuitive: you minimize an application because you plan on returning to it later and wish to skip shutting the application down and restarting it later, but sometimes maximizing it takes even longer than launching it fresh. What gives? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader Bart wants to know why he’s not saving any time with application minimization: I’m working in Photoshop CS6 and multiple browsers a lot. I’m not using them all at once, so sometimes some applications are minimized to taskbar for hours or days. The problem is, when I try to maximize them from the taskbar – it sometimes takes longer than starting them! Especially Photoshop feels really weird for many seconds after finally showing up, it’s slow, unresponsive and even sometimes totally freezes for minute or two. It’s not a hardware problem as it’s been like that since always on all on my PCs. Would I also notice it after upgrading my HDD to SDD and adding RAM (my main PC holds 4 GB currently)? Could guys with powerful pcs / macs tell me – does it also happen to you? I guess OSes somehow “focus” on active software and move all the resources away from the ones that run, but are not used. Is it possible to somehow set RAM / CPU / HDD priorities or something, for let’s say, Photoshop, so it won’t slow down after long period of inactivity? So what is the deal? Why does he find himself waiting to maximize a minimized app? The Answer SuperUser contributor Allquixotic explains why: Summary The immediate problem is that the programs that you have minimized are being paged out to the “page file” on your hard disk. This symptom can be improved by installing a Solid State Disk (SSD), adding more RAM to your system, reducing the number of programs you have open, or upgrading to a newer system architecture (for instance, Ivy Bridge or Haswell). Out of these options, adding more RAM is generally the most effective solution. Explanation The default behavior of Windows is to give active applications priority over inactive applications for having a spot in RAM. When there’s significant memory pressure (meaning the system doesn’t have a lot of free RAM if it were to let every program have all the RAM it wants), it starts putting minimized programs into the page file, which means it writes out their contents from RAM to disk, and then makes that area of RAM free. That free RAM helps programs you’re actively using — say, your web browser — run faster, because if they need to claim a new segment of RAM (like when you open a new tab), they can do so. This “free” RAM is also used as page cache, which means that when active programs attempt to read data on your hard disk, that data might be cached in RAM, which prevents your hard disk from being accessed to get that data. By using the majority of your RAM for page cache, and swapping out unused programs to disk, Windows is trying to improve responsiveness of the program(s) you are actively using, by making RAM available to them, and caching the files they access in RAM instead of the hard disk. The downside of this behavior is that minimized programs can take a while to have their contents copied from the page file, on disk, back into RAM. The time increases the larger the program’s footprint in memory. This is why you experience that delay when maximizing Photoshop. RAM is many times faster than a hard disk (depending on the specific hardware, it can be up to several orders of magnitude). An SSD is considerably faster than a hard disk, but it is still slower than RAM by orders of magnitude. Having your page file on an SSD will help, but it will also wear out the SSD more quickly than usual if your page file is heavily utilized due to RAM pressure. Remedies Here is an explanation of the available remedies, and their general effectiveness: Installing more RAM: This is the recommended path. If your system does not support more RAM than you already have installed, you will need to upgrade more of your system: possibly your motherboard, CPU, chassis, power supply, etc. depending on how old it is. If it’s a laptop, chances are you’ll have to buy an entire new laptop that supports more installed RAM. When you install more RAM, you reduce memory pressure, which reduces use of the page file, which is a good thing all around. You also make available more RAM for page cache, which will make all programs that access the hard disk run faster. As of Q4 2013, my personal recommendation is that you have at least 8 GB of RAM for a desktop or laptop whose purpose is anything more complex than web browsing and email. That means photo editing, video editing/viewing, playing computer games, audio editing or recording, programming / development, etc. all should have at least 8 GB of RAM, if not more. Run fewer programs at a time: This will only work if the programs you are running do not use a lot of memory on their own. Unfortunately, Adobe Creative Suite products such as Photoshop CS6 are known for using an enormous amount of memory. This also limits your multitasking ability. It’s a temporary, free remedy, but it can be an inconvenience to close down your web browser or Word every time you start Photoshop, for instance. This also wouldn’t stop Photoshop from being swapped when minimizing it, so it really isn’t a very effective solution. It only helps in some specific situations. Install an SSD: If your page file is on an SSD, the SSD’s improved speed compared to a hard disk will result in generally improved performance when the page file has to be read from or written to. Be aware that SSDs are not designed to withstand a very frequent and constant random stream of writes; they can only be written over a limited number of times before they start to break down. Heavy use of a page file is not a particularly good workload for an SSD. You should install an SSD in combination with a large amount of RAM if you want maximum performance while preserving the longevity of the SSD. Use a newer system architecture: Depending on the age of your system, you may be using an out of date system architecture. The “system architecture” is generally defined as the “generation” (think generations like children, parents, grandparents, etc.) of the motherboard and CPU. Newer generations generally support faster I/O (input/output), better memory bandwidth, lower latency, and less contention over shared resources, instead providing dedicated links between components. For example, starting with the “Nehalem” generation (around 2009), the Front-Side Bus (FSB) was eliminated, which removed a common bottleneck, because almost all system components had to share the same FSB for transmitting data. This was replaced with a “point to point” architecture, meaning that each component gets its own dedicated “lane” to the CPU, which continues to be improved every few years with new generations. You will generally see a more significant improvement in overall system performance depending on the “gap” between your computer’s architecture and the latest one available. For example, a Pentium 4 architecture from 2004 is going to see a much more significant improvement upgrading to “Haswell” (the latest as of Q4 2013) than a “Sandy Bridge” architecture from ~2010. Links Related questions: How to reduce disk thrashing (paging)? Windows Swap (Page File): Enable or Disable? Also, just in case you’re considering it, you really shouldn’t disable the page file, as this will only make matters worse; see here. And, in case you needed extra convincing to leave the Windows Page File alone, see here and here. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • Microsoft Enterprise Library Caching Application Block not thread safe?!

    - by AlanR
    Good aftenoon, I created a super simple console app to test out the Enterprise Library Caching Application Block, and the behavior is blaffling. I'm hoping I screwed something that's easy to fix in the setup. Have each item expire after 5 seconds for testing purposes. Basic setup -- "every second pick a number between 0 and 2. if the cache doesn't already have it, put it in there -- otherwise just grab it from the cache. Do this inside a LOCK statement to ensure thread safety. APP.CONFIG: <configuration> <configSections> <section name="cachingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Caching.Configuration.CacheManagerSettings, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> </configSections> <cachingConfiguration defaultCacheManager="Cache Manager"> <cacheManagers> <add expirationPollFrequencyInSeconds="1" maximumElementsInCacheBeforeScavenging="1000" numberToRemoveWhenScavenging="10" backingStoreName="Null Storage" type="Microsoft.Practices.EnterpriseLibrary.Caching.CacheManager, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Cache Manager" /> </cacheManagers> <backingStores> <add encryptionProviderName="" type="Microsoft.Practices.EnterpriseLibrary.Caching.BackingStoreImplementations.NullBackingStore, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Null Storage" /> </backingStores> </cachingConfiguration> </configuration> C#: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.EnterpriseLibrary.Common; using Microsoft.Practices.EnterpriseLibrary.Caching; using Microsoft.Practices.EnterpriseLibrary.Caching.Expirations; namespace ConsoleApplication1 { class Program { public static ICacheManager cache = CacheFactory.GetCacheManager("Cache Manager"); static void Main(string[] args) { while (true) { System.Threading.Thread.Sleep(1000); // sleep for one second. var key = new Random().Next(3).ToString(); string value; lock (cache) { if (!cache.Contains(key)) { cache.Add(key, key, CacheItemPriority.Normal, null, new SlidingTime(TimeSpan.FromSeconds(5))); } value = (string)cache.GetData(key); } Console.WriteLine("{0} --> '{1}'", key, value); //if (null == value) throw new Exception(); } } } } OUPUT -- How can I prevent the cache to returning nulls? 2 --> '2' 1 --> '1' 2 --> '2' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 0 --> '0' 1 --> '1' 2 --> '' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 2 --> '2' 1 --> '1' Press any key to continue . . . Thanks in advance, -Alan.

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  • I need to write a program that reads angles in radians from an input disk and converts them in degre

    - by Amadou
    Write a program that reads angles in radians from an input disk le and converts them into degrees, minutes, and seconds. Output should be written into another le. A sample input le could be: # this is a comment # your program should be able to skip comment lines # and blank lines # input radian numbers could be seperated by blanks 0.0 1.0 # or by a newline 3.141593 6.0

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  • Motherboard/PSU crippling USB and Sata

    - by celebdor
    I very recently bought a new desktop computer. The motherboard is: Z77MX-D3H and the power supply is ocz zs series 550w. The issue I have is that once I boot to the operating system (I have tried with fedora and Ubuntu with kernels 2.6.38 - 3.4.0), my hard drive (2.5" Magnetic) occasionally makes a power switch noise and it resets. Needless to say, when this drive is the OS drive, the OS crashes. I also have a SSD that works fine with the same OS configurations, but if I have the magnetic hard drive attached as second drive, it works erratically and the reconnects result in corrupted data. I also noticed that whenever I plug an external hard drive USB2.0 or USB3.0 to the computer the issue with the reconnects is even worse: [ 52.198441] sd 7:0:0:0: [sdc] Spinning up disk... [ 57.955811] usb 4-3: USB disconnect, device number 3 [ 58.023687] .ready [ 58.023914] sd 7:0:0:0: [sdc] READ CAPACITY(16) failed [ 58.023919] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.023932] sd 7:0:0:0: [sdc] Sense not available. [ 58.024061] sd 7:0:0:0: [sdc] READ CAPACITY failed [ 58.024063] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024064] sd 7:0:0:0: [sdc] Sense not available. [ 58.024099] sd 7:0:0:0: [sdc] Write Protect is off [ 58.024101] sd 7:0:0:0: [sdc] Mode Sense: 00 00 00 00 [ 58.024135] sd 7:0:0:0: [sdc] Asking for cache data failed [ 58.024137] sd 7:0:0:0: [sdc] Assuming drive cache: write through [ 58.024400] sd 7:0:0:0: [sdc] READ CAPACITY(16) failed [ 58.024402] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024405] sd 7:0:0:0: [sdc] Sense not available. [ 58.024448] sd 7:0:0:0: [sdc] READ CAPACITY failed [ 58.024450] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024451] sd 7:0:0:0: [sdc] Sense not available. [ 58.024469] sd 7:0:0:0: [sdc] Asking for cache data failed [ 58.024471] sd 7:0:0:0: [sdc] Assuming drive cache: write through [ 58.024472] sd 7:0:0:0: [sdc] Attached SCSI disk [ 58.407725] usb 4-3: new SuperSpeed USB device number 4 using xhci_hcd [ 58.424921] scsi8 : usb-storage 4-3:1.0 [ 59.424185] scsi 8:0:0:0: Direct-Access WD My Passport 0740 1003 PQ: 0 ANSI: 6 [ 59.424406] scsi 8:0:0:1: Enclosure WD SES Device 1003 PQ: 0 ANSI: 6 [ 59.425098] sd 8:0:0:0: Attached scsi generic sg2 type 0 [ 59.425176] ses 8:0:0:1: Attached Enclosure device [ 59.425248] ses 8:0:0:1: Attached scsi generic sg3 type 13 [ 61.845836] sd 8:0:0:0: [sdc] 976707584 512-byte logical blocks: (500 GB/465 GiB) [ 61.845838] sd 8:0:0:0: [sdc] 4096-byte physical blocks [ 61.846336] sd 8:0:0:0: [sdc] Write Protect is off [ 61.846338] sd 8:0:0:0: [sdc] Mode Sense: 47 00 10 08 [ 61.846718] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.846720] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.848105] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.848106] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.857147] sdc: sdc1 [ 61.858915] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.858916] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.858918] sd 8:0:0:0: [sdc] Attached SCSI disk [ 69.875809] usb 4-3: USB disconnect, device number 4 [ 70.275816] usb 4-3: new SuperSpeed USB device number 5 using xhci_hcd [ 70.293063] scsi9 : usb-storage 4-3:1.0 [ 71.292257] scsi 9:0:0:0: Direct-Access WD My Passport 0740 1003 PQ: 0 ANSI: 6 [ 71.292505] scsi 9:0:0:1: Enclosure WD SES Device 1003 PQ: 0 ANSI: 6 [ 71.293527] sd 9:0:0:0: Attached scsi generic sg2 type 0 [ 71.293668] ses 9:0:0:1: Attached Enclosure device [ 71.293758] ses 9:0:0:1: Attached scsi generic sg3 type 13 [ 73.323804] usb 4-3: USB disconnect, device number 5 [ 101.868078] ses 9:0:0:1: Device offlined - not ready after error recovery [ 101.868124] ses 9:0:0:1: Failed to get diagnostic page 0x50000 [ 101.868131] ses 9:0:0:1: Failed to bind enclosure -19 [ 101.868288] sd 9:0:0:0: [sdc] READ CAPACITY(16) failed [ 101.868292] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868296] sd 9:0:0:0: [sdc] Sense not available. [ 101.868428] sd 9:0:0:0: [sdc] READ CAPACITY failed [ 101.868434] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868439] sd 9:0:0:0: [sdc] Sense not available. [ 101.868468] sd 9:0:0:0: [sdc] Write Protect is off [ 101.868473] sd 9:0:0:0: [sdc] Mode Sense: 00 00 00 00 [ 101.868580] sd 9:0:0:0: [sdc] Asking for cache data failed [ 101.868584] sd 9:0:0:0: [sdc] Assuming drive cache: write through [ 101.868845] sd 9:0:0:0: [sdc] READ CAPACITY(16) failed [ 101.868849] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868854] sd 9:0:0:0: [sdc] Sense not available. [ 101.868894] sd 9:0:0:0: [sdc] READ CAPACITY failed [ 101.868898] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868903] sd 9:0:0:0: [sdc] Sense not available. [ 101.868961] sd 9:0:0:0: [sdc] Asking for cache data failed [ 101.868966] sd 9:0:0:0: [sdc] Assuming drive cache: write through [ 101.868969] sd 9:0:0:0: [sdc] Attached SCSI disk Now, if I plug the same drive to the powered usb 2.0 hub of my monitor, the issue is not reproduced (at least on a 20h long operation). Also the issue of the usb reconnects is less frequent if the hard drive is plugged before I switch on the computer. Does anybody have some advice as to what I could do? Which is the faulty part/s that I should replace? As for me, I really don't know if to point my finger to the PSU or the Motherboard (I have updated to the latest firmware and checked the BIOS settings several times). EDIT: The reconnects are happening both in the Sata connected drives and the USBX connected drives.

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  • Is it possible to gzip and upload this string to Amazon S3 without ever being written to disk?

    - by BigJoe714
    I know this is probably possible using Streams, but I wasn't sure the correct syntax. I would like to pass a string to the Save method and have it gzip the string and upload it to Amazon S3 without ever being written to disk. The current method inefficiently reads/writes to disk in between. The S3 PutObjectRequest has a constructor with InputStream input as an option. import java.io.*; import java.util.zip.GZIPOutputStream; import com.amazonaws.auth.PropertiesCredentials; import com.amazonaws.services.s3.AmazonS3; import com.amazonaws.services.s3.AmazonS3Client; import com.amazonaws.services.s3.model.PutObjectRequest; public class FileStore { public static void Save(String data) throws IOException { File file = File.createTempFile("filemaster-", ".htm"); file.deleteOnExit(); Writer writer = new OutputStreamWriter(new FileOutputStream(file)); writer.write(data); writer.flush(); writer.close(); String zippedFilename = gzipFile(file.getAbsolutePath()); File zippedFile = new File(zippedFilename); zippedFile.deleteOnExit(); AmazonS3 s3 = new AmazonS3Client(new PropertiesCredentials( new FileInputStream("AwsCredentials.properties"))); String bucketName = "mybucket"; String key = "test/" + zippedFile.getName(); s3.putObject(new PutObjectRequest(bucketName, key, zippedFile)); } public static String gzipFile(String filename) throws IOException { try { // Create the GZIP output stream String outFilename = filename + ".gz"; GZIPOutputStream out = new GZIPOutputStream(new FileOutputStream(outFilename)); // Open the input file FileInputStream in = new FileInputStream(filename); // Transfer bytes from the input file to the GZIP output stream byte[] buf = new byte[1024]; int len; while ((len = in.read(buf)) > 0) { out.write(buf, 0, len); } in.close(); // Complete the GZIP file out.finish(); out.close(); return outFilename; } catch (IOException e) { throw e; } } }

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  • Nginx & Apache Cannot get try_files to work with permalinks

    - by tcherokee
    I have been working on this for the past two weeks not and for some reason I cannot seem to get nginx's try_files to work with my wordpress permalinks. I am hoping someone will be able to tell me where I am going wrong and also hopefully tell me if I made any major errors with my configurations as well (I am an nginx newbie... but learning :) ). Here are my Configuration files nginx.conf user www-data; worker_processes 4; pid /var/run/nginx.pid; events { worker_connections 768; # multi_accept on; } http { ## # Basic Settings ## sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; # server_tokens off; # server_names_hash_bucket_size 64; # server_name_in_redirect off; include /etc/nginx/mime.types; default_type application/octet-stream; ## # Logging Settings ## # Defines the cache log format, cache log location # and the main access log location. log_format cache '***$time_local ' '$upstream_cache_status ' 'Cache-Control: $upstream_http_cache_control ' 'Expires: $upstream_http_expires ' '$host ' '"$request" ($status) ' '"$http_user_agent" ' ; access_log /var/log/nginx/access.log; error_log /var/log/nginx/error.log; include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } mydomain.com.conf server { listen 123.456.78.901:80; # IP goes here. server_name www.mydomain.com mydomain.com; #root /var/www/mydomain.com/prod; index index.php; ## mydomain.com -> www.mydomain.com (301 - Permanent) if ($host !~* ^(www|dev)) { rewrite ^/(.*)$ $scheme://www.$host/$1 permanent; } # Add trailing slash to */wp-admin requests. rewrite /wp-admin$ $scheme://$host$uri/ permanent; # All media (including uploaded) is under wp-content/ so # instead of caching the response from apache, we're just # going to use nginx to serve directly from there. location ~* ^/(wp-content|wp-includes)/(.*)\.(jpg|png|gif|jpeg|css|js|m$ root /var/www/mydomain.com/prod; } # Don't cache these pages. location ~* ^/(wp-admin|wp-login.php) { proxy_pass http://backend; } location / { if ($http_cookie ~* "wordpress_logged_in_[^=]*=([^%]+)%7C") { set $do_not_cache 1; } proxy_cache_key "$scheme://$host$request_uri $do_not_cache"; proxy_cache main; proxy_pass http://backend; proxy_cache_valid 30m; # 200, 301 and 302 will be cached. # Fallback to stale cache on certain errors. # 503 is deliberately missing, if we're down for maintenance # we want the page to display. #try_files $uri $uri/ /index.php?q=$uri$args; #try_files $uri =404; proxy_cache_use_stale error timeout invalid_header http_500 http_502 http_504 http_404; } # Cache purge URL - works in tandem with WP plugin. # location ~ /purge(/.*) { # proxy_cache_purge main "$scheme://$host$1"; # } # No access to .htaccess files. location ~ /\.ht { deny all; } } # End server gzip.conf # Gzip Configuration. gzip on; gzip_disable msie6; gzip_static on; gzip_comp_level 4; gzip_proxied any; gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript; proxy.conf # Set proxy headers for the passthrough proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_max_temp_file_size 0; client_max_body_size 10m; client_body_buffer_size 128k; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 90; proxy_buffer_size 4k; proxy_buffers 4 32k; proxy_busy_buffers_size 64k; proxy_temp_file_write_size 64k; add_header X-Cache-Status $upstream_cache_status; backend.conf upstream backend { # Defines backends. # Extracting here makes it easier to load balance # in the future. Needs to be specific IP as Plesk # doesn't have Apache listening on localhost. ip_hash; server 127.0.0.1:8001; # IP goes here. } cache.conf # Proxy cache and temp configuration. proxy_cache_path /var/www/nginx_cache levels=1:2 keys_zone=main:10m max_size=1g inactive=30m; proxy_temp_path /var/www/nginx_temp; proxy_cache_key "$scheme://$host$request_uri"; proxy_redirect off; # Cache different return codes for different lengths of time # We cached normal pages for 10 minutes proxy_cache_valid 200 302 10m; proxy_cache_valid 404 1m; The two commented out try_files in location \ of the mydomain config files are the ones I tried. This error I found in the error log can be found below. ...rewrite or internal redirection cycle while internally redirecting to "/index.php" Thanks in advance

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  • Why do updates inside of a SQL transaction still need disk IO?

    - by usr
    In SQL Profiler you can see that very simple updates to a table by primary key take about 10-30ms each. On about every 10th update the write column shows 1, on all other updates it shows 0. This must mean that about every 10th update statement still requires disk IO. I wonder why that is. Would it not be more efficient queue up all IO until the transaction commits?

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  • How to reduce virtual memory by optimising my PHP code?

    - by iCeR
    My current code (see below) uses 147MB of virtual memory! My provider has allocated 100MB by default and the process is killed once run, causing an internal error. The code is utilising curl multi and must be able to loop with more than 150 iterations whilst still minimizing the virtual memory. The code below is only set at 150 iterations and still causes the internal server error. At 90 iterations the issue does not occur. How can I adjust my code to lower the resource use / virtual memory? Thanks! <?php function udate($format, $utimestamp = null) { if ($utimestamp === null) $utimestamp = microtime(true); $timestamp = floor($utimestamp); $milliseconds = round(($utimestamp - $timestamp) * 1000); return date(preg_replace('`(?<!\\\\)u`', $milliseconds, $format), $timestamp); } $url = 'https://www.testdomain.com/'; $curl_arr = array(); $master = curl_multi_init(); for($i=0; $i<150; $i++) { $curl_arr[$i] = curl_init(); curl_setopt($curl_arr[$i], CURLOPT_URL, $url); curl_setopt($curl_arr[$i], CURLOPT_RETURNTRANSFER, 1); curl_setopt($curl_arr[$i], CURLOPT_SSL_VERIFYHOST, FALSE); curl_setopt($curl_arr[$i], CURLOPT_SSL_VERIFYPEER, FALSE); curl_multi_add_handle($master, $curl_arr[$i]); } do { curl_multi_exec($master,$running); } while($running > 0); for($i=0; $i<150; $i++) { $results = curl_multi_getcontent ($curl_arr[$i]); $results = explode("<br>", $results); echo $results[0]; echo "<br>"; echo $results[1]; echo "<br>"; echo udate('H:i:s:u'); echo "<br><br>"; usleep(100000); } ?> Processor Information Total processors: 8 Processor #1 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #2 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #3 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #4 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #5 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #6 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #7 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Processor #8 Vendor GenuineIntel Name Intel(R) Xeon(R) CPU E5405 @ 2.00GHz Speed 1995.120 MHz Cache 6144 KB Memory Information Memory for crash kernel (0x0 to 0x0) notwithin permissible range Memory: 8302344k/9175040k available (2176k kernel code, 80272k reserved, 901k data, 228k init, 7466304k highmem) System Information Linux server3.server.com 2.6.18-194.17.1.el5PAE #1 SMP Wed Sep 29 13:31:51 EDT 2010 i686 i686 i386 GNU/Linux Physical Disks SCSI device sda: 1952448512 512-byte hdwr sectors (999654 MB) sda: Write Protect is off sda: Mode Sense: 03 00 00 08 SCSI device sda: drive cache: write back SCSI device sda: 1952448512 512-byte hdwr sectors (999654 MB) sda: Write Protect is off sda: Mode Sense: 03 00 00 08 SCSI device sda: drive cache: write back sd 0:1:0:0: Attached scsi disk sda sd 4:0:0:0: Attached scsi removable disk sdb sd 0:1:0:0: Attached scsi generic sg4 type 0 sd 4:0:0:0: Attached scsi generic sg7 type 0 Current Memory Usage total used free shared buffers cached Mem: 8306672 7847384 459288 0 487912 6444548 -/+ buffers/cache: 914924 7391748 Swap: 4095992 496 4095496 Total: 12402664 7847880 4554784 Current Disk Usage Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup00-LogVol00 898G 307G 546G 36% / /dev/sda1 99M 19M 76M 20% /boot none 4.0G 0 4.0G 0% /dev/shm /var/tmpMnt 4.0G 1.8G 2.0G 48% /tmp

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  • iPhone: How can I store a high score to disk.

    - by Robert
    I have a int which is my high score: NSInterger highScore; I want to store it persistently to disk Do I have to convert it to a string, then write the string to a file, then parse it back when I want to read it. Or is there a better way to store small amounts of data?

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  • Dedicated hard disk for SE dbname.dbs files & dedicated ramdisk for /tmp files.

    - by Frank Computer
    INFORMIX-SE 7.2: I would like to dedicate a hard disk, exclusively for my dbname.dbs directory which holds all the .dat and .idx files, and create a ramdisk for my /tmp temporary files in order to improve performance. I would also like to strip down the OS from any unecessary files and processes to minimize overhead for my dedicated application. Is this a good idea and are there any roadmaps for accomplishing this?

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  • Can i get the particular disk space(like C: ) using Jav program..?

    - by Venkats
    I used SystemEnvironment class in java for getting system information. In that i can get only RAM size, i can't get the specific disk space like c: and D: code is, com.sun.management.OperatingSystemMXBean mxbean = (com.sun.management.OperatingSystemMXBean)ManagementFactory.getOperatingSystemMXBean(); System.out.println("Total RAM:"+mxbean.getTotalSwapSpaceSize()/(1024*1024*1024)+""+"GB"); Can i get this using in java program?

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