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  • Windows Azure Evolution &ndash; Caching (Preview)

    - by Shaun
    Caching is a popular topic when we are building a high performance and high scalable system not only on top of the cloud platform but the on-premise environment as well. On March 2011 the Windows Azure AppFabric Caching had been production launched. It provides an in-memory, distributed caching service over the cloud. And now, in this June 2012 update, the cache team announce a grand new caching solution on Windows Azure, which is called Windows Azure Caching (Preview). And the original Windows Azure AppFabric Caching was renamed to Windows Azure Shared Caching.   What’s Caching (Preview) If you had been using the Shared Caching you should know that it is constructed by a bunch of cache servers. And when you want to use you should firstly create a cache account from the developer portal and specify the size you want to use, which means how much memory you can use to store your data that wanted to be cached. Then you can add, get and remove them through your code through the cache URL. The Shared Caching is a multi-tenancy system which host all cached items across all users. So you don’t know which server your data was located. This caching mode works well and can take most of the cases. But it has some problems. The first one is the performance. Since the Shared Caching is a multi-tenancy system, which means all cache operations should go through the Shared Caching gateway and then routed to the server which have the data your are looking for. Even though there are some caches in the Shared Caching system it also takes time from your cloud services to the cache service. Secondary, the Shared Caching service works as a block box to the developer. The only thing we know is my cache endpoint, and that’s all. Someone may satisfied since they don’t want to care about anything underlying. But if you need to know more and want more control that’s impossible in the Shared Caching. The last problem would be the price and cost-efficiency. You pay the bill based on how much cache you requested per month. But when we host a web role or worker role, it seldom consumes all of the memory and CPU in the virtual machine (service instance). If using Shared Caching we have to pay for the cache service while waste of some of our memory and CPU locally. Since the issues above Microsoft offered a new caching mode over to us, which is the Caching (Preview). Instead of having a separated cache service, the Caching (Preview) leverage the memory and CPU in our cloud services (web role and worker role) as the cache clusters. Hence the Caching (Preview) runs on the virtual machines which hosted or near our cloud applications. Without any gateway and routing, since it located in the same data center and same racks, it provides really high performance than the Shared Caching. The Caching (Preview) works side-by-side to our application, initialized and worked as a Windows Service running in the virtual machines invoked by the startup tasks from our roles, we could get more information and control to them. And since the Caching (Preview) utilizes the memory and CPU from our existing cloud services, so it’s free. What we need to pay is the original computing price. And the resource on each machines could be used more efficiently.   Enable Caching (Preview) It’s very simple to enable the Caching (Preview) in a cloud service. Let’s create a new windows azure cloud project from Visual Studio and added an ASP.NET Web Role. Then open the role setting and select the Caching page. This is where we enable and configure the Caching (Preview) on a role. To enable the Caching (Preview) just open the “Enable Caching (Preview Release)” check box. And then we need to specify which mode of the caching clusters we want to use. There are two kinds of caching mode, co-located and dedicate. The co-located mode means we use the memory in the instances we run our cloud services (web role or worker role). By using this mode we must specify how many percentage of the memory will be used as the cache. The default value is 30%. So make sure it will not affect the role business execution. The dedicate mode will use all memory in the virtual machine as the cache. In fact it will reserve some for operation system, azure hosting etc.. But it will try to use as much as the available memory to be the cache. As you can see, the Caching (Preview) was defined based on roles, which means all instances of this role will apply the same setting and play as a whole cache pool, and you can consume it by specifying the name of the role, which I will demonstrate later. And in a windows azure project we can have more than one role have the Caching (Preview) enabled. Then we will have more caches. For example, let’s say I have a web role and worker role. The web role I specified 30% co-located caching and the worker role I specified dedicated caching. If I have 3 instances of my web role and 2 instances of my worker role, then I will have two caches. As the figure above, cache 1 was contributed by three web role instances while cache 2 was contributed by 2 worker role instances. Then we can add items into cache 1 and retrieve it from web role code and worker role code. But the items stored in cache 1 cannot be retrieved from cache 2 since they are isolated. Back to our Visual Studio we specify 30% of co-located cache and use the local storage emulator to store the cache cluster runtime status. Then at the bottom we can specify the named caches. Now we just use the default one. Now we had enabled the Caching (Preview) in our web role settings. Next, let’s have a look on how to consume our cache.   Consume Caching (Preview) The Caching (Preview) can only be consumed by the roles in the same cloud services. As I mentioned earlier, a cache contributed by web role can be connected from a worker role if they are in the same cloud service. But you cannot consume a Caching (Preview) from other cloud services. This is different from the Shared Caching. The Shared Caching is opened to all services if it has the connection URL and authentication token. To consume the Caching (Preview) we need to add some references into our project as well as some configuration in the Web.config. NuGet makes our life easy. Right click on our web role project and select “Manage NuGet packages”, and then search the package named “WindowsAzure.Caching”. In the package list install the “Windows Azure Caching Preview”. It will download all necessary references from the NuGet repository and update our Web.config as well. Open the Web.config of our web role and find the “dataCacheClients” node. Under this node we can specify the cache clients we are going to use. For each cache client it will use the role name to identity and find the cache. Since we only have this web role with the Caching (Preview) enabled so I pasted the current role name in the configuration. Then, in the default page I will add some code to show how to use the cache. I will have a textbox on the page where user can input his or her name, then press a button to generate the email address for him/her. And in backend code I will check if this name had been added in cache. If yes I will return the email back immediately. Otherwise, I will sleep the tread for 2 seconds to simulate the latency, then add it into cache and return back to the page. 1: protected void btnGenerate_Click(object sender, EventArgs e) 2: { 3: // check if name is specified 4: var name = txtName.Text; 5: if (string.IsNullOrWhiteSpace(name)) 6: { 7: lblResult.Text = "Error. Please specify name."; 8: return; 9: } 10:  11: bool cached; 12: var sw = new Stopwatch(); 13: sw.Start(); 14:  15: // create the cache factory and cache 16: var factory = new DataCacheFactory(); 17: var cache = factory.GetDefaultCache(); 18:  19: // check if the name specified is in cache 20: var email = cache.Get(name) as string; 21: if (email != null) 22: { 23: cached = true; 24: sw.Stop(); 25: } 26: else 27: { 28: cached = false; 29: // simulate the letancy 30: Thread.Sleep(2000); 31: email = string.Format("{0}@igt.com", name); 32: // add to cache 33: cache.Add(name, email); 34: } 35:  36: sw.Stop(); 37: lblResult.Text = string.Format( 38: "Cached = {0}. Duration: {1}s. {2} => {3}", 39: cached, sw.Elapsed.TotalSeconds.ToString("0.00"), name, email); 40: } The Caching (Preview) can be used on the local emulator so we just F5. The first time I entered my name it will take about 2 seconds to get the email back to me since it was not in the cache. But if we re-enter my name it will be back at once from the cache. Since the Caching (Preview) is distributed across all instances of the role, so we can scaling-out it by scaling-out our web role. Just use 2 instances and tweak some code to show the current instance ID in the page, and have another try. Then we can see the cache can be retrieved even though it was added by another instance.   Consume Caching (Preview) Across Roles As I mentioned, the Caching (Preview) can be consumed by all other roles within the same cloud service. For example, let’s add another web role in our cloud solution and add the same code in its default page. In the Web.config we add the cache client to one enabled in the last role, by specifying its role name here. Then we start the solution locally and go to web role 1, specify the name and let it generate the email to us. Since there’s no cache for this name so it will take about 2 seconds but will save the email into cache. And then we go to web role 2 and specify the same name. Then you can see it retrieve the email saved by the web role 1 and returned back very quickly. Finally then we can upload our application to Windows Azure and test again. Make sure you had changed the cache cluster status storage account to the real azure account.   More Awesome Features As a in-memory distributed caching solution, the Caching (Preview) has some fancy features I would like to highlight here. The first one is the high availability support. This is the first time I have heard that a distributed cache support high availability. In the distributed cache world if a cache cluster was failed, the data it stored will be lost. This behavior was introduced by Memcached and is followed by almost all distributed cache productions. But Caching (Preview) provides high availability, which means you can specify if the named cache will be backup automatically. If yes then the data belongs to this named cache will be replicated on another role instance of this role. Then if one of the instance was failed the data can be retrieved from its backup instance. To enable the backup just open the Caching page in Visual Studio. In the named cache you want to enable backup, change the Backup Copies value from 0 to 1. The value of Backup Copies only for 0 and 1. “0” means no backup and no high availability while “1” means enabled high availability with backup the data into another instance. But by using the high availability feature there are something we need to make sure. Firstly the high availability does NOT means the data in cache will never be lost for any kind of failure. For example, if we have a role with cache enabled that has 10 instances, and 9 of them was failed, then most of the cached data will be lost since the primary and backup instance may failed together. But normally is will not be happened since MS guarantees that it will use the instance in the different fault domain for backup cache. Another one is that, enabling the backup means you store two copies of your data. For example if you think 100MB memory is OK for cache, but you need at least 200MB if you enabled backup. Besides the high availability, the Caching (Preview) support more features introduced in Windows Server AppFabric Caching than the Windows Azure Shared Caching. It supports local cache with notification. It also support absolute and slide window expiration types as well. And the Caching (Preview) also support the Memcached protocol as well. This means if you have an application based on Memcached, you can use Caching (Preview) without any code changes. What you need to do is to change the configuration of how you connect to the cache. Similar as the Windows Azure Shared Caching, MS also offers the out-of-box ASP.NET session provider and output cache provide on top of the Caching (Preview).   Summary Caching is very important component when we building a cloud-based application. In the June 2012 update MS provides a new cache solution named Caching (Preview). Different from the existing Windows Azure Shared Caching, Caching (Preview) runs the cache cluster within the role instances we have deployed to the cloud. It gives more control, more performance and more cost-effect. So now we have two caching solutions in Windows Azure, the Shared Caching and Caching (Preview). If you need a central cache service which can be used by many cloud services and web sites, then you have to use the Shared Caching. But if you only need a fast, near distributed cache, then you’d better use Caching (Preview).   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Asp.Net WriteSubsitution vs PartialView - the right way

    - by radu-negrila
    Hi, I have a partial view that should not be cached in a output cached MVC view. Usually you write non-cached content by using Response.WriteSubstitution. The problem is that WriteSubstitution takes as a parameter a HttpResponseSubstitutionCallback callback which looks like this: public delegate string HttpResponseSubstitutionCallback(System.Web.HttpContext context) This is where things get complicated since there is no easy/fun way to generate the html on the fly. You have to do a hack like this. So the question is: Is there an easier way to make a partial view not cached ?

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  • How to reliably measure available memory in Linux?

    - by Alex B
    Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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  • Generated images fail to load in browser

    - by notJim
    I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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  • Browser timing out attempting to load images

    - by notJim
    I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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  • Optimal ASP.Net cache duration for a large site?

    - by HeroicLife
    I've read lots of material on how to do ASP.Net caching but little on the optimal duration that pages should be cached for. Let's say that I have a popular site with 50,000 pages. The content does not change frequently, so I could cache pages for up to an hour if I wanted. The server has 16 GB of RAM, but database connections are limited. How long should pages be cached for? My thinking is that if I set the cache duration too high (let's say 60 minutes), I will fill up memory with a fraction of the total content, which will continually be shuffled in and out of memory. Furthermore, let's say that 10% of the pages are responsible for 90% of traffic. If the popular pages are hit every second, and the unpopular ones every hour, then a 60 second cache would only keep the load-intensive content cached without sacrificing freshness. Should numerous but rarely-accessed content be cached at all?

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  • Creating HTML5 Offline Web Applications with ASP.NET

    - by Stephen Walther
    The goal of this blog entry is to describe how you can create HTML5 Offline Web Applications when building ASP.NET web applications. I describe the method that I used to create an offline Web application when building the JavaScript Reference application. You can read about the HTML5 Offline Web Application standard by visiting the following links: Offline Web Applications Firefox Offline Web Applications Safari Offline Web Applications Currently, the HTML5 Offline Web Applications feature works with all modern browsers with one important exception. You can use Offline Web Applications with Firefox, Chrome, and Safari (including iPhone Safari). Unfortunately, however, Internet Explorer does not support Offline Web Applications (not even IE 9). Why Build an HTML5 Offline Web Application? The official reason to build an Offline Web Application is so that you do not need to be connected to the Internet to use it. For example, you can use the JavaScript Reference Application when flying in an airplane, riding a subway, or hiding in a cave in Borneo. The JavaScript Reference Application works great on my iPhone even when I am completely disconnected from any network. The following screenshot shows the JavaScript Reference Application running on my iPhone when airplane mode is enabled (notice the little orange airplane):   Admittedly, it is becoming increasingly difficult to find locations where you can’t get Internet access. A second, and possibly better, reason to create Offline Web Applications is speed. An Offline Web Application must be downloaded only once. After it gets downloaded, all of the files required by your Web application (HTML, CSS, JavaScript, Image) are stored persistently on your computer. Think of Offline Web Applications as providing you with a super browser cache. Normally, when you cache files in a browser, the files are cached on a file-by-file basis. For each HTML, CSS, image, or JavaScript file, you specify how long the file should remain in the cache by setting cache headers. Unlike the normal browser caching mechanism, the HTML5 Offline Web Application cache is used to specify a caching policy for an entire set of files. You use a manifest file to list the files that you want to cache and these files are cached until the manifest is changed. Another advantage of using the HTML5 offline cache is that the HTML5 standard supports several JavaScript events and methods related to the offline cache. For example, you can be notified in your JavaScript code whenever the offline application has been updated. You can use JavaScript methods, such as the ApplicationCache.update() method, to update the cache programmatically. Creating the Manifest File The HTML5 Offline Cache uses a manifest file to determine the files that get cached. Here’s what the manifest file looks like for the JavaScript Reference application: CACHE MANIFEST # v30 Default.aspx # Standard Script Libraries Scripts/jquery-1.4.4.min.js Scripts/jquery-ui-1.8.7.custom.min.js Scripts/jquery.tmpl.min.js Scripts/json2.js # App Scripts App_Scripts/combine.js App_Scripts/combine.debug.js # Content (CSS & images) Content/default.css Content/logo.png Content/ui-lightness/jquery-ui-1.8.7.custom.css Content/ui-lightness/images/ui-bg_glass_65_ffffff_1x400.png Content/ui-lightness/images/ui-bg_glass_100_f6f6f6_1x400.png Content/ui-lightness/images/ui-bg_highlight-soft_100_eeeeee_1x100.png Content/ui-lightness/images/ui-icons_222222_256x240.png Content/ui-lightness/images/ui-bg_glass_100_fdf5ce_1x400.png Content/ui-lightness/images/ui-bg_diagonals-thick_20_666666_40x40.png Content/ui-lightness/images/ui-bg_gloss-wave_35_f6a828_500x100.png Content/ui-lightness/images/ui-icons_ffffff_256x240.png Content/ui-lightness/images/ui-icons_ef8c08_256x240.png Content/browsers/c8.png Content/browsers/es3.png Content/browsers/es5.png Content/browsers/ff3_6.png Content/browsers/ie8.png Content/browsers/ie9.png Content/browsers/sf5.png NETWORK: Services/EntryService.svc http://superexpert.com/resources/JavaScriptReference/ A Cache Manifest file always starts with the line of text Cache Manifest. In the manifest above, all of the CSS, image, and JavaScript files required by the JavaScript Reference application are listed. For example, the Default.aspx ASP.NET page, jQuery library, JQuery UI library, and several images are listed. Notice that you can add comments to a manifest by starting a line with the hash character (#). I use comments in the manifest above to group JavaScript and image files. Finally, notice that there is a NETWORK: section of the manifest. You list any file that you do not want to cache (any file that requires network access) in this section. In the manifest above, the NETWORK: section includes the URL for a WCF Service named EntryService.svc. This service is called to get the JavaScript entries displayed by the JavaScript Reference. There are two important things that you need to be aware of when using a manifest file. First, all relative URLs listed in a manifest are resolved relative to the manifest file. The URLs listed in the manifest above are all resolved relative to the root of the application because the manifest file is located in the application root. Second, whenever you make a change to the manifest file, browsers will download all of the files contained in the manifest (all of them). For example, if you add a new file to the manifest then any browser that supports the Offline Cache standard will detect the change in the manifest and download all of the files listed in the manifest automatically. If you make changes to files in the manifest (for example, modify a JavaScript file) then you need to make a change in the manifest file in order for the new version of the file to be downloaded. The standard way of updating a manifest file is to include a comment with a version number. The manifest above includes a # v30 comment. If you make a change to a file then you need to modify the comment to be # v31 in order for the new file to be downloaded. When Are Updated Files Downloaded? When you make changes to a manifest, the changes are not reflected the very next time you open the offline application in your web browser. Your web browser will download the updated files in the background. This can be very confusing when you are working with JavaScript files. If you make a change to a JavaScript file, and you have cached the application offline, then the changes to the JavaScript file won’t appear when you reload the application. The HTML5 standard includes new JavaScript events and methods that you can use to track changes and make changes to the Application Cache. You can use the ApplicationCache.update() method to initiate an update to the application cache and you can use the ApplicationCache.swapCache() method to switch to the latest version of a cached application. My heartfelt recommendation is that you do not enable your application for offline storage until after you finish writing your application code. Otherwise, debugging the application can become a very confusing experience. Offline Web Applications versus Local Storage Be careful to not confuse the HTML5 Offline Web Application feature and HTML5 Local Storage (aka DOM storage) feature. The JavaScript Reference Application uses both features. HTML5 Local Storage enables you to store key/value pairs persistently. Think of Local Storage as a super cookie. I describe how the JavaScript Reference Application uses Local Storage to store the database of JavaScript entries in a separate blog entry. Offline Web Applications enable you to store static files persistently. Think of Offline Web Applications as a super cache. Creating a Manifest File in an ASP.NET Application A manifest file must be served with the MIME type text/cache-manifest. In order to serve the JavaScript Reference manifest with the proper MIME type, I added two files to the JavaScript Reference Application project: Manifest.txt – This text file contains the actual manifest file. Manifest.ashx – This generic handler sends the Manifest.txt file with the MIME type text/cache-manifest. Here’s the code for the generic handler: using System.Web; namespace JavaScriptReference { public class Manifest : IHttpHandler { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/cache-manifest"; context.Response.WriteFile(context.Server.MapPath("Manifest.txt")); } public bool IsReusable { get { return false; } } } } The Default.aspx file contains a reference to the manifest. The opening HTML tag in the Default.aspx file looks like this: <html manifest="Manifest.ashx"> Notice that the HTML tag contains a manifest attribute that points to the Manifest.ashx generic handler. Internet Explorer simply ignores this attribute. Every other modern browser will download the manifest when the Default.aspx page is requested. Seeing the Offline Web Application in Action The experience of using an HTML5 Web Application is different with different browsers. When you first open the JavaScript Reference application with Firefox, you get the following warning: Notice that you are provided with the choice of whether you want to use the application offline or not. Browsers other than Firefox, such as Chrome and Safari, do not provide you with this choice. Chrome and Safari will create an offline cache automatically. If you click the Allow button then Firefox will download all of the files listed in the manifest. You can view the files contained in the Firefox offline application cache by typing about:cache in the Firefox address bar: You can view the actual items being cached by clicking the List Cache Entries link: The Offline Web Application experience is different in the case of Google Chrome. You can view the entries in the offline cache by opening the Developer Tools (hit Shift+CTRL+I), selecting the Storage tab, and selecting Application Cache: Notice that you view the status of the Application Cache. In the screen shot above, the status is UNCACHED which means that the files listed in the manifest have not been downloaded and cached yet. The different possible values for the status are included in the HTML5 Offline Web Application standard: UNCACHED – The Application Cache has not been initialized. IDLE – The Application Cache is not currently being updated. CHECKING – The Application Cache is being fetched and checked for updates. DOWNLOADING – The files in the Application Cache are being updated. UPDATEREADY – There is a new version of the Application. OBSOLETE – The contents of the Application Cache are obsolete. Summary In this blog entry, I provided a description of how you can use the HTML5 Offline Web Application feature in the context of an ASP.NET application. I described how this feature is used with the JavaScript Reference Application to store the entire application on a user’s computer. By taking advantage of this new feature of the HTML5 standard, you can improve the performance of your ASP.NET web applications by requiring users of your web application to download your application once and only once. Furthermore, you can enable users to take advantage of your applications anywhere -- regardless of whether or not they are connected to the Internet.

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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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  • SQL SERVER – SSIS Look Up Component – Cache Mode – Notes from the Field #028

    - by Pinal Dave
    [Notes from Pinal]: Lots of people think that SSIS is all about arranging various operations together in one logical flow. Well, the understanding is absolutely correct, but the implementation of the same is not as easy as it seems. Similarly most of the people think lookup component is just component which does look up for additional information and does not pay much attention to it. Due to the same reason they do not pay attention to the same and eventually get very bad performance. Linchpin People are database coaches and wellness experts for a data driven world. In this 28th episode of the Notes from the Fields series database expert Tim Mitchell (partner at Linchpin People) shares very interesting conversation related to how to write a good lookup component with Cache Mode. In SQL Server Integration Services, the lookup component is one of the most frequently used tools for data validation and completion.  The lookup component is provided as a means to virtually join one set of data to another to validate and/or retrieve missing values.  Properly configured, it is reliable and reasonably fast. Among the many settings available on the lookup component, one of the most critical is the cache mode.  This selection will determine whether and how the distinct lookup values are cached during package execution.  It is critical to know how cache modes affect the result of the lookup and the performance of the package, as choosing the wrong setting can lead to poorly performing packages, and in some cases, incorrect results. Full Cache The full cache mode setting is the default cache mode selection in the SSIS lookup transformation.  Like the name implies, full cache mode will cause the lookup transformation to retrieve and store in SSIS cache the entire set of data from the specified lookup location.  As a result, the data flow in which the lookup transformation resides will not start processing any data buffers until all of the rows from the lookup query have been cached in SSIS. The most commonly used cache mode is the full cache setting, and for good reason.  The full cache setting has the most practical applications, and should be considered the go-to cache setting when dealing with an untested set of data. With a moderately sized set of reference data, a lookup transformation using full cache mode usually performs well.  Full cache mode does not require multiple round trips to the database, since the entire reference result set is cached prior to data flow execution. There are a few potential gotchas to be aware of when using full cache mode.  First, you can see some performance issues – memory pressure in particular – when using full cache mode against large sets of reference data.  If the table you use for the lookup is very large (either deep or wide, or perhaps both), there’s going to be a performance cost associated with retrieving and caching all of that data.  Also, keep in mind that when doing a lookup on character data, full cache mode will always do a case-sensitive (and in some cases, space-sensitive) string comparison even if your database is set to a case-insensitive collation.  This is because the in-memory lookup uses a .NET string comparison (which is case- and space-sensitive) as opposed to a database string comparison (which may be case sensitive, depending on collation).  There’s a relatively easy workaround in which you can use the UPPER() or LOWER() function in the pipeline data and the reference data to ensure that case differences do not impact the success of your lookup operation.  Again, neither of these present a reason to avoid full cache mode, but should be used to determine whether full cache mode should be used in a given situation. Full cache mode is ideally useful when one or all of the following conditions exist: The size of the reference data set is small to moderately sized The size of the pipeline data set (the data you are comparing to the lookup table) is large, is unknown at design time, or is unpredictable Each distinct key value(s) in the pipeline data set is expected to be found multiple times in that set of data Partial Cache When using the partial cache setting, lookup values will still be cached, but only as each distinct value is encountered in the data flow.  Initially, each distinct value will be retrieved individually from the specified source, and then cached.  To be clear, this is a row-by-row lookup for each distinct key value(s). This is a less frequently used cache setting because it addresses a narrower set of scenarios.  Because each distinct key value(s) combination requires a relational round trip to the lookup source, performance can be an issue, especially with a large pipeline data set to be compared to the lookup data set.  If you have, for example, a million records from your pipeline data source, you have the potential for doing a million lookup queries against your lookup data source (depending on the number of distinct values in the key column(s)).  Therefore, one has to be keenly aware of the expected row count and value distribution of the pipeline data to safely use partial cache mode. Using partial cache mode is ideally suited for the conditions below: The size of the data in the pipeline (more specifically, the number of distinct key column) is relatively small The size of the lookup data is too large to effectively store in cache The lookup source is well indexed to allow for fast retrieval of row-by-row values No Cache As you might guess, selecting no cache mode will not add any values to the lookup cache in SSIS.  As a result, every single row in the pipeline data set will require a query against the lookup source.  Since no data is cached, it is possible to save a small amount of overhead in SSIS memory in cases where key values are not reused.  In the real world, I don’t see a lot of use of the no cache setting, but I can imagine some edge cases where it might be useful. As such, it’s critical to know your data before choosing this option.  Obviously, performance will be an issue with anything other than small sets of data, as the no cache setting requires row-by-row processing of all of the data in the pipeline. I would recommend considering the no cache mode only when all of the below conditions are true: The reference data set is too large to reasonably be loaded into SSIS memory The pipeline data set is small and is not expected to grow There are expected to be very few or no duplicates of the key values(s) in the pipeline data set (i.e., there would be no benefit from caching these values) Conclusion The cache mode, an often-overlooked setting on the SSIS lookup component, represents an important design decision in your SSIS data flow.  Choosing the right lookup cache mode directly impacts the fidelity of your results and the performance of package execution.  Know how this selection impacts your ETL loads, and you’ll end up with more reliable, faster packages. If you want me to take a look at your server and its settings, or if your server is facing any issue we can Fix Your SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SSIS

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  • Silverlight and WCF caching

    - by subodhnpushpak
    There are scenarios where Silverlight client calls WCF (or REST) service for data. Now, if the data is cached on the WCF layer, the calls can take considerable resources at the server if NOT cached. Keeping that in mind along with the fact that cache is an cross-cutting aspect, and therefore it should be as easy as possible to put Cache wherever required. The good thing about the solution is that it caches based on the inputs. The input can be basic type of any complex type. If input changes the data is fetched and then cached for further used. If same input is provided again, data id fetched from the cache. The cache logic itself is implemented as PostSharp aspect, and it is as easy as putting an attribute over service call to switch on cache. Notice how clean the code is:        [OperationContract]       [CacheOnArgs(typeof(int))] // based on actual value of cache        public string DoWork(int value)        {            return string.Format("You entered: {0} @ cached time {1}", value, System.DateTime.Now);        } The cache is implemented as POST Sharp as below 1: public override void OnInvocation(MethodInvocationEventArgs eventArgs) 2: { 3: try 4: { 5: object value = new object(); 6: object[] args = eventArgs.GetArgumentArray(); 7: if (args != null || args.Count() > 0) 8: { 9:   10: string key = string.Format("{0}_{1}", eventArgs.Method.Name, XMLUtility<object>.GetDataContractXml(args[0], null));// Compute the cache key (details omitted). 11:   12: 13: value = GetFromCache(key); 14: if (value == null) 15: { 16: eventArgs.Proceed(); 17: value = XMLUtility<object>.GetDataContractXml(eventArgs.ReturnValue, null); 18: value = eventArgs.ReturnValue; 19: AddToCache(key, value); 20: return; 21: } 22:   23:   24: Log(string.Format("Data returned from Cache {0}",value)); 25: eventArgs.ReturnValue = value; 26: } 27: } 28: catch (Exception ex) 29: { 30: //ApplicationLogger.LogException(ex.Message, Source.UtilityService); 31: } 32: } 33:   34: private object GetFromCache(string inputKey) { if (ServerConfig.CachingEnabled) { return WCFCache.Current[inputKey]; } return null; }private void AddToCache(string inputKey,object outputValue) 35: { 36: if (ServerConfig.CachingEnabled) 37: { 38: if (WCFCache.Current.CachedItemsNumber < ServerConfig.NumberOfCachedItems) 39: { 40: if (ServerConfig.SlidingExpirationTime <= 0 || ServerConfig.SlidingExpirationTime == int.MaxValue) 41: { 42: WCFCache.Current[inputKey] = outputValue; 43: } 44: else 45: { 46: WCFCache.Current.Insert(inputKey, outputValue, new TimeSpan(0, 0, ServerConfig.SlidingExpirationTime), true); 47:   48: // _bw.DoWork += bw_DoWork; 49: //string arg = string.Format("{0}|{1}", inputKey,outputValue); 50: //_bw.RunWorkerAsync(inputKey ); 51: } 52: } 53: } 54: }     The cache class can be extended to support Velocity / memcahe / Nache. the attribute can be used over REST services as well. Hope the above helps. Here is the code base for the same.   Please do provide your inputs / comments.

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  • A quick look at: sys.dm_os_buffer_descriptors

    - by fatherjack
    SQL Server places data into cache as it reads it from disk so as to speed up future queries. This dmv lets you see how much data is cached at any given time and knowing how this changes over time can help you ensure your servers run smoothly and are adequately resourced to run your systems. This dmv gives the number of cached pages in the buffer pool along with the database id that they relate to: USE [tempdb] GO SELECT COUNT(*) AS cached_pages_count , CASE database_id ...(read more)

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  • A quick look at: sys.dm_os_buffer_descriptors

    - by fatherjack
    SQL Server places data into cache as it reads it from disk so as to speed up future queries. This dmv lets you see how much data is cached at any given time and knowing how this changes over time can help you ensure your servers run smoothly and are adequately resourced to run your systems. This dmv gives the number of cached pages in the buffer pool along with the database id that they relate to: USE [tempdb] GO SELECT COUNT(*) AS cached_pages_count , CASE database_id ...(read more)

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  • error while installing the libmemcached

    - by Ahmet vardar
    I get this while installing libmemcached root@server [/libmemcached]# make make all-am make[1]: Entering directory `/libmemcached' if /bin/sh ./libtool --tag=CXX --mode=compile g++ -DHAVE_CONFIG_H -I. -I. -I. -I. -I. -ggdb -DBUILDING_HASHKIT -MT libhashkit/libhashkit_libhashkit_la-aes.lo -MD -MP -MF "libhashkit/.deps/libhashkit_libhashkit_la-aes.Tpo" -c -o libhashkit/libhashkit_libhashkit_la-aes.lo `test -f 'libhashkit/aes.cc' || echo './'`libhashkit/aes.cc; \ then mv -f "libhashkit/.deps/libhashkit_libhashkit_la-aes.Tpo" "libhashkit/.deps/libhashkit_libhashkit_la-aes.Plo"; else rm -f "libhashkit/.deps/libhashkit_libhashkit_la-aes.Tpo"; exit 1; fi ./libtool: line 866: X--tag=CXX: command not found ./libtool: line 899: libtool: ignoring unknown tag : command not found ./libtool: line 866: X--mode=compile: command not found ./libtool: line 1032: *** Warning: inferring the mode of operation is deprecated.: command not found ./libtool: line 1033: *** Future versions of Libtool will require --mode=MODE be specified.: command not found ./libtool: line 1176: Xg++: command not found ./libtool: line 1176: X-DHAVE_CONFIG_H: command not found ./libtool: line 1176: X-I.: command not found ./libtool: line 1176: X-I.: command not found ./libtool: line 1176: X-I.: command not found ./libtool: line 1176: X-I.: command not found ./libtool: line 1176: X-I.: command not found ./libtool: line 1176: X-ggdb: command not found ./libtool: line 1176: X-DBUILDING_HASHKIT: command not found ./libtool: line 1176: X-MT: command not found ./libtool: line 1176: Xlibhashkit/libhashkit_libhashkit_la-aes.lo: No such file or directory ./libtool: line 1176: X-MD: command not found ./libtool: line 1176: X-MP: command not found ./libtool: line 1176: X-MF: command not found ./libtool: line 1176: Xlibhashkit/.deps/libhashkit_libhashkit_la-aes.Tpo: No such file or directory ./libtool: line 1176: X-c: command not found ./libtool: line 1228: Xlibhashkit/libhashkit_libhashkit_la-aes.lo: No such file or directory ./libtool: line 1233: libtool: compile: cannot determine name of library object from `': command not found make[1]: *** [libhashkit/libhashkit_libhashkit_la-aes.lo] Error 1 make[1]: Leaving directory `/libmemcached' make: *** [all] Error 2 OUTPUT OF ./configure checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking target system type... x86_64-unknown-linux-gnu checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for gawk... gawk checking whether make sets $(MAKE)... yes checking for style of include used by make... GNU checking for gcc... gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking dependency style of gcc... gcc3 checking dependency style of gcc... (cached) gcc3 checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking minix/config.h usability... no checking minix/config.h presence... no checking for minix/config.h... no checking whether it is safe to define __EXTENSIONS__... yes checking for isainfo... no checking for g++... g++ checking whether we are using the GNU C++ compiler... yes checking whether g++ accepts -g... yes checking dependency style of g++... gcc3 checking dependency style of g++... (cached) gcc3 checking whether gcc and cc understand -c and -o together... yes checking how to create a ustar tar archive... gnutar checking whether __SUNPRO_C is declared... no checking whether __ICC is declared... no checking "C Compiler version--yes"... "gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52)" checking "C++ Compiler version"... "g++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52)" checking whether time.h and sys/time.h may both be included... yes checking whether struct tm is in sys/time.h or time.h... time.h checking for size_t... yes checking for special C compiler options needed for large files... no checking for _FILE_OFFSET_BITS value needed for large files... no checking for library containing clock_gettime... -lrt checking sys/socket.h usability... yes checking sys/socket.h presence... yes checking for sys/socket.h... yes checking size of off_t... 8 checking size of size_t... 8 checking size of long long... 8 checking if time_t is unsigned... no checking for setsockopt... yes checking for bind... yes checking whether the compiler provides atomic builtins... yes checking assert.h usability... yes checking assert.h presence... yes checking for assert.h... yes checking whether to enable assertions... yes checking whether it is safe to use -fdiagnostics-show-option... yes checking whether it is safe to use -floop-parallelize-all... no checking whether it is safe to use -Wextra... yes checking whether it is safe to use -Wformat... yes checking whether it is safe to use -Wconversion... no checking whether it is safe to use -Wmissing-declarations from C++... no checking whether it is safe to use -Wframe-larger-than... no checking whether it is safe to use -Wlogical-op... no checking whether it is safe to use -Wredundant-decls from C++... yes checking whether it is safe to use -Wattributes from C++... no checking whether it is safe to use -Wno-attributes... no checking for perl... perl checking for dpkg-gensymbols... no checking for lcov... no checking for genhtml... no checking for sphinx-build... no checking for working -pipe... yes checking for bison... bison checking for flex... flex checking how to print strings... printf checking for a sed that does not truncate output... /bin/sed checking for fgrep... /bin/grep -F checking for ld used by gcc... /usr/bin/ld checking if the linker (/usr/bin/ld) is GNU ld... yes checking for BSD- or MS-compatible name lister (nm)... /usr/bin/nm -B checking the name lister (/usr/bin/nm -B) interface... BSD nm checking whether ln -s works... yes checking the maximum length of command line arguments... 98304 checking whether the shell understands some XSI constructs... yes checking whether the shell understands "+="... yes checking how to convert x86_64-unknown-linux-gnu file names to x86_64-unknown-linux-gnu format... func_convert_file_noop checking how to convert x86_64-unknown-linux-gnu file names to toolchain format... func_convert_file_noop checking for /usr/bin/ld option to reload object files... -r checking for objdump... objdump checking how to recognize dependent libraries... pass_all checking for dlltool... no checking how to associate runtime and link libraries... printf %s\n checking for ar... ar checking for archiver @FILE support... @ checking for strip... strip checking for ranlib... ranlib checking command to parse /usr/bin/nm -B output from gcc object... ok checking for sysroot... no checking for mt... no checking if : is a manifest tool... no checking for dlfcn.h... yes checking for objdir... .libs checking if gcc supports -fno-rtti -fno-exceptions... no checking for gcc option to produce PIC... -fPIC -DPIC checking if gcc PIC flag -fPIC -DPIC works... yes checking if gcc static flag -static works... yes checking if gcc supports -c -o file.o... yes checking if gcc supports -c -o file.o... (cached) yes checking whether the gcc linker (/usr/bin/ld -m elf_x86_64) supports shared libraries... yes checking whether -lc should be explicitly linked in... no checking dynamic linker characteristics... GNU/Linux ld.so checking how to hardcode library paths into programs... immediate checking whether stripping libraries is possible... yes checking if libtool supports shared libraries... yes checking whether to build shared libraries... yes checking whether to build static libraries... yes checking how to run the C++ preprocessor... g++ -E checking for ld used by g++... /usr/bin/ld -m elf_x86_64 checking if the linker (/usr/bin/ld -m elf_x86_64) is GNU ld... yes checking whether the g++ linker (/usr/bin/ld -m elf_x86_64) supports shared libraries... yes checking for g++ option to produce PIC... -fPIC -DPIC checking if g++ PIC flag -fPIC -DPIC works... yes checking if g++ static flag -static works... yes checking if g++ supports -c -o file.o... yes checking if g++ supports -c -o file.o... (cached) yes checking whether the g++ linker (/usr/bin/ld -m elf_x86_64) supports shared libraries... yes checking dynamic linker characteristics... (cached) GNU/Linux ld.so checking how to hardcode library paths into programs... immediate checking whether the -Werror option is usable... yes checking for simple visibility declarations... yes checking for ISO C++ 98 include files... checking whether memcached executable path has been provided... no checking for memcached... /usr/local/bin/memcached checking whether memcached_sasl executable path has been provided... no checking for memcached_sasl... no checking whether gearmand executable path has been provided... no checking for gearmand... no checking libgearman/gearmand.h usability... no checking libgearman/gearmand.h presence... no checking for libgearman/gearmand.h... no checking for library containing getopt_long... none required checking for library containing gethostbyname... none required checking for the pthreads library -lpthreads... no checking whether pthreads work without any flags... yes checking for joinable pthread attribute... PTHREAD_CREATE_JOINABLE checking if more special flags are required for pthreads... no checking for PTHREAD_PRIO_INHERIT... yes checking the location of cstdint... configure: WARNING: Could not find a cstdint header. <stdint.h> checking the location of cinttypes... configure: WARNING: Could not find a cinttypes header. <inttypes.h> checking whether byte ordering is bigendian... no checking for htonll... no checking for working SO_SNDTIMEO... yes checking for working SO_RCVTIMEO... yes checking for supported struct padding... yes checking for alarm... yes checking for dup2... yes checking for getline... yes checking for gettimeofday... yes checking for memchr... yes checking for memmove... yes checking for memset... yes checking for pipe2... no checking for select... yes checking for setenv... yes checking for socket... yes checking for sqrt... yes checking for strcasecmp... yes checking for strchr... yes checking for strdup... yes checking for strerror... yes checking for strtol... yes checking for strtoul... yes checking for strtoull... yes checking arpa/inet.h usability... yes checking arpa/inet.h presence... yes checking for arpa/inet.h... yes checking fcntl.h usability... yes checking fcntl.h presence... yes checking for fcntl.h... yes checking libintl.h usability... yes checking libintl.h presence... yes checking for libintl.h... yes checking limits.h usability... yes checking limits.h presence... yes checking for limits.h... yes checking malloc.h usability... yes checking malloc.h presence... yes checking for malloc.h... yes checking netdb.h usability... yes checking netdb.h presence... yes checking for netdb.h... yes checking netinet/in.h usability... yes checking netinet/in.h presence... yes checking for netinet/in.h... yes checking stddef.h usability... yes checking stddef.h presence... yes checking for stddef.h... yes checking sys/time.h usability... yes checking sys/time.h presence... yes checking for sys/time.h... yes checking execinfo.h usability... yes checking execinfo.h presence... yes checking for execinfo.h... yes checking cxxabi.h usability... yes checking cxxabi.h presence... yes checking for cxxabi.h... yes checking sys/sysctl.h usability... yes checking sys/sysctl.h presence... yes checking for sys/sysctl.h... yes checking umem.h usability... no checking umem.h presence... no checking for umem.h... no checking for C++ compiler vendor... gnu checking for working alloca.h... yes checking for alloca... yes checking for error_at_line... yes checking for pid_t... yes checking vfork.h usability... no checking vfork.h presence... no checking for vfork.h... no checking for fork... yes checking for vfork... yes checking for working fork... yes checking for working vfork... (cached) yes checking for stdlib.h... (cached) yes checking for GNU libc compatible malloc... yes checking for stdlib.h... (cached) yes checking for GNU libc compatible realloc... yes checking whether strerror_r is declared... yes checking for strerror_r... yes checking whether strerror_r returns char *... yes checking for stdbool.h that conforms to C99... yes checking for _Bool... no checking for int16_t... yes checking for int32_t... yes checking for int64_t... yes checking for int8_t... yes checking for off_t... yes checking for pid_t... (cached) yes checking for ssize_t... yes checking for uint16_t... yes checking for uint32_t... yes checking for uint64_t... yes checking for uint8_t... yes checking whether byte ordering is bigendian... (cached) no checking for an ANSI C-conforming const... yes checking for inline... inline checking for working volatile... yes checking for C/C++ restrict keyword... __restrict checking whether the compiler supports GCC C++ ABI name demangling... yes checking sasl/sasl.h usability... no checking sasl/sasl.h presence... no checking for sasl/sasl.h... no checking uuid/uuid.h usability... yes checking uuid/uuid.h presence... yes checking for uuid/uuid.h... yes checking for main in -luuid... yes checking for clock_gettime in -lrt... yes checking for floor in -lm... yes checking for sigignore... yes checking atomic.h usability... no checking atomic.h presence... no checking for atomic.h... no checking for setppriv... no checking for winsock2.h... no checking for poll.h... yes checking for sys/wait.h... yes checking for fnmatch.h... yes checking for MSG_NOSIGNAL... yes checking for MSG_DONTWAIT... yes checking for MSG_MORE... yes checking event.h usability... yes checking event.h presence... yes checking for event.h... yes checking for main in -levent... yes checking for endianness... little configure: creating ./config.status config.status: creating Makefile config.status: creating docs/conf.py config.status: creating libhashkit-1.0/configure.h config.status: creating libmemcached-1.0/configure.h config.status: creating libmemcached-1.2/configure.h config.status: creating libmemcached-2.0/configure.h config.status: creating support/libmemcached.pc config.status: creating support/libmemcached.spec config.status: creating support/libmemcached-fc.spec config.status: creating libtest/version.h config.status: creating config.h config.status: config.h is unchanged config.status: executing depfiles commands config.status: executing libtool commands --- Configuration summary for libmemcached version 1.0.6 * Installation prefix: /usr/local * System type: unknown-linux-gnu * Host CPU: x86_64 * C Compiler: gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52) * Assertions enabled: yes * Debug enabled: no * Warnings as failure: no * SASL support: --- anyone knows how to solve this ?

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  • APC File Cache not working but user cache is fine

    - by danishgoel
    I have just got a VPS (with cPanel/WHM) to test what gains i could get in my application with using apc file cache AND user cache. So firstly I got the PHP 5.3 compiled in as a DSO (apache module). Then installed APC via PECL through SSH. (First I tried with WHM Module installer, it also had the same problem, so I tried it via ssh) All seemed fine and phpinfo showed apc loaded and enabled. Then I checked with apc.php. All seemed OK But as I started testing my php application, the stats in apc for File Cache Information state: Cached Files 0 ( 0.0 Bytes) Hits 1 Misses 0 Request Rate (hits, misses) 0.00 cache requests/second Hit Rate 0.00 cache requests/second Miss Rate 0.00 cache requests/second Insert Rate 0.00 cache requests/second Cache full count 0 Which meant no PHP files were being cached, even though I had browsed through over 10 PHP files having multiple includes. So there must have been some Cached Files. But the user cache is functioning fine. User Cache Information Cached Variables 0 ( 0.0 Bytes) Hits 1000 Misses 1000 Request Rate (hits, misses) 0.84 cache requests/second Hit Rate 0.42 cache requests/second Miss Rate 0.42 cache requests/second Insert Rate 0.84 cache requests/second Cache full count 0 Its actually from an APC caching test script which tries to retrieve and store 1000 entries and gives me the times. A sort of simple benchmark. Can anyone help me here. Even though apc.cache_by_default = 1, no php files are being cached. This is my apc config Runtime Settings apc.cache_by_default 1 apc.canonicalize 1 apc.coredump_unmap 0 apc.enable_cli 0 apc.enabled 1 apc.file_md5 0 apc.file_update_protection 2 apc.filters apc.gc_ttl 3600 apc.include_once_override 0 apc.lazy_classes 0 apc.lazy_functions 0 apc.max_file_size 1M apc.mmap_file_mask apc.num_files_hint 1000 apc.preload_path apc.report_autofilter 0 apc.rfc1867 0 apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.serializer default apc.shm_segments 1 apc.shm_size 32M apc.slam_defense 1 apc.stat 1 apc.stat_ctime 0 apc.ttl 0 apc.use_request_time 1 apc.user_entries_hint 4096 apc.user_ttl 0 apc.write_lock 1 Also most php files are under 20KB, thus, apc.max_file_size = 1M is not the cause. I have also tried using 'apc_compile_file ' to force some files into opcode cache with no luck. I have also re-installed APC with Debugging enabled, but nothing shows in the error_log I have also tried setting mmap_file_mask to /dev/zero and /tmp/apc.xxxxxx, i have also set /tmp permissions to 777 to no avail Any clue anyone. Update: I have tried following things and none cause APC file cache to populate 1. set apc.enable_cli = 1 AND run a script from cli 2. Set apc.max_file_size = 5M (just in case) 3. switched php handler from dso to FastCGI in WHM (then switched it back to dso as it did not solve the problem) 4. Even tried restarting the container

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  • Force caching of handler output which actively resists caching

    - by deceze
    I'm trying to force caching of a very obnoxious piece of PHP script which actively tries to resist caching for no good reason by actively setting all the anti-cache headers: Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0 Content-Type: text/html; charset=UTF-8 Date: Thu, 22 May 2014 08:43:53 GMT Expires: Thu, 19 Nov 1981 08:52:00 GMT Last-Modified: Pragma: no-cache Set-Cookie: ECSESSID=...; path=/ Vary: User-Agent,Accept-Encoding Server: Apache/2.4.6 (Ubuntu) X-Powered-By: PHP/5.5.3-1ubuntu2.3 If at all avoidable I do not want to have to modify this 3rd party piece of code at all and instead just get Apache to cache the page for a while. I'm doing this very selectively to only very specific pages which have no real impact on session cookies or the like, i.e. which do not contain any personalised information. CacheDefaultExpire 600 CacheMinExpire 600 CacheMaxExpire 1800 CacheHeader On CacheDetailHeader On CacheIgnoreHeaders Set-Cookie CacheIgnoreCacheControl On CacheIgnoreNoLastMod On CacheStoreExpired On CacheStoreNoStore On CacheLock On CacheEnable disk /the/script.php Apache is caching the page alright: [cache:debug] AH00698: cache: Key for entity /the/script.php?(null) is http://example.com:80/the/script.php? [cache_disk:debug] AH00709: Recalled cached URL info header http://example.com:80/the/script.php? [cache_disk:debug] AH00720: Recalled headers for URL http://example.com:80/the/script.php? [cache:debug] AH00695: Cached response for /the/script.php isn't fresh. Adding conditional request headers. [cache:debug] AH00750: Adding CACHE_SAVE filter for /the/script.php [cache:debug] AH00751: Adding CACHE_REMOVE_URL filter for /the/script.php [cache:debug] AH00769: cache: Caching url: /the/script.php [cache:debug] AH00770: cache: Removing CACHE_REMOVE_URL filter. [cache_disk:debug] AH00737: commit_entity: Headers and body for URL http://example.com:80/the/script.php? cached. However, it is always insisting that the "cached response isn't fresh" and is never serving the cached version. I guess this has to do with the Expires header, which marks the document as expired (but I don't know whether that's the correct assumption). I've tried to overwrite and unset headers using mod_headers, but this doesn't help; whatever combination I try the cache is not impressed at all. I'm guessing that the order of operation is wrong, and headers are being rewritten after the cache sees them. early header processing doesn't help either. I've experimented with CacheQuickHandler Off and trying to set explicit filter chains, but nothing is helping. But I'm really mostly poking in the dark, as I do not have a lot of experience with configuring Apache filter chains. Is there a straight forward solution for how to cache this obnoxious piece of code?

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  • swapping or trashing with vast amounts of unmapped pagecache

    - by Marco
    I'm using kubuntu jaunty (i386 32bit), kernel 2.6.28-13-generic. I've 4Gb of RAM, of which only 3317Mb are seen by the system (I guess because of the 32bit system). I'm seeing that the pagecache utilization is continually growing, up to the point that the system is unusable (after a few days). This happens also when I don't do anything (all user applications closed and the bare minimum of services enabled). If enabled, the system starts to use swap space (using it all in the end). Even if swap is disabled, disk activity becomes continuous, with the system unresponsive. For example, right now the system is working (albeit a tad slow), with only firefox and wing ide running, and I have 2Gb cached with only 45Mb mapped: $ free total used free shared buffers cached Mem: 3346388 3247328 99060 0 8416 2117980 -/+ buffers/cache: 1120932 2225456 Swap: 2144668 519448 1625220 $ cat /proc/meminfo MemTotal: 3346388 kB MemFree: 97128 kB Buffers: 7872 kB Cached: 2120224 kB SwapCached: 413860 kB Active: 2304596 kB Inactive: 865984 kB Active(anon): 2279168 kB Inactive(anon): 830236 kB Active(file): 25428 kB Inactive(file): 35748 kB Unevictable: 32 kB Mlocked: 32 kB HighTotal: 2492940 kB HighFree: 5456 kB LowTotal: 853448 kB LowFree: 91672 kB SwapTotal: 2144668 kB SwapFree: 1625244 kB Dirty: 84 kB Writeback: 0 kB AnonPages: 629304 kB Mapped: 45768 kB Slab: 45600 kB SReclaimable: 21756 kB SUnreclaim: 23844 kB PageTables: 4468 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 3817860 kB Committed_AS: 3735020 kB VmallocTotal: 122880 kB VmallocUsed: 9352 kB VmallocChunk: 66600 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 4096 kB DirectMap4k: 16376 kB DirectMap4M: 888832 kB If I try to drop the caches, little happes: # sync ; echo 3 > /proc/sys/vm/drop_caches ; free total used free shared buffers cached Mem: 3346388 3220580 125808 0 3020 2100600 -/+ buffers/cache: 1116960 2229428 Swap: 2144668 519356 1625312 Right now I've vm.swappiness = 5, but I've tried also with 0 and 1 (without noticeable differences). I've also tried vm.vfs_cache_pressure = 50 and 150 (again, no differences). As I said the pagecache eats all memory even with swapping turned off. What is happening? How to avoid this? TIA, Marco

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  • swapping or trashing with vast amounts of unmapped pagecache

    - by Marco
    I'm using kubuntu jaunty (i386 32bit), kernel 2.6.28-13-generic. I've 4Gb of RAM, of which only 3317Mb are seen by the system (I guess because of the 32bit system). I'm seeing that the pagecache utilization is continually growing, up to the point that the system is unusable (after a few days). This happens also when I don't do anything (all user applications closed and the bare minimum of services enabled). If enabled, the system starts to use swap space (using it all in the end). Even if swap is disabled, disk activity becomes continuous, with the system unresponsive. For example, right now the system is working (albeit a tad slow), with only Firefox and wing ide running, and I have 2Gb cached with only 45Mb mapped: $ free total used free shared buffers cached Mem: 3346388 3247328 99060 0 8416 2117980 -/+ buffers/cache: 1120932 2225456 Swap: 2144668 519448 1625220 $ cat /proc/meminfo MemTotal: 3346388 kB MemFree: 97128 kB Buffers: 7872 kB Cached: 2120224 kB SwapCached: 413860 kB Active: 2304596 kB Inactive: 865984 kB Active(anon): 2279168 kB Inactive(anon): 830236 kB Active(file): 25428 kB Inactive(file): 35748 kB Unevictable: 32 kB Mlocked: 32 kB HighTotal: 2492940 kB HighFree: 5456 kB LowTotal: 853448 kB LowFree: 91672 kB SwapTotal: 2144668 kB SwapFree: 1625244 kB Dirty: 84 kB Writeback: 0 kB AnonPages: 629304 kB Mapped: 45768 kB Slab: 45600 kB SReclaimable: 21756 kB SUnreclaim: 23844 kB PageTables: 4468 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 3817860 kB Committed_AS: 3735020 kB VmallocTotal: 122880 kB VmallocUsed: 9352 kB VmallocChunk: 66600 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 4096 kB DirectMap4k: 16376 kB DirectMap4M: 888832 kB If I try to drop the caches, little happens: # sync ; echo 3 > /proc/sys/vm/drop_caches ; free total used free shared buffers cached Mem: 3346388 3220580 125808 0 3020 2100600 -/+ buffers/cache: 1116960 2229428 Swap: 2144668 519356 1625312 Right now I've vm.swappiness = 5, but I've tried also with 0 and 1 (without noticeable differences). I've also tried vm.vfs_cache_pressure = 50 and 150 (again, no differences). As I said the pagecache eats all memory even with swapping turned off. What is happening? How to avoid this?

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  • Nginx + uWSGI + Django performance stuck on 100rq/s

    - by dancio
    I have configured Nginx with uWSGI and Django on CentOS 6 x64 (3.06GHz i3 540, 4GB), which should easily handle 2500 rq/s but when I run ab test ( ab -n 1000 -c 100 ) performance stops at 92 - 100 rq/s. Nginx: user nginx; worker_processes 2; events { worker_connections 2048; use epoll; } uWSGI: Emperor /usr/sbin/uwsgi --master --no-orphans --pythonpath /var/python --emperor /var/python/*/uwsgi.ini [uwsgi] socket = 127.0.0.2:3031 master = true processes = 5 env = DJANGO_SETTINGS_MODULE=x.settings env = HTTPS=on module = django.core.handlers.wsgi:WSGIHandler() disable-logging = true catch-exceptions = false post-buffering = 8192 harakiri = 30 harakiri-verbose = true vacuum = true listen = 500 optimize = 2 sysclt changes: # Increase TCP max buffer size setable using setsockopt() net.ipv4.tcp_rmem = 4096 87380 8388608 net.ipv4.tcp_wmem = 4096 87380 8388608 net.core.rmem_max = 8388608 net.core.wmem_max = 8388608 net.core.netdev_max_backlog = 5000 net.ipv4.tcp_max_syn_backlog = 5000 net.ipv4.tcp_window_scaling = 1 net.core.somaxconn = 2048 # Avoid a smurf attack net.ipv4.icmp_echo_ignore_broadcasts = 1 # Optimization for port usefor LBs # Increase system file descriptor limit fs.file-max = 65535 I did sysctl -p to enable changes. Idle server info: top - 13:34:58 up 102 days, 18:35, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 118 total, 1 running, 117 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3983068k total, 2125088k used, 1857980k free, 262528k buffers Swap: 2104504k total, 0k used, 2104504k free, 606996k cached free -m total used free shared buffers cached Mem: 3889 2075 1814 0 256 592 -/+ buffers/cache: 1226 2663 Swap: 2055 0 2055 **During the test:** top - 13:45:21 up 102 days, 18:46, 1 user, load average: 3.73, 1.51, 0.58 Tasks: 122 total, 8 running, 114 sleeping, 0 stopped, 0 zombie Cpu(s): 93.5%us, 5.2%sy, 0.0%ni, 0.2%id, 0.0%wa, 0.1%hi, 1.1%si, 0.0%st Mem: 3983068k total, 2127564k used, 1855504k free, 262580k buffers Swap: 2104504k total, 0k used, 2104504k free, 608760k cached free -m total used free shared buffers cached Mem: 3889 2125 1763 0 256 595 -/+ buffers/cache: 1274 2615 Swap: 2055 0 2055 iotop 30141 be/4 nginx 0.00 B/s 7.78 K/s 0.00 % 0.00 % nginx: wo~er process Where is the bottleneck ? Or what am I doing wrong ?

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  • Outlook Shared Address book and contact not displaying

    - by user224061
    We have a shared Exchange addressbook with distribution email groups. When someone connects to the shared addressbook, composes an email to a group, the email distribution list is empty, then the distribution list is expanded. In troubleshooting, I noticed that when we expand the distribution list to view the recipients, most of the recipients are missing and only semicolons appear. CLICK HERE FOR IMAGE Further troubleshooting, I notice that when I open the distribution list with my Outlook client and click on the Update Now icon, and then go to create the email then when I expand the group the email addresses now appear. CLICK HERE FOR IMAGE Now, my Outlook profile is a cached profile. The shared contact list that I pulled the distribution list from is an online/non-cached shared contact list. What I also found is that if I switched my Outlook client to be online only(not cached) the share address book lists appear properly when expanded. Is there any way to make this list appear correctly without having to click on update now for each and every distribution list in the shared contacts list we have on the server? I would really prefer that every time one wants to use this shared contact list, they do not have o click the update not button or switch from cached mode to make this work. T.I.A

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  • How to clear Outlook's Exchance cache address book information

    - by Assaf
    When a new email address is added to our company's Exchange server it doesn't show up immediately on my Outlook, and I suspect that it's because of the "cached mode". When I disable cached mode and restart outlook I see the new address fine. But when I restore cached mode and restart outlook it's missing again. So I guess the cache wasn't updated by this move. I tried deleting the .nk2 file in %appdata%\Microsoft\Outlook, but that didn't help. How can I force Outlook to clear its address book cache?

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  • In Windows XP, is it possible to disable user credential caching for particular users

    - by kdt
    I understand that when windows caches user credentials, these can sometimes be used by malicious parties to access other machines once a machine containing cached credentials is compromised, a method known as "pass the hash"[1]. For this reason I would like to get control over what's cached to reduce the risk of cached credentials being used maliciously. It is possible to prevent all caching by zeroing HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\CachedLogonsCount, but this is too indiscriminate: laptops users need to be able to login when away from the network. What I would like to do is prevent the caching of credentials of certain users, such as administrators -- is there any way to do that in Windows XP? http://www.lbl.gov/cyber/systems/pass-the-hash.html

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  • SAS disk performance drops a while after reboot.

    - by Flamewires
    So we have some workstations with identical hardware. The Fedora14 box has a couple weeks uptime and still get good performance. hdparm -tT /dev/sda /dev/sda: Timing cached reads: 21766 MB in 2.00 seconds = 10902.12 MB/sec Timing buffered disk reads: 586 MB in 3.00 seconds = 195.20 MB/sec The Cent 5.5 boxes however seem to be okay after a reboot, /dev/sda: Timing cached reads: 34636 MB in 2.00 seconds = 17354.64 MB/sec Timing buffered disk reads: 498 MB in 3.01 seconds = 165.62 MB/sec but some time later( unsure exactly, tested at approx 1 day uptime) /dev/sda: Timing cached reads: 2132 MB in 2.00 seconds = 1064.96 MB/sec Timing buffered disk reads: 160 MB in 3.01 seconds = 53.16 MB/sec drop to this. This is with very low load. I believe they all have the same bios settings. Any ideas what could cause this on Cent? Ask for more info. It might also be worth noting, that passing the --direct flag causes the slow boxes to perform similarly to the non-slow ones for buffered disk reads.

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  • Caching static content from Adobe, Microsoft, etc

    - by Tim
    I'm currently running the Apple SUS on a Mac OS X Server in a small office environment. It works well for Apple updates, but I'm still stuck with either manually downloading and installing Adobe/Microsoft updates on each computer or running them through a Squid cache, with the blind faith that Squid will keep the files I actually want to stay cached. What is the best way to cache updates locally for applications like the Adobe Updater or Microsoft AutoUpdate? Ideally cached in such a way that I can tell which files I do or do not have cached. It would also be nice to be able to cache things for other software like Firefox and Sparkle-enabled apps, but these are usually small enough to ignore.

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  • slow software raid

    - by Jure1873
    I've got software raid 1 for / and /home and it seems I'm not getting the right speed out of it. Reading from md0 I get around 100 MB/sec Reading from sda or sdb I get around 95-105 MB/sec I thought I would get more speed (while reading data) from two drives. I don't know what is the problem. I'm using kernel 2.6.31-18 hdparm -tT /dev/md0 /dev/md0: Timing cached reads: 2078 MB in 2.00 seconds = 1039.72 MB/sec Timing buffered disk reads: 304 MB in 3.01 seconds = 100.96 MB/sec hdparm -tT /dev/sda /dev/sda: Timing cached reads: 2084 MB in 2.00 seconds = 1041.93 MB/sec Timing buffered disk reads: 316 MB in 3.02 seconds = 104.77 MB/sec hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 2150 MB in 2.00 seconds = 1075.94 MB/sec Timing buffered disk reads: 302 MB in 3.01 seconds = 100.47 MB/sec Edit: Raid 1

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  • How do I fully clear Firefox's cache of CSS and JS files?

    - by Mike Webb
    I work on a website at my work. The issue is that if I visit the site, which uses the cached versions of the CSS and JS files, and then upload an updated copy of a CSS/JS file, Firefox will still use the cached version. I can go to 'Tools-Clear Recent History' and clear the Cache of "Everything" and it still uses the cached version of the files. It will eventually updated and use the new files, but it can takes hours for this change to occur. So, how do I completely clear Firefox's cache of these files?

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