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• Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

  - by James D

  Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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• Lightweight alternative to Manual/AutoResetEvent in C#

  - by sweetlilmre

  Hi, I have written what I hope is a lightweight alternative to using the ManualResetEvent and AutoResetEvent classes in C#/.NET. The reasoning behind this was to have Event like functionality without the weight of using a kernel locking object. Although the code seems to work well in both testing and production, getting this kind of thing right for all possibilities can be a fraught undertaking and I would humbly request any constructive comments and or criticism from the StackOverflow crowd on this. Hopefully (after review) this will be useful to others. Usage should be similar to the Manual/AutoResetEvent classes with Notify() used for Set(). Here goes: using System; using System.Threading; public class Signal { private readonly object _lock = new object(); private readonly bool _autoResetSignal; private bool _notified; public Signal() : this(false, false) { } public Signal(bool initialState, bool autoReset) { _autoResetSignal = autoReset; _notified = initialState; } public virtual void Notify() { lock (_lock) { // first time? if (!_notified) { // set the flag _notified = true; // unblock a thread which is waiting on this signal Monitor.Pulse(_lock); } } } public void Wait() { Wait(Timeout.Infinite); } public virtual bool Wait(int milliseconds) { lock (_lock) { bool ret = true; // this check needs to be inside the lock otherwise you can get nailed // with a race condition where the notify thread sets the flag AFTER // the waiting thread has checked it and acquires the lock and does the // pulse before the Monitor.Wait below - when this happens the caller // will wait forever as he "just missed" the only pulse which is ever // going to happen if (!_notified) { ret = Monitor.Wait(_lock, milliseconds); } if (_autoResetSignal) { _notified = false; } return (ret); } } }

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• In app purchase on iphone.: How to receive your available products *before* someone may be able to b

  - by Thorsten S.

  Currently I am loading my supported products from a plist and after that I send a SKProductsRequest to guarantee that my SKProducts are still valid. So I set up the request, start it and get the response in: (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response Now, so far all functions correctly. Problem: From calling the request until receiving the response it may last several seconds. Until that my app is already loaded and the user may be able to choose and buy a product. But because no products have been received, the available products are not in sync with the validated products - unlikely, but possible error. So my idea is to wait until the data is loaded and only continue when the list is validated. (Just a few seconds waiting...). I have a singleton instance managing all products. + (MyClass *) sharedInstance { if (!sharedInstance) sharedInstance = [MyClass new]; // Now wait until we have our data [condition lock]; while (noEntriesYet) // is yes at begin [condition wait]; [condition unlock]; return sharedInstance; } - productsRequest: didReceiveResponse: { [condition lock]; // I have my data noEntriesYet = false; [condition signal]; [condition unlock]; } Problem: The app freezes. Everything works fine if didReceiveResponse is completed before the sharedInstance is queried. There are different threads, the lock is working if wait is reached during didReceiveResponse, everything fine. But if not, didReceiveResponse is never called even if the request was sent. The lock is released, everything looks ok. I have tried to send the product request in a separate NSThread, with NSOperationQueue...without avail. Why ? What is happening ? How to solve the problem ?

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• How to make a thread that runs at x:00 x:15 x:30 and x:45 do something different at 2:00.

  - by rmarimon

  I have a timer thread that needs to run at a particular moments of the day to do an incremental replication with a database. Right now it runs at the hour, 15 minutes past the hour, 30 minutes past the hour and 45 minutes past the hour. This is the code I have which is working ok: public class TimerRunner implements Runnable { private static final Semaphore lock = new Semaphore(1); private static final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(); public static void initialize() { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } public static void destroy() { executor.shutdownNow(); } private static long getDelay() { Calendar now = Calendar.getInstance(); long p = 15 * 60; // run at 00, 15, 30 and 45 minutes past the hour long second = now.get(Calendar.MINUTE) * 60 + now.get(Calendar.SECOND); return p - (second % p); } public static void replicate() { if (lock.tryAcquire()) { try { Thread t = new Thread(new Runnable() { public void run() { try { // here is where the magic happens } finally { lock.release(); } } }); t.start(); } catch (Exception e) { lock.release(); } } else { throw new IllegalStateException("already running a replicator"); } } public void run() { try { TimerRunner.replicate(); } finally { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } } } This process is started by calling TimerRunner.initialize() when a server starts and calling TimerRunner.destroy(). I have created a full replication process (as opposed to incremental) that I would like to run at a certain moment of the day, say 2:00am. How would change the above code to do this? I think that it should be very simple something like if it is now around 2:00am and it's been a long time since I did the full replication then do it now, but I can't get the if right. Beware that sometimes the replicate process takes way longer to complete. Sometimes beyond the 15 minutes, posing a problem in running at around 2:00am.

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• BASH echo write mysql input

  - by jmituzas

  Have a bash menu where variables write to file for mysql input. heres what I have: echo "CREATE DATABASE '$mysqldbn'; #GRANT ALL PRIVILEGES ON *.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup' WITH GRANT OPTION; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myip' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'localhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES< LOCK TABLES on '$mysqldbn'.* TO '$mysqlu'@'$rip' IDENTIFIED BY '$mysqlup';" > nmysql.db mysql -u root -p$mypass < nmysql.db problem is to get variables to show I had to put them in single quotes, the single quotes show up as I want for instances like '$mysqlu'@'localhost'. But how can I remove the quotes and still get to use the variable in the instance like, CREATE DATABASE '$mysqldbn' ? Double quotes wont work either, I am at a loss. Thanks in advance, Joe

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• ReaderWriterLockSlim and Pulse/Wait

  - by Jono

  Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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• problem with implementing a simple work queue

  - by John Deerikio

  Hi all, I am having troubles with implementing a simple work queue. Doing some analysis, I am facing a subtle problem. The work queue is backed by a regular linked list. The code looks like this (simplified): 0. while (true) 1. while (enabled == true) 2. acquire lock on the list and get the next action to be executed (blocking operation) (store it in a local variable) 3. execute the action (outside the lock on the list on previous line) 4. get lock on this work queue 5. wait until this work queue has been notified (triggered when setEnabled(true) has been callled) The setEnabled(e) operation looks like this (simplified): enabled = e if (enabled == true) acquire lock on this work queue and do notify() Although this works, there is a condition in which a deadlock occurs. It happens in the following rare situation: while an action is being executed, setEnabled(false) is called just before step (4) is entered, setEnabled(true) is called now step (5) keeps waiting forever, because this work queue has already been notified How do I solve this? I have been looking at this for some time, but I cannot come up with a solution. Please note I am fairly new to thread synchronization. Thanks a lot.

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• Is there a better way to write this repetitive event-declaration code in C# when implementing an int

  - by Damien Wildfire

  I have a lot of code like the following, where I explicitly implement some events required by an interface. public class IMicrowaveNotifier { event EventHandler<EventArgs> DoorClosed; event EventHandler<EventArgs> LightbulbOn; // ... } public class Microwave : IMicrowaveNotifier { private EventHandler<EventArgs> _doorClosed; event EventHandler<EventArgs> IMicrowaveNotifier.DoorClosed { add { lock (this) _doorClosed += value; } remove { lock (this) _doorClosed -= value; } } private EventHandler<EventArgs> _lightbulbOn; event EventHandler<EventArgs> IMicrowaveNotifier.LightbulbOn { add { lock (this) _lightbulbOn += value; } remove { lock (this) _lightbulbOn -= value; } } // ... } You can see that much of this is boilerplate. In Ruby I'd be able to do something like this: class Microwave has_events :door_closed, :lightbulb_on, ... end Is there a similar shorter way of removing this boilerplate in C#? Update: I left a very important part out of my example: namely, the events getting implemented are part of an interface, and I want to implement it explicitly. Sorry for not mentioning this earlier!

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• Does Monitor.Wait ensure that fields are re-read?

  - by Marc Gravell

  It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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• Thread-Safe lazy instantiating using MEF

  - by Xaqron

  // Member Variable private static readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { // It seems the `IsValueCreated` is not up-to-date if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile static int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. I should notice the CompositionContainer has a thread-safe option in constructor which is already used. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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• Asynchronous Webcrawling F#, something wrong ?

  - by jlezard

  Not quite sure if it is ok to do this but, my question is: Is there something wrong with my code ? It doesn't go as fast as I would like, and since I am using lots of async workflows maybe I am doing something wrong. The goal here is to build something that can crawl 20 000 pages in less than an hour. open System open System.Text open System.Net open System.IO open System.Text.RegularExpressions open System.Collections.Generic open System.ComponentModel open Microsoft.FSharp open System.Threading //This is the Parallel.Fs file type ComparableUri ( uri: string ) = inherit System.Uri( uri ) let elts (uri:System.Uri) = uri.Scheme, uri.Host, uri.Port, uri.Segments interface System.IComparable with member this.CompareTo( uri2 ) = compare (elts this) (elts(uri2 :?> ComparableUri)) override this.Equals(uri2) = compare this (uri2 :?> ComparableUri ) = 0 override this.GetHashCode() = 0 ///////////////////////////////////////////////Funtions to retreive html string////////////////////////////// let mutable error = Set.empty<ComparableUri> let mutable visited = Set.empty<ComparableUri> let getHtmlPrimitiveAsyncDelay (delay:int) (uri : ComparableUri) = async{ try let req = (WebRequest.Create(uri)) :?> HttpWebRequest // 'use' is equivalent to ‘using’ in C# for an IDisposable req.UserAgent<-"Mozilla" //Console.WriteLine("Waiting") do! Async.Sleep(delay * 250) let! resp = (req.AsyncGetResponse()) Console.WriteLine(uri.AbsoluteUri+" got response after delay "+string delay) use stream = resp.GetResponseStream() use reader = new StreamReader(stream) let html = reader.ReadToEnd() return html with | _ as ex -> Console.WriteLine( ex.ToString() ) lock error (fun () -> error<- error.Add uri ) lock visited (fun () -> visited<-visited.Add uri ) return "BadUri" } ///////////////////////////////////////////////Active Pattern Matching to retreive href////////////////////////////// let (|Matches|_|) (pat:string) (inp:string) = let m = Regex.Matches(inp, pat) // Note the List.tl, since the first group is always the entirety of the matched string. if m.Count > 0 then Some (List.tail [ for g in m -> g.Value ]) else None let (|Match|_|) (pat:string) (inp:string) = let m = Regex.Match(inp, pat) // Note the List.tl, since the first group is always the entirety of the matched string. if m.Success then Some (List.tail [ for g in m.Groups -> g.Value ]) else None ///////////////////////////////////////////////Find Bad href////////////////////////////// let isEmail (link:string) = link.Contains("@") let isMailto (link:string) = if Seq.length link >=6 then link.[0..5] = "mailto" else false let isJavascript (link:string) = if Seq.length link >=10 then link.[0..9] = "javascript" else false let isBadUri (link:string) = link="BadUri" let isEmptyHttp (link:string) = link="http://" let isFile (link:string)= if Seq.length link >=6 then link.[0..5] = "file:/" else false let containsPipe (link:string) = link.Contains("|") let isAdLink (link:string) = if Seq.length link >=6 then link.[0..5] = "adlink" elif Seq.length link >=9 then link.[0..8] = "http://adLink" else false ///////////////////////////////////////////////Find Bad href////////////////////////////// let getHref (htmlString:string) = let urlPat = "href=\"([^\"]+)" match htmlString with | Matches urlPat urls -> urls |> List.map( fun href -> match href with | Match (urlPat) (link::[]) -> link | _ -> failwith "The href was not in correct format, there was more than one match" ) | _ -> Console.WriteLine( "No links for this page" );[] |> List.filter( fun link -> not(isEmail link) ) |> List.filter( fun link -> not(isMailto link) ) |> List.filter( fun link -> not(isJavascript link) ) |> List.filter( fun link -> not(isBadUri link) ) |> List.filter( fun link -> not(isEmptyHttp link) ) |> List.filter( fun link -> not(isFile link) ) |> List.filter( fun link -> not(containsPipe link) ) |> List.filter( fun link -> not(isAdLink link) ) let treatAjax (href:System.Uri) = let link = href.ToString() let firstPart = (link.Split([|"#"|],System.StringSplitOptions.None)).[0] new Uri(firstPart) //only follow pages with certain extnsion or ones with no exensions let followHref (href:System.Uri) = let valid2 = set[".py"] let valid3 = set[".php";".htm";".asp"] let valid4 = set[".php3";".php4";".php5";".html";".aspx"] let arrLength = href.Segments |> Array.length let lastExtension = (href.Segments).[arrLength-1] let lengthLastExtension = Seq.length lastExtension if (lengthLastExtension <= 3) then not( lastExtension.Contains(".") ) else //test for the 2 case let last4 = lastExtension.[(lengthLastExtension-1)-3..(lengthLastExtension-1)] let isValid2 = valid2|>Seq.exists(fun validEnd -> last4.EndsWith( validEnd) ) if isValid2 then true else if lengthLastExtension <= 4 then not( last4.Contains(".") ) else let last5 = lastExtension.[(lengthLastExtension-1)-4..(lengthLastExtension-1)] let isValid3 = valid3|>Seq.exists(fun validEnd -> last5.EndsWith( validEnd) ) if isValid3 then true else if lengthLastExtension <= 5 then not( last5.Contains(".") ) else let last6 = lastExtension.[(lengthLastExtension-1)-5..(lengthLastExtension-1)] let isValid4 = valid4|>Seq.exists(fun validEnd -> last6.EndsWith( validEnd) ) if isValid4 then true else not( last6.Contains(".") ) && not(lastExtension.[0..5] = "mailto") //Create the correct links / -> add the homepage , make them a comparabel Uri let hrefLinksToUri ( uri:ComparableUri ) (hrefLinks:string list) = hrefLinks |> List.map( fun link -> try if Seq.length link <4 then Some(new Uri( uri, link )) else if link.[0..3] = "http" then Some(new Uri(link)) else Some(new Uri( uri, link )) with | _ as ex -> Console.WriteLine(link); lock error (fun () ->error<-error.Add uri) None ) |> List.filter( fun link -> link.IsSome ) |> List.map( fun o -> o.Value) |> List.map( fun uri -> new ComparableUri( string uri ) ) //Treat uri , removing ajax last part , and only following links specified b Benoit let linksToFollow (hrefUris:ComparableUri list) = hrefUris |>List.map( treatAjax ) |>List.filter( fun link -> followHref link ) |>List.map( fun uri -> new ComparableUri( string uri ) ) |>Set.ofList let needToVisit uri = ( lock visited (fun () -> not( visited.Contains uri) ) ) && (lock error (fun () -> not( error.Contains uri) )) let getLinksToFollowAsyncDelay (delay:int) ( uri: ComparableUri ) = async{ let! links = getHtmlPrimitiveAsyncDelay delay uri lock visited (fun () ->visited<-visited.Add uri) let linksToFollow = getHref links |> hrefLinksToUri uri |> linksToFollow |> Set.filter( needToVisit ) |> Set.map( fun link -> if uri.Authority=link.Authority then link else link ) return linksToFollow } //Add delays if visitng same authority let getDelay(uri:ComparableUri) (authorityDelay:Dictionary<string,int>) = let uriAuthority = uri.Authority let hasAuthority,delay = authorityDelay.TryGetValue(uriAuthority) if hasAuthority then authorityDelay.[uriAuthority] <-delay+1 delay else authorityDelay.Add(uriAuthority,1) 0 let rec getLinksToFollowFromSetAsync maxIteration ( uris: seq<ComparableUri> ) = let authorityDelay = Dictionary<string,int>() if maxIteration = 100 then Console.WriteLine("Finished") else //Unite by authority add delay for those we same authority others ignore let stopwatch= System.Diagnostics.Stopwatch() stopwatch.Start() let newLinks = uris |> Seq.map( fun uri -> let delay = lock authorityDelay (fun () -> getDelay uri authorityDelay ) getLinksToFollowAsyncDelay delay uri ) |> Async.Parallel |> Async.RunSynchronously |> Seq.concat stopwatch.Stop() Console.WriteLine("\n\n\n\n\n\n\nTimeElapse : "+string stopwatch.Elapsed+"\n\n\n\n\n\n\n\n\n") getLinksToFollowFromSetAsync (maxIteration+1) newLinks getLinksToFollowFromSetAsync 0 (seq[ComparableUri( "http://twitter.com/" )]) Console.WriteLine("Finished") Some feedBack would be great ! Thank you (note this is just something I am doing for fun)

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• Creating a dynamic proxy generator – Part 1 – Creating the Assembly builder, Module builder and cach

  - by SeanMcAlinden

  I’ve recently started a project with a few mates to learn the ins and outs of Dependency Injection, AOP and a number of other pretty crucial patterns of development as we’ve all been using these patterns for a while but have relied totally on third part solutions to do the magic. We thought it would be interesting to really get into the details by rolling our own IoC container and hopefully learn a lot on the way, and you never know, we might even create an excellent framework. The open source project is called Rapid IoC and is hosted at http://rapidioc.codeplex.com/ One of the most interesting tasks for me is creating the dynamic proxy generator for enabling Aspect Orientated Programming (AOP). In this series of articles, I’m going to track each step I take for creating the dynamic proxy generator and I’ll try my best to explain what everything means - mainly as I’ll be using Reflection.Emit to emit a fair amount of intermediate language code (IL) to create the proxy types at runtime which can be a little taxing to read. It’s worth noting that building the proxy is without a doubt going to be slightly painful so I imagine there will be plenty of areas I’ll need to change along the way. Anyway lets get started…   Part 1 - Creating the Assembly builder, Module builder and caching mechanism Part 1 is going to be a really nice simple start, I’m just going to start by creating the assembly, module and type caches. The reason we need to create caches for the assembly, module and types is simply to save the overhead of recreating proxy types that have already been generated, this will be one of the important steps to ensure that the framework is fast… kind of important as we’re calling the IoC container ‘Rapid’ – will be a little bit embarrassing if we manage to create the slowest framework. The Assembly builder The assembly builder is what is used to create an assembly at runtime, we’re going to have two overloads, one will be for the actual use of the proxy generator, the other will be mainly for testing purposes as it will also save the assembly so we can use Reflector to examine the code that has been created. Here’s the code: DynamicAssemblyBuilder using System; using System.Reflection; using System.Reflection.Emit; namespace Rapid.DynamicProxy.Assembly {     /// <summary>     /// Class for creating an assembly builder.     /// </summary>     internal static class DynamicAssemblyBuilder     {         #region Create           /// <summary>         /// Creates an assembly builder.         /// </summary>         /// <param name="assemblyName">Name of the assembly.</param>         public static AssemblyBuilder Create(string assemblyName)         {             AssemblyName name = new AssemblyName(assemblyName);               AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(                     name, AssemblyBuilderAccess.Run);               DynamicAssemblyCache.Add(assembly);               return assembly;         }           /// <summary>         /// Creates an assembly builder and saves the assembly to the passed in location.         /// </summary>         /// <param name="assemblyName">Name of the assembly.</param>         /// <param name="filePath">The file path.</param>         public static AssemblyBuilder Create(string assemblyName, string filePath)         {             AssemblyName name = new AssemblyName(assemblyName);               AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(                     name, AssemblyBuilderAccess.RunAndSave, filePath);               DynamicAssemblyCache.Add(assembly);               return assembly;         }           #endregion     } }   So hopefully the above class is fairly explanatory, an AssemblyName is created using the passed in string for the actual name of the assembly. An AssemblyBuilder is then constructed with the current AppDomain and depending on the overload used, it is either just run in the current context or it is set up ready for saving. It is then added to the cache.   DynamicAssemblyCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions;   namespace Rapid.DynamicProxy.Assembly {     /// <summary>     /// Cache for storing the dynamic assembly builder.     /// </summary>     internal static class DynamicAssemblyCache     {         #region Declarations           private static object syncRoot = new object();         internal static AssemblyBuilder Cache = null;           #endregion           #region Adds a dynamic assembly to the cache.           /// <summary>         /// Adds a dynamic assembly builder to the cache.         /// </summary>         /// <param name="assemblyBuilder">The assembly builder.</param>         public static void Add(AssemblyBuilder assemblyBuilder)         {             lock (syncRoot)             {                 Cache = assemblyBuilder;             }         }           #endregion           #region Gets the cached assembly                  /// <summary>         /// Gets the cached assembly builder.         /// </summary>         /// <returns></returns>         public static AssemblyBuilder Get         {             get             {                 lock (syncRoot)                 {                     if (Cache != null)                     {                         return Cache;                     }                 }                   throw new RapidDynamicProxyAssertionException(AssertionResources.NoAssemblyInCache);             }         }           #endregion     } } The cache is simply a static property that will store the AssemblyBuilder (I know it’s a little weird that I’ve made it public, this is for testing purposes, I know that’s a bad excuse but hey…) There are two methods for using the cache – Add and Get, these just provide thread safe access to the cache.   The Module Builder The module builder is required as the create proxy classes will need to live inside a module within the assembly. Here’s the code: DynamicModuleBuilder using System.Reflection.Emit; using Rapid.DynamicProxy.Assembly; namespace Rapid.DynamicProxy.Module {     /// <summary>     /// Class for creating a module builder.     /// </summary>     internal static class DynamicModuleBuilder     {         /// <summary>         /// Creates a module builder using the cached assembly.         /// </summary>         public static ModuleBuilder Create()         {             string assemblyName = DynamicAssemblyCache.Get.GetName().Name;               ModuleBuilder moduleBuilder = DynamicAssemblyCache.Get.DefineDynamicModule                 (assemblyName, string.Format("{0}.dll", assemblyName));               DynamicModuleCache.Add(moduleBuilder);               return moduleBuilder;         }     } } As you can see, the module builder is created on the assembly that lives in the DynamicAssemblyCache, the module is given the assembly name and also a string representing the filename if the assembly is to be saved. It is then added to the DynamicModuleCache. DynamicModuleCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions; namespace Rapid.DynamicProxy.Module {     /// <summary>     /// Class for storing the module builder.     /// </summary>     internal static class DynamicModuleCache     {         #region Declarations           private static object syncRoot = new object();         internal static ModuleBuilder Cache = null;           #endregion           #region Add           /// <summary>         /// Adds a dynamic module builder to the cache.         /// </summary>         /// <param name="moduleBuilder">The module builder.</param>         public static void Add(ModuleBuilder moduleBuilder)         {             lock (syncRoot)             {                 Cache = moduleBuilder;             }         }           #endregion           #region Get           /// <summary>         /// Gets the cached module builder.         /// </summary>         /// <returns></returns>         public static ModuleBuilder Get         {             get             {                 lock (syncRoot)                 {                     if (Cache != null)                     {                         return Cache;                     }                 }                   throw new RapidDynamicProxyAssertionException(AssertionResources.NoModuleInCache);             }         }           #endregion     } }   The DynamicModuleCache is very similar to the assembly cache, it is simply a statically stored module with thread safe Add and Get methods.   The DynamicTypeCache To end off this post, I’m going to create the cache for storing the generated proxy classes. I’ve spent a fair amount of time thinking about the type of collection I should use to store the types and have finally decided that for the time being I’m going to use a generic dictionary. This may change when I can actually performance test the proxy generator but the time being I think it makes good sense in theory, mainly as it pretty much maintains it’s performance with varying numbers of items – almost constant (0)1. Plus I won’t ever need to loop through the items which is not the dictionaries strong point. Here’s the code as it currently stands: DynamicTypeCache using System; using System.Collections.Generic; using System.Security.Cryptography; using System.Text; namespace Rapid.DynamicProxy.Types {     /// <summary>     /// Cache for storing proxy types.     /// </summary>     internal static class DynamicTypeCache     {         #region Declarations           static object syncRoot = new object();         public static Dictionary<string, Type> Cache = new Dictionary<string, Type>();           #endregion           /// <summary>         /// Adds a proxy to the type cache.         /// </summary>         /// <param name="type">The type.</param>         /// <param name="proxy">The proxy.</param>         public static void AddProxyForType(Type type, Type proxy)         {             lock (syncRoot)             {                 Cache.Add(GetHashCode(type.AssemblyQualifiedName), proxy);             }         }           /// <summary>         /// Tries the type of the get proxy for.         /// </summary>         /// <param name="type">The type.</param>         /// <returns></returns>         public static Type TryGetProxyForType(Type type)         {             lock (syncRoot)             {                 Type proxyType;                 Cache.TryGetValue(GetHashCode(type.AssemblyQualifiedName), out proxyType);                 return proxyType;             }         }           #region Private Methods           private static string GetHashCode(string fullName)         {             SHA1CryptoServiceProvider provider = new SHA1CryptoServiceProvider();             Byte[] buffer = Encoding.UTF8.GetBytes(fullName);             Byte[] hash = provider.ComputeHash(buffer, 0, buffer.Length);             return Convert.ToBase64String(hash);         }           #endregion     } } As you can see, there are two public methods, one for adding to the cache and one for getting from the cache. Hopefully they should be clear enough, the Get is a TryGet as I do not want the dictionary to throw an exception if a proxy doesn’t exist within the cache. Other than that I’ve decided to create a key using the SHA1CryptoServiceProvider, this may change but my initial though is the SHA1 algorithm is pretty fast to put together using the provider and it is also very unlikely to have any hashing collisions. (there are some maths behind how unlikely this is – here’s the wiki if you’re interested http://en.wikipedia.org/wiki/SHA_hash_functions)   Anyway, that’s the end of part 1 – although I haven’t started any of the fun stuff (by fun I mean hairpulling, teeth grating Relfection.Emit style fun), I’ve got the basis of the DynamicProxy in place so all we have to worry about now is creating the types, interceptor classes, method invocation information classes and finally a really nice fluent interface that will abstract all of the hard-core craziness away and leave us with a lightning fast, easy to use AOP framework. Hope you find the series interesting. All of the source code can be viewed and/or downloaded at our codeplex site - http://rapidioc.codeplex.com/ Kind Regards, Sean.

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• Curious about IObservable? Here’s a quick example to get you started!

  - by Roman Schindlauer

  Have you heard about IObservable/IObserver support in Microsoft StreamInsight 1.1? Then you probably want to try it out. If this is your first incursion into the IObservable/IObserver pattern, this blog post is for you! StreamInsight 1.1 introduced the ability to use IEnumerable and IObservable objects as event sources and sinks. The IEnumerable case is pretty straightforward, since many data collections are already surfacing as this type. This was already covered by Colin in his blog. Creating your own IObservable event source is a little more involved but no less exciting – here is a primer: First, let’s look at a very simple Observable data source. All it does is publish an integer in regular time periods to its registered observers. (For more information on IObservable, see http://msdn.microsoft.com/en-us/library/dd990377.aspx ). sealed class RandomSubject : IObservable<int>, IDisposable {     private bool _done;     private readonly List<IObserver<int>> _observers;     private readonly Random _random;     private readonly object _sync;     private readonly Timer _timer;     private readonly int _timerPeriod;       /// <summary>     /// Random observable subject. It produces an integer in regular time periods.     /// </summary>     /// <param name="timerPeriod">Timer period (in milliseconds)</param>     public RandomSubject(int timerPeriod)     {         _done = false;         _observers = new List<IObserver<int>>();         _random = new Random();         _sync = new object();         _timer = new Timer(EmitRandomValue);         _timerPeriod = timerPeriod;         Schedule();     }       public IDisposable Subscribe(IObserver<int> observer)     {         lock (_sync)         {             _observers.Add(observer);         }         return new Subscription(this, observer);     }       public void OnNext(int value)     {         lock (_sync)         {             if (!_done)             {                 foreach (var observer in _observers)                 {                     observer.OnNext(value);                 }             }         }     }       public void OnError(Exception e)     {         lock (_sync)         {             foreach (var observer in _observers)             {                 observer.OnError(e);             }             _done = true;         }     }       public void OnCompleted()     {         lock (_sync)         {             foreach (var observer in _observers)             {                 observer.OnCompleted();             }             _done = true;         }     }       void IDisposable.Dispose()     {         _timer.Dispose();     }       private void Schedule()     {         lock (_sync)         {             if (!_done)             {                 _timer.Change(_timerPeriod, Timeout.Infinite);             }         }     }       private void EmitRandomValue(object _)     {         var value = (int)(_random.NextDouble() * 100);         Console.WriteLine("[Observable]\t" + value);         OnNext(value);         Schedule();     }       private sealed class Subscription : IDisposable     {         private readonly RandomSubject _subject;         private IObserver<int> _observer;           public Subscription(RandomSubject subject, IObserver<int> observer)         {             _subject = subject;             _observer = observer;         }           public void Dispose()         {             IObserver<int> observer = _observer;             if (null != observer)             {                 lock (_subject._sync)                 {                     _subject._observers.Remove(observer);                 }                 _observer = null;             }         }     } }   So far, so good. Now let’s write a program that consumes data emitted by the observable as a stream of point events in a Streaminsight query. First, let’s define our payload type: class Payload {     public int Value { get; set; }       public override string ToString()     {         return "[StreamInsight]\tValue: " + Value.ToString();     } }   Now, let’s write the program. First, we will instantiate the observable subject. Then we’ll use the ToPointStream() method to consume it as a stream. We can now write any query over the source - here, a simple pass-through query. class Program {     static void Main(string[] args)     {         Console.WriteLine("Starting observable source...");         using (var source = new RandomSubject(500))         {             Console.WriteLine("Started observable source.");             using (var server = Server.Create("Default"))             {                 var application = server.CreateApplication("My Application");                   var stream = source.ToPointStream(application,                     e => PointEvent.CreateInsert(DateTime.Now, new Payload { Value = e }),                     AdvanceTimeSettings.StrictlyIncreasingStartTime,                     "Observable Stream");                   var query = from e in stream                             select e;                   [...]   We’re done with consuming input and querying it! But you probably want to see the output of the query. Did you know you can turn a query into an observable subject as well? Let’s do precisely that, and exploit the Reactive Extensions for .NET (http://msdn.microsoft.com/en-us/devlabs/ee794896.aspx) to quickly visualize the output. Notice we’re subscribing “Console.WriteLine()” to the query, a pattern you may find useful for quick debugging of your queries. Reminder: you’ll need to install the Reactive Extensions for .NET (Rx for .NET Framework 4.0), and reference System.CoreEx and System.Reactive in your project.                 [...]                   Console.ReadLine();                 Console.WriteLine("Starting query...");                 using (query.ToObservable().Subscribe(Console.WriteLine))                 {                     Console.WriteLine("Started query.");                     Console.ReadLine();                     Console.WriteLine("Stopping query...");                 }                 Console.WriteLine("Stopped query.");             }             Console.ReadLine();             Console.WriteLine("Stopping observable source...");             source.OnCompleted();         }         Console.WriteLine("Stopped observable source.");     } }   We hope this blog post gets you started. And for bonus points, you can go ahead and rewrite the observable source (the RandomSubject class) using the Reactive Extensions for .NET! The entire sample project is attached to this article. Happy querying! Regards, The StreamInsight Team

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• osx snow leopard freezes

  - by lydonchandra

  Hi I got this error: Timexxxx In 'CFPasteboardCopyData', file /SourceCache/CF/CF-550.13/AppServices.subproj/CFPasteboard.c, line 1951, during lock, spin lock 0x15457a0c8 has value 0xf0000000, which is neither locked nor unlocked. The memory has been smashed. My Mac freezes except the mouse and keyboard. What is happening and how can I prevent this from happening in the future?

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• Cannot Start Nginx Compiled from Source

  - by Jason Alan Kennedy

  I am trying to compile Nginx from source based on the original compiled Nginx server running on my DigitalOcean server ( Ubuntu-14.04 64x ) but with a few extra modules. I can get everything installed smoothly but I can not get it to start. I am sure the ini is correct because I copied the original source off the current running Nginx server [ Even though I see that Nginx now adds the ini when compiling fron source ]. Below is the [ lengthy process ] that I am performing - add sorry but I wanted to be thorough for those who are in need of the info ]. Because I am a newB to Nginx, I am sure I am missing something or just have it all wrong. If you may look over what I have done and see if you spot anything I need/need to change, I will greatly appreciate it. Thnx! With the original Nginx server still running: I check the current/running Nginx configuration so I can build the new Nginx instance the same but with the added modules: nginx -V # The out-put: configure arguments: --with-cc-opt='-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_addition_module --with-http_dav_module --with-http_geoip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_spdy_module --with-http_sub_module --with-http_xslt_module NOTE: The configure arguments below return errors during 'make' so I removed them. I don't know what they are - could this be related to my issue??? --with-cc-opt='-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro' Moving on: # So I don't have to sudo every line: sudo bash # Check for updates first thing: apt-get update # Install various prerequisites needed to compile Nginx: apt-get install build-essential libgd2-xpm-dev lsb-base zlib1g-dev libpcre3 libpcre3-dev libbz2-dev libxslt1-dev libxml2 libssl-dev libgeoip-dev tar unzip openssl # Create System users [ if it doesn't exist - but I see its there on DigitalOceans' Droplets all-ready ]: adduser --system --no-create-home --disabled-login --disabled-password --group www-data # Download NGINX wget http://nginx.org/download/nginx-1.7.4.tar.gz tar -xvzf nginx-1.7.4.tar.gz # Then Google PageSpeed: wget https://github.com/pagespeed/ngx_pagespeed/archive/release-1.8.31.4-beta.zip unzip release-1.8.31.4-beta.zip # cd into the PageSpeed Directory cd ngx_pagespeed-release-1.8.31.4-beta/ # and add the PSOL files in there: wget https://dl.google.com/dl/page-speed/psol/1.8.31.4.tar.gz tar -xzvf 1.8.31.4.tar.gz # Get back to the root directory: cd # I add the ngx_cache_purge module and will install the Nginx Helper plugin for WP later: wget https://github.com/FRiCKLE/ngx_cache_purge/archive/2.1.zip unzip 2.1.zip # Add the headers-more-nginx-module: wget https://github.com/openresty/headers-more-nginx-module/archive/v0.25.zip unzip v0.25.zip # and the naxsi module for added security: wget https://github.com/nbs-system/naxsi/archive/0.53-2.tar.gz tar -xvzf 0.53-2.tar.gz # cd to the new Nginx directory cd nginx-1.7.4 # Set up the configuration build based on the current running Nginx config args and add my additional modules: ./configure \ --add-module=$HOME/naxsi-0.53-2/naxsi_src \ --prefix=/usr/share/nginx \ --conf-path=/etc/nginx/nginx.conf \ --http-log-path=/var/log/nginx/access.log \ --error-log-path=/var/log/nginx/error.log \ --lock-path=/var/lock/nginx.lock \ --pid-path=/run/nginx.pid \ --http-client-body-temp-path=/var/lib/nginx/body \ --http-fastcgi-temp-path=/var/lib/nginx/fastcgi \ --http-proxy-temp-path=/var/lib/nginx/proxy \ --http-scgi-temp-path=/var/lib/nginx/scgi \ --http-uwsgi-temp-path=/var/lib/nginx/uwsgi \ --user=www-data \ --group=www-data \ --with-debug \ --with-pcre-jit \ --with-ipv6 \ --with-http_ssl_module \ --with-http_stub_status_module \ --with-http_realip_module \ --with-http_addition_module \ --with-http_dav_module \ --with-http_geoip_module \ --with-http_gzip_static_module \ --with-http_image_filter_module \ --with-http_spdy_module \ --with-http_sub_module \ --with-http_xslt_module \ --with-mail \ --with-mail_ssl_module \ --add-module=$HOME/ngx_pagespeed-release-1.8.31.4-beta \ --add-module=$HOME/ngx_cache_purge-2.1 \ --add-module=$HOME/headers-more-nginx-module-0.25 [ENTER] Configuration Summary: Configuration summary + using system PCRE library + using system OpenSSL library + md5: using OpenSSL library + sha1: using OpenSSL library + using system zlib library nginx path prefix: "/usr/share/nginx" nginx binary file: "/usr/share/nginx/sbin/nginx" nginx configuration prefix: "/etc/nginx" nginx configuration file: "/etc/nginx/nginx.conf" nginx pid file: "/run/nginx.pid" nginx error log file: "/var/log/nginx/error.log" nginx http access log file: "/var/log/nginx/access.log" nginx http client request body temporary files: "/var/lib/nginx/body" nginx http proxy temporary files: "/var/lib/nginx/proxy" nginx http fastcgi temporary files: "/var/lib/nginx/fastcgi" nginx http uwsgi temporary files: "/var/lib/nginx/uwsgi" nginx http scgi temporary files: "/var/lib/nginx/scgi" Next step: I cd to root and I check the old Nginx folder locations and double checked the 'make' output to see that they are the same: whereis nginx #Output: nginx: /usr/sbin/nginx /etc/nginx /usr/share/nginx NOTE: Not sure about the '/usr/sbin/nginx' - Possible issue??? Next I copy the old /etc/nginx/nginx.conf, /etc/nginx/sites-available/default, /etc/nginx/sites-enabled/default, /etc/init.d/nginx to a text file locally for safe keeping to use in the new Nginx server. Then stop the running Nginx server: service nginx stop , verify it's stopped: service --status-all and the output is: [ - ] nginx To verify that there are two Nginx directories, I cd to: cd nginx* and the output is an error indicating there are two nginx folders - Cool Beans! :) Now Install the new Nginx server: cd nginx-1.7.4 make install # INSTALL OUTPUT ######################################## make -f objs/Makefile install make[1]: Entering directory `/home/walkingfish/nginx-1.7.4' test -d '/usr/share/nginx' || mkdir -p '/usr/share/nginx' test -d '/usr/share/nginx/sbin' || mkdir -p '/usr/share/nginx/sbin' test ! -f '/usr/share/nginx/sbin/nginx' || mv '/usr/share/nginx/sbin/nginx' '/usr/share/nginx/sbin/nginx.old' cp objs/nginx '/usr/share/nginx/sbin/nginx' test -d '/etc/nginx' || mkdir -p '/etc/nginx' cp conf/koi-win '/etc/nginx' cp conf/koi-utf '/etc/nginx' cp conf/win-utf '/etc/nginx' test -f '/etc/nginx/mime.types' || cp conf/mime.types '/etc/nginx' cp conf/mime.types '/etc/nginx/mime.types.default' test -f '/etc/nginx/fastcgi_params' || cp conf/fastcgi_params '/etc/nginx' cp conf/fastcgi_params '/etc/nginx/fastcgi_params.default' test -f '/etc/nginx/fastcgi.conf' || cp conf/fastcgi.conf '/etc/nginx' cp conf/fastcgi.conf '/etc/nginx/fastcgi.conf.default' test -f '/etc/nginx/uwsgi_params' || cp conf/uwsgi_params '/etc/nginx' cp conf/uwsgi_params '/etc/nginx/uwsgi_params.default' test -f '/etc/nginx/scgi_params' || cp conf/scgi_params '/etc/nginx' cp conf/scgi_params '/etc/nginx/scgi_params.default' test -f '/etc/nginx/nginx.conf' || cp conf/nginx.conf '/etc/nginx/nginx.conf' cp conf/nginx.conf '/etc/nginx/nginx.conf.default' test -d '/run' || mkdir -p '/run' test -d '/var/log/nginx' || mkdir -p '/var/log/nginx' test -d '/usr/share/nginx/html' || cp -R html '/usr/share/nginx' test -d '/var/log/nginx' || mkdir -p '/var/log/nginx' ######################################################### I copy/create the files that I saved earlier to txt files in sites-available, the config, default and ini files then symlink them to sites-enabled, and so on. And now to start the server: service nginx start And this is where s#!+ hits the fan - Nada. I check to see if Nginx is running with service --status-all and its not. Also with nginx -V and its not installed??? I reboot the system too and still nothing. So I am not sure what is wrong here. The ini was copied over from the old server along with all the other config files after deleting the old files. When I opened the new compiled files, the nginx default data was present so I replaced them with my old original data prior to starting the new server for the first time. Also to be safe, I rm /etc/nginx/sites-enabled/default and symlinked with ln -s /etc/nginx/sites-available/default /etc/nginx/sites-enabled/default with no errors and I verified that the data was in the sites-enabled/default file. I don't think the server really/fully installed because of the nginx -V result: The program 'nginx' can be found in the following packages: * nginx-core * nginx-extras * nginx-full * nginx-light * nginx-naxsi Try: apt-get install <selected package> Do/should I apt-get install nginx-1.7.4 ?? Or what package do I use being that its a custom package and make install earlier did nothing?? If you need to see the conf files I copied over from the old to the custom server, LMK and I'll post them. Again your help here would be appreciated!

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• Mac OS Snow Leopard freezes

  - by lydonchandra

  I got this error: Timexxxx In 'CFPasteboardCopyData', file /SourceCache/CF/CF-550.13/AppServices.subproj/CFPasteboard.c, line 1951, during lock, spin lock 0x15457a0c8 has value 0xf0000000, which is neither locked nor unlocked. The memory has been smashed. My Mac freezes except the mouse and keyboard. What is happening and how can I prevent this from happening in the future?

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• Explanation of the init.d/scripts Fedora

  - by Shahmir Javaid

  Below is a copy of vsftpd, i need some explanations of some of the scripts mentioned below in this script: #!/bin/bash # ### BEGIN INIT INFO # Provides: vsftpd # Required-Start: $local_fs $network $named $remote_fs $syslog # Required-Stop: $local_fs $network $named $remote_fs $syslog # Short-Description: Very Secure Ftp Daemon # Description: vsftpd is a Very Secure FTP daemon. It was written completely from # scratch ### END INIT INFO # vsftpd This shell script takes care of starting and stopping # standalone vsftpd. # # chkconfig: - 60 50 # description: Vsftpd is a ftp daemon, which is the program \ # that answers incoming ftp service requests. # processname: vsftpd # config: /etc/vsftpd/vsftpd.conf # Source function library. . /etc/rc.d/init.d/functions # Source networking configuration. . /etc/sysconfig/network RETVAL=0 prog="vsftpd" start() { # Start daemons. # Check that networking is up. [ ${NETWORKING} = "no" ] && exit 1 [ -x /usr/sbin/vsftpd ] || exit 1 if [ -d /etc/vsftpd ] ; then CONFS=`ls /etc/vsftpd/*.conf 2>/dev/null` [ -z "$CONFS" ] && exit 6 for i in $CONFS; do site=`basename $i .conf` echo -n $"Starting $prog for $site: " daemon /usr/sbin/vsftpd $i RETVAL=$? echo if [ $RETVAL -eq 0 ]; then touch /var/lock/subsys/$prog break else if [ -f /var/lock/subsys/$prog ]; then RETVAL=0 break fi fi done else RETVAL=1 fi return $RETVAL } stop() { # Stop daemons. echo -n $"Shutting down $prog: " killproc $prog RETVAL=$? echo [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$prog return $RETVAL } # See how we were called. case "$1" in start) start ;; stop) stop ;; restart|reload) stop start RETVAL=$? ;; condrestart|try-restart|force-reload) if [ -f /var/lock/subsys/$prog ]; then stop start RETVAL=$? fi ;; status) status $prog RETVAL=$? ;; *) echo $"Usage: $0 {start|stop|restart|try-restart|force-reload|status}" exit 1 esac exit $RETVAL Question I What the hell is the difference between the && and || signs in the below commands, and is it just an easy way to do a simple if check or is it completely different to a if[..something..]; then ..something.. fi: # Check that networking is up. [ ${NETWORKING} = "no" ] && exit 1 [ -x /usr/sbin/vsftpd ] || exit 1 Question II i get what -eq and -gt is (equal to, greater than) but is there a simple website that explains what -x, -d and -f are? Any help would be apreciated Running Fedora 12 on my OS. Script copied from /etc/init.d/vsftpd Question III It says required starts are $local_fs $network $named $remote_fs $syslog but i cant see any where it checks for those.

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• Backing up MySQL DB wtih mixture of innodb and myisam tables

  - by madphp

  I have a large database (almost 1GB) and it has a mixture of innodb and myisam tables. Does anyone have any general tips when backing it up or more specifically the commands i should send to mysqldump. I see that i should lock myisam tables, and that single transactions for innodb, but what if i have both. Also, what is actually happening when i lock an entire (very big) table on a production database.

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• Change Logon DPI setting in Windows 8.1

  - by jmc302005

  I love how M$ keeps making decisions for me about how I want my desktop to look. Now they have added per-user dpi settings. The problem this has created is that there is no adjustable dpi setting for the Lock/Logon screen. Let me explain. you can change the dpi setting to be the same across all displays and this does affect the icons and font on the lock/logon screen. However it does not affect any app/program that can run on the lock/logon screen. Ex. I use a 44" flat screen tv for my monitor on my desktop. Big enough for me to sit in my recliner and use my comp. But I don't have a wireless keyboard. And it sucks having the wire from the keyboard running across the floor. Plus I really don't want to keep a keyboard next to me. So I use the on screen keyboard for logging in and quick typing (search, web address, etc.) So the problem is that with the new dpi setup my on screen keyboard takes up nearly half the screen. Does M$ think we are all blind? Oh no I remember they think desktops should look like tablets and phones. I tried looking through the registry to see if I could find a setting for it. In the key HKEY_USERS.DEFAULT\Control Panel\Desktop there is a string value named "LogicalDPIOverride" with a value of -1. I have a feeling this is where I can fix the issue. I tried changing the value to 0 and to 1 with no change in the result. Instead I noticed that after logging out and back in the -1 value was back in the registry. So now M$ has also added a way for us to not be able to change a setting in the registry. They are making it harder and harder for us power users to be able to do anything with the settings in windows. Soon we will all have the same exact Windows with absolutely no customization. ok sorry for the quick rant. The real question here is. How can I change this defualt dpi crap? Can I use the LogPixels string that worked for dpi in Windows 7? Here are 2 Screen shots 1 of the Lock Screen and 1 of the Logon Screen http://i.imgur.com/6RM5ufE.jpg http://i.imgur.com/cnY5bmm.jpg Please any help will be appreciated.

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• A proper way to create non-interactive accounts?

  - by AndreyT

  In order to use password-protected file sharing in a basic home network I want to create a number of non-interactive user accounts on a Windows 8 Pro machine in addition to the existing set of interactive accounts. The users that corresponds to those extra accounts will not use this machine interactively, so I don't want their accounts to be available for logon and I don't want their names to appear on welcome screen. In older versions of Windows Pro (up to Windows 7) I did this by first creating the accounts as members of "Users" group, and then including them into "Deny logon locally" list in Local Security Policy settings. This always had the desired effect. However, my question is whether this is the right/best way to do it. The reason I'm asking is that even though this method works in Windows 8 Pro as well, it has one little quirk: interactive users from "User" group are still able to see these extra user names when they go to the Metro screen and hit their own user name in the top-right corner (i.e. open "Sign out/Lock" menu). The command list that drops out contains "Sign out" and "Lock" commands as well as the names of other users (for "switch user" functionality). For some reason that list includes the extra users from "Deny logon locally" list. It is interesting to note that this happens when the current user belongs to "Users" group, but it does not happen when the current user is from "Administrators". For example, let's say I have three accounts on the machine: "Administrator" (from "Administrators", can logon locally), "A" (from "Users", can logon locally), "B" (from "Users", denied logon locally). When "Administrator" is logged in, he can only see user "A" listed in his Metro "Sign out/Lock" menu, i.e. all works as it should. But when user "A" is logged in, he can see both "Administrator" and user "B" in his "Sign out/Lock" menu. Expectedly, in the above example trying to switch from user "A" to user "B" by hitting "B" in the menu does not work: Windows jumps to welcome screen that lists only "Administrator" and "A". Anyway, on the surface this appears to be an interface-level bug in Windows 8. However, I'm wondering if going through "Deny logon locally" setting is the right way to do it in Windows 8. Is there any other way to create a hidden non-interactive user account?

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• Delete set of files using find command

  - by Dave Jarvis

  Background Delete a set of files, scattered across different directories. Problem The following code does not work (the unescaped | causes issues); for %i in (dir /s/b | find "lock") do echo del %i Question Without writing a batch file, how would you delete all files named "lock" (i.e., found using the find command) within the current directory and all subdirectories (including hidden directories)? Thank you!

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• pre-commit hook in svn: could not be translated from the native locale to UTF-8

  - by Alexandre Moraes

  Hi everybody, I have a problem with my pre-commit hook. This hook test if a file is locked when the user commits. When a bad condition happens, it should output that the another user is locking this file or if nobody is locking, it should show "you are not locking this file message (file´s name)". The error happens when the file´s name has some latin character like "ç" and tortoise show me this in the output. Commit failed (details follow): Commit blocked by pre-commit hook (exit code 1) with output: [Erro output could not be translated from the native locale to UTF-8.] Do you know how can I solve this? Thanks, Alexandre My shell script is here: #!/bin/sh REPOS="$1" TXN="$2" export LANG="en_US.UTF-8" /app/svn/hooks/ensure-has-need-lock.pl "$REPOS" "$TXN" if [ $? -ne 0 ]; then exit 1; fi exit 0 And my perl is here: !/usr/bin/env perl #Turn on warnings the best way depending on the Perl version. BEGIN { if ( $] >= 5.006_000) { require warnings; import warnings; } else { $^W = 1; } } use strict; use Carp; &usage unless @ARGV == 2; my $repos = shift; my $txn = shift; my $svnlook = "/usr/local/bin/svnlook"; my $user; my $ok = 1; foreach my $program ($svnlook) { if (-e $program) { unless (-x $program) { warn "$0: required program $program' is not executable, ", "edit $0.\n"; $ok = 0; } } else { warn "$0: required program $program' does not exist, edit $0.\n"; $ok = 0; } } exit 1 unless $ok; unless (-e $repos){ &usage("$0: repository directory $repos' does not exist."); } unless (-d $repos){ &usage("$0: repository directory $repos' is not a directory."); } foreach my $user_tmp (&read_from_process($svnlook, 'author', $repos, '-t', $txn)) { $user = $user_tmp; } my @errors; foreach my $transaction (&read_from_process($svnlook, 'changed', $repos, '-t', $txn)){ if ($transaction =~ /^U. (.*[^\/])$/){ my $file = $1; my $err = 0; foreach my $locks (&read_from_process($svnlook, 'lock', $repos, $file)){ $err = 1; if($locks=~ /Owner: (.*)/){ if($1 != $user){ push @errors, "$file : You are not locking this file!"; } } } if($err==0){ push @errors, "$file : You are not locking this file!"; } } elsif($transaction =~ /^D. (.*[^\/])$/){ my $file = $1; my $tchan = &read_from_process($svnlook, 'lock', $repos, $file); foreach my $locks (&read_from_process($svnlook, 'lock', $repos, $file)){ push @errors, "$1 : cannot delete locked Files"; } } elsif($transaction =~ /^A. (.*[^\/])$/){ my $needs_lock; my $path = $1; foreach my $prop (&read_from_process($svnlook, 'proplist', $repos, '-t', $txn, '--verbose', $path)){ if ($prop =~ /^\s*svn:needs-lock : (\S+)/){ $needs_lock = $1; } } if (not $needs_lock){ push @errors, "$path : svn:needs-lock is not set. Pleas ask TCC for support."; } } } if (@errors) { warn "$0:\n\n", join("\n", @errors), "\n\n"; exit 1; } else { exit 0; } sub usage { warn "@_\n" if @_; die "usage: $0 REPOS TXN-NAME\n"; } sub safe_read_from_pipe { unless (@_) { croak "$0: safe_read_from_pipe passed no arguments.\n"; } print "Running @_\n"; my $pid = open(SAFE_READ, '-|'); unless (defined $pid) { die "$0: cannot fork: $!\n"; } unless ($pid) { open(STDERR, ">&STDOUT") or die "$0: cannot dup STDOUT: $!\n"; exec(@_) or die "$0: cannot exec @_': $!\n"; } my @output; while (<SAFE_READ>) { chomp; push(@output, $_); } close(SAFE_READ); my $result = $?; my $exit = $result >> 8; my $signal = $result & 127; my $cd = $result & 128 ? "with core dump" : ""; if ($signal or $cd) { warn "$0: pipe from @_' failed $cd: exit=$exit signal=$signal\n"; } if (wantarray) { return ($result, @output); } else { return $result; } } sub read_from_process { unless (@_) { croak "$0: read_from_process passed no arguments.\n"; } my ($status, @output) = &safe_read_from_pipe(@_); if ($status) { if (@output) { die "$0: @_' failed with this output:\n", join("\n", @output), "\n"; } else { die "$0: @_' failed with no output.\n"; } } else { return @output; } }

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• A question about some code from TBB book, Thanks.

  - by Jackie

  I am reading the book: Intel Threading Building Blocks. I often have difficulties understanding them. For example,the following code is from the book(page 112): Node* AllocateNode() { Node* n; FreeListMutexType::scoped_lock lock; lock.acquire(FreeListMutex); n=FreeList; if(n) Freelist=n->next; lock.release(); if(!n) n=new Node(); return n; } There is other introduction regarding this code. I can not understand it. What does it means? How can I understand this book better? Thanks.

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• MySQL configuration that allows for locking many tables?

  - by Floyd Bonne

  I need to do a MySQLDump on a DB with ~700 tables and when I try with my current configuration, I get an error: mysqldump: Got error: 1016: Can't open file: './my_db/content_node_field_instance.frm' (errno: 24) when using LOCK TABLES Searching around I've found that this happens because it tries to lock all tables and fails because they are "too many". I know I can try lock-tables=no and get a dump, but this way my DB might be in an inconsistent state. So, does anyone know what is the MySQL configuration setting I need to change in order to be able to do the locking I need? I'm running 5.1.37-1ubuntu5.1 with MyISAM. Thanks!

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• Monitor.Wait, Pulse - When worker thread should conditionally behave as an actual worker thread

  - by Griever

  My particular scenario: - Main thread starts a worker thread. - Main thread needs to block itself until either worker thread is completed (yeah funny) or worker thread itself informs main thread to go on Alright, so what I did in main thread: wokerThread.Start(lockObj); lock(lockObj) Monitor.Wait(lockObj); Somewhere in worker thread: if(mainThreadShouldGoOn) lock(lockObj) Monitor.Pulse(lockObj); Also, at the end of worker thread: lock(lockObj) Monitor.Pulse(lockObj); So far, it's working perfect. But is it a good solution? Is there a better one?

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