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  • Linux IO scheduler on databases with RAID

    - by Raghu
    Hi, I have a linux database(MySQL) server(Dell 2950) with a 6-disk RAID 10. The default IO scheduler on it is CFQ. However, from what I have read and heard, there is no need for a scheduler like CFQ when reordering/scheduling is also done by underlying RAID controller; on the contrary since it does not account underlying RAID configuration into account performance may actually degrade with CFQ. The primary concern is to reduce CPU usage and improve throughput. Also, I have seen recommendations of using noop/deadline IO scheduler for databases primarily because of the nature of their R/W access.

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  • Silverlight changes the io.Stream to byte[]

    - by Sai
    I have created a WCF service for uploading images , which accepts System.IO.Stream as input parameter and am using streaming. When I added the service reference in Silverlight project then it automatically changed the parameter of my WCF method from System.IO.Stream to byte[]. Can anyone suggest if there is a way around this so that I can get System.IO.Stream type rather than byte[]. Thanks in advance

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  • Delphi - How can I prevent the main form capturing keystrokes in a TMemo on another non-modal form?

    - by user89691
    I have an app that opens a non-modal form from the main form. The non-modal form has a TMemo on it. The main form menu uses "space" as one of its accelerator characters. When the non-modal form is open and the memo has focus, every time I try to enter a space into the memo on the non-modal form, the main form event for the "space" shortcut fires! I have tried turning MainForm.KeyPreview := false while the other form is open but no dice. Any ideas? TIA

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  • Fragment method and socket.io

    - by Tolgay Toklar
    I have a method,this method updates an array list in fragment.I can call this method in main activity like this public void getFromUser(String message) { addMessageToFragment("ok"); } public void addMessageToFragment(String message) { Log.w("Step 1",message); frgObj.addMessageToList("asd"); } getFromUser is calling from fragment(when user presses the button) this is working as well.But I am using socket.io in my app,when I try to call this method from socket.io,app is not working. public void on(String event, IOAcknowledge ack, Object... args) { try{ addMessageToFragment("ok"); } catch (JSONException e) {} } When this callback function calls,app is giving this errors: 08-19 11:57:24.813: W/System.err(4962): io.socket.SocketIOException: Exception was thrown in on(String, JSONObject[]). 08-19 11:57:24.813: W/System.err(4962): Message was: 5:::{"name":"listele","args":[{"mesaj":"123","gonderen":"781722165-tolgay007-DKSMIcIYGahPuKXriM83","alici":"tolgay007","blck_id":"781722165-tolgay007","out_username":"Anony-781722","ars_status":1,"longinf":"3aqghef","a_status":1}]} 08-19 11:57:24.813: W/System.err(4962): at io.socket.IOConnection.transportMessage(IOConnection.java:702) 08-19 11:57:24.813: W/System.err(4962): at io.socket.WebsocketTransport.onMessage(WebsocketTransport.java:82) 08-19 11:57:24.813: W/System.err(4962): at org.java_websocket.client.WebSocketClient.onWebsocketMessage(WebSocketClient.java:361) 08-19 11:57:24.813: W/System.err(4962): at org.java_websocket.WebSocketImpl.deliverMessage(WebSocketImpl.java:565) 08-19 11:57:24.813: W/System.err(4962): at org.java_websocket.WebSocketImpl.decodeFrames(WebSocketImpl.java:331) 08-19 11:57:24.813: W/System.err(4962): at org.java_websocket.WebSocketImpl.decode(WebSocketImpl.java:152) 08-19 11:57:24.813: W/System.err(4962): at org.java_websocket.client.WebSocketClient.interruptableRun(WebSocketClient.java:247) 08-19 11:57:24.823: W/System.err(4962): at org.java_websocket.client.WebSocketClient.run(WebSocketClient.java:193) 08-19 11:57:24.823: W/System.err(4962): at java.lang.Thread.run(Thread.java:841) 08-19 11:57:24.823: W/System.err(4962): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6094) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewRootImpl.focusableViewAvailable(ViewRootImpl.java:2800) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.ViewGroup.focusableViewAvailable(ViewGroup.java:650) 08-19 11:57:24.823: W/System.err(4962): at android.view.View.setFlags(View.java:8878) 08-19 11:57:24.823: W/System.err(4962): at android.view.View.setFocusableInTouchMode(View.java:6114) 08-19 11:57:24.823: W/System.err(4962): at android.widget.AdapterView.checkFocus(AdapterView.java:718) 08-19 11:57:24.823: W/System.err(4962): at android.widget.AdapterView$AdapterDataSetObserver.onChanged(AdapterView.java:813) 08-19 11:57:24.823: W/System.err(4962): at android.widget.AbsListView$AdapterDataSetObserver.onChanged(AbsListView.java:6280) 08-19 11:57:24.823: W/System.err(4962): at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:37) 08-19 11:57:24.823: W/System.err(4962): at android.widget.BaseAdapter.notifyDataSetChanged(BaseAdapter.java:50) 08-19 11:57:24.823: W/System.err(4962): at android.widget.ArrayAdapter.notifyDataSetChanged(ArrayAdapter.java:286) 08-19 11:57:24.823: W/System.err(4962): at com.impact.ribony.ConversationFragment.addMessageToList(ConversationFragment.java:91) 08-19 11:57:24.823: W/System.err(4962): at com.impact.ribony.MainActivity.addMessageToFragment(MainActivity.java:344) 08-19 11:57:24.823: W/System.err(4962): at com.impact.ribony.MainActivity$2.on(MainActivity.java:183) 08-19 11:57:24.823: W/System.err(4962): at io.socket.IOConnection.on(IOConnection.java:908) 08-19 11:57:24.883: W/System.err(4962): at io.socket.IOConnection.transportMessage(IOConnection.java:697) I didn't understand this error.What can be cause this error ?

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  • NULL pointer dereference in swiotlb_unmap_sg_attrs() on disk IO

    - by Inductiveload
    I'm getting an error I really don't understand when reading or writing files using a PCIe block device driver. I seem to be hitting an issue in swiotlb_unmap_sg_attrs(), which appears to be doing a NULL dereference of the sg pointer, but I don't know where this is coming from, as the only scatterlist I use myself is allocated as part of the device info structure and persists as long as the driver does. There is a stacktrace to go with the problem. It tends to vary a bit in exact details, but it always crashes in swiotlb_unmap_sq_attrs(). I think it's likely I have a locking issue, as I am not sure how to handle the locks around the IO functions. The lock is already held when the request function is called, I release it before the IO functions themselves are called, as they need an (MSI) IRQ to complete. The IRQ handler updates a "status" value, which the IO function is waiting for. When the IO function returns, I then take the lock back up and return to request queue handling. The crash happens in blk_fetch_request() during the following: if (!__blk_end_request(req, res, bytes)){ printk(KERN_ERR "%s next request\n", DRIVER_NAME); req = blk_fetch_request(q); } else { printk(KERN_ERR "%s same request\n", DRIVER_NAME); } where bytes is updated by the request handler to be the total length of IO (summed length of each scatter-gather segment).

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  • Introducing functional programming constructs in non-functional programming languages

    - by Giorgio
    This question has been going through my mind quite a lot lately and since I haven't found a convincing answer to it I would like to know if other users of this site have thought about it as well. In the recent years, even though OOP is still the most popular programming paradigm, functional programming is getting a lot of attention. I have only used OOP languages for my work (C++ and Java) but I am trying to learn some FP in my free time because I find it very interesting. So, I started learning Haskell three years ago and Scala last summer. I plan to learn some SML and Caml as well, and to brush up my (little) knowledge of Scheme. Well, a lot of plans (too ambitious?) but I hope I will find the time to learn at least the basics of FP during the next few years. What is important for me is how functional programming works and how / whether I can use it for some real projects. I have already developed small tools in Haskell. In spite of my strong interest for FP, I find it difficult to understand why functional programming constructs are being added to languages like C#, Java, C++, and so on. As a developer interested in FP, I find it more natural to use, say, Scala or Haskell, instead of waiting for the next FP feature to be added to my favourite non-FP language. In other words, why would I want to have only some FP in my originally non-FP language instead of looking for a language that has a better support for FP? For example, why should I be interested to have lambdas in Java if I can switch to Scala where I have much more FP concepts and access all the Java libraries anyway? Similarly: why do some FP in C# instead of using F# (to my knowledge, C# and F# can work together)? Java was designed to be OO. Fine. I can do OOP in Java (and I would like to keep using Java in that way). Scala was designed to support OOP + FP. Fine: I can use a mix of OOP and FP in Scala. Haskell was designed for FP: I can do FP in Haskell. If I need to tune the performance of a particular module, I can interface Haskell with some external routines in C. But why would I want to do OOP with just some basic FP in Java? So, my main point is: why are non-functional programming languages being extended with some functional concept? Shouldn't it be more comfortable (interesting, exciting, productive) to program in a language that has been designed from the very beginning to be functional or multi-paradigm? Don't different programming paradigms integrate better in a language that was designed for it than in a language in which one paradigm was only added later? The first explanation I could think of is that, since FP is a new concept (it isn't new at all, but it is new for many developers), it needs to be introduced gradually. However, I remember my switch from imperative to OOP: when I started to program in C++ (coming from Pascal and C) I really had to rethink the way in which I was coding, and to do it pretty fast. It was not gradual. So, this does not seem to be a good explanation to me. Or can it be that many non-FP programmers are not really interested in understanding and using functional programming, but they find it practically convenient to adopt certain FP-idioms in their non-FP language? IMPORTANT NOTE Just in case (because I have seen several language wars on this site): I mentioned the languages I know better, this question is in no way meant to start comparisons between different programming languages to decide which is better / worse. Also, I am not interested in a comparison of OOP versus FP (pros and cons). The point I am interested in is to understand why FP is being introduced one bit at a time into existing languages that were not designed for it even though there exist languages that were / are specifically designed to support FP.

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  • Business person turned into coder? How and why? Inspire the non-technical.

    - by huisjames
    I graduated with a Business degree. Two years later, I finally realized the power of programming - the power to "invent." I wish I realized this in high school. Nevertheless, I tried to self-teach C# but found it difficult. Then I pivoted to learn PHP two months ago and I have been able to build things I thought was beyond my abilities. Has anyone had the same experience? Or self-taught programming? What lessons did you learn?

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  • Why do System.IO.Log SequenceNumbers have variable length?

    - by Doug McClean
    I'm trying to use the System.IO.Log features to build a recoverable transaction system. I understand it to be implemented on top of the Common Log File System. The usual ARIES approach to write-ahead logging involves persisting log record sequence numbers in places other than the log (for example, in the header of the database page modified by the logged action). Interestingly, the documentation for CLFS says that such sequence numbers are always 64-bit integers. Confusingly, however, the .Net wrapper around those SequenceNumbers can be constructed from a byte[] but not from a UInt64. It's value can also be read as a byte[], but not as a UInt64. Inspecting the implementation of SequenceNumber.GetBytes() reveals that it can in fact return arrays of either 8 or 16 bytes. This raises a few questions: Why do the .Net sequence numbers differ in size from the CLFS sequence numbers? Why are the .Net sequence numbers variable in length? Why would you need 128 bits to represent such a sequence number? It seems like you would truncate the log well before using up a 64-bit address space (16 exbibytes, or around 10^19 bytes, more if you address longer words)? If log sequence numbers are going to be represented as 128 bit integers, why not provide a way to serialize/deserialize them as pairs of UInt64s instead of rather-pointlessly incurring heap allocations for short-lived new byte[]s every time you need to write/read one? Alternatively, why bother making SequenceNumber a value type at all? It seems an odd tradeoff to double the storage overhead of log sequence numbers just so you can have an untruncated log longer than a million terabytes, so I feel like I'm missing something here, or maybe several things. I'd much appreciate it if someone in the know could set me straight.

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  • 10035 error on a blocking socket

    - by Andrew
    Does anyone have any idea what could cause a 10035 error (EWOULDBLOCK) when reading on a blocking socket with a timeout? This is under Windows XP using the .NET framework version 3.5 socket library. I've never managed to get this myself, but one of my colleagues is getting it all the time. He's sending reasonably large amounts of data to a much slower device and then waiting for a response, which often gives a 10035 error. I'm wondering if there could be issues with TCP buffers filling up, but in that case I would expect the read to wait or timeount. The socket is definitely blocking, not non-blocking.

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  • SQL SERVER – PREEMPTIVE and Non-PREEMPTIVE – Wait Type – Day 19 of 28

    - by pinaldave
    In this blog post, we are going to talk about a very interesting subject. I often get questions related to SQL Server 2008 Book-Online about various Preemptive wait types. I got a few questions asking what these wait types are and how they could be interpreted. To get current wait types of the system, you can read this article and run the script: SQL SERVER – DMV – sys.dm_os_waiting_tasks and sys.dm_exec_requests – Wait Type – Day 4 of 28. Before we continue understanding them, let us study first what PREEMPTIVE and Non-PREEMPTIVE waits in SQL Server mean. PREEMPTIVE: Simply put, this wait means non-cooperative. While SQL Server is executing a task, the Operating System (OS) interrupts it. This leads to SQL Server to involuntarily give up the execution for other higher priority tasks. This is not good for SQL Server as it is a particular external process which makes SQL Server to yield. This kind of wait can reduce the performance drastically and needs to be investigated properly. Non-PREEMPTIVE: In simple terms, this wait means cooperative. SQL Server manages the scheduling of the threads. When SQL Server manages the scheduling instead of the OS, it makes sure its own priority. In this case, SQL Server decides the priority and one thread yields to another thread voluntarily. In the earlier version of SQL Server, there was no preemptive wait types mentioned and the associated task status with them was marked as suspended. In SQL Server 2005, preemptive wait types were not listed as well, but their associated task status was marked as running. In SQL Server 2008, preemptive wait types are properly listed and their associated task status is also marked as running. Now, SQL Server is in Non-Preemptive mode by default and it works fine. When CLR, extended Stored Procedures and other external components run, they run in Preemptive mode, leading to the creation of these wait types. There are a wide variety of preemptive wait types. If you see consistent high value in the Preemptive wait types, I strongly suggest that you look into the wait type and try to know the root cause. If you are still not sure, you can send me an email or leave a comment about it and I will do my best to help you reduce this wait type. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • RabbitMQ and persistence (blocking writes?)

    - by daharon
    I want to create a RabbitMQ server on a virtual machine (VMware) to be used in production. It will contain persistent queues. I'm wondering if it is a bad idea to store the server on a NAS that's accessed over NFS. Basically my questions are: Will RabbitMQ's writes be blocking? Will the entire queue's operation halt on a write? How much performance degradation should I expect when persisting over NFS?

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  • Non-Unicode strings in VB.NET? (7 replies)

    I've been reading the MSDN documentation on the System.Char and System.String types and they mention Unicode throughout without even mentioning non Unicode versions. How do I get a gool 'ol one byte char and non Unicode string in .NET? Thanks, Alain

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  • Non-Unicode strings in VB.NET? (7 replies)

    I've been reading the MSDN documentation on the System.Char and System.String types and they mention Unicode throughout without even mentioning non Unicode versions. How do I get a gool 'ol one byte char and non Unicode string in .NET? Thanks, Alain

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  • Programming and Ubiquitous Language (DDD) in a non-English domain

    - by Sandor Drieënhuizen
    I know there are some questions already here that are closely related to this subject but none of them take Ubiquitous Language as the starting point so I think that justifies this question. For those who don't know: Ubiquitous Language is the concept of defining a (both spoken and written) language that is equally used across developers and domain experts to avoid inconsistencies and miscommunication due to translation problems and misunderstanding. You will see the same terminology show up in code, conversations between any team member, functional specs and whatnot. So, what I was wondering about is how to deal with Ubiquitous Language in non-English domains. Personally, I strongly favor writing programming code in English completely, including comments but ofcourse excluding constants and resources. However, in a non-English domain, I'm forced to make a decision either to: Write code reflecting the Ubiquitous Language in the natural language of the domain. Translate the Ubiquitous Language to English and stop communicating in the natural language of the domain. Define a table that defines how the Ubiquitous Language translates to English. Here are some of my thoughts based on these options: 1) I have a strong aversion against mixed-language code, that is coding using type/member/variable names etc. that are non-English. Most programming languages 'breathe' English to a large extent and most of the technical literature, design pattern names etc. are in English as well. Therefore, in most cases there's just no way of writing code entirely in a non-English language so you end up with mixed languages anyway. 2) This will force the domain experts to start thinking and talking in the English equivalent of the UL, something that will probably not come naturally to them and therefore hinders communication significantly. 3) In this case, the developers communicate with the domain experts in their native language while the developers communicate with each other in English and most importantly, they write code using the English translation of the UL. I'm sure I don't want to go for the first option and I think option 3 is much better than option 2. What do you think? Am I missing other options? UPDATE Today, about year later, having dealt with this issue on a daily basis, I have to say that option 3 has worked out pretty well for me. It wasn't as tedious as I initially feared and translating in real time while talking to the client wasn't a problem either. I also found the following advantages to be true, based on my experience. Translating the UL makes you pay more attention to defining the UL and even the domain itself, especially when you don't know how to translate a term and you have to start looking through dictionaries etc. This has even caused me to reconsider domain modeling decisions a few times. It helps you make your knowledge of the English language more profound. Obviously, your code is much more pleasant to look at instead of being a mind boggling obscenity.

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  • How to handle non-existent subdirectories?

    - by Question Overflow
    I have a dynamic website with friendly URLs. Example: Instead of /user.php?id=123, I have /user/123 Instead of /index.php?category=fishes, I have /fishes But, how do I handle non-existent subdirectories such as /about/123? Currently it gives a 200 success instead of a 404 not found error. Is there a way to deal with non-existent subdirectories in Apache config and at the same time allow for friendly URLs? Or do I have to handle this individually for each PHP script?

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  • Want to use apache, ISP blocking port 80

    - by Will
    I am attempting to set up a small web server on my home network, but my ISP is blocking incoming port 80 ( and no, i'm not paying $50/month extra for them to unblock it). I am looking for some ways around this, obviously I can change the port # but I don't find this ideal. really appreciate any ideas for this

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  • Fast (non-blocking) way to transfer many files to another server

    - by Nyxynyx
    I am currently attempting to transfer over 1 million files from one server to another. Using wget, it seems to be extremely slow, probably because it starts a new transfer after the previous one has been completed. Question: Is there a faster non-blocking (asynchronous) way to do the transfer? I do not have enough space on the first server to compress the files into tar.gz and transferring them over. Thanks!

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  • Blocking specific IP requests

    - by user42908
    Hi, I own a VPS running Ubuntu with Apache stuff. Recently I am getting continous request from IP static-195.22.94.120.addr.tdcsong.se.54303 : 12337 I already installed the 'arno-iptables-firewall'. Have iptables blocking 195.22.94.120 Still then I get the request from that IP if i see via tcpdump. May I know what else i can do to protect my VPS? Thank you.

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  • xp_cmdshell for Non-System Admin Individuals

    There may be times when you want to allow non-System Admin logins to be able to execute the xp_cmdshell extended stored procedure. In this articleGreg Larson will show you how to setup xp_cmdshell so non-System Admins can use this extended stored procedure. ‘10 Tips for Efficient Disaster Recovery’Steve Jones gives the final lesson in the ‘Top 5 Hard-earned Lessons of a DBA’. Read now and learn from the best.

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  • Blocking IP addresses Load Balanced Cluster

    - by Dom
    Hi We're using HAproxy as a front end load balancer / proxy and are looking for solutions to block random IP addresses from jamming the cluster. Is anyone familiar with a conf for HAProxy that can block requests if they exceed a certain threshold from a single IP within a defined period of time. Or can anyone suggest a software solution which could be placed in front of HAProxy to handle this kind of blocking. Thanks Dom--

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