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  • License for Opensource project

    - by asterisk
    I am newbie in the open source community world. I am planning to develop a open source project, hosted on github. The project would be using other open source components like- NHibernate, FNH, Log4net, CommonLibrary, Autofac, Quartz.Net Scheduler etc etc My questions are: Would there be any restrictions on using above OSS components? for example: I plan to use MIT license, but Quartz.Net Scheduler uses Apache license, would there be any restrictions? How do I get a license for my own project? Do I need to register my project somewhere? What is the best practice to mention credits to the OSS compoenents used? Many thanks,

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  • Tuning Default WorkManager - Advantages and Disadvantages

    - by Murali Veligeti
    Before discussing on Tuning Default WorkManager, lets have a brief introduction on What is Default WorkManger Before Weblogic Server 9.0 release, we had the concept of Execute Queues. WebLogic Server (before WLS 9.0), processing was performed in multiple execute queues. Different classes of work were executed in different queues, based on priority and ordering requirements, and to avoid deadlocks. In addition to the default execute queue, weblogic.kernel.default, there were pre-configured queues dedicated to internal administrative traffic, such as weblogic.admin.HTTP and weblogic.admin.RMI.Users could control thread usage by altering the number of threads in the default queue, or configure custom execute queues to ensure that particular applications had access to a fixed number of execute threads, regardless of overall system load. From WLS 9.0 release onwards WebLogic Server uses is a single thread pool (single thread pool which is called Default WorkManager), in which all types of work are executed. WebLogic Server prioritizes work based on rules you define, and run-time metrics, including the actual time it takes to execute a request and the rate at which requests are entering and leaving the pool.The common thread pool changes its size automatically to maximize throughput. The queue monitors throughput over time and based on history, determines whether to adjust the thread count. For example, if historical throughput statistics indicate that a higher thread count increased throughput, WebLogic increases the thread count. Similarly, if statistics indicate that fewer threads did not reduce throughput, WebLogic decreases the thread count. This new strategy makes it easier for administrators to allocate processing resources and manage performance, avoiding the effort and complexity involved in configuring, monitoring, and tuning custom executes queues. The Default WorkManager is used to handle thread management and perform self-tuning.This Work Manager is used by an application when no other Work Managers are specified in the application’s deployment descriptors. In many situations, the default Work Manager may be sufficient for most application requirements. WebLogic Server’s thread-handling algorithms assign each application its own fair share by default. Applications are given equal priority for threads and are prevented from monopolizing them. The default work-manager, as its name tells, is the work-manager defined by default.Thus, all applications deployed on WLS will use it. But sometimes, when your application is already in production, it's obvious you can't take your EAR / WAR, update the deployment descriptor(s) and redeploy it.The default work-manager belongs to a thread-pool, as initial thread-pool comes with only five threads, that's not much. If your application has to face a large number of hits, you may want to start with more than that.Well, that's quite easy. You have  two option to do so.1) Modify the config.xmlJust add the following line(s) in your server definition : <server> <name>AdminServer</name> <self-tuning-thread-pool-size-min>100</self-tuning-thread-pool-size-min> <self-tuning-thread-pool-size-max>200</self-tuning-thread-pool-size-max> [...] </server> 2) Adding some JVM parameters Add the following system property in setDomainEnv.sh/setDomainEnv.cmd or startWebLogic.sh/startWebLogic.cmd : -Dweblogic.threadpool.MinPoolSize=100 -Dweblogic.threadpool.MaxPoolSize=100 Reboot WLS and see the option has been taken into account . Disadvantage: So far its fine. But here there is an disadvantage in tuning Default WorkManager. Internally Weblogic Server has many work managers configured for different types of work.  if we run out of threads in the self-tuning pool(because of system property -Dweblogic.threadpool.MaxPoolSize) due to being undersized, then important work that WLS might need to do could be starved.  So, while limiting the self-tuning would limit the default WorkManager and internally it also limits all other internal WorkManagers which WLS uses.So the best alternative is to override the default WorkManager that means creating a WorkManager for the Application and assign the WorkManager for the application instead of tuning the Default WorkManager.

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  • C# How do I replace an actual asterisk character (*) in a Regex expression?

    - by fraXis
    Hello, I have a statement: I have a string such as content = "* test *" I want to search and replace it with so when I am done the string contains this: content = "(*) test (*)" My code is: content = Regex.Replace(content, "*", "(*)"); But this causes an error in C# because it thinks that the * is part of the Regular Expressions Syntax. How can I modify this code so it changes all asterisks in my string to (*) instead without causing a runtime error? Thanks.

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  • C++ MySQL++ Delete query statement brain killer question

    - by shauny
    Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • How to play WAV file through Network Paging Interface

    - by BGM
    In our building we have a Viking Paging ZPI-4 Interface for our intercom. The interface receives data from our Asterisk Phone system via a Cisco SPA112 Port Adapter which has it's own IP address on the network and converts digital into analog. Asterisk plays the "5" tone and then allows the user's voice to commence over the connection. Now, what I want to do is to play a wav file over this Viking Paging device using the Cisco Port Adapter. I know how to get Asterisk to do it, but I want to do this without Asterisk. I want some kind of program that can talk to the Cisco Port Adapter and then transmit the wav file into the Viking Paging Device. What kind of program do I need to get or make? Now, I found this link if it helps anyone with ideas. I also found this information, but I'm not sure how to apply it. I also found this, but it involves an arduino. However, I already have the analog-to-digital convertor, and the Viking will handle sending sound over the paging speakers. I just need to know how to send the wav file to the Viking via the Port Adapter. So far, I know my wav file should be formatted as 8bit mono, and I need to send the "5" tone to open the Viking Pager's channel. [update] I am trying to figure out if I can use VLC player to stream to the ipaddress of the Port Adapter. So far I'm not having success with that, and don't even know if it will work. Windows Media Player has a streaming option too. I am thinking that since the Cisco Port Adapter thinks it is a sort of phone, that the only way this can be done is via SIP.

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  • Trying to write priority queue in Java but getting "Exception in thread "main" java.lang.ClassCastEx

    - by Dan
    For my data structure class, I am trying to write a program that simulates a car wash and I want to give fancy cars a higher priority than regular ones using a priority queue. The problem I am having has something to do with Java not being able to type cast "Object" as an "ArrayQueue" (a simple FIFO implementation). What am I doing wrong and how can I fix it? public class PriorityQueue<E> { private ArrayQueue<E>[] queues; private int highest=0; private int manyItems=0; public PriorityQueue(int h) { highest=h; queues = (ArrayQueue[]) new Object[highest+1]; <----problem is here } public void add(E item, int priority) { queues[priority].add(item); manyItems++; } public boolean isEmpty( ) { return (manyItems == 0); } public E remove() { E answer=null; int counter=0; do { if(!queues[highest-counter].isEmpty()) { answer = queues[highest-counter].remove(); counter=highest+1; } else counter++; }while(highest-counter>=0); return answer; } }

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  • How to make a queue switches from FIFO mode to priority mode?

    - by enzom83
    I would like to implement a queue capable of operating both in the FIFO mode and in the priority mode. This is a message queue, and the priority is first of all based on the message type: for example, if the messages of A type have higher priority than the messages of the B type, as a consequence all messages of A type are dequeued first, and finally the messages of B type are dequeued. Priority mode: my idea consists of using multiple queues, one for each type of message; in this way, I can manage a priority based on the message type: just take first the messages from the queue at a higher priority and progressively from lower priority queues. FIFO mode: how to handle FIFO mode using multiple queues? In other words, the user does not see multiple queues, but it uses the queue as if it were a single queue, so that the messages leave the queue in the order they arrive when the priority mode is disabled. In order to achieve this second goal I have thought to use a further queue to manage the order of arrival of the types of messages: let me explain better with the following code snippet. int NUMBER_OF_MESSAGE_TYPES = 4; int CAPACITY = 50; Queue[] internalQueues = new Queue[NUMBER_OF_MESSAGE_TYPES]; Queue<int> queueIndexes = new Queue<int>(CAPACITY); void Enqueue(object message) { int index = ... // the destination queue (ie its index) is chosen according to the type of message. internalQueues[index].Enqueue(message); queueIndexes.Enqueue(index); } object Dequeue() { if (fifo_mode_enabled) { // What is the next type that has been enqueued? int index = queueIndexes.Dequeue(); return internalQueues[index].Dequeue(); } if (priority_mode_enabled) { for(int i=0; i < NUMBER_OF_MESSAGE_TYPES; i++) { int currentQueueIndex = i; if (!internalQueues[currentQueueIndex].IsEmpty()) { object result = internalQueues[currentQueueIndex].Dequeue(); // The following statement is fundamental to a subsequent switching // from priority mode to FIFO mode: the messages that have not been // dequeued (since they had lower priority) remain in the order in // which they were queued. queueIndexes.RemoveFirstOccurrence(currentQueueIndex); return result; } } } } What do you think about this idea? Are there better or more simple implementations?

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  • More useful Sql Server Serivce Broker Queries

    - by ChrisD
    SELECT 'Checking Broker Service Status...' IF (select Top 1 is_broker_enabled from sys.databases where name = 'NWMESSAGE')=1     SELECT ' Broker Service IS Enabled'  -- Should return a 1. ELSE     SELECT '** Broker Service IS DISABLED ***' /* If Is_Broker_enabled returns 0, uncomment and run this code ALTER DATABASE NWMESSAGE SET SINGLE_USER WITH ROLLBACK IMMEDIATE GO Alter Database NWMESSAGE Set enable_broker GO ALTER DATABASE NWDataChannel SET MULTI_USER GO */ SELECT 'Checking For Disabled Queues....' -- ensure the queues are enabled --  0 indicates the queue is disabled. Select '** Receive Queue Disabled: '+name from sys.service_queues where is_receive_enabled = 0 --select [name], is_receive_enabled from sys.service_queues; /*If the queue is disabled, to enable it alter queue QUEUENAME with status=on; – replace QUEUENAME with the name of your queue */ -- Get General information about the queues --select * from sys.service_queues -- Get the message counts in each queue SELECT 'Checking Message Count for each Queue...' select q.name, p.rows from sys.objects as o join sys.partitions as p on p.object_id = o.object_id join sys.objects as q on o.parent_object_id = q.object_id join sys.service_queues sq on sq.name = q.name where p.index_id = 1 -- Ensure all the queue activiation sprocs are present SELECT 'Checking for Activation Stored Procedures....' SELECT  '** Missing Procedure:  '+q.name  From sys.service_queues q Where NOT Exists(Select * from sysobjects where xtype='p' and name='activation_'+q.name) and q.activation_procedure is not null DECLARE @sprocs Table (Name Varchar(2000)) Insert into @sprocs Values ('Echo') Insert into @sprocs Values ('HTTP_POST') Insert into @sprocs Values ('InitializeRecipients') Insert into @sprocs Values ('sp_EnableRecipient') Insert into @sprocs Values ('sp_ProcessReceivedMessage') Insert into @sprocs Values ('sp_SendXmlMessage') SELECT 'Checking for required stored procedures...' SELECT  '** Missing Procedure:  '+s.name  From @sprocs s Where NOT Exists(Select * from sysobjects where xtype='p' and name=s.name) GO -- Check the services Select 'Checking Recipient Message Services...' Select '** Missing Message Service:' + r.RecipientName +'MessageService' From Recipient r Where not exists (Select * from sys.services s where  s.name  COLLATE SQL_Latin1_General_CP1_CI_AS= r.RecipientName+'MessageService') DECLARE @svcs Table (Name Varchar(2000)) Insert into @svcs Values ('XmlMessageSendingService') SELECT  '** Missing Service:  '+s.name  From @svcs s Where NOT Exists(Select * from sys.services where name=s.name COLLATE SQL_Latin1_General_CP1_CI_AS) GO /*** To Test a message send Run: sp_SendXmlMessage  'TSQLTEST', 'CommerceEngine','<Root><Text>Test</Text></Root>' */ Select CAST(message_body as XML) as xml, * From XmlMessageSendingQueue /*** clean out all queues declare @handle uniqueidentifier declare conv cursor for   select conversation_handle from sys.conversation_endpoints open conv fetch next from conv into @handle while @@FETCH_STATUS = 0 Begin    END Conversation @handle with cleanup    fetch next from conv into @handle End close conv deallocate conv ***********************

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  • replace only one variable in web.py templates

    - by Asterisk
    I am passing variable to template in web.py and have the same condition in some places. Like this: $if myvar=="string1": $passed argument1 ............ $if myvar =="striung2": $passed argument2 If say myvar is "string1" and I pass passed = "AAA" then I have AAA argument1 on my page, but the other if statements get replaced by empty string? How to avoid that? I.e. how to leave other statements intact?

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  • MIX 2010 Covert Operations Day 4

    - by GeekAgilistMercenary
    The Microsoft Azure Cloud is looking pretty solid compared to just a few months ago.  The storage mechanisms in the cloud now are blobs, drives, tables, and queues.  Also, not to forget, is SQL Azure.  I won’t dive too much into that, as most will know what SQL Server is, and SQL Azure is pretty much just a hosted SQL Server instance. The blobs are generally geared toward holding binary type data, images and those types of things.  The tables are huge key value type stores.  The drives are VHD, which are virtual hard drives.  The queues are just queues used for workflow and also to store messages back and forth in a queue. These methods are accessible via REST, which makes application development against the storage services extremely easy.  This is a big plus point as REST services are a preferred way to connect and interact with data storage.  It also sets up Silverlight as a prime framework to utilize services. Day 4 I pretty much dedicated to reviewing these cloud services and finishing up work related development.  With that, I'm wrapping up my MIX 2010 blog coverage.  Now back to your regularly scheduled programming. Original entry.

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  • How Do I Enable CUPS Browsing Across A Network?

    - by David Mackintosh
    I have a CUPS server with two print queues defined. Once this was defined, all the CUPS clients on the same subnet could see the two print queues automatically, no problem. Now I have a collection of machines on a separate subnet, reachable from the first subnet by a router. How do I enable CUPS browsing on the second set of machines so that they can see the print queues defined on the first machine? Let's call the server A.B.C.7. The first subnet is A.B.C.0/24. The second subnet is A.B.D.0/24, and there is a router with arms on both networks.

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  • Turn old rack server into a telephone server

    - by Jake Elsley
    I have an old server lying around and I am thinking of using it as an internal telephone server. Its main use would be to set up a 1 to 1 telephone system that could be used internally to connect to different users in different offices. I have looked at software like Asterisk, but it seems that this is mainly for external telephone systems. Is this possible to do with Asterisk (or other software) or is this not possible without involving a VOIP company?

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  • Is it possible to add wildcard serveralias to virtualhost without modifying httpd.conf manually?

    - by Favourite Chigozie Onwuemene
    Is it possible to add wildcard serveralias (example: *.somesite.com) in an apache server without modifying httpd.conf manually? I use a DNS different from my hosting server and i have added asterisk A record to my DNS to point all request like (test.somesite.com,test2.somesite.com) to my hosting servers IP, but i don't see anyway of adding asterisk serveraliases to apache httpd.conf file in my cpanel. Pls is there a solution?

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  • Application file (Real world example)

    - by aalhamad
    Looking for guidelines to create application file. For example I have an application that store user input into a file (Textbox, DataGrid, ListBox etc). I'm looking for WPF-C# implementation. I would like to have the following: If user edit a any form(Textbox, etc) an asterisk is displayed to the window title. When window is closed and asterisk is still there, a promote "Would you like to save changes" appears. If then saved the asterisk disappear. What do real applications use to create their application file? (Note: I'm not looking for database saving or SQL) I'm just looking for hints and guidelines. Thank you.

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  • How To Apply Online For New Passport Or Renewal Of Your Passport [Indian Websites]

    - by Gopinath
    Are you bored wasting time and energy in standing lengthy queues at Passport offices in India to apply a new passport or renew it? Indian Government Passport Office has an online portal that lets you apply for new passport or renew your expiring passport by filling details online. By filling the details online you can complete half of the required formalities sitting at home and the rest of tasks like submitting required proofs, paying money etc at your regional passport office. Saves lot of time. Advantages of Applying For Passport Online Ask anyone who already obtained a passport by visiting the passport office, they will narrate stories of spending long time in queues. In certain office, the length of queues may require you to stand 3 to 4 hours. And sometimes by the time your turn comes, the officers may break for lunch, coffee or the day if your time is very bad. The main advantage of applying for passport using this online portal is – we can skip the process of standing in long queues to obtain tokens for submitting tokens and also we get a pre booked appointment with passport issuing officer for submitting the proofs and paying fees. When you submit the application online, an appointment will be booked automatically for submitting the required documents and fees so that  you can just walk-in to passport office 15 minutes ahead of your appointment. List Of Passport Offices Accepting Online Application Forms I know that you are excited and all set to apply online, but hold on. The online Passport application submission is supported in 37 regional passport offices across India as I write this post. If you are residing in any of these cities, then only you can apply online – Ahemdabad,  Amritsar, Bareilly, Bhopal, Bhubneswar, Chennai, Cochin, Coimbatore, Dehradun, Delhi, Ghaziabad, Guwahati, Hyderabad, Jaipur, Jalandhar, Jammu, Kolkata, Kozhikode, Lucknow, Madurai, Malappuram, Mumbai, Nagpur, Panaji, Patna, Pune, Raipur, Ranchi, Shimla, Srinagar, Surat, Thane, Trichy, Trivandrum, Visakhapatnam. Others should approach the passport office directly. Government is trying to expand this to other locations, so please check if place accepting online registration by visiting registration page(link given below). Types Of Applications Accepted Online The online system accepts following types of passport applications Fresh Passport / Renewal New Passport in lieu of Damaged/Lost Passport Passport for Children up to 15 Years of Age Re-issue of Passport / Additional Booklet Indian Govt. Passport Office Website And Online Application URL To apply for passport online visit the url https://passport.gov.in/pms/Information.jsp using Internet Explorer browser. This site may not work on your Firefox, Chrome or other browsers as the site request users to use Internet Explorer. Here are few other links that will help you get more details on passport application Govt. Of India Passport Office Website Passport Application Fee Structure Information Passport Application Filling Guidelines Passport Application Check List URL For NRIs To Apply Online If you are an NRI then the above links and the list of supported Passport offices are not for you. NRIs should use the URL http://passport.gov.in/nri/OnlineRegistration.jsp for applying passport related services online. For more details you can visit special NRI section on Passport website. CC Image credit: LucasTheExperience This article titled,How To Apply Online For New Passport Or Renewal Of Your Passport [Indian Websites], was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • Service Broker, not ETL

    - by jamiet
    I have been very quiet on this blog of late and one reason for that is I have been very busy on a client project that I would like to talk about a little here. The client that I have been working for has a website that runs on a distributed architecture utilising a messaging infrastructure for communication between different endpoints. My brief was to build a system that could consume these messages and produce analytical information in near-real-time. More specifically I basically had to deliver a data warehouse however it was the real-time aspect of the project that really intrigued me. This real-time requirement meant that using an Extract transformation, Load (ETL) tool was out of the question and so I had no choice but to write T-SQL code (i.e. stored-procedures) to process the incoming messages and load the data into the data warehouse. This concerned me though – I had no way to control the rate at which data would arrive into the system yet we were going to have end-users querying the system at the same time that those messages were arriving; the potential for contention in such a scenario was pretty high and and was something I wanted to minimise as much as possible. Moreover I did not want the processing of data inside the data warehouse to have any impact on the customer-facing website. As you have probably guessed from the title of this blog post this is where Service Broker stepped in! For those that have not heard of it Service Broker is a queuing technology that has been built into SQL Server since SQL Server 2005. It provides a number of features however the one that was of interest to me was the fact that it facilitates asynchronous data processing which, in layman’s terms, means the ability to process some data without requiring the system that supplied the data having to wait for the response. That was a crucial feature because on this project the customer-facing website (in effect an OLTP system) would be calling one of our stored procedures with each message – we did not want to cause the OLTP system to wait on us every time we processed one of those messages. This asynchronous nature also helps to alleviate the contention problem because the asynchronous processing activity is handled just like any other task in the database engine and hence can wait on another task (such as an end-user query). Service Broker it was then! The stored procedure called by the OLTP system would simply put the message onto a queue and we would use a feature called activation to pick each message off the queue in turn and process it into the warehouse. At the time of writing the system is not yet up to full capacity but so far everything seems to be working OK (touch wood) and crucially our users are seeing data in near-real-time. By near-real-time I am talking about latencies of a few minutes at most and to someone like me who is used to building systems that have overnight latencies that is a huge step forward! So then, am I advocating that you all go out and dump your ETL tools? Of course not, no! What this project has taught me though is that in certain scenarios there may be better ways to implement a data warehouse system then the traditional “load data in overnight” approach that we are all used to. Moreover I have really enjoyed getting to grips with a new technology and even if you don’t want to use Service Broker you might want to consider asynchronous messaging architectures for your BI/data warehousing solutions in the future. This has been a very high level overview of my use of Service Broker and I have deliberately left out much of the minutiae of what has been a very challenging implementation. Nonetheless I hope I have caused you to reflect upon your own approaches to BI and question whether other approaches may be more tenable. All comments and questions gratefully received! Lastly, if you have never used Service Broker before and want to kick the tyres I have provided below a very simple “Service Broker Hello World” script that will create all of the objects required to facilitate Service Broker communications and then send the message “Hello World” from one place to anther! This doesn’t represent a “proper” implementation per se because it doesn’t close down down conversation objects (which you should always do in a real-world scenario) but its enough to demonstrate the capabilities! @Jamiet ----------------------------------------------------------------------------------------------- /*This is a basic Service Broker Hello World app. Have fun! -Jamie */ USE MASTER GO CREATE DATABASE SBTest GO --Turn Service Broker on! ALTER DATABASE SBTest SET ENABLE_BROKER GO USE SBTest GO -- 1) we need to create a message type. Note that our message type is -- very simple and allowed any type of content CREATE MESSAGE TYPE HelloMessage VALIDATION = NONE GO -- 2) Once the message type has been created, we need to create a contract -- that specifies who can send what types of messages CREATE CONTRACT HelloContract (HelloMessage SENT BY INITIATOR) GO --We can query the metadata of the objects we just created SELECT * FROM   sys.service_message_types WHERE name = 'HelloMessage'; SELECT * FROM   sys.service_contracts WHERE name = 'HelloContract'; SELECT * FROM   sys.service_contract_message_usages WHERE  service_contract_id IN (SELECT service_contract_id FROM sys.service_contracts WHERE name = 'HelloContract') AND        message_type_id IN (SELECT message_type_id FROM sys.service_message_types WHERE name = 'HelloMessage'); -- 3) The communication is between two endpoints. Thus, we need two queues to -- hold messages CREATE QUEUE SenderQueue CREATE QUEUE ReceiverQueue GO --more querying metatda SELECT * FROM sys.service_queues WHERE name IN ('SenderQueue','ReceiverQueue'); --we can also select from the queues as if they were tables SELECT * FROM SenderQueue   SELECT * FROM ReceiverQueue   -- 4) Create the required services and bind them to be above created queues CREATE SERVICE Sender   ON QUEUE SenderQueue CREATE SERVICE Receiver   ON QUEUE ReceiverQueue (HelloContract) GO --more querying metadata SELECT * FROM sys.services WHERE name IN ('Receiver','Sender'); -- 5) At this point, we can begin the conversation between the two services by -- sending messages DECLARE @conversationHandle UNIQUEIDENTIFIER DECLARE @message NVARCHAR(100) BEGIN   BEGIN TRANSACTION;   BEGIN DIALOG @conversationHandle         FROM SERVICE Sender         TO SERVICE 'Receiver'         ON CONTRACT HelloContract WITH ENCRYPTION=OFF   -- Send a message on the conversation   SET @message = N'Hello, World';   SEND  ON CONVERSATION @conversationHandle         MESSAGE TYPE HelloMessage (@message)   COMMIT TRANSACTION END GO --check contents of queues SELECT * FROM SenderQueue   SELECT * FROM ReceiverQueue   GO -- Receive a message from the queue RECEIVE CONVERT(NVARCHAR(MAX), message_body) AS MESSAGE FROM ReceiverQueue GO --If no messages were received and/or you can't see anything on the queues you may wish to check the following for clues: SELECT * FROM sys.transmission_queue -- Cleanup DROP SERVICE Sender DROP SERVICE Receiver DROP QUEUE SenderQueue DROP QUEUE ReceiverQueue DROP CONTRACT HelloContract DROP MESSAGE TYPE HelloMessage GO USE MASTER GO DROP DATABASE SBTest GO

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  • Websphere MQ using JMS, closed connections stuck on the MQ

    - by Ahmad
    I have a simple JMS application deployed on OC4J under AIX server, in my application I'm listening to some queues and sending to other queues on a Websphere MQ deployed under AS400 server. The problem is that my connections to these queues are terminated/closed when it stays idle for some time with the error MQJMS1016 (this is not the problem), and when that happens I attempt to recover the connection and it works, however, the old connection is stuck at the MQ and would not terminate until it is terminated manually. The recovery code goes as follows: public void recover() { cleanup(); init(); } public void cleanup(){ if (session != null) { try { session .close(); } catch (JMSException e) { } } if (connection != null) { try { connection.close(); } catch (JMSException e) { } } } public void init(){ // typical initialization of the connection, session and queue... }

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  • Reliable applicance for routing IT emergency calls (SIP and ISDN)

    - by chiborg
    We have a fairly big IT installation and our IT staff needs to be reachable 24/7. At the moment we have the following setup for "emergency" calls to our IT staff on our main Asterisk box: An incoming emergency number (connected via SIP trunk and a BRI card in case the SIP trunk goes down). When the number is called during the office hours, all the SIP phones of the IT staff are called simultaneously. When the number is called out of office hours interface, a list of mobile phone numbers is called, one after another until someone picks up. The list can be changed by the IT staff via command line script. The setup works well, but the Asterisk is heavily used in a call center, has experienced some outages and misconfigurations, each of them bringing down the IT emergency number. So we'd like to put the IT emergency call functionality on a separate device. This does not need to be a big server, it even does not need to be Asterisk, it only has one purpose and should do it reliably. It should be very low-maintenance. Any suggestions for hard- and software?

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