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  • [Rais] OAuth with Digg API

    - by Karl
    I'm attempting to get Rails to play nice with the Digg API's OAuth. I'm using the oauth gem (ruby one, not the rails one). My code looks approximately like this: @consumer = OAuth::Consumer.new(API_KEY, API_SECRET, :scheme => :header, :http_method => :post, :oauth_callback => "http://locahost:3000", :request_token_url => 'http://services.digg.com/1.0/endpoint?method=oauth.getRequestToken', :access_token_url => 'http://services.digg.com/1.0/endpoint?method=oauth.getAccessToken', :authorize_url => 'http://digg.com/oauth/authorize') @request_token = @consumer.get_request_token session[:request_token] = @request_token.token session[:request_token_secret] = @request_token.secret redirect_to @request_token.authorize_url Which is by-the-book in terms of what the gem documentation gave me. However, Digg spits a "400 Bad Request" error back at me when @consumer.get_request_token is called. I can't figure out what I'm doing wrong. Any ideas?

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  • Logging in with WebFinger and OpenID

    - by Ryan
    I would like to apologize in advance for the ugly formatting. In order to talk about the problem, I need to be posting a bunch of URLs, but the excessive URLs and my lack of reputation makes StackOverflow think I could be a spammer. Any instance of 'ht~tp' is supposed to be 'http'. '{dot}' is supposed to be '.' and '{colon}' is supposed to be ':'. Also, my lack of reputation has prevented me from tagging my question with 'webfinger' and 'google-profiles'. Onto my question: I am messing around with WebFinger and trying to create a small rails app that enables a user to log in using nothing but their WebFinger account. I can succesfully finger myself, and I get back an XRD file with the following snippet: Link rel="ht~tp://specs{dot}openid{dot}net/auth/2.0/provider" href="ht~tp://www{dot}google{dot}com/profiles/{redacted}"/ Which, to me, reads, "I have an OpenID 2.0 login at the url: ht~tp://www{dot}google{dot}com/profiles/{redacted}". But when I try to use that URL to log in, I get the following error OpenID::DiscoveryFailure (Failed to fetch identity URL ht~tp://www{dot}google{dot}com/profiles/{redacted} : Error encountered in redirect from ht~tp://www{dot}google{dot}com/profiles/{redacted}: Error fetching /profiles/{Redacted}: Connection refused - connect(2)): When I replace the profile URL with 'ht~tps://www{dot}google{dot}com/accounts/o8/id', the login works perfectly. here is the code that I am using (I'm using RedFinger as a plugin, and JanRain's ruby-openid, installed without the gem) require "openid" require 'openid/store/filesystem.rb' class SessionsController < ApplicationController def new @session = Session.new #render a textbox requesting a webfinger address, and a submit button end def create ####################### # # Pay Attention to this section right here # ####################### #use given webfinger address to retrieve openid login finger = Redfinger.finger(params[:session][:webfinger_address]) openid_url = finger.open_id.first.to_s #openid_url is now: ht~tp://www{dot}google{dot}com/profiles/{redacted} #Get needed info about the acquired OpenID login file_store = OpenID::Store::Filesystem.new("./noncedir/") consumer = OpenID::Consumer.new(session,file_store) response = consumer.begin(openid_url) #ERROR HAPPENS HERE #send user to OpenID login for verification redirect_to response.redirect_url('ht~tp://localhost{colon}3000/','ht~tp://localhost{colon}3000/sessions/complete') end def complete #interpret return parameters file_store = OpenID::Store::Filesystem.new("./noncedir/") consumer = OpenID::Consumer.new(session,file_store) response = consumer.complete params case response.status when OpenID::SUCCESS session[:openid] = response.identity_url #redirect somehwere here end end end Is it possible for me to use the URL I received from my WebFinger to log in with OpenID?

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  • Closing Connections on asynchronous messaging in JMS

    - by The Elite Gentleman
    Hi Everyone! I have created a JMS wrapper (similar to Springs JmsTemplate since I'm not using Springs) and I was wondering: If I setup asynchronous messaging, when is a good time to close connections and JMS relates resources (so that the Connection Factory in the Resource Pool can be available)? Thanks Here's the source code for receiving JMS messages public Message receive() throws JMSException { QueueConnection connection = null; QueueSession session = null; QueueReceiver consumer = null; try { // TODO Auto-generated method stub connection = factory.createQueueConnection(); if (connection != null && getExceptionListener() != null) { connection.setExceptionListener(getExceptionListener()); } session = connection.createQueueSession(isSessionTransacted(), getAcknowledgeMode()); consumer = session.createReceiver(queue); if (getMessageListener() != null) { consumer.setMessageListener(getMessageListener()); } //Begin connection.start(); if (getMessageListener() == null) { return null; } return receive(session, consumer); } catch (JMSException e) { // TODO: handle exception logger.error(e.getLocalizedMessage(), e); throw e; } finally { JMSUtil.closeMessageConsumer(consumer); JMSUtil.closeSession(session, false); //false = don't commit. JMSUtil.closeConnection(connection, true); //true = stop before close. } As you can see, if getMessageListener() != null then apply it to the MessageConsumer. Am I doing this correctly? The same approach has also been taken for JMS Topic.

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  • "Invalid signature": oAuth provider with Django-piston

    - by Martin Eve
    Hi, I'm working with django-piston to attempt to create an API that supports oAuth. I started out using the tutorial at: http://blog.carduner.net/2010/01/26/django-piston-and-oauth/ I added a consumer to piston's admin interface with key and secret both set to "abcd" for test purposes. The urls are successfully wired-up and the oAuth provider is called. However, running my get request token tests with tripit (python get_request_token.py "http://127.0.0.1:8000/api" abcd abcd), I receive the following error: Invalid signature. Expected signature base string: GET&http%3A%2F%2F127.0.0.1%3A8000%2Fapi%2Foauth%2Frequest_token%2F&oauth_consumer_key%3Dabcd%26oauth_nonce%3D0c0bdded5b1afb8eddf94f7ccc672658%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1275135410%26oauth_version%3D1.0 The problem seems to lie inside the _check_signature method of Piston's oauth.py, where valid_sig = signature_method.check_signature(oauth_request, consumer, token, signature) is returning false. I can't, however, work out how to get the signature validated. Any ideas? -----Update----- If I remove the test consumer from piston's backend, the response returned is correctly set to "Invalid consumer", so this lookup appears to be working.

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  • How to write custom (odd) authentication plugins for Wordpress, Joomla and MediaWiki?

    - by Bart van Heukelom
    On our network (a group of related websites - not a LAN) we have a common authentication system which works like this: On a network site ("consumer") the user clicks on a login link This redirects the user to a login page on our auth system ("RAS"). Upon successful login the user is directed back to the consumer site. Extra data is passed in the query string. This extra data does not include any information about the user yet. The consumer site's backend contacts RAS, with this extra data, to get the information about the logged in user (id, name, email, preferences, etc.). So as you can see, the consumer site knows nothing about the authentication method. It doesn't know if it's by username/password, fingerprint, smartcard, or winning a game of poker. This is the main problem I'm encountering when trying to find out how I could write custom authentication plugins for these packages, acting as consumer sites: Wordpress Joomla MediaWiki For example Joomla offers a pretty simple auth plugin system, but it depends on a username/password entered on the Joomla site. Any hints on where to start?

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  • nHibernate query looking for the related object's related object

    - by code-zoop
    I have an nHibernate querie issue that looks quite straight forward, but I can't seem to get my head around it! I am creating some simple example classes to illustrate my problem: public class Car { public int Id { get; set; } public IList<Interior> InteriorParts { get; set; } } public class Interior { public int Id { get; set; } public InteriorProducer Producer { get; set; } } public class InteriorProducer { public int Id { get; set; } } Now to the query: I have the id of the InteriorProducer, but need to get a list of Cars where the interior have been produced by the interior producer. So in a simple, pseudo SQL, it looks something like this: select cars where car.InteriorParts.Producer.Id = Id I have a really hard time getting my head around this to create an nHibernate query. Any Ideas? Thanks

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  • Can I use manifests to specify an optional dependency on a COM server?

    - by sharptooth
    I'd like to use manifests to specify a dependency on a COM server (reg-free COM). The consumer application will mostly work fine without the COM server - only something like 1,7% of its functionality uses the COM server. So with plain old regsvr32 it would start and work fine until the user would do something that would trigger CoCreateInstance() call and at that point the consumer would get an error message. Now I've played with manifests for a while and it looks like the consumer wouldn't even start unless the COM server assembly it depends on is present in the file system. That's no good. Is there a way to use reg-free COM with manifests and make the dependency optional - so that the consumer program starts and works fine until CoCreateInstance() is actually called?

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  • OAuth Request token = null in android app

    - by jonney
    Hi, i am trying to authenticate something(in this case LinkedIn) using OAuth but the requested token always returns null? Here is my code below: public void authenticateAppOauthApi() { Log.d(TAG, "authenticateAppOauthApi"); OAuthServiceProvider provider = new OAuthServiceProvider( REQUEST_TOKEN_PATH, AUTHORIZE_PATH, ACCESS_TOKEN_PATH); OAuthConsumer consumer = new OAuthConsumer(CALLBACK_URL, API_KEY, SECRET_KEY, provider); OAuthAccessor accessor = new OAuthAccessor(consumer); Intent intent = new Intent(Intent.ACTION_VIEW); Log.d(TAG, "Intent intent = new Intent(Intent.ACTION_VIEW );"); // intent.setData(Uri.parse(url)); String url = accessor.consumer.serviceProvider.userAuthorizationURL + "?oauth_token=" + accessor.requestToken + "&oauth_callback=" + accessor.consumer.callbackURL; intent.setData(Uri.parse(url)); Log.d(TAG, "intent.setData(Uri.parse(url)); = " + url); mContext.startActivity(intent); Log.d(TAG, "finish authenticateApp"); } I basicaly followed the example here http://donpark.org/blog/2009/01/24/android-client-side-oauth thanks in advance

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  • JMS - How do message selectors work with multiple queue and topic consumers?

    - by Stephen Harmon
    Say you have a JMS queue, and multiple consumers are watching the queue for messages. You want one of the consumers to get all of a particular type of message, so you decide to employ message selectors. For example, you define a property to go in your JMS message header named, "targetConsumer." Your message selector, which you apply to the consumer known as, "A," is something like "WHERE targetConsumer = "CONSUMER_A." It's clear that consumer A will now just grab messages with the property set like it is in in the example. Will the other consumers have awareness of that, though? IOW, will another consumer, unconstrained by a message selector, grab the "CONSUMER_A" messages, if it looks at the queue before Consumer A? Do I need to apply message selectors like, "WHERE targetConsumer < "CONSUMER_A" to the others? I am RTFMing and gathering empirical data now, but was hoping someone might know off the top of their head.

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  • Sharepoint connected web parts question

    - by philj
    I have one web part (the provider) which displays insurance claims in a gridview. When user clicks on one this value(case number) is passed via IWebPartField interface to another web part(consumer) which displays detailed info about the claim. So far so good. I can select different claims in the provider and the details show up in the consumer just fine. The moment I add a TextBox to the consumer, the consumer no longer recognizes the case number passed. I need the user to be able to enter a value in the textbox and click a button to update that claim info. I can debug and attach to process and it looks like it is getting the case in the callback function, etc, but when it is setting parameters for the stored proc in CreateChildControls, it is null. Comment out the TextBox and it works fine. Any clues as to what is going on? Brand new to Sharepoint web parts...any help appreciated! thanks, PhilJ

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  • Using a backwards relation (i.e FOO_set) for ModelChoiceField in Django

    - by Bwmat
    I have a model called Movie, which has a ManyToManyField called director to a model called Person, and I'm trying to create a form with ModelChoiceField like so: class MovieSearchForm(forms.Form): producer = forms.ModelChoiceField(label='Produced by', queryset=movies.models.Person.producer_set, required=False) but this seems to be failing to compile (I'm getting a ViewDoesNotExist exception for the view that uses the form, but it goes away if I just replace the queryset with all the person objects), I'm guessing because '.producer_set' is being evaluated too 'early'. How can I get this work? here are the relevant parts of the movie/person classes: class Person(models.Model): name = models.CharField(max_length=100) class Movie(models.Model): ... producer = models.ForeignKey(Person, related_name="producers") director = models.ForeignKey(Person, related_name="directors") What I'm trying to do is get ever Person who is used in the producer field of some Movie.

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  • Carrot (Python) [errno 10054] An existing connection was forcibly closed by the remote host

    - by Meditation
    Hi all, We are using Carrot in our Python project. I wrote a Python script acting as the consumer of the message queue. I invoked this Python script using command line shell in Windows 7 as python consumer.py However, after a while, the running session was aborted and the error is: [errno 10054] An existing connection was forcibly closed by the remote host The producer session is still running fine on the Linux server. Just wondering how can I fix this and have a long running consumer session on Windows Thanks in advance.

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  • How to retrieve base class only (entity framework)?

    - by Juvaly
    Hi All, I've been scratching my head here for a while now... I have a Consumer class and a BillableConsumer class that inherits Consumer. They are both a part of the Consumers set. The problem is that this following query: Consumer consumer = (from c in _ctx.Consumers where c.ID = id select c).First(); returns a BillableConsumer instance! Just the same as this query: BillableConsumer bconsumer = (from c in _ctx.Consumers.OfType<BillableConsumer>() where c.ID = id select c).First(); How can I return an instance of just the base class? (these are separate tables in the data store).

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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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  • Use Case Diagrams - should I create a diagram just for a view business rule?

    - by Periback
    I'm modeling a UCD where I have two actors ( a content producer and a developer).. the content producer is going to create and specify details of a storyboard functionality, and the other actor (developer) will only be able to view this storyboard ( he'll log in the application and read the storyboard to start developing what it says, outside the application..) I'm working on the specification of this storyboard functionality and I'd like to know it would be like a best-practice if I describe something like " actor- developer", "UCD - read scenes of storyboard" . This is the specification of an application I developed for my thesis and they asked me to add some specification...

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  • ActiveMQ 5.2.0 + REST + HTTP POST = java.lang.OutOfMemoryError

    - by Bruce Loth
    First off, I am a newbie when it comes to JMS & ActiveMQ. I have been looking into a messaging solution to serve as middleware for a message producer that will insert XML messages into a queue via HTTP POST. The producer is an existing system written in C++ that cannot be modified (so Java and the C++ API are out). Using the "demo" examples and some trial and error, I have cobbled together a working example of what I want to do (on a windows box). The web.xml I configured in a test directory under "webapps" specifies that the HTTP POST messages received from the producer are to be handled by the MessageServlet. I added a line for the text app in "activemq.xml" ('ow' is the test app dir): I created a test script to "insert" messages into the queue which works well. The problem I am running into is that it as I continue to insert messages via REST/HTTP POST, the memory consumption and thread count used by ActiveMQ continues to rise (It happens when I have timely consumers as well as slow or non-existent consumers). When memory consumption gets around 250MB's and the thread count exceeds 5000 (as shown in windows task manager), ActiveMQ crashes and I see this in the log: Exception in thread "ActiveMQ Transport Initiator: vm://localhost#3564" java.lang.OutOfMemoryError: unable to create new native thread It is as if Jetty is spawning a new thread to handle each HTTP POST and the thread never dies. I did look at this page: http://activemq.apache.org/javalangoutofmemory.html and tried but that didn't fix the problem (although I didn't fully understand the implications of the change either). Does anyone have any ideas? Thanks! Bruce Loth PS - I included the "test message producer" python script below for what it is worth. I created batches of 100 messages and continued to run the script manually from the command line while watching the memory consumption and thread count of ActiveMQ in task manager. def foo(): import httplib, urllib body = "<?xml version='1.0' encoding='UTF-8'?>\n \ <ROOT>\n \ [snip: xml deleted to save space] </ROOT>" headers = {"content-type": "text/xml", "content-length": str(len(body))} conn = httplib.HTTPConnection("127.0.0.1:8161") conn.request("POST", "/ow/message/RDRCP_Inbox?type=queue", body, headers) response = conn.getresponse() print response.status, response.reason data = response.read() conn.close() ## end method definition ## Begin test code count = 0; while(count < 100): # Test with batches of 100 msgs count += 1 foo()

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  • Multithreading, when to yield versus sleep

    - by aaa
    hello. To clarify terminology, yield is when thread gives up its time slice. My platform of interest is POSIX threads, but I think question is general. Suppose I have consumer/producer pattern. If I want to throttle either consumer or producer, which is better to use, sleep or yield? I am mostly interested in efficiency of using either function. Thanks

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  • What are common uses of condition variables in C++?

    - by jasonline
    I'm trying to learn about condition variables. I would like to know what are the common situations where condition variables are used. One example is in a blocking queue, where two threads access the queue - the producer thread pushes an item into the queue, while the consumer thread pops an item from the queue. If the queue is empty, the consumer thread is waiting until a signal is sent by the producer thread. What are other design situations where you need a condition variable to be used?

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  • Fork two processes and kill the second when the first is done

    - by User1
    The title says it all. I want to create a bash script that will launch two processes and kill the second process when the first is done. Here's an example: #fork first process producer& #fork second process consumer& #wait for producer to finish ... #kill the consumer ... I have a feeling this can get ugly but has a very simple solution. Please help me fill in the blanks.

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  • Question regarding xsd

    - by Hima
    I have an application which reads the data from the database, creates an object out of the data, marshalls it into an xml and enqueue the xml to a queue which is producer. The xml is dequeued from the queue by a consumer. I need to use xsds at two different places. For database access while reading the data from the database and For interaction between producer and consumer Can the same xsd be used in both the cases? Or do I need to use different xsds?

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  • You Can't Win on Price

    - by David Dorf
    This year I did the majority of my Christmas shopping from the comfort of my home office. There aren't many things in stores you can't find online these days. I find it easier to search, research, and compare products online rather than walking the mall anyway. But there's a segment of the population that likes to be in the store, touching the products. For those people, smartphones avail them some of the e-commerce features I mentioned right there in the aisles. First it was RedLaser, then TheFind, ShopSavvy and many others. But the one that should be scaring retailers is Amazon's PriceCheck application. It lets you scan the product barcode, take a picture of the product, or speak the product's name. Once the product is identified, it shows the online prices, with Amazon at the top of the list. Within 10 seconds you can order the item and Amazon Prime members get free 2-day shipping too. I don't think fashion and grocery retailers need to worry much, but I have to believe smartphones are helping Amazon win a little more of the brand-name hardgoods market. So what's a retailer to do? Best Buy has begun to put QR Codes on their shelf labels that are easily scanned by smartphones and take the consumer to a Best Buy Web page where they can get extended information about the product. The consumer is getting the additional information they want, and Best Buy avoids the price comparisons. Of course if a consumer chooses to use the Amazon PriceCheck app, then all bets are off. That's when Best Buy has to hope the in-store experience and customer service will save the sale. My point is that the internet makes information available to everyone, and smartphones make it available anywhere. Unless you want your store to be Amazon's local showroom, you need to be price-competitive but differentiate on other aspects of the shopping experience. With the cost of running a physical store, you can't win on price.

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  • 3 Key Trends For Mobile Commerce – Location, Location, Location

    - by Michael Hylton
    This past weekend I was at a major bookstore chain and looking for a particular book.  Rather than ask the clerk, I went to my smartphone and went online to find the book title, author, and competing price.  I know I’m not alone in this effort and more and more individuals (and businesses) will use the power of mobility to tilt the scale in their favor. Armed with a mobile device – smartphone or tablet – folks will use them to research, compare, and ultimately purchase.  A recent PayPal survey found that 46% of respondents plan to use a mobile device this holiday season to make a purchase.   An astounding 27% of consumers in an e-tailing group survey commissioned by Oracle, use a tablet device daily or several times a week to research products and services. Beyond researching or making purchases, 35% of consumers use their smartphone to receive offers and coupons, and 32% access coupons and redeem them at their local retail store.  And with GPS capabilities in smartphones and tablet (and with user’s approval), retailers will start pushing coupons and offers directly to phone users based on their proximity to their store (or their competitors). Security is one concern that both shoppers, companies and phone manufacturers will have to deal with in the coming years.  In that same Oracle-sponsored e-tailing group consumer survey, 32% of consumers were concerned about giving their credit card information via a smartphone. You can gain further insight into the mind of today’s consumer by reading the e-tailing group white paper, titled “the connected consumer”.

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  • 3 Key Trends For Mobile Commerce – Location, Location, Location

    - by Michael Hylton
    This past weekend I was at a major bookstore chain and looking for a particular book.  Rather than ask the clerk, I went to my smartphone and went online to find the book title, author, and competing price.  I know I’m not alone in this effort and more and more individuals (and businesses) will use the power of mobility to tilt the scale in their favor. Armed with a mobile device – smartphone or tablet – folks will use them to research, compare, and ultimately purchase.  A recent PayPal survey found that 46% of respondents plan to use a mobile device this holiday season to make a purchase.   An astounding 27% of consumers in an e-tailing group survey commissioned by Oracle, use a tablet device daily or several times a week to research products and services. Beyond researching or making purchases, 35% of consumers use their smartphone to receive offers and coupons, and 32% access coupons and redeem them at their local retail store.  And with GPS capabilities in smartphones and tablet (and with user’s approval), retailers will start pushing coupons and offers directly to phone users based on their proximity to their store (or their competitors). Security is one concern that both shoppers, companies and phone manufacturers will have to deal with in the coming years.  In that same Oracle-sponsored e-tailing group consumer survey, 32% of consumers were concerned about giving their credit card information via a smartphone. You can gain further insight into the mind of today’s consumer by reading the e-tailing group white paper, titled “the connected consumer”.

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  • This is the End of Business as Usual...

    - by Michael Snow
    This week, we'll be hosting our last Social Business Thought Leader Series Webcast for 2012. Our featured guest this week will be Brian Solis of Altimeter Group. As we've been going through the preparations for Brian's webcast, it became very clear that an hour's time is barely scraping the surface of the depth of Brian's insights and analysis. Accordingly, in the spirit of sharing Brian's perspective for all of our readers, we'll be featuring guest posts all this week pulled from Brian's larger collection of blog postings on his own website. If you like what you've read here this week, we highly recommend digging deeper into his tome of wisdom. Guest Post by Brian Solis, Analyst, Altimeter Group as originally featured on his site with the minor change of the video addition at the beginning of the post. This is the End of Business as Usual and the Beginning of a New Era of Relevance - Brian Solis, Principal Analyst, Altimeter Group The Times They Are A-Changin’ Come gather ’round people Wherever you roam And admit that the waters Around you have grown And accept it that soon You’ll be drenched to the bone If your time to you Is worth savin’ Then you better start swimmin’ Or you’ll sink like a stone For the times they are a-changin’. - Bob Dylan I’m sure you are wondering why I chose lyrics to open this article. If you skimmed through them, stop here for a moment. Go back through the Dylan’s words and take your time. Carefully read, and feel, what it is he’s saying and savor the moment to connect the meaning of his words to the challenges you face today. His message is as important and true today as it was when they were first written in 1964. The tide is indeed once again turning. And even though the 60s now live in the history books, right here, right now, Dylan is telling us once again that this is our time to not only sink or swim, but to do something amazing. This is your time. This is our time. But, these times are different and what comes next is difficult to grasp. How people communicate. How people learn and share. How people make decisions. Everything is different now. Think about this…you’re reading this article because it was sent to you via email. Yet more people spend their online time in social networks than they do in email. Duh. According to Nielsen, of the total time spent online 22.5% are connecting and communicating in social networks. To put that in perspective, the time spent in the likes of Facebook, Twitter, and Youtube is greater than online gaming at 9.8%, email at 7.6% and search at 4%. Imagine for a moment if you and I were connected to one another in Facebook, which just so happens to be the largest social network in the world. How big? Well, Facebook is the size today of the entire Internet in 2004. There are over 1 billion people friending, Liking, commenting, sharing, and engaging in Facebook…that’s roughly 12% of the world’s population. Twitter has over 200 million users. Ever hear of tumblr? More time is spent on this popular microblogging community than Twitter. The point is that the landscape for communication and all that’s affected by human interaction is profoundly different than how you and I learned, shared or talked to one another yesterday. This transformation is only becoming more pervasive and, it’s not going back. Survival of the Fitting But social media is just one of the channels we can use to reach people. I must be honest. I’m as much a part of tomorrow as I am of yesteryear. It’s why I spend all of my time researching the evolution of media and its impact on business and culture. Because of you, I share everything I learn in newsletters, emails, blogs, Youtube videos, and also traditional books. I’m dedicated to helping everyone not only understand, but grasp the change that’s before you. Technologies such as social, mobile, virtual, augmented, et al compel us adapt our story and value proposition and extend our reach to be part of communities we don’t realize exist. The people who will keep you in business or running tomorrow are the very people you’re not reaching today. Before you continue to read on, allow me to clarify my point of view. My inspiration for writing this is to help you augment, not necessarily replace, the programs you’re running today. We must still reach those whom matter to us in the ways they prefer to be engaged. To reach what I call the connected consumer of Geneeration-C we must too reach them in the ways they wish to be engaged. And in all of my work, how they connect, talk to one another, influence others, and make decisions are not at all like the traditional consumers of the past. Nor are they merely the kids…the Millennial. Connected consumers are representative across every age group and demographic. As you can see, use of social networks, media sharing sites, microblogs, blogs, etc. equally span across Gen Y, Gen X, and Baby Boomers. The DNA of connected customers is indiscriminant of age or any other demographic for that matter. This is more about psychographics, the linkage of people through common interests (than it is their age, gender, education, nationality or level of income. Once someone is introduced to the marvels of connectedness, the sensation becomes a contagion. It touches and affects everyone. And, that’s why this isn’t going anywhere but normalcy. Social networking isn’t just about telling people what you’re doing. Nor is it just about generic, meaningless conversation. Today’s connected consumer is incredibly influential. They’re connected to hundreds and even thousands of other like-minded people. What they experiences, what they support, it’s shared throughout these networks and as information travels, it shapes and steers impressions, decisions, and experiences of others. For example, if we revisit the Nielsen research, we get an idea of just how big this is becoming. 75% spend heavily on music. How does that translate to the arts? I’d imagine the number is equally impressive. If 53% follow their favorite brand or organization, imagine what’s possible. Just like this email list that connects us, connections in social networks are powerful. The difference is however, that people spend more time in social networks than they do in email. Everything begins with an understanding of the “5 W’s and H.E.” – Who, What, When, Where, How, and to What Extent? The data that comes back tells you which networks are important to the people you’re trying to reach, how they connect, what they share, what they value, and how to connect with them. From there, your next steps are to create a community strategy that extends your mission, vision, and value and it align it with the interests, behavior, and values of those you wish to reach and galvanize. To help, I’ve prepared an action list for you, otherwise known as the 10 Steps Toward New Relevance: 1. Answer why you should engage in social networks and why anyone would want to engage with you 2. Observe what brings them together and define how you can add value to the conversation 3. Identify the influential voices that matter to your world, recognize what’s important to them, and find a way to start a dialogue that can foster a meaningful and mutually beneficial relationship 4. Study the best practices of not just organizations like yours, but also those who are successfully reaching the type of people you’re trying to reach – it’s benching marking against competitors and benchmarking against undefined opportunities 5. Translate all you’ve learned into a convincing presentation written to demonstrate tangible opportunity to your executive board, make the case through numbers, trends, data, insights – understanding they have no idea what’s going on out there and you are both the scout and the navigator (start with a recommended pilot so everyone can learn together) 6. Listen to what they’re saying and develop a process to learn from activity and adapt to interests and steer engagement based on insights 7. Recognize how they use social media and innovate based on what you observe to captivate their attention 8. Align your objectives with their objectives. If you’re unsure of what they’re looking for…ask 9. Invest in the development of content, engagement 10. Build a community, invest in values, spark meaningful dialogue, and offer tangible value…the kind of value they can’t get anywhere else. Take advantage of the medium and the opportunity! The reality is that we live and compete in a perpetual era of Digital Darwinism, the evolution of consumer behavior when society and technology evolve faster than our ability to adapt. This is why it’s our time to alter our course. We must connect with those who are defining the future of engagement, commerce, business, and how the arts are appreciated and supported. Even though it is the end of business as usual, it is the beginning of a new age of opportunity. The consumer revolution is already underway, and the question is: How do you better understand the role you play in this production as a connected or social consumer as well as business professional? Again, this is your time to define a new era of engagement and relevance. Originally written for The National Arts Marketing Project Connect with Brian via: Twitter | LinkedIn | Facebook | Google+ --- Note from Michael: If you really like this post above - check out Brian's TEDTalk and his thought process for preparing it in this post: 12.00 Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} http://www.briansolis.com/2012/10/tedtalk-reinventing-consumer-capitalism-screw-business-as-usual/

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  • Will Your Brand Survive the Age of Digital Darwinism?

    - by Christie Flanagan
    It’s the end of business as usual.  Trends such as the mobile web, social media, gamification and real-time are forcing businesses to rethink the way they operate.  At the same time, people are embracing a new digital culture across ever expanding networks.  Together, these trends have given rise to a new breed of connected consumer, one that is ready to shake the very foundation of business today.  This is the age of Digital Darwinism – where society and technology evolve faster than your ability to adapt.  How well poised is your brand to survive and thrive in this new environment? Attend this webcast to hear Altimeter Group digital analyst and futurist, Brian Solis, discuss the rise of connected consumerism and learn how brands can survive Digital Darwinism by better understanding customer expectations, disruptive technology, and the new opportunities that arise from them. You will learn: How brands are being redefined in the digital consumer landscape and what they can do to create and steer these experiences Why consumer influence is growing and how businesses can use this to their advantage How to connect with a rising audience through new touchpoints between consumers, brands, and influencers Why you need to create a culture of change to earn trust, influence and significance among today’s connected customers Register now.

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