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• Access Control Service: Protocol and Token Transition

  - by Your DisplayName here!

  ACS v2 supports a number of protocols (WS-Federation, WS-Trust, OpenId, OAuth 2 / WRAP) and a number of token types (SWT, SAML 1.1/2.0) – see Vittorio’s Infographic here. Some protocols are designed for active client (WS-Trust, OAuth / WRAP) and some are designed for passive clients (WS-Federation, OpenID). One of the most obvious advantages of ACS is that it allows to transition between various protocols and token types. Once example would be using WS-Federation/SAML between your application and ACS to sign in with a Google account. Google is using OpenId and non-SAML tokens, but ACS transitions into WS-Federation and sends back a SAML token. This way you application only needs to understand a single protocol whereas ACS acts as a protocol bridge (see my ACS2 sample here). Another example would be transformation of a SAML token to a SWT. This is achieved by using the WRAP endpoint – you send a SAML token (from a registered identity provider) to ACS, and ACS turns it into a SWT token for the requested relying party, e.g. (using the WrapClient from Thinktecture.IdentityModel): [TestMethod] public void GetClaimsSamlToSwt() {     // get saml token from idp     var samlToken = Helper.GetSamlIdentityTokenForAcs();     // send to ACS for SWT converion     var swtToken = Helper.GetSimpleWebToken(samlToken);     var client = new HttpClient(Constants.BaseUri);     client.SetAccessToken(swtToken, WebClientTokenSchemes.OAuth);     // call REST service with SWT     var response = client.Get("wcf/client");     Assert.AreEqual<HttpStatusCode>(HttpStatusCode.OK, response.StatusCode); } There are more protocol transitions possible – but they are not so obvious. A popular example would be how to call a REST/SOAP service using e.g. a LiveId login. In the next post I will show you how to approach that scenario.

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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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• What Problems Are Better Solved By SOAP Over REST?

  In the battle for web service supremacy SOAP and REST have been battling for years. In my personal opinion this debate should have never existed. Yes, both forms can be used to create an interactive web service, but each form of a service was developed independent of each other to solve two different yet similar problems. Based my research and experience I would have to say that REST should be the preferred web service methodology and SOAP should only be used in specific situations. Note, I did not say that I was against SOAP, and in fact I actually like to use SOAP when it is needed. Criteria for using SOAP: Does the service need a guaranteed level of reliability and security? Did the provider and consumer of the service agreed on a standardized data exchange format? Does the service need data context and state management? If you answer yes to any of these questions, then you may want to consider SOAP as the format for the web service. Another way to look at the relationship between REST and SOAP is to look at the medical field.  For most things a general doctor or you family health care provider can acceptably treat most conditions from the case of a common cold to a broken bone. A general doctor more aligns with REST in my opinion because for most service requirements REST fulfills a projects needs, but what happens if you need more of an advanced examination, you would go to a specialist. A specialist would already have experience dealing with specific issues that you are experiencing giving them specific context to how best treat you going forward. SOAP acts more like a specialist doctor giving that they understand the context of an issue and can treat it based on the state of other patients they have already treated. An example of where I would use SOAP over REST in real life would be a single sign-on application. I n these cases I need to check validate a username and password for authentication and authorization of a web page request. This service would need to maintain state while it authenticated a user and while it validated access to a web page on a subsequent request. This service must process every request for access and not allow caching to ensure that every request is processed and the appropriate users are allowed to view selected web pages. References: Rozlog, M. (2010). REST and SOAP: When Should I Use Each (or Both)? Retrieved 11 20, 2011, from Infoq.com: http://www.infoq.com/articles/rest-soap-when-to-use-each

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• Twitte API for Java - Hello Twitter Servlet (TOTD #178)

  - by arungupta

  There are a few Twitter APIs for Java that allow you to integrate Twitter functionality in a Java application. This is yet another API, built using JAX-RS and Jersey stack. I started this effort earlier this year and kept delaying to share because wanted to provide a more comprehensive API. But I've delayed enough and releasing it as a work-in-progress. I'm happy to take contributions in order to evolve this API and make it complete, useful, and robust. Drop a comment on the blog if you are interested or ping me at @arungupta. How do you get started ? Just add the following to your "pom.xml": <dependency> <groupId>org.glassfish.samples</groupId> <artifactId>twitter-api</artifactId> <version>1.0-SNAPSHOT</version></dependency> The implementation of this API uses Jersey OAuth Filters for authentication with Twitter and so the following dependencies are required if any API that requires authentication, which is pretty much all the APIs ;-) <dependency> <groupId>com.sun.jersey.contribs.jersey-oauth</groupId>     <artifactId>oauth-client</artifactId>     <version>${jersey.version}</version> </dependency> <dependency>     <groupId>com.sun.jersey.contribs.jersey-oauth</groupId>     <artifactId>oauth-signature</artifactId>     <version>${jersey.version}</version> </dependency> Once the dependencies are added to your project, inject Twitter  API in your Servlet (or any other Java EE component) as: @Inject Twitter twitter; Here is a simple non-secure invocation of the API to get you started: SearchResults result = twitter.search("glassfish", SearchResults.class);for (SearchResultsTweet t : result.getResults()) { out.println(t.getText() + "<br/>");} This code returns the tweets that matches the query "glassfish". The source code for the complete project can be downloaded here. Download it, unzip, and mvn package will build the .war file. And then deploy it on GlassFish or any other Java EE 6 compliant application server! The source code for the API also acts as the javadocs and can be checked out from here. A more detailed sample using security and several other API from this library is coming soon!

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• Oracle releases new Java Embedded products

  - by Henrik Stahl

  With less than one week to go to JavaOne 2012, we've spiced things up a little by releasing not one but two net new embedded Java products. This is an important step towards realizing the vision of Java as the standard platform for the Internet of Things that I outlined in a recent blog post. The two new products are: Java ME Embedded 3.2. Based on same code as the widely deployed Oracle Java Wireless Client for feature phones, this new product provides a Java ME implementation optimized for very small microcontroller-based devices and adds - among other things - a new Device Access API that enables interaction with peripherals common in edge devices such as various types of sensors. In addition to the new Java ME Embedded platform, we have also released an update of the Java ME SDK which adds support for the development of small embedded devices. Java Embedded Suite 7.0. This is an integrated middleware stack for embedded devices, incorporating Java SE Embedded and versions of JavaDB, GlassFish and a Web Services stack optimized for remote operation and small footprint. A typical Internet of Things (or M2M) infrastructure contains three types of compute nodes: The edge device which is typically a sensor or control point of some kind. These devices can be connected directly to a backend through a mobile network if they are installed in - for example - a remote vending machine; or, they can be part of a local short-range network and be connected to the backend through a more powerful gateway device. A gateway is the second type of compute node and acts as an aggregator and control point for a local network. A good example of this could be a generalized home Internet access point, or home gateway. Gateways are mostly using normal wall power and are used for multiple applications, deployed by multiple service providers. Finally, the last type of compute node is the normal enterprise or cloud backend. Java ME Embedded and Java Embedded Suite are perfect base software stacks for the edge devices and the gateway respectively, providing the Java promise of a platform independent runtime and a complete set of libraries as well as allowing a programmer to focus on the business logic rather than plumbing. We are very thrilled with these new releases that open up exciting opportunities for Java developers to extend services and enterprise applications in ways that will make organizations more efficient and touch our daily lives. To find out more, come to the JavaOne conference (for technical content) and to the Java Embedded @ JavaOne subconference (for business content). There will be plenty of cool demos showing complete end-to-end applications, provided by Oracle and our partners, as well as keynotes and numerous sessions where you can learn more about the technology and business opportunities.

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• Composite-like pattern and SRP violation

  - by jimmy_keen

  Recently I've noticed myself implementing pattern similar to the one described below. Starting with interface: public interface IUserProvider { User GetUser(UserData data); } GetUser method's pure job is to somehow return user (that would be an operation speaking in composite terms). There might be many implementations of IUserProvider, which all do the same thing - return user basing on input data. It doesn't really matter, as they are only leaves in composite terms and that's fairly simple. Now, my leaves are used by one own them all composite class, which at the moment follows this implementation: public interface IUserProviderComposite : IUserProvider { void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider); } public class UserProviderComposite : IUserProviderComposite { public User GetUser(SomeUserData data) ... public void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider) ... } Idea behind UserProviderComposite is simple. You register providers, and this class acts as a reusable entry-point. When calling GetUser, it will use whatever registered provider matches predicate for requested user data (if that helps, it stores key-value map of predicates and providers internally). Now, what confuses me is whether RegisterProvider method (brings to mind composite's add operation) should be a part of that class. It kind of expands its responsibilities from providing user to also managing providers collection. As far as my understanding goes, this violates Single Responsibility Principle... or am I wrong here? I thought about extracting register part into separate entity and inject it to the composite. As long as it looks decent on paper (in terms of SRP), it feels bit awkward because: I would be essentially injecting Dictionary (or other key-value map) ...or silly wrapper around it, doing nothing more than adding entires This won't be following composite anymore (as add won't be part of composite) What exactly is the presented pattern called? Composite felt natural to compare it with, but I realize it's not exactly the one however nothing else rings any bells. Which approach would you take - stick with SRP or stick with "composite"/pattern? Or is the design here flawed and given the problem this can be done in a better way?

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• Correcting color-shifted mirrored i915 driver in 12.04?

  - by Will Martin

  I was called in to fix a friend's malfunctioning HP Pavilion. She's not sure exactly which model, but the sticker on the bottom says "G60". The problem was a failed upgrade to 12.04. I was able to mostly repair it with sudo apt-get -f install, which ran setup and configuration for several hundred packages. The biggest problem at the moment is Xorg. The login screen (lightdm) loads normally but at a reduced resolution (1024x768 instead of 1366x768). But once you log in, it looks like this: Observe that the colors of the dock on the left and the bar at the top are normal. But the background is filled with bizarro color-skewed ghost images of the desktop. In all cases, the actual contents of any programs you run is a totally illegible mess, except that the bar at the top of any program windows looks and acts normally. And the ghost images are interactive! For example, if you click the icon in the top right corner to get the "shut down" menu, the same menu will appear in the ghost images below. Starting a terminal will start a terminal window in both the real desktop and the ghost images, and moving it around updates both the real and ghost desktops. I suspect Xorg is using some kind of wrong driver and/or parameter for the graphics hardware. Here is the graphics-relevant portion of the lspci -v output: 00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 09) Subsystem: Hewlett-Packard Company Device 360b Flags: bus master, fast devsel, latency 0 Capabilities: [e0] Vendor Specific Information: Len=0a <?> Kernel driver in use: agpgart-intel 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller]) Subsystem: Hewlett-Packard Company Device 360b Flags: bus master, fast devsel, latency 0, IRQ 44 Memory at d0000000 (64-bit, non-prefetchable) [size=4M] Memory at c0000000 (64-bit, prefetchable) [size=256M] I/O ports at 5110 [size=8] Expansion ROM at <unassigned> [disabled] Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit- Capabilities: [d0] Power Management version 3 Kernel driver in use: i915 Kernel modules: i915 00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 09) Subsystem: Hewlett-Packard Company Device 360b Flags: bus master, fast devsel, latency 0 Memory at d2500000 (64-bit, non-prefetchable) [size=1M] Capabilities: [d0] Power Management version 3 I'm not sure what to check next. I would ordinarily check xorg.conf to see what it says, but that apparently doesn't exist any more, and my googling has not yielded any useful techniques for getting Xorg to tell me what settings it decided to use. The weird part is that it works fine on the login screen. It's only when you actually log in as a user that the display gets screwed up. Suggestions?

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• Ubuntu Server and setting up two nic cards

  - by kmalik

  I have ubuntu server on a computer with a wireless and hardwired nic card. The wireless needs to get the internet and pass it to the ubuntu server as well as pass it along to the hardwired nic card to more computers. I am having issues getting the basic set up as I believe the route table is grabbing from the wrong nic card. The router is 192.168.1.0 and the server is set to 192.168.1.11 on the wireless card through DHCP ETH0 (wired nic card) is set up to be 10.10.10.0 and the server is 10.10.10.1) I am not a linux or networking guru but basically I am trying to have internet come from a guest network 192.168.1.0 i believe to give internet to the ubuntu server then the ubuntu server will also A) have the wired nic serve DHCP addresses to other computers via a switch or router (that acts as a switch) via 10.10.10.0 addresses. And I would love if it also passed along internet capabilities as well if possible. Bu really at this point my hope is to at least get the internet working on the server and the DHCP to pass correctly. At the moment the specific issue I am having is getting ubuntu server to connect to the internet and have both nic cards up and running correctly. Any help would be appreciated! The route table is as follows: Destination Gateway GM Flags Metric Iface 0.0.0.0 10.10.10.1 0.0.0.0 UG 100 eth0 10.10.10.0 0.0.0.0 255.255.255.0 U 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 eth0 1992.168.1.0 0.0.0.0 255.255.255.255.0 U 0 eth1 My interfaces is set up as follows: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 10.10.10.1 netmask 255.255.255.0 network 10.10.10.0 broadcast 10.10.10.255 gateway 10.10.10.1 domain-name-servers 192.168.1.0 auto eth1 iface eth1 inet dhcp netmask 255.255.255.0 gateway 192.168.1.0 wpa-driver wext wpa-ssid "ssid_name" wpa-ap-scan 1 wpa-proto wpa wpa-pairwise ccmp wpa-group ccmp wpa-key-mgmt wpa-psk wpa-psk "HASH" My DHCPD.conf (as there is a domain name server on here is as follows): ddns-update-style none default-lease-time 600 max-lease-time 7200 authoritative option domain-name "Kamron's Network" option subnet-mask 255.255.255.0 option broadcast-address 10.10.10.255 option routers 192.168.1.0 option domain-name-server 192.168.1.0 98.223.128.213 ooption subnet 10.10.10.0 netmask 255.255.255.0 { range 10.10.10.10 10.10.10.99 } log-facility local7

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• Is it ok to initialize an RB_ConstraintActor in PostBeginPlay?

  - by Almo

  I have a KActorSpawnable subclass that acts weird. In PostBeginPlay, I initialize an RB_ConstraintActor; the default is not to allow rotation. If I create one in the editor, it's fine, and won't rotate. If I spawn one, it rotates. Here's the class: class QuadForceKActor extends KActorSpawnable placeable; var(Behavior) bool bConstrainRotation; var(Behavior) bool bConstrainX; var(Behavior) bool bConstrainY; var(Behavior) bool bConstrainZ; var RB_ConstraintActor PhysicsConstraintActor; simulated event PostBeginPlay() { Super.PostBeginPlay(); PhysicsConstraintActor = Spawn(class'RB_ConstraintActorSpawnable', self, '', Location, rot(0, 0, 0)); if(bConstrainRotation) { PhysicsConstraintActor.ConstraintSetup.bSwingLimited = true; PhysicsConstraintActor.ConstraintSetup.bTwistLimited = true; } SetLinearConstraints(bConstrainX, bConstrainY, bConstrainZ); PhysicsConstraintActor.InitConstraint(self, None); } function SetLinearConstraints(bool InConstrainX, bool InConstrainY, bool InConstrainZ) { if(InConstrainX) { PhysicsConstraintActor.ConstraintSetup.LinearXSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearXSetup.bLimited = 0; } if(InConstrainY) { PhysicsConstraintActor.ConstraintSetup.LinearYSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearYSetup.bLimited = 0; } if(InConstrainZ) { PhysicsConstraintActor.ConstraintSetup.LinearZSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearZSetup.bLimited = 0; } } DefaultProperties { bConstrainRotation=true bConstrainX=false bConstrainY=false bConstrainZ=false bSafeBaseIfAsleep=false bNoEncroachCheck=false } Here's the code I use to spawn one. It's a subclass of the one above, but it doesn't reference the constraint at all. local QuadForceKCreateBlock BlockActor; BlockActor = spawn(class'QuadForceKCreateBlock', none, 'PowerCreate_Block', BlockLocation(), m_PreparedRotation, , false); BlockActor.SetDuration(m_BlockDuration); BlockActor.StaticMeshComponent.SetNotifyRigidBodyCollision(true); BlockActor.StaticMeshComponent.ScriptRigidBodyCollisionThreshold = 0.001; BlockActor.StaticMeshComponent.SetStaticMesh(m_ValidCreationBlock.StaticMesh); BlockActor.StaticMeshComponent.AddImpulse(m_InitialVelocity); I used to initialize an RB_ConstraintActor where I spawned it from the outside. This worked, which is why I'm pretty sure it has nothing to do with the other code in QuadForceKCreateBlock. I then added the internal constraint in QuadForceKActor for other purposes. When I realized I had two constraints on the CreateBlock doing the same thing, I removed the constraint code from the place where I spawn it. Then it started rotating. Is there a reason I should not be initializing an RB_ConstraintActor in PostBeginPlay? I feel like there's some basic thing about how the engine works that I'm missing.

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• ArchBeat Facebook Friday: Top 10 Shared Links - May 23-29, 2014

  - by OTN ArchBeat

  Among the 5,144 fans of the OTN ArchBeat Facebook Page the following Top 10 items were the most popular over the last seven days, May 23-29, 2014. GlassFish/Java EE Community Open Forum Today! | Reza Rahman Have questions about Glassfish? Java EE/GlassFish evangelist Reza Rahman has answers, and you can pick his brain tomorrow during an online forum organized by the London Glassfish User Group and C2B2. The event is free, but you must register in order to participate. Click the link for more information. Twitter Tuesday - Top 10 @ArchBeat Tweets - May 20-26, 2014 The top 10 @OTNArchBeat tweets for the week of May 20-26, 2014. Topics covered include ADF, Cloud, GoldenGate, KScope14, OBIEE, ODI, WebLogic, WebCenter, and more. FrameworkFolders Support has come to Oracle WebCenter Portal | JayJay Zheng Interested in working with Framework Folders in Oracle WebCenter Portal? Oracle ACE JayJay Zheng reviews the essentials. Video: Programming Best Practices - ADF Business Components | Frank Nimphius Frank Nimphius discusses best practices and recommendations for ADF Business Components in the latest video from ADF Architecture TV. Video: Kscope 2014 Preview: Data Modeling and Moving Meditation with Kent Graziano For your mind and your body! Oracle ACE Director Kent Graziano previews his Kscope 2014 data modeling presentations and the early morning Chi Gung sessions he will once again lead for Kscope attendees. OAG and OES Integration for Web API Security: skin and guts | Andre Correa A-Team architect Andre Correa's post examines a strategy for web API security that uses OAG (Oracle API Gateway) and OES (Oracle Entitlements Server). Getting Started with Coherence*Web in WebLogic Server 12.1.2 | Tim Middleton Solution architect Tim Middleton shows you how to configure Coherence*Web in WebLogic Server 12.1.2 and deploy a basic web application. SOA and Business Processes: You are the Process! Part of the 13-part "Industrial SOA" article series, this article looks at best practices for modeling and managing effective business processes. Authentication in Oracle Identity Federation/ IdP | Damien Carru Damien Carru discuss authentication when OIF acts as an IdP and how the server can be configured to use specific OAM Authentication Schemes to challenge the user. Caveats on Using WebLogic Server with JDK7 | JayJay Zheng Quick tech tips from Oracle ACE JayJay Zheng.

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• What Counts for a DBA: Passion

  - by drsql

  One of my first questions, when interviewing for a DBA/Programmer position, is always: “Why do you want this job?” The answers I receive range from cheesy hyperbole (“I want to enhance your services with my vast knowledge”) to deadpan realism (“I have N kids who all have a hole in the front of their face where food goes"). Both answers are fine in their own way, at least displaying some self-confidence, humour and honesty, but once in a while, I'll hear the answer that is music to me ears... “I LOVE DATABASES!” Whenever I hear it, my nerves tingle in hopeful anticipation; have I found someone for whom working with database isn't just a job, but a passion? Inevitably, I'm often disappointed. What initially seemed like passion turns out to be rather shallow enthusiasm; the person is enthusiastic about working with databases in the same way he or she might be about eating a bag of Cajun spiced kettle chips; enjoyable, but not something to think about too deeply or take too seriously. Enthusiasm comes, and enthusiasm goes. I've seen countless technical forum users burst onto the scene in a blaze of frantic question-answering, only to fade away within days, never to be heard from again. Passion, however, is more of a longstanding commitment. The biographies of the great technologists and authors of the recent past are full of the sort of passion and engrossment that lead a person to write a novel non-stop for a fortnight with no sleep and only dog food to eat (Philip K. Dick), or refuse to leave the works of the first tunnel under the Thames, even though it was flooded (Brunel). In a similar (though more modest) way, my passion for working with databases has led me to acts that might cause someone for whom it was "just a job" to roll their eyes in disbelief. Most evenings you're more likely to find me reading a database book than watching TV. I've spent hundreds of hours of my spare time writing blogs and articles (some of which are only read by tens of people); I've spent hundreds of dollars travelling to conferences, paying my own flight and hotel expenses, so that I can share a little of what I know, and mix with some like-minded people. And I know I'm far from alone in this, in the SQL Server community. Passion isn't everything, of course, and it isn't always accompanied by any great skill, but in almost every case, that skill can be cultivated over time. If you are doing what you are passionate about, work turns into more than just a way to feed your kids; it becomes your hobby, entertainment, and preoccupation. And it is this passion that gives a DBA the obsessive stubbornness, the refusal to be beaten by even the most difficult problem, which is often so crucial. A final word of warning though: passion without limits can turn weird. Never let it get in the way of your wife, kids, bills, or personal hygiene.

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• What's the best way to create a static utility class in python? Is using metaclasses code smell?

  - by rsimp

  Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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• Client-Server connection response timeout issues

  - by Srikar

  User creates a folder in client and in the client-side code I hit an API to the server to make this persistent for that user. But in some cases, my server is so busy that the request timesout. The server has executed my request but timedout before sending a response back to client. The timeout set is 10 seconds in client. At this point the client thinks that server has not executed its request (of creating a folder) and ends up sending it again. Now I have 2 folders on the server but the user has created only 1 folder in the client. How to prevent this? One of the ways to solve this is to use a unique ID with each new request. So the ID acts as a distinguisher between old and new requests from client. But this leads to storing these IDs on my server and do a lookup for each API call which I want to avoid. Other way is to increase the timeout duration. But I dont want to change this from 10 seconds. Something tells me that there are better solutions. I have posted this question in stackoverflow but I think its better suited here. UPDATE: I will make my problem even more explicit. The client is a webbrowser and the server is running nginx+django+mysql (standard stack). The user creates a folder in webbrowser. As a result I need to hit a server API. The API call responds back, thereby client knows API call was success. This is normal scenario. Sometimes though, server successfully completes the API request but the client-side (webbrowser) connection timesout before server can respond back. The client has no clue at this point. The user thinks the request was a fail & clicks again. This time it was a success but when the UI refreshes he sees 2 folders. I want to remedy this situation.

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• Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

  - by Rowan Freeman

  Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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• Loading another domain's content in a modal iframe - acceptable?

  - by user568458

  Is it okay to load another page in an iframe in a modal pop-up window - in terms of legal and ethical standards around displaying 3rd party content? I remember a few years ago there was controversy and a debate about whether it was okay to load another domain's page content on your domain in a full-width iframe, with your site providing a masthead with controls for favouriting, linking etc (e.g. like StumbleUpon). I seem to recall that the consensus was, that it was okay so long as you were clearly in no way claiming ownership of the 3rd party content or attempting to modify the content and so long as there was a 'go to site' button or equivalent; and that sites could ask you to exclude them, but generally speaking, it's an acceptable practice. How acceptable would it be considered to be to load another site's page within a modal (lightbox-like) popup box (following all the above principles: clear attribution and a prominent button that kills the iframe and gives them the 3rd party original)? My expectation would be that it would follow the same principles, and be acceptable so long as these conditions were met. Note that I'm asking about the likely legitimate responses of the 3rd party sites and possible legal position, not about usability or UX. I'm aware that this should never ever ever ever ever be the standard way external links are loaded, and that 99% of the time linking to external content like this would be terrible for usability. My specific use case is one of those 1% of cases where loading a separate page in this tab actually wouldn't be the expected behaviour of a link: an interactive data visualisation tool that also acts as a 'browser' of external content (science papers underlying the data it navigates). All other links within the interactive will change something while staying on the same page. If the user clicked one of these external links by mistake (as people often do, even when they are clearly, noisily labelled) and then had to back-button back, they would lose their fine-grained position in the interactive tool (jquery bbq hashchanges being not appropriate for all elements of the tool). New window/tab will simply open the target page on the 3rd party domain. Opening a new window/tab would also be an alternative option (and has its own disadvantages) - my question is, whether this is an alternative that could be considered (in terms of acceptable practice around intellectual property etc), irrespective of which option is best for UX: which is something we'll decide the proper way, based on actual UX testing.

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• I need help with specific types of movement.

  - by IronGiraffe

  I'm adding movable crates to my game and I need some help with my movement code. The way I've set up my movement code the crate's X and Y are moved according to a vector2 unless it hits a wall. Here's the movement code: if (frameCount % (delay / 2) == 0) { for (int i = 0; i < Math.Abs(cSpeed.X); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X += Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } else { if (!Level.CollideTiles(crateBounds.X - (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X -= Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } } for (int i = 0; i < Math.Abs(cSpeed.Y); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y += Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } else { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y - Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y -= Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } } } The frameCount and delay variables just slow down the movement somewhat. Anyway, I've added a tool to my game that acts as a gravity well (drawing objects into it's center; the closer they get to the center the faster they go) and what I'm trying to do is make it so that the crate will bounce off the player (and vice versa) when they collide. Thus far, my code only keeps the crate and player from getting stuck inside each other (the player can still get stuck under the crate, but I'll fix that later.) So what I'd like to know is how I can best make the crate bounce off the player. The other movement problem I'm having is related to another tool which allows the player to pick up crates and move around with them. The problem is that the crate's movement while being carried isn't tied to the movement script (it moves the crate itself, instead of adding to speed), which makes the crate go through walls and such. I know what I have to do: make the crate's speed match the player's speed while the player is holding it, but I need the crate to snap to a certain position (just in front of the player) when the player grabs it and it needs to switch to another position (just in front of the player on the other side) when they player faces the other direction while holding it. What would be the best way to make it switch places while keeping all the movement tied to the speed vector?

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• Storing hierarchical template into a database

  - by pduersteler

  If this title is ambiguous, feel free to change it, I don't know how to put this in a one-liner. Example: Let's assume you have a html template which contains some custom tags, like <text_field />. We now create a page based on a template containing more of those custom tags. When a user wants to edit the page, he sees a text field. he can input things and save it. This looks fairly easy to set up. You either have something like a template_positions table which stores the content of those fields. Case: I now have a bit of a blockade keeping things as simple as possible. Assume you have the same tag given in your example, and additionally, <layout> and <repeat> tags. Here's an example how they should be used: <repeat> <layout name="image-left"> <image /> <text_field /> </layout> <layout name="image-right"> <text_field /> <image /> </layout> </repeat> We now have a block which can be repeated, obviously. This means: when creting/editing a page containing such a template block, I can choose between a layout image-left and image-right which then gets inserted as content element (where content for <image /> and <text_field /> gets stored). And because this is inside a <repeat>, content elements from the given layouts can be inserted multiple times. How do you store this? Simply said, this could be stored with the same setup I've wrote in the example above, I just need to add a parent_id or something similiar to maintain a hierarchy. but I think I am missing something. At least the relation between an inserted content element and the origin/insertion point is missing. And what happens when I update the template file? Do I have to give every custom tag that acts as editable part of a template an identifier that matches an identifier in the template to substitue them correctly? Or can you think of a clean solution that might be better?

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• A Simple Entity Tagger

  - by Elton Stoneman

  In the REST world, ETags are your gateway to performance boosts by letting clients cache responses. In the non-REST world, you may also want to add an ETag to an entity definition inside a traditional service contract – think of a scenario where a consumer persists its own representation of your entity, and wants to keep it in sync. Rather than load every entity by ID and check for changes, the consumer can send in a set of linked IDs and ETags, and you can return only the entities where the current ETag is different from the consumer’s version.  If your entity is a projection from various sources, you may not have a persistent ETag, so you need an efficient way to generate an ETag which is deterministic, so an entity with the same state always generates the same ETag. I have an implementation for a generic ETag generator on GitHub here: EntityTagger code sample. The essence is simple - we get the entity, serialize it and build a hash from the serialized value. Any changes to either the state or the structure of the entity will result in a different hash. To use it, just call SetETag, passing your populated object and a Func<> which acts as an accessor to the ETag property: EntityTagger.SetETag(user, x => x.ETag); The implementation is all in at 80 lines of code, which is all pretty straightforward: var eTagProperty = AsPropertyInfo(eTagPropertyAccessor); var originalETag = eTagProperty.GetValue(entity, null); try { ResetETag(entity, eTagPropertyAccessor); string json; var serializer = new DataContractJsonSerializer(entity.GetType()); using (var stream = new MemoryStream()) { serializer.WriteObject(stream, entity); json = Encoding.UTF8.GetString(stream.GetBuffer(), 0, (int)stream.Length); } var guid = GetDeterministicGuid(json); eTagProperty.SetValue(entity, guid.ToString(), null); //... There are a couple of helper methods to check if the object has changed since the ETag value was last set, and to reset the ETag. This implementation uses JSON to do the serializing rather than XML. Benefit - should be marginally more efficient as your hashing a much smaller serialized string; downside, JSON doesn't include namespaces or class names at the root level, so if you have two classes with the exact same structure but different names, then instances which have the same content will have the same ETag. You may want that behaviour, but change to use the XML DataContractSerializer if you think that will be an issue. If you can persist the ETag somewhere, it will save you server processing to load up the entity, but that will only apply to scenarios where you can reliably invalidate your ETag (e.g. if you control all the entry points where entity contents can be updated, then you can calculate and persist the new ETag with each update).

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• URL slugs: ideal length, and the real SEO effects of these slugs

  - by tattvamasi

  this question is addressed widely on SO and outside it, but for some reason, instead of taking it as a good load of great advice, all this information is confusing me. ** Problem ** I already had, on one of my sites, "prettified" urls. I had taken out the query strings, rewritten the URLS, and the link was short enough for me, but had a problem: the ID of the item or post in the URL isn't good for users. One of the users asked is there's a way to get rid of numbers, and I thought it was better for users to just see a clue of the page content in the URL. ** Solution ** With this in mind, I am trying with a section of the site.Armed with 301 redirects, some parsing work, and a lot of patience, I have added the URL slugs to some blog entries, and the slug of the URL reports the title of the article (something close to http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ ** Problems after Solution ** The problem, as I see it, is that now the URL of those blog articles is very descriptive for sure, but it is also impossible to remember. So, this brings me to the same issue I had with my previous problem: if numbers say nothing and can't be remembered, what's the use of these slugs? I prefer to see http://example.com/my-news/1/ than http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ To avoid forcing my user to memorize my URLS, I have added a script that finds the closest match to the URL you type, and redirects there. This is something I like, because the page now acts as a sort of little search engine, and users can play with the URLS to find articles. ** Open questions ** I still have some open questions, and don't seem to be able to find an answer, because answers tend to contradict one another. 1) How many characters should an URL ideally be long? I've read the magic number 115 and am sticking to that, but am not sure. 2) Is this really good for SEO? One of those blog articles I have redirected, with ID number in the URL and all, ranked second on Google. I've just found this question, and the answer seems to be consistent with what I think URL slug and SEO - structure (but see this other question with the opposite opinion) 3) To make a question with a specific example, would this URL risk to be penalized? Is it acceptable? Is it too long? StackOverflow seems to have comparably long URLs, but I'm not sure it's a winning strategy in my case. I just wanted to facilitate my users without running into Google's algorithms.

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• Hotmail Senders receiving NDR : "550-Please turn on SMTP Authentication in your mail client..."

  - by DKNUCKLES

  Recently, senders from Hotmail have begun to get the following NDR when trying to e-mail our domain. EDIT : Full NDR Message Action: failed Status: 5.5.0 Diagnostic-Code: smtp;550-Please turn on SMTP Authentication in your mail client, or login to the 550-IMAP/POP3 server before sending your message. 550-snt0-omc3-s36.snt0.hotmail.com [65.55.90.175]:49271 is not permitted to 550 relay through this server without authentication This is seemingly out of the blue and I'm at a loss as to why this is happening. Pertinent Information We have multiple domains hooked up to our Exchange server. We changed our company name in January of this year, and the old primary domain (olddomain.com) will accept e-mails from Hotmail accounts, however e-mails sent to the new primary domain (newdomain.com) bounce back with the NDR listed above. The bounces only appear to be happening when the Hotmail sender is sending a new e-mail, and not if they are responding to an e-mail sent from our end. We have made no changes to the configuration of our server recently. This e-mail first appeared last Friday. As far as I can tell, the mail doesn't even seem to get to our server We performed an Exchange 2003 to 2010 migration last year. The 2003 acts as a Smart Host Any advice on this issue would be greatly appreciated! I'm at a loss

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• Exchange 2010 DAG Automatic Failover Testing/Issue. Not always automatically failing over to health

  - by Richard

  Ok I've got 2 exchange 2010 servers that run client access/hub transport/mailbox roles and one exchange 2010 server running just client access/hub transport roles and acts as my bridgehead. The two mailbox servers are running one database setup in a DAG. Server A shows the DB Mounted and Server B shows Healthy. If I reboot Server A via windows GUI Server B switches from healthy to mounted and I see hardly any interruption in service using Outlook 2007. Server A shows "Service down", then "Failed" then "Healthy" and leaves the DB mounted on Server B. This is how it should work, so far so good. Now if I test Server A being shut down cold, or unplugging both nics from network to simulate failure, Server B switches from Healthy to Mounted and server A switches to "Service Down" but my outlook client never connects to the DB mounted on server B! I can connect to server C (client access/hub transport) and get to my email and even send new email out, but incoming email doesn't deliver until Server A is brought back online and it's DB goes back to Healthy status. So I don't understand why it auto fail-overs when I reboot the server with the mounted DB copy, causing very little outlook 2007 hiccup if any. But when I shutdown or DC the mounted DB server it DOES mount the healthy copy but outlook 2007 clients can't connect.. I hope the picture I'm trying to paint makes some sense, it's driving me a little batty. Any help would be appreciated!

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• Task scheduler "hidden" only hides task, not process

  - by Brandi

  I am trying to make an application that acts like a desktop application for all the computers in our network. I have already got a windows forms app that works like I want it to, and I'm using the task scheduler to start it on login. We would really like it if the process as well as the task is hidden from the task manager in order to avoid accidental deletion. Selecting "Hidden" in the task scheduler hides the task (good!) but the process is still visible (not good enough). I tried using the option to run as "SYSTEM" or "LOCAL SERVICE" so that the user would get "access denied" when trying to delete or just wouldn't even view it by default. However, running as a service makes the process invisible on Vista and 7, and the point of my app is to display information interactively. (User can click, sort, etc). Is there any other alternatives to either run the process as someone/something besides the logged in user and still have the logged on user be able to see and interact with it? (Therefore it would list as someone else's app?) From what I've read on the internet, the only ways to actually hide something from the task manager seem hacky and/or difficult and rather involved. I don't really want to write a bunch of C or whatever only to maybe not have it work on Vista/7 anyway. Besides which, for a legitimate app with a legitimate use, I shouldn't have to go to those extremes... I see "Access Denied" all the time for system processes... why is it so hard for me to do the same? So does anyone have any simple solutions? Is it easier than I think to just list something in the task manager as another user? Thanks in advance for any replies.

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• Cisco Spam Blocker, Iron Port, Lotus Domino, Integration Help

  - by NickToyota

  Hi serverfault universe, I work for a medium sized (roughly 200 user) company. We are attempting to intagrate our new Cisco Spam Video Blocker (ironport) device into our network so that it acts as an incoming filter then passes it off to our Lotus domino mail server. And also vise versa. The way our network is setup currently has an mx record pointing to our Domino mail SMTP incoming server which is currently setup to be an inbound gateway and filter (using symantec domino mail software). We want to replace the inbound gateway with the ironport. Our company has also invested in a pool of external IP addresses which I believe has been currently assigned to our web, email, servers. What would the proper course of action be to successfully integrate the device be? Mx record change? Replace the domino gateway completely with the ironport? We attempted to set the ironport device to the external IP of what our mx record is pointing to without much success. Any help on proper setup would be greatly appreciated.

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• mysqld crashes on any statement

  - by ??iu

  I restarted my slave to change configuration settings to skip reverse hostname lookup on connecting and to enable the slow query log. I edited /etc/my.cnf making only these changes, then restarted mysqld with /etc/init.d/mysql restart All appeared to be well but when I connect to msyqld remotely or locally though it connects okay a slight problem is that mysqld crashes whenever you try to issue any kind of statement. The client looks like: Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.1.31-1ubuntu2-log Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show tables; ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 1 Current database: mydb ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away Bus error The mysqld error log looks like: 101210 16:35:51 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:35:51 InnoDB: Assertion failure in thread 140245598570832 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:35:51 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=3 max_threads=600 threads_connected=3 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18209220 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f8d791580d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f902a76a080] /lib/libc.so.6(gsignal+0x35) [0x7f90291f8fb5] /lib/libc.so.6(abort+0x183) [0x7f90291fabc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f902a7623ba] /lib/libc.so.6(clone+0x6d) [0x7f90292abfcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18213c70 = thd->thread_id=3 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:35:51 mysqld_safe Number of processes running now: 0 101210 16:35:51 mysqld_safe mysqld restarted InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 101210 16:35:54 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... 101210 16:35:56 InnoDB: Started; log sequence number 456 143528628 101210 16:35:56 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 16:35:56 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 16:35:56 [Note] Event Scheduler: Loaded 0 events 101210 16:35:56 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 16:36:11 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:36:11 InnoDB: Assertion failure in thread 139955151501648 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:36:11 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18588720 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f49d916f0d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f4c8a73f080] /lib/libc.so.6(gsignal+0x35) [0x7f4c891cdfb5] /lib/libc.so.6(abort+0x183) [0x7f4c891cfbc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f4c8a7373ba] /lib/libc.so.6(clone+0x6d) [0x7f4c89280fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18599950 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:36:11 mysqld_safe Number of processes running now: 0 101210 16:36:11 mysqld_safe mysqld restarted The config is [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] innodb_file_per_table innodb_buffer_pool_size=10G innodb_log_buffer_size=4M innodb_flush_log_at_trx_commit=2 innodb_thread_concurrency=8 skip-slave-start server-id=3 # # * IMPORTANT # If you make changes to these settings and your system uses apparmor, you may # also need to also adjust /etc/apparmor.d/usr.sbin.mysqld. # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /DB2/mysql tmpdir = /tmp skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. #bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 128K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP max_connections = 600 #table_cache = 64 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M query_cache_size = 32M # skip-federated slow-query-log skip-name-resolve Update: I followed the instructions as per http://dev.mysql.com/doc/refman/5.1/en/forcing-innodb-recovery.html and set innodb_force_recovery = 4 and the logs are showing a different error but the behavior is still the same: 101210 19:14:15 mysqld_safe mysqld restarted 101210 19:14:19 InnoDB: Started; log sequence number 456 143528628 InnoDB: !!! innodb_force_recovery is set to 4 !!! 101210 19:14:19 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 19:14:19 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 19:14:19 [Note] Event Scheduler: Loaded 0 events 101210 19:14:19 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 19:14:32 InnoDB: error: space object of table mydb/__twitter_friend, InnoDB: space id 1602 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/access_request, InnoDB: space id 1318 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/activity, InnoDB: space id 1595 did not exist in memory. Retrying an open. 101210 19:14:32 - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x1753c070 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f7a0b5800d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f7cbc350080] /usr/sbin/mysqld(ha_innobase::innobase_get_index(unsigned int)+0x46) [0x77c516] /usr/sbin/mysqld(ha_innobase::innobase_initialize_autoinc()+0x40) [0x77c640] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x3f3) [0x781f23] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f7cbc3483ba] /lib/libc.so.6(clone+0x6d) [0x7f7cbae91fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x1754d690 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash.

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• Windows 2008 Server cannot access any network share

  - by Ramesh

  Hello friends I run a Windows 2008 server with SP2. This server acts as a desktop alone. Recently, I switched between two networks (corporate and other) using this system. Ever since, I am unable to access any network share on the original network from where I installed and configured the desktop. The message I get is "Network path was not found". Note that I am able to access the internet and my corporate mail server. I am told this is a Vista and Windows 2008 specific problem and I have done everything I could think of: a) Deleted the second network settings from the desktop b) Installed a patch from MS that supposed took care of this problem (with MS clearly saying they had not tested this enough) c) The SP2 install was after the problem occurred and I went ahead with it in the hope that SP2 may have something that would fix this Some additional details: a) A system admin can log into this system from a remote terminal b) I cannot get into my own system using the hidden share C$ - for instance \mymachine\C$ gives me the same message as above - Network path not found c) I can log into my system remotely using mstsc d) I cannot create shares on this system - as an extension network printers are not detected I have an update for you: The error message is as follows - **Network Error** Windows cannot access \\network_share Check the spelling of the name. Otherwise there might a problem with your network. To try to identify and resolve network problems, click Diagnose. Clicking Diagnose gives Error Code: 0x80070035 The network path was not found. Any help will be appreciated Thanks

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