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• JDK bug migration: components and subcomponents

  - by darcy

  One subtask of the JDK migration from the legacy bug tracking system to JIRA was reclassifying bugs from a three-level taxonomy in the legacy system, (product, category, subcategory), to a fundamentally two-level scheme in our customized JIRA instance, (component, subcomponent). In the JDK JIRA system, there is technically a third project-level classification, but by design a large majority of JDK-related bugs were migrated into a single "JDK" project. In the end, over 450 legacy subcategories were simplified into about 120 subcomponents in JIRA. The 120 subcomponents are distributed among 17 components. A rule of thumb used was that a subcategory had to have at least 50 bugs in it for it to be retained. Below is a listing the component / subcomponent classification of the JDK JIRA project along with some notes and guidance on which OpenJDK email addresses cover different areas. Eventually, a separate incidents project to host new issues filed at bugs.sun.com will use a slightly simplified version of this scheme. The preponderance of bugs and subcomponents for the JDK are in library-related areas, with components named foo-libs and subcomponents primarily named after packages. While there was an overall condensation of subcomponents in the migration, in some cases long-standing informal divisions in core libraries based on naming conventions in the description were promoted to formal subcomponents. For example, hundreds of bugs in the java.util subcomponent whose descriptions started with "(coll)" were moved into java.util:collections. Likewise, java.lang bugs starting with "(reflect)" and "(proxy)" were moved into java.lang:reflect. client-libs (Predominantly discussed on 2d-dev and awt-dev and swing-dev.) 2d demo java.awt java.awt:i18n java.beans (See beans-dev.) javax.accessibility javax.imageio javax.sound (See sound-dev.) javax.swing core-libs (See core-libs-dev.) java.io java.io:serialization java.lang java.lang.invoke java.lang:class_loading java.lang:reflect java.math java.net java.nio (Discussed on nio-dev.) java.nio.charsets java.rmi java.sql java.sql:bridge java.text java.util java.util.concurrent java.util.jar java.util.logging java.util.regex java.util:collections java.util:i18n javax.annotation.processing javax.lang.model javax.naming (JNDI) javax.script javax.script:javascript javax.sql org.openjdk.jigsaw (See jigsaw-dev.) security-libs (See security-dev.) java.security javax.crypto (JCE: includes SunJCE/MSCAPI/UCRYPTO/ECC) javax.crypto:pkcs11 (JCE: PKCS11 only) javax.net.ssl (JSSE, includes javax.security.cert) javax.security javax.smartcardio javax.xml.crypto org.ietf.jgss org.ietf.jgss:krb5 other-libs corba corba:idl corba:orb corba:rmi-iiop javadb other (When no other subcomponent is more appropriate; use judiciously.) Most of the subcomponents in the xml component are related to jaxp. xml jax-ws jaxb javax.xml.parsers (JAXP) javax.xml.stream (JAXP) javax.xml.transform (JAXP) javax.xml.validation (JAXP) javax.xml.xpath (JAXP) jaxp (JAXP) org.w3c.dom (JAXP) org.xml.sax (JAXP) For OpenJDK, most JVM-related bugs are connected to the HotSpot Java virtual machine. hotspot (See hotspot-dev.) build compiler (See hotspot-compiler-dev.) gc (garbage collection, see hotspot-gc-dev.) jfr (Java Flight Recorder) jni (Java Native Interface) jvmti (JVM Tool Interface) mvm (Multi-Tasking Virtual Machine) runtime (See hotspot-runtime-dev.) svc (Servicability) test core-svc (See serviceability-dev.) debugger java.lang.instrument java.lang.management javax.management tools The full JDK bug database contains entries related to legacy virtual machines that predate HotSpot as well as retired APIs. vm-legacy jit (Sun Exact VM) jit_symantec (Symantec VM, before Exact VM) jvmdi (JVM Debug Interface ) jvmpi (JVM Profiler Interface ) runtime (Exact VM Runtime) Notable command line tools in the $JDK/bin directory have corresponding subcomponents. tools appletviewer apt (See compiler-dev.) hprof jar javac (See compiler-dev.) javadoc(tool) (See compiler-dev.) javah (See compiler-dev.) javap (See compiler-dev.) jconsole launcher updaters (Timezone updaters, etc.) visualvm Some aspects of JDK infrastructure directly affect JDK Hg repositories, but other do not. infrastructure build (See build-dev and build-infra-dev.) licensing (Covers updates to the third party readme, licenses, and similar files.) release_eng (Release engineering) staging (Staging of web pages related to JDK releases.) The specification subcomponent encompasses the formal language and virtual machine specifications. specification language (The Java Language Specification) vm (The Java Virtual Machine Specification) The code for the deploy and install areas is not currently included in OpenJDK. deploy deployment_toolkit plugin webstart install auto_update install servicetags In the JDK, there are a number of cross-cutting concerns whose organization is essentially orthogonal to other areas. Since these areas generally have dedicated teams working on them, it is easier to find bugs of interest if these bugs are grouped first by their cross-cutting component rather than by the affected technology. docs doclet guides hotspot release_notes tools tutorial embedded build hotspot libraries globalization locale-data translation performance hotspot libraries The list of subcomponents will no doubt grow over time, but my inclination is to resist that growth since the addition of each subcomponent makes the system as a whole more complicated and harder to use. When the system gets closer to being externalized, I plan to post more blog entries describing recommended use of various custom fields in the JDK project.

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• Polite busy-waiting with WRPAUSE on SPARC

  - by Dave

  Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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• Subterranean IL: The ThreadLocal type

  - by Simon Cooper

  I came across ThreadLocal<T> while I was researching ConcurrentBag. To look at it, it doesn't really make much sense. What's all those extra Cn classes doing in there? Why is there a GenericHolder<T,U,V,W> class? What's going on? However, digging deeper, it's a rather ingenious solution to a tricky problem. Thread statics Declaring that a variable is thread static, that is, values assigned and read from the field is specific to the thread doing the reading, is quite easy in .NET: [ThreadStatic] private static string s_ThreadStaticField; ThreadStaticAttribute is not a pseudo-custom attribute; it is compiled as a normal attribute, but the CLR has in-built magic, activated by that attribute, to redirect accesses to the field based on the executing thread's identity. TheadStaticAttribute provides a simple solution when you want to use a single field as thread-static. What if you want to create an arbitary number of thread static variables at runtime? Thread-static fields can only be declared, and are fixed, at compile time. Prior to .NET 4, you only had one solution - thread local data slots. This is a lesser-known function of Thread that has existed since .NET 1.1: LocalDataStoreSlot threadSlot = Thread.AllocateNamedDataSlot("slot1"); string value = "foo"; Thread.SetData(threadSlot, value); string gettedValue = (string)Thread.GetData(threadSlot); Each instance of LocalStoreDataSlot mediates access to a single slot, and each slot acts like a separate thread-static field. As you can see, using thread data slots is quite cumbersome. You need to keep track of LocalDataStoreSlot objects, it's not obvious how instances of LocalDataStoreSlot correspond to individual thread-static variables, and it's not type safe. It's also relatively slow and complicated; the internal implementation consists of a whole series of classes hanging off a single thread-static field in Thread itself, using various arrays, lists, and locks for synchronization. ThreadLocal<T> is far simpler and easier to use. ThreadLocal ThreadLocal provides an abstraction around thread-static fields that allows it to be used just like any other class; it can be used as a replacement for a thread-static field, it can be used in a List<ThreadLocal<T>>, you can create as many as you need at runtime. So what does it do? It can't just have an instance-specific thread-static field, because thread-static fields have to be declared as static, and so shared between all instances of the declaring type. There's something else going on here. The values stored in instances of ThreadLocal<T> are stored in instantiations of the GenericHolder<T,U,V,W> class, which contains a single ThreadStatic field (s_value) to store the actual value. This class is then instantiated with various combinations of the Cn types for generic arguments. In .NET, each separate instantiation of a generic type has its own static state. For example, GenericHolder<int,C0,C1,C2> has a completely separate s_value field to GenericHolder<int,C1,C14,C1>. This feature is (ab)used by ThreadLocal to emulate instance thread-static fields. Every time an instance of ThreadLocal is constructed, it is assigned a unique number from the static s_currentTypeId field using Interlocked.Increment, in the FindNextTypeIndex method. The hexadecimal representation of that number then defines the specific Cn types that instantiates the GenericHolder class. That instantiation is therefore 'owned' by that instance of ThreadLocal. This gives each instance of ThreadLocal its own ThreadStatic field through a specific unique instantiation of the GenericHolder class. Although GenericHolder has four type variables, the first one is always instantiated to the type stored in the ThreadLocal<T>. This gives three free type variables, each of which can be instantiated to one of 16 types (C0 to C15). This puts an upper limit of 4096 (163) on the number of ThreadLocal<T> instances that can be created for each value of T. That is, there can be a maximum of 4096 instances of ThreadLocal<string>, and separately a maximum of 4096 instances of ThreadLocal<object>, etc. However, there is an upper limit of 16384 enforced on the total number of ThreadLocal instances in the AppDomain. This is to stop too much memory being used by thousands of instantiations of GenericHolder<T,U,V,W>, as once a type is loaded into an AppDomain it cannot be unloaded, and will continue to sit there taking up memory until the AppDomain is unloaded. The total number of ThreadLocal instances created is tracked by the ThreadLocalGlobalCounter class. So what happens when either limit is reached? Firstly, to try and stop this limit being reached, it recycles GenericHolder type indexes of ThreadLocal instances that get disposed using the s_availableIndices concurrent stack. This allows GenericHolder instantiations of disposed ThreadLocal instances to be re-used. But if there aren't any available instantiations, then ThreadLocal falls back on a standard thread local slot using TLSHolder. This makes it very important to dispose of your ThreadLocal instances if you'll be using lots of them, so the type instantiations can be recycled. The previous way of creating arbitary thread-static variables, thread data slots, was slow, clunky, and hard to use. In comparison, ThreadLocal can be used just like any other type, and each instance appears from the outside to be a non-static thread-static variable. It does this by using the CLR type system to assign each instance of ThreadLocal its own instantiated type containing a thread-static field, and so delegating a lot of the bookkeeping that thread data slots had to do to the CLR type system itself! That's a very clever use of the CLR type system.

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• 4 Ways Your Brand Can Jump From the Edge of Space

  - by Mike Stiles

  Can your brand’s social media content captivate the world and make it hold its collective breath? Can you put something on the screen that’s so compelling that your audience can’t look away? Will they want to make sure their friends see it so they can talk about it? If not, you’re probably not with Red Bull. I was impressed with Red Bull’s approach to social content even before Felix Baumgartner’s stunning skydive from the edge of space. And then they did this. According to Visible Measures, videos of the jump scored 50 million views in 4 days. 1,700 clips were generated from both official and organic sources. The live stream was the most watched YouTube Stream of all time (8 million concurrent viewers). The 2nd most watched live stream was…Felix’ first attempt Oct. 9. Are you ready to compete with that? I ask that question because some brands are still out there tying themselves up in knots about whether or not they should tweet. The public’s time and attention are scarce commodities, commodities they value greatly. The competition amongst brands for that time and attention is intense and going up like Felix’s capsule. If you still view your press releases as “content,” you won’t even be counted as being among the competition. Here are 5 lessons learned from Red Bull’s big leap: 1. They have a total understanding of their target market and audience. Not only do they have an understanding of it, they do something about it. They act on it. They fill the majority of their thoughts with what the audience wants. They hunger for wild applause from that audience. They want to do things that embrace the audience’s lifestyle and immerse in it so the target will identify the brand as “one of them.” Takeaway: BE your target market. 2. They deliver content that strikes the audience right where they emotionally live. If you want your content to have impact, you have to make your audience’s heart race, or make them tear up, or make them laugh. Label them “data points” all you want, but humans are emotional creatures. No message connects that’s not carried in on an emotion. Takeaway: You’re on the inside. If your content doesn’t make you say “wow,” it’s unlikely it will register with fans. 3. They put aside old school marketing and don’t let their content be degraded into a commercial. Their execs seem to understand the value in keeping a lid on the hard sell. So many brands just can’t bring themselves to disconnect advertising and social content. The result is, otherwise decent content gets contaminated with a desperation the viewer can smell a mile away. Think the Baumgartner skydive didn’t do Red Bull any good since he wasn’t drinking one on the way down while singing a jingle? Analysis company Taykey discovered that at the peak of the skydive buzz, about 1% of all online conversation was about the jump. Mentions of Red Bull constituted 1/3 of 1% of all Internet activity. Views of other Red Bull videos also shot up. Takeaway: Chill out with the ads. Your brand will get full credit for entertaining/informing fans in a relevant way, provided you do it. 4. They don’t hesitate to ask, “What can we do next”? Most corporate cultures are a virtual training facility for “we can’t do that.” Few are encouraged to innovate or think big, if think at all. Thinking big involves faith, and work. It means freedom and letting employees run a little wild with their ideas. There will always be the opportunity to let fear of everything that moves creep in and kill grand visions dead in their tracks. Experimenting must be allowed. Failure must be allowed. Red Bull didn’t think big. They thought mega. They tried to outdo themselves. Felix could have gone ahead and jumped halfway up, thinking, “This is still relatively high up. Good enough.” But that wouldn’t have left us breathless. Takeaway: Go for it. Jump. In putting up social properties and gathering fans of your brand, you’ve basically invited people to a party. A good host doesn’t just set out warm beer and stale chips because that’s inexpensive and easy. Be on the lookout for ways to make your guests walk away saying, “That was epic.”

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• The architecture and technologies to use for a secure, fast, reliable and easily scalable web application

  - by DSoul

  ^ For actual questions, skip to the lists down below I understand, that his is a vague topic, but please, before you turn the other way and disregard me, hear me out. I am currently doing research for a web application(I don't know if application is the correct word for it, but I will proceed w/ that for now), that one day might need to be everything mentioned in the title. I am bound by nothing. That means that every language, OS and framework is acceptable, but only if it proves it's usefulness. And if you are going to say, that scalability and speed depend on the code I write for this application, then I agree, but I am just trying to find something, that wouldn't stand in my way later on. I have done quite a bit reading on this subject, but I still don't have a clear picture, to what suits my needs, so I come to you, StackOverflow, to give me directions. I know you all must be wondering what I'm building, but I assure you, that it doesn't matter. I have heard of 12 factor app though, if you have any similar guidelines or what is, to suggest the please, go ahead. For the sake of keeping your answers as open as possible, I'm not gonna provide you my experience regarding anything written in this question. ^ Skippers, start here First off - the weights of the requirements are probably something like that (on a scale of 10): Security - 10 Speed - 5 Reliability (concurrency) - 7.5 Scalability - 10 Speed and concurrency are not a top priority, in the sense, that the program can be CPU intensive, and therefore slow, and only accept a not-that-high number of concurrent users, but both of these factors must be improvable by scaling the system Anyway, here are my questions: How many layers should the application have, so it would be future-proof and could best fulfill the aforementioned requirements? For now, what I have in mind is the most common version: Completely separated front end, that might be a web page or an MMI application or even both. Some middle-ware handling communication between the front and the back end. This is probably a server that communicates w/ the front end via HTTP. How the communication w/ the back end should be handled is probably dependent on the back end. The back end. Something that handles data through resources like DB and etc. and does various computations w/ the data. This, as the highest priority part of the software, must be easily spread to multiple computers later on and have no known security holes. I think ideally the middle-ware should send a request to a queue from where one of the back end processes takes this request, chops it up to smaller parts and buts these parts of the request back onto the same queue as the initial request, after what these parts will be then handled by other back end processes. Something *map-reduce*y, so to say. What frameworks, languages and etc. should these layers use? The technologies used here are not that important at this moment, you can ignore this part for now I've been pointed to node.js for this part. Do you guys know any better alternatives, or have any reasons why I should (not) use node.js for this particular job. I actually have no good idea, what to use for this job, there are too many options out there, so please direct me. This part (and the 2. one also, I think) depend a lot on the OS, so suggest any OSs alongside w/ the technologies/frameworks. Initially, all computers (or 1 for starters) hosting the back end are going to be virtual machines. Please do give suggestions to any part of the question, that you feel you have comprehensive knowledge and/or experience of. And also, point out if you feel that any part of the current set-up means an instant (or even distant) failure or if I missed a very important aspect to consider. I'm not looking for a definitive answer for how to achieve my goals, because there certainly isn't one, for I haven't provided you w/ all the required information. I'm just looking for recommendations and directions on what to look into. Also, bare in mind, that this isn't something that I have to get done quickly, to sell and let it be re-written by the new owner (which, I've been told for multiple times, is what I should aim for). I have all the time in the world and I really just want to learn doing something really high-end. Also, excuse me if my language isn't the best, I'm not a native. Anyway. Thanks in advance to anyone, who takes the time to help me out here. PS. When I do seem to come up w/ a good architecture/design for this project, I will certainly make it an open project and keep you guys up to date w/ it's development. As in what you could have told me earlier and etc. For obvious reasons the very same question got closed on SO, but could you guys still help me?.

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• Invalid or expired security context token in WCF web service

  - by Damian

  All, I have a WCF web service (let's called service "B") hosted under IIS using a service account (VM, Windows 2003 SP2). The service exposes an endpoint that use WSHttpBinding with the default values except for maxReceivedMessageSize, maxBufferPoolSize, maxBufferSize and some of the time outs that have been increased. The web service has been load tested using Visual Studio Load Test framework with around 800 concurrent users and successfully passed all tests with no exceptions being thrown. The proxy in the unit test has been created from configuration. There is a sharepoint application that use the Office Sharepoint Server Search service to call web services "A" and "B". The application will get data from service "A" to create a request that will be sent to service "B". The response coming from service "B" is indexed for search. The proxy is created programmatically using the ChannelFactory. When service "A" takes less than 10 minutes, the calls to service "B" are successfull. But when service "A" takes more time (~20 minutes) the calls to service "B" throw the following exception: Exception Message: An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail Inner Exception Message: The message could not be processed. This is most likely because the action 'namespace/OperationName' is incorrect or because the message contains an invalid or expired security context token or because there is a mismatch between bindings. The security context token would be invalid if the service aborted the channel due to inactivity. To prevent the service from aborting idle sessions prematurely increase the Receive timeout on the service endpoint's binding. The binding settings are the same, the time in both client server and web service server are synchronize with the Windows Time service, same time zone. When i look at the server where web service "B" is hosted i can see the following security errors being logged: Source: Security Category: Logon/Logoff Event ID: 537 User NT AUTHORITY\SYSTEM Logon Failure: Reason: An error occurred during logon Logon Type: 3 Logon Process: Kerberos Authentication Package: Kerberos Status code: 0xC000006D Substatus code: 0xC0000133 After reading some of the blogs online, the Status code means STATUS_LOGON_FAILURE and the substatus code means STATUS_TIME_DIFFERENCE_AT_DC. but i already checked both server and client clocks and they are syncronized. I also noticed that the security token seems to be cached somewhere in the client server because they have another process that calls the web service "B" using the same service account and successfully gets data the first time is called. Then they start the proccess to update the office sharepoint server search service indexes and it fails. Then if they called the first proccess again it will fail too. Has anyone experienced this type of problems or have any ideas? Regards, --Damian

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• Unable to resolve class in build.gradle using Android Studio 0.60/Gradle 0.11

  - by saywhatnow

  Established app working fine using Android Studio 0.5.9/ Gradle 0.9 but upgrading to Android Studio 0.6.0/ Gradle 0.11 causes the error below. Somehow Studio seems to have lost the ability to resolve the android tools import at the top of the build.gradle file. Anyone got any ideas on how to solve this? build file 'Users/[me]/Repositories/[project]/[module]/build.gradle': 1: unable to resolve class com.android.builder.DefaultManifestParser @ line 1, column 1. import com.android.builder.DefaultManifestParser 1 error at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:302) at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:858) at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:548) at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:497) at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:306) at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:287) at org.gradle.groovy.scripts.internal.DefaultScriptCompilationHandler.compileScript(DefaultScriptCompilationHandler.java:115) ... 77 more 2014-06-09 10:15:28,537 [ 92905] INFO - .BaseProjectImportErrorHandler - Failed to import Gradle project at '/Users/[me]/Repositories/[project]' org.gradle.tooling.BuildException: Could not run build action using Gradle distribution 'http://services.gradle.org/distributions/gradle-1.12-all.zip'. at org.gradle.tooling.internal.consumer.ResultHandlerAdapter.onFailure(ResultHandlerAdapter.java:53) at org.gradle.tooling.internal.consumer.async.DefaultAsyncConsumerActionExecutor$1$1.run(DefaultAsyncConsumerActionExecutor.java:57) at org.gradle.internal.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:64) [project]/[module]/build.gradle import com.android.builder.DefaultManifestParser apply plugin: 'android-sdk-manager' apply plugin: 'android' android { sourceSets { main { manifest.srcFile 'src/main/AndroidManifest.xml' res.srcDirs = ['src/main/res'] } debug { res.srcDirs = ['src/debug/res'] } release { res.srcDirs = ['src/release/res'] } } compileSdkVersion 19 buildToolsVersion '19.0.0' defaultConfig { minSdkVersion 14 targetSdkVersion 19 } signingConfigs { release } buildTypes { release { runProguard false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt' signingConfig signingConfigs.release applicationVariants.all { variant -> def file = variant.outputFile def manifestParser = new DefaultManifestParser() def wmgVersionCode = manifestParser.getVersionCode(android.sourceSets.main.manifest.srcFile) println wmgVersionCode variant.outputFile = new File(file.parent, file.name.replace("-release.apk", "_" + wmgVersionCode + ".apk")) } } } packagingOptions { exclude 'META-INF/LICENSE.txt' exclude 'META-INF/NOTICE.txt' } } def Properties props = new Properties() def propFile = file('signing.properties') if (propFile.canRead()){ props.load(new FileInputStream(propFile)) if (props!=null && props.containsKey('STORE_FILE') && props.containsKey('STORE_PASSWORD') && props.containsKey('KEY_ALIAS') && props.containsKey('KEY_PASSWORD')) { println 'RELEASE BUILD SIGNING' android.signingConfigs.release.storeFile = file(props['STORE_FILE']) android.signingConfigs.release.storePassword = props['STORE_PASSWORD'] android.signingConfigs.release.keyAlias = props['KEY_ALIAS'] android.signingConfigs.release.keyPassword = props['KEY_PASSWORD'] } else { println 'RELEASE BUILD NOT FOUND SIGNING PROPERTIES' android.buildTypes.release.signingConfig = null } }else { println 'RELEASE BUILD NOT FOUND SIGNING FILE' android.buildTypes.release.signingConfig = null } repositories { maven { url 'https://repo.commonsware.com.s3.amazonaws.com' } maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' } } dependencies { compile 'com.github.gabrielemariotti.changeloglib:library:1.4.+' compile 'com.google.code.gson:gson:2.2.4' compile 'com.google.android.gms:play-services:+' compile 'com.android.support:appcompat-v7:+' compile 'com.squareup.okhttp:okhttp:1.5.+' compile 'com.octo.android.robospice:robospice:1.4.11' compile 'com.octo.android.robospice:robospice-cache:1.4.11' compile 'com.octo.android.robospice:robospice-retrofit:1.4.11' compile 'com.commonsware.cwac:security:0.1.+' compile 'com.readystatesoftware.sqliteasset:sqliteassethelper:+' compile 'com.android.support:support-v4:19.+' compile 'uk.co.androidalliance:edgeeffectoverride:1.0.1+' compile 'de.greenrobot:eventbus:2.2.1+' compile project(':captureActivity') compile ('de.keyboardsurfer.android.widget:crouton:1.8.+') { exclude group: 'com.google.android', module: 'support-v4' } compile files('libs/CWAC-LoaderEx.jar') }

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• Memory Leak Issue in Weblogic, SUN, Apache and Oracle classes Options

  - by Amit

  Hi All, Please find below the description of memory leaks issues. Statistics show major growth in the perm area (static classes). Flows were ran for 8 hours , Heap dump was taken after 2 hours and at the end. A growth in Perm area was identified Statistics show from our last run 240MB growth in 6 hour,40mb growth every hour 2GB heap –can hold ¾ days ,heap will be full in ¾ days Heap dump show –growth in area as mentioned below JMS connection/session Area Apache org.apache.xml.dtm.DTM[] org.apache.xml.dtm.ref.ExpandedNameTable$ExtendedType org.jdom.AttributeList org.jdom.Content[] org.jdom.ContentList org.jdom.Element SUN * ConstantPoolCacheKlass * ConstantPoolKlass * ConstMethodKlass * MethodDataKlass * MethodKlass * SymbolKlass byte[] char[] com.sun.org.apache.xml.internal.dtm.DTM[] com.sun.org.apache.xml.internal.dtm.ref.ExtendedType java.beans.PropertyDescriptor java.lang.Class java.lang.Long java.lang.ref.WeakReference java.lang.ref.SoftReference java.lang.String java.text.Format[] java.util.concurrent.ConcurrentHashMap$Segment java.util.LinkedList$Entry Weblogic com.bea.console.cvo.ConsoleValueObject$PropertyInfo com.bea.jsptools.tree.TreeNode com.bea.netuix.servlets.controls.content.StrutsContent com.bea.netuix.servlets.controls.layout.FlowLayout com.bea.netuix.servlets.controls.layout.GridLayout com.bea.netuix.servlets.controls.layout.Placeholder com.bea.netuix.servlets.controls.page.Book com.bea.netuix.servlets.controls.window.Window[] com.bea.netuix.servlets.controls.window.WindowMode javax.management.modelmbean.ModelMBeanAttributeInfo weblogic.apache.xerces.parsers.SecurityConfiguration weblogic.apache.xerces.util.AugmentationsImpl weblogic.apache.xerces.util.AugmentationsImpl$SmallContainer weblogic.apache.xerces.util.SymbolTable$Entry weblogic.apache.xerces.util.XMLAttributesImpl$Attribute weblogic.apache.xerces.xni.QName weblogic.apache.xerces.xni.QName[] weblogic.ejb.container.cache.CacheKey weblogic.ejb20.manager.SimpleKey weblogic.jdbc.common.internal.ConnectionEnv weblogic.jdbc.common.internal.StatementCacheKey weblogic.jms.common.Item weblogic.jms.common.JMSID weblogic.jms.frontend.FEConnection weblogic.logging.MessageLogger$1 weblogic.logging.WLLogRecord weblogic.rjvm.BubblingAbbrever$BubblingAbbreverEntry weblogic.rjvm.ClassTableEntry weblogic.rjvm.JVMID weblogic.rmi.cluster.ClusterableRemoteRef weblogic.rmi.internal.CollocatedRemoteRef weblogic.rmi.internal.PhantomRef weblogic.rmi.spi.ServiceContext[] weblogic.security.acl.internal.AuthenticatedSubject weblogic.security.acl.internal.AuthenticatedSubject$SealableSet weblogic.servlet.internal.ServletRuntimeMBeanImpl weblogic.transaction.internal.XidImpl weblogic.utils.collections.ConcurrentHashMap$Entry Oracle XA Transaction oracle.jdbc.driver.Binder[] oracle.jdbc.driver.OracleDatabaseMetaData oracle.jdbc.driver.T4C7Ocommoncall oracle.jdbc.driver.T4C7Oversion oracle.jdbc.driver.T4C8Oall oracle.jdbc.driver.T4C8Oclose oracle.jdbc.driver.T4C8TTIBfile oracle.jdbc.driver.T4C8TTIBlob oracle.jdbc.driver.T4C8TTIClob oracle.jdbc.driver.T4C8TTIdty oracle.jdbc.driver.T4C8TTILobd oracle.jdbc.driver.T4C8TTIpro oracle.jdbc.driver.T4C8TTIrxh oracle.jdbc.driver.T4C8TTIuds oracle.jdbc.driver.T4CCallableStatement oracle.jdbc.driver.T4CClobAccessor oracle.jdbc.driver.T4CConnection oracle.jdbc.driver.T4CMAREngine oracle.jdbc.driver.T4CNumberAccessor oracle.jdbc.driver.T4CPreparedStatement oracle.jdbc.driver.T4CTTIdcb oracle.jdbc.driver.T4CTTIk2rpc oracle.jdbc.driver.T4CTTIoac oracle.jdbc.driver.T4CTTIoac[] oracle.jdbc.driver.T4CTTIoauthenticate oracle.jdbc.driver.T4CTTIokeyval oracle.jdbc.driver.T4CTTIoscid oracle.jdbc.driver.T4CTTIoses oracle.jdbc.driver.T4CTTIOtxen oracle.jdbc.driver.T4CTTIOtxse oracle.jdbc.driver.T4CTTIsto oracle.jdbc.driver.T4CXAConnection oracle.jdbc.driver.T4CXAResource oracle.jdbc.oracore.OracleTypeADT[] oracle.jdbc.xa.OracleXAResource$XidListEntry oracle.net.ano.Ano oracle.net.ns.ClientProfile oracle.net.ns.ClientProfile oracle.net.ns.NetInputStream oracle.net.ns.NetOutputStream oracle.net.ns.SessionAtts oracle.net.nt.ConnOption oracle.net.nt.ConnStrategy oracle.net.resolver.AddrResolution oracle.sql.CharacterSet1Byte we are using Oracle BEA Weblogic 9.2 MP3 JDK 1.5.12 Oracle versoin 10.2.0.4 (for oracle we found one path which is needed to applied to avoid XA transaction memory leaks). But we are stuck to resolve SUN, BEA Weblgogic and Apache leaks. please suggest... regards, Amit J.

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• tapestry 4 session expired

  - by cometta

  is below caused by user session expired? if yes, how to exend session on tapestry 4 ? or any other way to solve this problem? Unable to process client request: Unable to forward to local resource '/app?service=page&page=Home&id=692': java.lang.NullPointerException: Property 'webRequest' of <OuterProxy for tapestry.globals.RequestGlobals(org.apache.tapestry.services.RequestGlobals)> is null. Apr 22, 2010 5:14:43 PM org.apache.catalina.core.ApplicationContext log SEVERE: app: ServletException javax.servlet.ServletException: java.lang.NullPointerException: Property 'webRequest' of <OuterProxy for tapestry.globals.RequestGlobals(org.apache.tapestry.services.RequestGlobals)> is null. at org.apache.tapestry.services.impl.WebRequestServicerPipelineBridge.service(WebRequestServicerPipelineBridge.java:65) at $ServletRequestServicer_128043b52ea.service($ServletRequestServicer_128043b52ea.java) at org.apache.tapestry.request.DecodedRequestInjector.service(DecodedRequestInjector.java:55) at $ServletRequestServicerFilter_128043b52e6.service($ServletRequestServicerFilter_128043b52e6.java) at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java) at org.apache.tapestry.multipart.MultipartDecoderFilter.service(MultipartDecoderFilter.java:52) at $ServletRequestServicerFilter_128043b52e4.service($ServletRequestServicerFilter_128043b52e4.java) at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java) at org.apache.tapestry.services.impl.SetupRequestEncoding.service(SetupRequestEncoding.java:53) at $ServletRequestServicerFilter_128043b52e8.service($ServletRequestServicerFilter_128043b52e8.java) at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java) at $ServletRequestServicer_128043b52de.service($ServletRequestServicer_128043b52de.java) at org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java:126) at org.apache.tapestry.ApplicationServlet.doPost(ApplicationServlet.java:171) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:378) at org.springframework.security.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109) at org.springframework.security.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.ui.SessionFixationProtectionFilter.doFilterHttp(SessionFixationProtectionFilter.java:67) at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.ui.ntlm.NtlmProcessingFilter.doFilterHttp(NtlmProcessingFilter.java:358) at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.ui.ExceptionTranslationFilter.doFilterHttp(ExceptionTranslationFilter.java:101) at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.context.HttpSessionContextIntegrationFilter.doFilterHttp(HttpSessionContextIntegrationFilter.java:235) at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.concurrent.ConcurrentSessionFilter.doFilterHttp(ConcurrentSessionFilter.java:99) at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) at org.springframework.security.util.FilterChainProxy.doFilter(FilterChainProxy.java:175) at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:236) at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:619)

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• multiple stateful iframes per page will overwrite JSESSIONID?

  - by Nikita

  Hello, Looking for someone to either confirm or refute my theory that deploying two iframes pointing to two different stateful pages on the same domain can lead to JSESSIONIDs being overwritten. Here's what I mean: Setup suppose you have two pages that require HttpSession state (session affinity) to function correctly - deployed at http://www.foo.com/page1 and http://www.foo.com/page2 assume www.foo.com is a single host running a Tomcat (6.0.20, fwiw) that uses JSESSIONID for session id's. suppose these pages are turned into two iframe widgets to be embedded on 3rd party sites: http://www.site.com/page1" / (and /page2 respectively) suppose there a 3rd party site that wishes to place both widgets on the same page at http://www.bar.com/foowidgets.html Can the following race condition occur? a new visitor goes to http://www.bar.com/foowidgets.html browser starts loading URLs in foowidgets.html including the two iframe 'src' URLs because browsers open multiple concurrent connections against the same host (afaik up to 6 in chrome/ff case) the browser happens to simultaneously issue requests for http://www.foo.com/page1 and http://www.foo.com/page2 The tomcat @ foo.com receives both requests at about the same time, calls getSession() for the first time (on two different threads) and lazily creates two HttpSessions and, thus, two JSESSIONIDs, with values $Page1 and $Page2. The requests also stuff data into respective sessions (that data will be required to process subsequent requests) assume that the browser first receives response to the page1 request. Browser sets cookie JSESSIONID=$Page1 for HOST www.foo.com next response to the page2 request is received and the browser overwrites cookie JSESSIONID for HOST www.foo.com with $Page2 user clicks on something in 'page1' iframe on foowidgets.html; browser issues 2nd request to http://www.foo.com/page1?action=doSomethingStateful. That request carries JSESSIONID=$Page2 (and not $Page1 - because cookie value was overwritten) when foo.com receives this request it looks up the wrong HttpSession instance (because JSESSIONID key is $Page2 and NOT $Page1). Foobar! Can the above happen? I think so, but would appreciate a confirmation. If the above is clearly possible, what are some solutions given that we'd like to support multiple iframes per page? We don't have a firm need for the iframes to share the same HttpSession, though that would be nice. In the event that the solution will still stipulate a separate HttpSession per iframe, it is - of course - mandatory that iframe 1 does not end up referencing httpSession state for iframe 2 instead of own. off top of my head I can think of: map page1 and page2 to different domains (ops overhead) use URL rewriting and never cookies (messes up analytics) anything else? thanks a lot, -nikita

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• debugging JBoss 100% CPU usage

  - by NateS

  Originally posted on Server Fault, where it was suggested this question might better asked here. We are using JBoss to run two of our WARs. One is our web app, the other is our web service. The web app accesses a database on another machine and makes requests to the web service. The web service makes JMS requests to other machines, aggregates the data, and returns it. At our biggest client, about once a month the JBoss Java process takes 100% of all CPUs. The machine running JBoss has 8 CPUs. Our web app is still accessible during this time, however pages take about 3 minutes to load. Restarting JBoss restores everything to normal. The database machine and all the other machines are fine, only the machine running JBoss is affected. Memory usage is normal. Network utilization is normal. There are no suspect error messages in the JBoss logs. I have set up a test environment as close as possible to the client's production environment and I've done load testing with as much as 2x the number of concurrent users. I have not gotten my test environment to replicate the problem. Where do we go from here? How can we narrow down the problem? Currently the only plan we have is to wait until the problem occurs in production on its own, then do some debugging to determine the cause. So far people have just restarted JBoss when the problem occurred to minimize down time. Next time it happens they will get a developer to take a look. The question is, next time it happens, what can be done to determine the cause? We could setup a separate JBoss instance on the same box and install the web app separately from the web service. This way when the problem next occurs we will know which WAR has the problem (assuming it is our code). This doesn't narrow it down much though. Should I enable JMX remote? This way the next time the problem occurs I can connect with VisualVM and see which threads are taking the CPU and what the hell they are doing. However, is there a significant down side to enabling JMX remote in a production environment? Is there another way to see what threads are eating the CPU and to get a stacktrace to see what they are doing? Any other ideas? Thanks!

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• Is this (Lock-Free) Queue Implementation Thread-Safe?

  - by Hosam Aly

  I am trying to create a lock-free queue implementation in Java, mainly for personal learning. The queue should be a general one, allowing any number of readers and/or writers concurrently. Would you please review it, and suggest any improvements/issues you find? Thank you. import java.util.concurrent.atomic.AtomicReference; public class LockFreeQueue<T> { private static class Node<E> { E value; volatile Node<E> next; Node(E value) { this.value = value; } } private AtomicReference<Node<T>> head, tail; public LockFreeQueue() { // have both head and tail point to a dummy node Node<T> dummyNode = new Node<T>(null); head = new AtomicReference<Node<T>>(dummyNode); tail = new AtomicReference<Node<T>>(dummyNode); } /** * Puts an object at the end of the queue. */ public void putObject(T value) { Node<T> newNode = new Node<T>(value); Node<T> prevTailNode = tail.getAndSet(newNode); prevTailNode.next = newNode; } /** * Gets an object from the beginning of the queue. The object is removed * from the queue. If there are no objects in the queue, returns null. */ public T getObject() { Node<T> headNode, valueNode; // move head node to the next node using atomic semantics // as long as next node is not null do { headNode = head.get(); valueNode = headNode.next; // try until the whole loop executes pseudo-atomically // (i.e. unaffected by modifications done by other threads) } while (valueNode != null && !head.compareAndSet(headNode, valueNode)); T value = (valueNode != null ? valueNode.value : null); // release the value pointed to by head, keeping the head node dummy if (valueNode != null) valueNode.value = null; return value; }

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• Tomcat JNDI Connection Pool docs - Random Connection Closed Exceptions

  - by Andy Faibishenko

  I found this in the Tomcat documentation here What I don't understand is why they close all the JDBC objects twice - once in the try{} block and once in the finally{} block. Why not just close them once in the finally{} clause? This is the relevant docs: Random Connection Closed Exceptions These can occur when one request gets a db connection from the connection pool and closes it twice. When using a connection pool, closing the connection just returns it to the pool for reuse by another request, it doesn't close the connection. And Tomcat uses multiple threads to handle concurrent requests. Here is an example of the sequence of events which could cause this error in Tomcat: Request 1 running in Thread 1 gets a db connection. Request 1 closes the db connection. The JVM switches the running thread to Thread 2 Request 2 running in Thread 2 gets a db connection (the same db connection just closed by Request 1). The JVM switches the running thread back to Thread 1 Request 1 closes the db connection a second time in a finally block. The JVM switches the running thread back to Thread 2 Request 2 Thread 2 tries to use the db connection but fails because Request 1 closed it. Here is an example of properly written code to use a db connection obtained from a connection pool: Connection conn = null; Statement stmt = null; // Or PreparedStatement if needed ResultSet rs = null; try { conn = ... get connection from connection pool ... stmt = conn.createStatement("select ..."); rs = stmt.executeQuery(); ... iterate through the result set ... rs.close(); rs = null; stmt.close(); stmt = null; conn.close(); // Return to connection pool conn = null; // Make sure we don't close it twice } catch (SQLException e) { ... deal with errors ... } finally { // Always make sure result sets and statements are closed, // and the connection is returned to the pool if (rs != null) { try { rs.close(); } catch (SQLException e) { ; } rs = null; } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { ; } stmt = null; } if (conn != null) { try { conn.close(); } catch (SQLException e) { ; } conn = null; } }

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• iPhone: Speeding up a search that's polling 17,000 Core Data objects

  - by randombits

  I have a class that conforms to UISearchDisplayDelegate and contains a UISearchBar. This view is responsible for allowing the user to poll a store of about 17,000 objects that are currently managed by Core Data. Everytime the user types in a character, I created an instance of a SearchOperation (subclasses NSOperation) that queries Core Data to find results that might match the search. The code in the search controller looks something like: - (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope { // Update the filtered array based on the search text and scope in a secondary thread if ([searchText length] < 3) { [filteredList removeAllObjects]; // First clear the filtered array. [self setFilteredList:NULL]; [self.tableView reloadData]; return; } NSDictionary *searchdict = [NSDictionary dictionaryWithObjectsAndKeys:scope, @"scope", searchText, @"searchText", nil]; [aSearchQueue cancelAllOperations]; SearchOperation *searchOp = [[SearchOperation alloc] initWithDelegate:self dataDict:searchdict]; [aSearchQueue addOperation:searchOp]; } And my search is rather straight forward. SearchOperation is a subclass of NSOperation. I overwrote the main method with the following code: - (void)main { if ([self isCancelled]) { return; } NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:entity]; NSPredicate *predicate = NULL; predicate = [NSPredicate predicateWithFormat:@"(someattr contains[cd] %@)", searchText]; [fetchRequest setPredicate:predicate]; NSError *error = NULL; NSArray *fetchResults = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; if (self.delegate != nil) [self.delegate didFinishSearching:fetchResults]; [pool drain]; } This code works, but it has several issues. It's slow. Even though I have the search happening in a separate thread other than the UI thread, querying 17,000 objects is clearly not optimal. If I'm not careful, crashes can happen. I set the max concurrent searches in my NSOperationQueue to 1 to avoid this. What else can I do to make this search faster? I think preloading all 17,000 objects into memory might be risky. There has to be a smarter way to conduct this search to give results back to the user faster.

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• Core-Data + AFNetworking + UI Updating (Responsiveness)

  - by Mustafa

  Here's the scenario: I'm writing a DownloadManager, that allows the user to download, pause, cancel, download all, and pause all. The DownloadManager is a singleton, and uses AFNetworking to download files. It has it's own private managed object context, so that user can freely use other parts of the application (by adding, editing, deleting) core-data objects. I have a core-data entity DownloadInfo that stores the download information i.e. fileURL, fileSize, bytesRead, etc. The DownloadManager updates the download progress in DownloadInfo (one for each file). I have a DownloadManagerViewController which uses NSFetchedResultsController to show the download status to the user. This download view controller is using the main managed object context. Now let's say that I have 20 files in the download queue. And let's say that only 3 concurrent downloads are allowed. The download manager should download the file, and show the download progress. Problem: The DownloadInfo objects are being updated by the DownloadManager at a very high rate. The DownloadManagerViewController (responsible for showing the download progress) is updating the list using NSFetchedResultsControllerDelegate methods. The result is that a lot is happening in the main queue and application has very poor responsiveness. How can I fix this? How can I make the application responsive, while showing the download progress? I don't know how else to communicate that the download status between DownloadManager and DownloadManagerViewController. Is there another/ a better way to do this? I don't want to use main managed object context in my DownloadManager, for reasons mentioned above. Note, that the DownloadManager is using AFNetworking which is handling the requests asynchronously, but eventually the DownloadInfo objects are updated in the main thread (as a result of the callback methods). Maybe there's a way to handle the downloads and status update operations in a background thread? but how? How will I communicate between the main thread and the background thread i.e. how will I tell the background thread to queue another file for download? Thanks.

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• Using VCL for the web (intraweb) as a trick for adding web interface to a legacy non-tiered (2 tiers

  - by user193655

  My team is maintaining a huge Client Server win32 Delphi application. It is a client/server application (Thick client) that uses DevArt (SDAC) components to connect to SQL Server. The business logic is often "trapped" in Component's event handlers, anyway with some degree of refactoring it is doable to move the business logic in common units (a big part of this work has already been done during refactoring... Maintaing legacy applications someone else wrote is very frustrating, but this is a very common job). Now there is the request of a web interface, I have several options of course, in this question i want to focus on the VCL for the web (intraweb) option. The idea is to use the common code (the same pas files) for both the client/server application and the web application. I heard of many people that moved legacy apps from delphi to intraweb, but here I am trying to keep the Thick client too. The idea is to use common code, may be with some compiler directives to write specific code: {$IFDEF CLIENTSERVER} {here goes the thick client specific code} {$ELSE} {here goes the Intraweb specific code} {$ENDIF} Then another problem is the "migration plan", let's say I have 300 features and on the first release I will have only 50 of them available in the web application. How to keep track of it? I was thinking of (ab)using Delphi interfaces to handle this. For example for the User Authentication I could move all the related code in a procedure and declare an interface like: type IUserAuthentication= interface['{0D57624C-CDDE-458B-A36C-436AE465B477}'] procedure UserAuthentication; end; In this way as I implement the IUserAuthentication interface in both the applications (Thick Client and Intraweb) I know that That feature has been "ported" to the web. Anyway I don't know if this approach makes sense. I made a prototype to simulate the whole process. It works for a "Hello world" application, but I wonder if it makes sense on a large application or this Interface idea is only counter-productive and can backfire. My question is: does this approach make sense? (the Interface idea is just an extra idea, it is not so important as the common code part described above) Is it a viable option? I understand it depends a lot of the kind of application, anyway to be generic my one is in the CRM/Accounting domain, and the number of concurrent users on a single installation is typically less than 20 with peaks of 50. EXTRA COMMENT (UPDATE): I ask this question because since I don't have a n-tier application I see Intraweb as the unique option for having a web application that has common code with the thick client. Developing webservices from the Delphi code makes no sense in my specific case, so the alternative I have is to write the web interface using ASP.NET (duplicating the business logic), but in this case I cannot take advantage of the common code in an easy way. Yes I could use dlls maybe, but my code is not suitable for that.

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• Fairness: Where can it be better handled?

  - by Srinivas Nayak

  Hi, I would like to share one of my practical experience with multiprogramming here. Yesterday I had written a multiprogram. Modifications to sharable resources were put under critical sections protected by P(mutex) and V(mutex) and those critical section code were put in a common library. The library will be used by concurrent applications (of my own). I had three applications that will use the common code from library and do their stuff independently. my library --------- work_on_shared_resource { P(mutex) get_shared_resource work_with_it V(mutex) } --------- my application ----------- application1 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application2 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application3 { *[ work_on_shared_resource ] } *[...] denote a loop. ------------ I had to run the applications on Linux OS. I had a thought in my mind, hanging over years, that, OS shall schedule all the processes running under him with all fairness. In other words, it will give all the processes, their pie of resource-usage equally well. When first two applications were put to work, they run perfectly well without deadlock. But when the third application started running, always the third one got the resources, but since it is not doing anything in its non-critical region, it gets the shared resource more often when other tasks are doing something else. So the other two applications were found almost totally halted. When the third application got terminated forcefully, the previous two applications resumed their work as before. I think, this is a case of starvation, first two applications had to starve. Now how can we ensure fairness? Now I started believing that OS scheduler is innocent and blind. It depends upon who won the race; he got the largest pie of CPU and resource. Shall we attempt to ensure fairness of resource users in the critical-section code in library? Or shall we leave it up to the applications to ensure fairness by being liberal, not greedy? To my knowledge, adding code to ensure fairness to the common library shall be an overwhelming task. On the other hand, believing on the applications will also never ensure 100% fairness. The application which does a very little task after working with shared resources shall win the race where as the application which does heavy processing after their work with shared resources shall always starve. What is the best practice in this case? Where we ensure fairness and how? Sincerely, Srinivas Nayak

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• C++ Unlocking a std::mutex before calling std::unique_lock wait

  - by Sant Kadog

  I have a multithreaded application (using std::thread) with a manager (class Tree) that executes some piece of code on different subtrees (embedded struct SubTree) in parallel. The basic idea is that each instance of SubTree has a deque that store objects. If the deque is empty, the thread waits until a new element is inserted in the deque or the termination criteria is reached. One subtree can generate objects and push them in the deque of another subtree. For convenience, all my std::mutex, std::locks and std::variable_condition are stored in a struct called "locks". The class Tree creates some threads that run the following method (first attempt) : void Tree::launch(SubTree & st, Locks & locks ) { /* some code */ std::lock_guard<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem is that "deque_lock" is still locked while the thread is waiting. Hence no object can be added in the deque of the current thread by a concurrent one. So I turned the lock_guard into a unique_lock and managed the lock/unlock manually : void launch(SubTree & st, Locks & locks ) { /* some code */ std::unique_lock<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { deque_lock.unlock() ; // unlock the access to the deque to enable the other threads to add objects // DATA RACE : nothing must happen to the unprotected deque here !!!!!! // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem now, is that there is a data race, and I would like to make sure that the "wait" instruction is performed directly after the "deque_lock.unlock()" one. Would anyone know a way to create such a critical instruction sequence with the standard library ? Thanks in advance.

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• Available Coroutine Libraries in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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• Dynamic data-entry value store

  - by simendsjo

  I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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• Variable lenght arguments in log4cxx LOG4CXX_ macros

  - by Horacio

  I am using log4cxx in a big C++ project but I really don't like how log4cxx handles multiple variables when logging: LOG4CXX_DEBUG(logger, "test " << var1 << " and " << var3 " and .....) I prefer using printf like variable length arguments: LOG4CXX_DEBUG(logger, "test %d and %d", var1, var3) So I implemented this small wrapper on top of log4cxx #include <string.h> #include <stdio.h> #include <stdarg.h> #include <log4cxx/logger.h> #include "log4cxx/basicconfigurator.h" const char * log_format(const char *fmt, ...); #define MYLOG_TRACE(logger, fmt, ...) LOG4CXX_TRACE(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_DEBUG(logger, fmt, ...) LOG4CXX_DEBUG(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_INFO(logger, fmt, ...) LOG4CXX_INFO(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_WARN(logger, fmt, ...) LOG4CXX_WARN(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_ERROR(logger, fmt, ...) LOG4CXX_ERROR(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_FATAL(logger, fmt, ...) LOG4CXX_FATAL(logger, log_format(fmt, ## __VA_ARGS__)) static log4cxx::LoggerPtr logger(log4cxx::Logger::getRootLogger()); int main(int argc, char **argv) { log4cxx::BasicConfigurator::configure(); MYLOG_INFO(logger, "Start "); MYLOG_WARN(logger, log_format("In running this in %d threads safe?", 1000)); MYLOG_INFO(logger, "End "); return 0; } const char *log_format(const char *fmt, ...) { va_list va; static char formatted[1024]; va_start(va, fmt); vsprintf(formatted, 1024, fmt, va); va_end(va); return formatted; } And this works perfectly but I know using that static variable (formatted) can become problematic if I start using threads and each thread logging to the same place. I am no expert in log4cxx so I was wondering if the LOG4CXX macros are handling concurrent thread access automatically? or do I have to implement some sort of locking around the log_format method? something that I wan't to avoid due to performance implications. Also I would like to ask why if I replace the vsprintf inside the log_format method with vsnprintf (that is more secure) then I get nothing printed? To compile and test this program (in Ubuntu) use : g++ -o loggertest loggertest.cpp -llog4cxx

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• java concurrency: many writers, one reader

  - by Janning

  I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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• question about book example - Java Concurrency in Practice, Listing 4.12

  - by mike

  Hi, I am working through an example in Java Concurrency in Practice and am not understanding why a concurrent-safe container is necessary in the following code. I'm not seeing how the container "locations" 's state could be modified after construction; so since it is published through an 'unmodifiableMap' wrapper, it appears to me that an ordinary HashMap would suffice. EG, it is accessed concurrently, but the state of the map is only accessed by readers, no writers. The value fields in the map are syncronized via delegation to the 'SafePoint' class, so while the points are mutable, the keys for the hash, and their associated values (references to SafePoint instances) in the map never change. I think my confusion is based on what precisely the state of the collection is in the problem. Thanks!! -Mike Listing 4.12, Java Concurrency in Practice, (this listing available as .java here, and also in chapter form via google) /////////////begin code @ThreadSafe public class PublishingVehicleTracker { private final Map<String, SafePoint> locations; private final Map<String, SafePoint> unmodifiableMap; public PublishingVehicleTracker( Map<String, SafePoint> locations) { this.locations = new ConcurrentHashMap<String, SafePoint>(locations); this.unmodifiableMap = Collections.unmodifiableMap(this.locations); } public Map<String, SafePoint> getLocations() { return unmodifiableMap; } public SafePoint getLocation(String id) { return locations.get(id); } public void setLocation(String id, int x, int y) { if (!locations.containsKey(id)) throw new IllegalArgumentException( "invalid vehicle name: " + id); locations.get(id).set(x, y); } } // monitor protected helper-class @ThreadSafe public class SafePoint { @GuardedBy("this") private int x, y; private SafePoint(int[] a) { this(a[0], a[1]); } public SafePoint(SafePoint p) { this(p.get()); } public SafePoint(int x, int y) { this.x = x; this.y = y; } public synchronized int[] get() { return new int[] { x, y }; } public synchronized void set(int x, int y) { this.x = x; this.y = y; } } ///////////end code

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• Coroutines in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7?

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• JPA Inheritance and Relations - Clarification question

  - by Michael

  Here the scenario: I have a unidirectional 1:N Relation from Person Entity to Address Entity. And a bidirectional 1:N Relation from User Entity to Vehicle Entity. Here is the Address class: @Entity public class Address implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) privat Long int ... The Vehicles Class: @Entity public class Vehicle implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne private User owner; ... @PreRemove protected void preRemove() { //this.owner.removeVehicle(this); } public Vehicle(User owner) { this.owner = owner; ... The Person Class: @Entity @Inheritance(strategy = InheritanceType.JOINED) @DiscriminatorColumn(name="PERSON_TYP") public class Person implements Serializable { @Id protected String username; @OneToMany(cascade = CascadeType.ALL, orphanRemoval=true) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME"), inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) protected List<Address> addresses; ... @PreRemove protected void prePersonRemove(){ this.addresses = null; } ... The User Class which is inherited from the Person class: @Entity @Table(name = "Users") @DiscriminatorValue("USER") public class User extends Person { @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; ... When I try to delete a User who has an address I have to use orphanremoval=true on the corresponding relation (see above) and the preRemove function where the address List is set to null. Otherwise (no orphanremoval and adress list not set to null) a foreign key contraint fails. When i try to delete a user who has an vehicle a concurrent Acces Exception is thrown when do not uncomment the "this.owner.removeVehicle(this);" in the preRemove Function of the vehicle. The thing i do not understand is that before i used this inheritance there was only a User class which had all relations: @Entity @Table(name = "Users") public class User implements Serializable { @Id protected String username; @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; @OneToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME") inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) ptivate List<Address> addresses; ... No orphanremoval, and the vehicle class has used the uncommented statement above in its preRemove function. And - I could delte a user who has an address and i could delte a user who has a vehicle. So why doesn't everything work without changes when i use inheritance? I use JPA 2.0, EclipseLink 2.0.2, MySQL 5.1.x and Netbeans 6.8

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