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• Where does static variable work in C# page. At Application level or Page Level

  - by Shantanu Gupta

  I had an interview today and every thing was going very good, but then an interviewer asked me a question Where Does Static Variable Work in C#- At Application Level or At Page Level. I was not very much clear about this answer as I only knew that static variables are stored on heap and I didn't knew anything about web related thing about it. Then tried to make me more clear by giving an example that in a page I am using static variable and three users are accessing the page one of the user updates the value of static variable, What value will be visible to remaining two users an old copy or the update will be reflected.

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• mysql select from multi tables problem

  - by moustafa

  this is the query SELECT members.memberID, members.salutation, members.firstName, members.middleName, members.lastName, members.suffix, members.company, addresses.address1, addresses.address2, addresses.city, addresses.state, addresses.postalCode, addresses.country, addresses.memberID, email.email, email.memberID, phonenumbers.phoneNumber, phonenumbers.memberId, subscriptions.year, subscriptions.memberID FROM members, addresses, email, phonenumbers, subscriptions WHERE subscriptions.year = '%s' AND subscriptions.memberID = members.memberID AND subscriptions.memberID = addresses.memberID AND subscriptions.memberID = email.memberID AND subscriptions.memberID = phonenumbers.memberID ORDER BY members.lastName, members.firstName, members.company LIMIT 0, 10 my problem is its a huge query so Im trying to limit it to so many at a time... its supposed to have over 5000 results... anyway the only limit that works is limit 0, 10 if you do anything else 5, 10 it doesnt work 0, 50 doesnt work... only 0, 10 works... and when I do 0, 10 the query returns blake firstName, middleName, lastName, and a few others... and when I do a print_r() on the $result it shows them blank as well and there is most def data in the database and there is also no typos for that...

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• How to implement a private virtual function within derived classes?

  - by Dane

  Hi, I know why I want to use private virtual functions, but how exactly can I implement them? For example: class Base{ [...] private: virtual void func() = 0; [...] } class Derived1: puplic Base{ void func() { //short implementation is ok here } } class Derived2: puplic Base{ void func(); //long implementation elsewhere (in cpp file) } [...] void Derived2::func() { //long implementation } The first version is ok but not always possible. Isn't the second version simply name hiding? How do you define the Base::func() of Derived2, if you cannot do it within the class declaration of Dereived2? Thanks

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• Use nested static class as ActionListener for the Outer class

  - by Digvijay Yadav

  I want to use an nested static class as an actionListener for the enclosing class's GUI elements. I did something like this: public class OuterClass { public static void myImplementation() { OuterClass.StartupHandler startupHandler = new OuterClass.StartupHandler(); exitMenuItem.addActionListener(startupHandler); // error Line } public static class StartupHandler implements ActionListener { @Override public void actionPerformed(ActionEvent e) { //throw new UnsupportedOperationException("Not supported yet."); if (e.getSource() == exitMenuItem) { System.exit(1); } else if (e.getSource() == helpMenuItem) { // show help menu } } } } But when I invoke this code I get the NullPointerException at the //error Line. Is this the right method to do do this or there is something I did am missing?

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• How to free static member variable in C++?

  - by user299831

  Can anybody explain how to free memory of a static member Variable? In my understanding it can only be freed if all the instances of the class are destroyed. I am a little bit helpless at this point... Some Code to explain it: class ball { private: static SDL_Surface *ball_image; }; //FIXME: how to free static Variable? SDL_Surface* ball::ball_image = SDL_LoadBMP("ball.bmp");

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• Some confusion with a class variable, but with a twist...

  - by Omega

  I have a class called MyPackage.WebServer and it has a property called DBEngine. I am also dynamically loading a module and class using load_module. Inside this class, it attempts to reference MyPackage.WebServer. When it does though, DBEngine is not set to the value given when WebServer is instantiated. It's the default (None). Would the fact that I'm using load_module cause a different object graph to be created and thus isolate my dynamically loaded class from the rest of my python app?

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• What is the right way to implement communication between java objects?

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes, each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• How to pass a member function to a function used in another member function?

  - by Tommaso Ferrari

  I found something about my problem, but I don't already understand very well. I need to do something like this: class T{ double a; public: double b; void setT(double par){ a=par; }; double funct(double par1) { return par1/a; } void exec(){ b=extfunct(funct, 10); } } double extfunct(double (*f)(double),double par2){ return f(par2)+5; } Operation and function are only for example, but the structure is that. The reason of this structure is that I have a precostituited class which finds the minimum of a gived function (it's extfunct in the example). So I have to use it on a function member of a class. I understood the difference between pointer to function and pointer to member function, but I don't understand how to write it. Thanks, and sorry for the poor explanation of the problem.

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• The right way to implement communication between java objects

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that I has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• how to get child members value from dynamically casted class?

  - by Baka-Maru Lama

  Well I'm tring to get class members values from a dynamically casted class but I'm unable to find its child class members values. Right now I'm getting TotalWeight members property, but I also want to get child member property of AnotherClass like AnotherClass.child. How can I get those members? string ClassName="something"; Type types = Type.GetType(ClassName, false); var d = from source in types.GetMembers().ToList() where source.MemberType == MemberTypes.Property select source; List<MemberInfo> members = d.Where(memberInfo => d.Select(c => c.Name) .ToList() .Contains(memberInfo.Name)) .ToList(); PropertyInfo propertyInfo; object value; foreach (var memberInfo in members) { propertyInfo = typeof(T).GetProperty(memberInfo.Name); if (myobj.GetType().GetProperty(memberInfo.Name) != null) { value = myobj.GetType() .GetProperty(memberInfo.Name) .GetValue(myobj, null); //how to get child members value here? } } //Where class something has member public class something { private decimal _totalWeight; private Anotherclass _another; public decimal TotalWeight { get { return this._totalWeight; } set { this._totalWeight = value; } } public Anotherclass Another { get { return this._another; } set { this._another= value; } } }

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• On what basis would you split donation money among your open source team members without any strife?

  - by Vigneshwaran

  I am a developer of an open source project which is hosted in SourceForge. It started out as a little app then after some releases, it got more and more popular and it started consuming more time and responsibility from me. So I have enabled the donation option in SourceForge. I'm passionate to continue developing it for free but if (ever) any money comes in, how should I split it with my team? Should I split the amount equally among the number of team members? (50-50 as it is two-member team now) Number of classes, commits or any other valuable submissions by team members? Any other idea? What would you do in such situation? Please give your opinions. I hope this question will be useful for others.

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• 64-bit Archives Needed

  - by user9154181

  A little over a year ago, we received a question from someone who was trying to build software on Solaris. He was getting errors from the ar command when creating an archive. At that time, the ar command on Solaris was a 32-bit command. There was more than 2GB of data, and the ar command was hitting the file size limit for a 32-bit process that doesn't use the largefile APIs. Even in 2011, 2GB is a very large amount of code, so we had not heard this one before. Most of our toolchain was extended to handle 64-bit sized data back in the 1990's, but archives were not changed, presumably because there was no perceived need for it. Since then of course, programs have continued to get larger, and in 2010, the time had finally come to investigate the issue and find a way to provide for larger archives. As part of that process, I had to do a deep dive into the archive format, and also do some Unix archeology. I'm going to record what I learned here, to document what Solaris does, and in the hope that it might help someone else trying to solve the same problem for their platform. Archive Format Details Archives are hardly cutting edge technology. They are still used of course, but their basic form hasn't changed in decades. Other than to fix a bug, which is rare, we don't tend to touch that code much. The archive file format is described in /usr/include/ar.h, and I won't repeat the details here. Instead, here is a rough overview of the archive file format, implemented by System V Release 4 (SVR4) Unix systems such as Solaris: Every archive starts with a "magic number". This is a sequence of 8 characters: "!<arch>\n". The magic number is followed by 1 or more members. A member starts with a fixed header, defined by the ar_hdr structure in/usr/include/ar.h. Immediately following the header comes the data for the member. Members must be padded at the end with newline characters so that they have even length. The requirement to pad members to an even length is a dead giveaway as to the age of the archive format. It tells you that this format dates from the 1970's, and more specifically from the era of 16-bit systems such as the PDP-11 that Unix was originally developed on. A 32-bit system would have required 4 bytes, and 64-bit systems such as we use today would probably have required 8 bytes. 2 byte alignment is a poor choice for ELF object archive members. 32-bit objects require 4 byte alignment, and 64-bit objects require 64-bit alignment. The link-editor uses mmap() to process archives, and if the members have the wrong alignment, we have to slide (copy) them to the correct alignment before we can access the ELF data structures inside. The archive format requires 2 byte padding, but it doesn't prohibit more. The Solaris ar command takes advantage of this, and pads ELF object members to 8 byte boundaries. Anything else is padded to 2 as required by the format. The archive header (ar_hdr) represents all numeric values using an ASCII text representation rather than as binary integers. This means that an archive that contains only text members can be viewed using tools such as cat, more, or a text editor. The original designers of this format clearly thought that archives would be used for many file types, and not just for objects. Things didn't turn out that way of course — nearly all archives contain relocatable objects for a single operating system and machine, and are used primarily as input to the link-editor (ld). Archives can have special members that are created by the ar command rather than being supplied by the user. These special members are all distinguished by having a name that starts with the slash (/) character. This is an unambiguous marker that says that the user could not have supplied it. The reason for this is that regular archive members are given the plain name of the file that was inserted to create them, and any path components are stripped off. Slash is the delimiter character used by Unix to separate path components, and as such cannot occur within a plain file name. The ar command hides the special members from you when you list the contents of an archive, so most users don't know that they exist. There are only two possible special members: A symbol table that maps ELF symbols to the object archive member that provides it, and a string table used to hold member names that exceed 15 characters. The '/' convention for tagging special members provides room for adding more such members should the need arise. As I will discuss below, we took advantage of this fact to add an alternate 64-bit symbol table special member which is used in archives that are larger than 4GB. When an archive contains ELF object members, the ar command builds a special archive member known as the symbol table that maps all ELF symbols in the object to the archive member that provides it. The link-editor uses this symbol table to determine which symbols are provided by the objects in that archive. If an archive has a symbol table, it will always be the first member in the archive, immediately following the magic number. Unlike member headers, symbol tables do use binary integers to represent offsets. These integers are always stored in big-endian format, even on a little endian host such as x86. The archive header (ar_hdr) provides 15 characters for representing the member name. If any member has a name that is longer than this, then the real name is written into a special archive member called the string table, and the member's name field instead contains a slash (/) character followed by a decimal representation of the offset of the real name within the string table. The string table is required to precede all normal archive members, so it will be the second member if the archive contains a symbol table, and the first member otherwise. The archive format is not designed to make finding a given member easy. Such operations move through the archive from front to back examining each member in turn, and run in O(n) time. This would be bad if archives were commonly used in that manner, but in general, they are not. Typically, the ar command is used to build an new archive from scratch, inserting all the objects in one operation, and then the link-editor accesses the members in the archive in constant time by using the offsets provided by the symbol table. Both of these operations are reasonably efficient. However, listing the contents of a large archive with the ar command can be rather slow. Factors That Limit Solaris Archive Size As is often the case, there was more than one limiting factor preventing Solaris archives from growing beyond the 32-bit limits of 2GB (32-bit signed) and 4GB (32-bit unsigned). These limits are listed in the order they are hit as archive size grows, so the earlier ones mask those that follow. The original Solaris archive file format can handle sizes up to 4GB without issue. However, the ar command was delivered as a 32-bit executable that did not use the largefile APIs. As such, the ar command itself could not create a file larger than 2GB. One can solve this by building ar with the largefile APIs which would allow it to reach 4GB, but a simpler and better answer is to deliver a 64-bit ar, which has the ability to scale well past 4GB. Symbol table offsets are stored as 32-bit big-endian binary integers, which limits the maximum archive size to 4GB. To get around this limit requires a different symbol table format, or an extension mechanism to the current one, similar in nature to the way member names longer than 15 characters are handled in member headers. The size field in the archive member header (ar_hdr) is an ASCII string capable of representing a 32-bit unsigned value. This places a 4GB size limit on the size of any individual member in an archive. In considering format extensions to get past these limits, it is important to remember that very few archives will require the ability to scale past 4GB for many years. The old format, while no beauty, continues to be sufficient for its purpose. This argues for a backward compatible fix that allows newer versions of Solaris to produce archives that are compatible with older versions of the system unless the size of the archive exceeds 4GB. Archive Format Differences Among Unix Variants While considering how to extend Solaris archives to scale to 64-bits, I wanted to know how similar archives from other Unix systems are to those produced by Solaris, and whether they had already solved the 64-bit issue. I've successfully moved archives between different Unix systems before with good luck, so I knew that there was some commonality. If it turned out that there was already a viable defacto standard for 64-bit archives, it would obviously be better to adopt that rather than invent something new. The archive file format is not formally standardized. However, the ar command and archive format were part of the original Unix from Bell Labs. Other systems started with that format, extending it in various often incompatible ways, but usually with the same common shared core. Most of these systems use the same magic number to identify their archives, despite the fact that their archives are not always fully compatible with each other. It is often true that archives can be copied between different Unix variants, and if the member names are short enough, the ar command from one system can often read archives produced on another. In practice, it is rare to find an archive containing anything other than objects for a single operating system and machine type. Such an archive is only of use on the type of system that created it, and is only used on that system. This is probably why cross platform compatibility of archives between Unix variants has never been an issue. Otherwise, the use of the same magic number in archives with incompatible formats would be a problem. I was able to find information for a number of Unix variants, described below. These can be divided roughly into three tribes, SVR4 Unix, BSD Unix, and IBM AIX. Solaris is a SVR4 Unix, and its archives are completely compatible with those from the other members of that group (GNU/Linux, HP-UX, and SGI IRIX). AIX AIX is an exception to rule that Unix archive formats are all based on the original Bell labs Unix format. It appears that AIX supports 2 formats (small and big), both of which differ in fundamental ways from other Unix systems: These formats use a different magic number than the standard one used by Solaris and other Unix variants. They include support for removing archive members from a file without reallocating the file, marking dead areas as unused, and reusing them when new archive items are inserted. They have a special table of contents member (File Member Header) which lets you find out everything that's in the archive without having to actually traverse the entire file. Their symbol table members are quite similar to those from other systems though. Their member headers are doubly linked, containing offsets to both the previous and next members. Of the Unix systems described here, AIX has the only format I saw that will have reasonable insert/delete performance for really large archives. Everyone else has O(n) performance, and are going to be slow to use with large archives. BSD BSD has gone through 4 versions of archive format, which are described in their manpage. They use the same member header as SVR4, but their symbol table format is different, and their scheme for long member names puts the name directly after the member header rather than into a string table. GNU/Linux The GNU toolchain uses the SVR4 format, and is compatible with Solaris. HP-UX HP-UX seems to follow the SVR4 model, and is compatible with Solaris. IRIX IRIX has 32 and 64-bit archives. The 32-bit format is the standard SVR4 format, and is compatible with Solaris. The 64-bit format is the same, except that the symbol table uses 64-bit integers. IRIX assumes that an archive contains objects of a single ELFCLASS/MACHINE, and any archive containing ELFCLASS64 objects receives a 64-bit symbol table. Although they only use it for 64-bit objects, nothing in the archive format limits it to ELFCLASS64. It would be perfectly valid to produce a 64-bit symbol table in an archive containing 32-bit objects, text files, or anything else. Tru64 Unix (Digital/Compaq/HP) Tru64 Unix uses a format much like ours, but their symbol table is a hash table, making specific symbol lookup much faster. The Solaris link-editor uses archives by examining the entire symbol table looking for unsatisfied symbols for the link, and not by looking up individual symbols, so there would be no benefit to Solaris from such a hash table. The Tru64 ld must use a different approach in which the hash table pays off for them. Widening the existing SVR4 archive symbol tables rather than inventing something new is the simplest path forward. There is ample precedent for this approach in the ELF world. When ELF was extended to support 64-bit objects, the approach was largely to take the existing data structures, and define 64-bit versions of them. We called the old set ELF32, and the new set ELF64. My guess is that there was no need to widen the archive format at that time, but had there been, it seems obvious that this is how it would have been done. The Implementation of 64-bit Solaris Archives As mentioned earlier, there was no desire to improve the fundamental nature of archives. They have always had O(n) insert/delete behavior, and for the most part it hasn't mattered. AIX made efforts to improve this, but those efforts did not find widespread adoption. For the purposes of link-editing, which is essentially the only thing that archives are used for, the existing format is adequate, and issues of backward compatibility trump the desire to do something technically better. Widening the existing symbol table format to 64-bits is therefore the obvious way to proceed. For Solaris 11, I implemented that, and I also updated the ar command so that a 64-bit version is run by default. This eliminates the 2 most significant limits to archive size, leaving only the limit on an individual archive member. We only generate a 64-bit symbol table if the archive exceeds 4GB, or when the new -S option to the ar command is used. This maximizes backward compatibility, as an archive produced by Solaris 11 is highly likely to be less than 4GB in size, and will therefore employ the same format understood by older versions of the system. The main reason for the existence of the -S option is to allow us to test the 64-bit format without having to construct huge archives to do so. I don't believe it will find much use outside of that. Other than the new ability to create and use extremely large archives, this change is largely invisible to the end user. When reading an archive, the ar command will transparently accept either form of symbol table. Similarly, the ELF library (libelf) has been updated to understand either format. Users of libelf (such as the link-editor ld) do not need to be modified to use the new format, because these changes are encapsulated behind the existing functions provided by libelf. As mentioned above, this work did not lift the limit on the maximum size of an individual archive member. That limit remains fixed at 4GB for now. This is not because we think objects will never get that large, for the history of computing says otherwise. Rather, this is based on an estimation that single relocatable objects of that size will not appear for a decade or two. A lot can change in that time, and it is better not to overengineer things by writing code that will sit and rot for years without being used. It is not too soon however to have a plan for that eventuality. When the time comes when this limit needs to be lifted, I believe that there is a simple solution that is consistent with the existing format. The archive member header size field is an ASCII string, like the name, and as such, the overflow scheme used for long names can also be used to handle the size. The size string would be placed into the archive string table, and its offset in the string table would then be written into the archive header size field using the same format "/ddd" used for overflowed names.

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• Why the static data members have to be defined outside the class separately in C++ (unlike Java)?

  - by iammilind

  class A { static int foo () {} // ok static int x; // <--- needed to be defined separately in .cpp file }; I don't see a need of having A::x defined separately in a .cpp file (or same file for templates). Why can't be A::x declared and defined at the same time? Has it been forbidden for historical reasons? My main question is, will it affect any functionality if static data members were declared/defined at the same time (same as Java) ?

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• Oracle Coherence, Split-Brain and Recovery Protocols In Detail

  - by Ricardo Ferreira

  This article provides a high level conceptual overview of Split-Brain scenarios in distributed systems. It will focus on a specific example of cluster communication failure and recovery in Oracle Coherence. This includes a discussion on the witness protocol (used to remove failed cluster members) and the panic protocol (used to resolve Split-Brain scenarios). Note that the removal of cluster members does not necessarily indicate a Split-Brain condition. Oracle Coherence does not (and cannot) detect a Split-Brain as it occurs, the condition is only detected when cluster members that previously lost contact with each other regain contact. Cluster Topology and Configuration In order to create an good didactic for the article, let's assume a cluster topology and configuration. In this example we have a six member cluster, consisting of one JVM on each physical machine. The member IDs are as follows: Member ID  IP Address  1  10.149.155.76  2  10.149.155.77  3  10.149.155.236  4  10.149.155.75  5  10.149.155.79  6  10.149.155.78 Members 1, 2, and 3 are connected to a switch, and members 4, 5, and 6 are connected to a second switch. There is a link between the two switches, which provides network connectivity between all of the machines. Member 1 is the first member to join this cluster, thus making it the senior member. Member 6 is the last member to join this cluster. Here is a log snippet from Member 6 showing the complete member set: 2010-02-26 15:27:57.390/3.062 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=6): Started DefaultCacheServer... SafeCluster: Name=cluster:0xDDEB Group{Address=224.3.5.3, Port=35465, TTL=4} MasterMemberSet ( ThisMember=Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) OldestMember=Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ActualMemberSet=MemberSet(Size=6, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) RecycleMillis=120000 RecycleSet=MemberSet(Size=0, BitSetCount=0 ) ) At approximately 15:30, the connection between the two switches is severed: Thirty seconds later (the default packet timeout in development mode) the logs indicate communication failures across the cluster. In this example, the communication failure was caused by a network failure. In a production setting, this type of communication failure can have many root causes, including (but not limited to) network failures, excessive GC, high CPU utilization, swapping/virtual memory, and exceeding maximum network bandwidth. In addition, this type of failure is not necessarily indicative of a split brain. Any communication failure will be logged in this fashion. Member 2 logs a communication failure with Member 5: 2010-02-26 15:30:32.638/196.928 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) ) The Coherence clustering protocol (TCMP) is a reliable transport mechanism built on UDP. In order for the protocol to be reliable, it requires an acknowledgement (ACK) for each packet delivered. If a packet fails to be acknowledged within the configured timeout period, the Coherence cluster member will log a packet timeout (as seen in the log message above). When this occurs, the cluster member will consult with other members to determine who is at fault for the communication failure. If the witness members agree that the suspect member is at fault, the suspect is removed from the cluster. If the witnesses unanimously disagree, the accuser is removed. This process is known as the witness protocol. Since Member 2 cannot communicate with Member 5, it selects two witnesses (Members 1 and 4) to determine if the communication issue is with Member 5 or with itself (Member 2). However, Member 4 is on the switch that is no longer accessible by Members 1, 2 and 3; thus a packet timeout for member 4 is recorded as well: 2010-02-26 15:30:35.648/199.938 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) Member 1 has the ability to confirm the departure of member 4, however Member 6 cannot as it is also inaccessible. At the same time, Member 3 sends a request to remove Member 6, which is followed by a report from Member 3 indicating that Member 6 has departed the cluster: 2010-02-26 15:30:35.706/199.996 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft request for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) 2010-02-26 15:30:35.709/199.999 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft notification for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) The log for Member 3 determines how Member 6 departed the cluster: 2010-02-26 15:30:35.161/191.694 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=3): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ) 2010-02-26 15:30:35.165/191.698 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=3): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ); removing Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) In this case, Member 3 happened to select two witnesses that it still had connectivity with (Members 1 and 2) thus resulting in a simple decision to remove Member 6. Given the departure of Member 6, Member 2 is left with a single witness to confirm the departure of Member 4: 2010-02-26 15:30:35.713/200.003 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=2): Member departure confirmed by MemberSet(Size=1, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ); removing Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) In the meantime, Member 4 logs a missing heartbeat from the senior member. This message is also logged on Members 5 and 6. 2010-02-26 15:30:07.906/150.453 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=PacketListenerN, member=4): Scheduled senior member heartbeat is overdue; rejoining multicast group. Next, Member 4 logs a TcpRing failure with Member 2, thus resulting in the termination of Member 2: 2010-02-26 15:30:21.421/163.968 Oracle Coherence GE 3.5.3/465p2 <D4> (thread=Cluster, member=4): TcpRing: Number of socket exceptions exceeded maximum; last was "java.net.SocketTimeoutException: connect timed out"; removing the member: 2 For quick process termination detection, Oracle Coherence utilizes a feature called TcpRing which is a sparse collection of TCP/IP-based connections between different members in the cluster. Each member in the cluster is connected to at least one other member, which (if at all possible) is running on a different physical box. This connection is not used for any data transfer, only heartbeat communications are sent once a second per each link. If a certain number of exceptions are thrown while trying to re-establish a connection, the member throwing the exceptions is removed from the cluster. Member 5 logs a packet timeout with Member 3 and cites witnesses Members 4 and 6: 2010-02-26 15:30:29.791/165.037 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=5): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) 2010-02-26 15:30:29.798/165.044 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=5): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ); removing Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Eventually we are left with two distinct clusters consisting of Members 1, 2, 3 and Members 4, 5, 6, respectively. In the latter cluster, Member 4 is promoted to senior member. The connection between the two switches is restored at 15:33. Upon the restoration of the connection, the cluster members immediately receive cluster heartbeats from the two senior members. In the case of Members 1, 2, and 3, the following is logged: 2010-02-26 15:33:14.970/369.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): The member formerly known as Member(Id=4, Timestamp=2010-02-26 15:30:35.341, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. Likewise for Members 4, 5, and 6: 2010-02-26 15:33:14.343/336.890 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=4): The member formerly known as Member(Id=1, Timestamp=2010-02-26 15:30:31.64, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. This message indicates that a senior heartbeat is being received from members that were previously removed from the cluster, in other words, something that should not be possible. For this reason, the recipients of these messages will initially ignore them. After several iterations of these messages, the existence of multiple clusters is acknowledged, thus triggering the panic protocol to reconcile this situation. When the presence of more than one cluster (i.e. Split-Brain) is detected by a Coherence member, the panic protocol is invoked in order to resolve the conflicting clusters and consolidate into a single cluster. The protocol consists of the removal of smaller clusters until there is one cluster remaining. In the case of equal size clusters, the one with the older Senior Member will survive. Member 1, being the oldest member, initiates the protocol: 2010-02-26 15:33:45.970/400.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): An existence of a cluster island with senior Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) containing 3 nodes have been detected. Since this Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) is the senior of an older cluster island, the panic protocol is being activated to stop the other island's senior and all junior nodes that belong to it. Member 3 receives the panic: 2010-02-26 15:33:45.803/382.336 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=3): Received panic from senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) caused by Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member 4, the senior member of the younger cluster, receives the kill message from Member 3: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. In turn, Member 4 requests the departure of its junior members 5 and 6: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:43.343/349.015 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=6): Received a Kill message from a valid Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer); stopping cluster service. Once Members 4, 5, and 6 restart, they rejoin the original cluster with senior member 1. The log below is from Member 4. Note that it receives a different member id when it rejoins the cluster. 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:46.921/369.468 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Service Cluster left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:InvocationService, member=4): Service InvocationService left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=OptimisticCache, member=4): Service OptimisticCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=ReplicatedCache, member=4): Service ReplicatedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=DistributedCache, member=4): Service DistributedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:Management, member=4): Service Management left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service Management with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service DistributedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service ReplicatedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service OptimisticCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service InvocationService with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member(Id=6, Timestamp=2010-02-26 15:33:47.046, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) left Cluster with senior member 4 2010-02-26 15:33:49.218/371.765 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=n/a): Restarting cluster 2010-02-26 15:33:49.421/371.968 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=n/a): Service Cluster joined the cluster with senior service member n/a 2010-02-26 15:33:49.625/372.172 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=n/a): This Member(Id=5, Timestamp=2010-02-26 15:33:50.499, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=1) joined cluster "cluster:0xDDEB" with senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) Cool isn't it?

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• Can an aggregate root hold references of members of another aggregate root?

  - by Rushino

  Hello, I know outside aggregates cant change anything inside an aggregate without passing by his root. That said i would like to know if an aggregate root can hold references of members (objects insides) of another aggregate root? (fellowing DDD rules) Example : a Calendar contain a list of phases which contain a list of sequences which contain a list of assignations Calendar is root because phases and sequences and assignations only work in context of a calendar. You also have Students and Groups of student (called groups) It is possible (fellowing DDD rules) to make Groups holding references of assignations or it need to pass by the root for accessing groups from assignations ? Thanks.

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• What are good reasons to use explicit interface implementation for the sole purpose of hiding members?

  - by Nathanus

  During one of my studies into the intricacies of C#, I came across an interesting passage concerning explicit interface implementation. While this syntax is quite helpful when you need to resolve name clashes, you can use explicit interface implementation simply to hide more "advanced" members from the object level. The difference between allowing the use of object.method() or requiring the casting of ((Interface)object).method() seems like mean-spirited obfuscation to my inexperienced eyes. The text noted that this will hide the method from Intellisense at the object level, but why would you want to do that if it was not necessary to avoid name conflicts?

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• Are all public read/write members serialized with XmlSerializer?

  - by David

  I have a handful of public read/write members that are not being serialized and I can't figure out why. Reviewing some code, and my root class is marked serializable: [Serializable] public class MyClass I have a default constructor that initializes 10-15 string members. There are about 50 public read/write string members in MyClass with get and set--no explicit serialization attributes are set on any of these. Serialization looks like this: XmlSerializer x = new XmlSerializer(typeof(MyClass)); TextWriter twWriter = new StreamWriter(sFileName); x.Serialize(twWriter, this); twWriter.Close(); only a handful (20-30) of these members are actually seralized to my xml file. what am i missing or misunderstanding about the XmlSerializer class?

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• PASS: Election Changes for 2011

  - by Bill Graziano

  Last year after the election, the PASS Board created an Election Review Committee.  This group was charged with reviewing our election procedures and making suggestions to improve the process.  You can read about the formation of the group and review some of the intermediate work on the site – especially in the forums. I was one of the members of the group along with Joe Webb (Chair), Lori Edwards, Brian Kelley, Wendy Pastrick, Andy Warren and Allen White.  This group worked from October to April on our election process.  Along the way we: Interviewed interested parties including former NomCom members, Board candidates and anyone else that came forward. Held a session at the Summit to allow interested parties to discuss the issues Had numerous conference calls and worked through the various topics I can’t thank these people enough for the work they did.  They invested a tremendous number of hours thinking, talking and writing about our elections.  I’m proud to say I was a member of this group and thoroughly enjoyed working with everyone (even if I did finally get tired of all the calls.) The ERC delivered their recommendations to the PASS Board prior to our May Board meeting.  We reviewed those and made a few modifications.  I took their recommendations and rewrote them as procedures while incorporating those changes.  Their original recommendations as well as our final document are posted at the ERC documents page.  Please take a second and read them BEFORE we start the elections.  If you have any questions please post them in the forums on the ERC site. (My final document includes a change log at the end that I decided to leave in.  If you want to know which areas to pay special attention to that’s a good start.) Many of those recommendations were already posted in the forums or in the blogs of individual ERC members.  Hopefully nothing in the ERC document is too surprising. In this post I’m going to walk through some of the key changes and talk about what I remember from both ERC and Board discussions.  I’ll pay a little extra attention to things the Board changed from the ERC.  I’d also encourage any of the Board or ERC members to blog their thoughts on this. The Nominating Committee will continue to exist.  Personally, I was curious to see what the non-Board ERC members would think about the NomCom.  There was broad agreement that a group to vet candidates had value to the organization. The NomCom will be composed of five members.  Two will be Board members and three will be from the membership at large.  The only requirement for the three community members is that you’ve volunteered in some way (and volunteering is defined very broadly).  We expect potential at-large NomCom members to participate in a forum on the PASS site to answer questions from the other PASS members. We’re going to hold an election to determine the three community members.  It will be closer to voting for Summit sessions than voting for Board members.  That means there won’t be multiple dedicated emails.  If you’re at all paying attention it will be easy to participate.  Personally I wanted it easy for those that cared to participate but not overwhelm those that didn’t care.  I think this strikes a good balance. There’s also a clause that in order to be considered a winner in this NomCom election, you must receive 10 votes.  This is something I suggested.  I have no idea how popular the NomCom election is going to be.  I just wanted a fallback that if no one participated and some random person got in with one or two votes.  Any open slots will be filled by the NomCom chair (usually the PASS Immediate Past President).  My assumption is that they would probably take the next highest vote getters unless they were throwing flames in the forums or clearly unqualified.  As a final check, the Board still approves the final NomCom. The NomCom is going to rank candidates instead of rating them.  This has interesting implications.  This was championed by another ERC member and I’m hoping they write something about it.  This will really force the NomCom to make decisions between candidates.  You can’t just rate everyone a 3 and be done with it.  It may also make candidates appear further apart than they actually are.  I’m looking forward talking with the NomCom after this election and getting their feedback on this. The PASS Board added an option to remove a candidate with a unanimous vote of the NomCom.  This was primarily put in place to handle people that lied on their application or had a criminal background or some other unusual situation and we figured it out. We list an explicit goal of three candidate per open slot. We also wanted an easy way to find the NomCom candidate rankings from the ballot.  Hopefully this will satisfy those that want a broad candidate pool and those that want the NomCom to identify the most qualified candidates. The primary spokesperson for the NomCom is the committee chair.  After the issues around the election last year we didn’t have a good communication plan in place.  We should have and that was a failure on the part of the Board.  If there is criticism of the election this year I hope that falls squarely on the Board.  The community members of the NomCom shouldn’t be fielding complaints over the election process.  That said, the NomCom is ranking candidates and we are forcing them to rank some lower than others.  I’m sure you’ll each find someone that you think should have been ranked differently.  I also want to highlight one other change to the process that we started last year and isn’t included in these documents.  I think the candidate forums on the PASS site were tremendously helpful last year in helping people to find out more about candidates.  That gives our members a way to ask hard questions of the candidates and publicly see their answers. This year we have two important groups to fill.  The first is the NomCom.  We need three people from our membership to step up and fill this role.  It won’t be easy.  You will have to make subjective rankings of your fellow community members.  Your actions will be important in deciding who the future leaders of PASS will be.  There’s a 50/50 chance that one of the people you interview will be the President of PASS someday.  This is not a responsibility to be taken lightly. The second is the slate of candidates.  If you’ve ever thought about running for the Board this is the year.  We’ve never had nine candidates on the ballot before.  Your chance of making it through the NomCom are higher than in any previous year.  Unfortunately the more of you that run, the more of you that will lose in the election.  And hopefully that competition will mean more community involvement and better Board members for PASS. Is this the end of changes to the election process?  It isn’t.  Every year that I’ve been on the Board the election process has changed.  Some years there have been small changes and some years there have been large changes.  After this election we’ll look at how the process worked and decide what steps to take – just like we do every year.

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• Why does Farseer 2.x store temporaries as members and not on the stack? (.NET)

  - by Andrew Russell

  UPDATE: This question refers to Farseer 2.x. The newer 3.x doesn't seem to do this. I'm using Farseer Physics Engine quite extensively at the moment, and I've noticed that it seems to store a lot of temporary value types as members of the class, and not on the stack as one might expect. Here is an example from the Body class: private Vector2 _worldPositionTemp = Vector2.Zero; private Matrix _bodyMatrixTemp = Matrix.Identity; private Matrix _rotationMatrixTemp = Matrix.Identity; private Matrix _translationMatrixTemp = Matrix.Identity; public void GetBodyMatrix(out Matrix bodyMatrix) { Matrix.CreateTranslation(position.X, position.Y, 0, out _translationMatrixTemp); Matrix.CreateRotationZ(rotation, out _rotationMatrixTemp); Matrix.Multiply(ref _rotationMatrixTemp, ref _translationMatrixTemp, out bodyMatrix); } public Vector2 GetWorldPosition(Vector2 localPosition) { GetBodyMatrix(out _bodyMatrixTemp); Vector2.Transform(ref localPosition, ref _bodyMatrixTemp, out _worldPositionTemp); return _worldPositionTemp; } It looks like its a by-hand performance optimisation. But I don't see how this could possibly help performance? (If anything I think it would hurt by making objects much larger).

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• What level of detail to use in an interface members descriptions?

  - by famousgarkin

  I am extracting interfaces from some classes in .NET, and I am not completely sure about what level of detail of description to use for some of the interface members (properties, methods). An example: interface ISomeInterface { /// <summary> /// Checks if the object is checked out. /// </summary> /// <returns> /// Returns true if the object is checked out, or if the object locking is not enabled, /// otherwise returns false. /// </returns> bool IsObjectCheckedOut(); } class SomeImplementation : ISomeInterface { public bool IsObjectCheckedOut() { // An implementation of the method that returns true if the object is checked out, // or if the object locking is not enabled } } The part in question is the <returns>...</returns> section of the IsObjectCheckedOut description in the interface. Is it ok to include such a detail about return value in the interface itself, as the code that will work with the interface should know exactly what that method will do? All the current implementations of the method will do just that. But is it ok to limit the possible other/future implementations by description this way? Or should this not be included in the interface description, as there is no way to actually ensure that other/future implementations will do exactly this? Is it better to be as general as possible regarding the interface in such circumstances? I am currently inclined to the latter option.

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• MDX using EXISTING, AGGREGATE, CROSSJOIN and WHERE

  - by James Rogers

  It is a well-published approach to using the EXISTING function to decode AGGREGATE members and nested sub-query filters.  Mosha wrote a good blog on it here and a more recent one here.  The use of EXISTING in these scenarios is very useful and sometimes the only option when dealing with multi-select filters.  However, there are some limitations I have run across when using the EXISTING function against an AGGREGATE member:   The AGGREGATE member must be assigned to the Dimension.Hierarchy being detected by the EXISTING function in the calculated measure. The AGGREGATE member cannot contain a crossjoin from any other dimension or hierarchy or EXISTING will not be able to detect the members in the AGGREGATE member.   Take the following query (from Adventure Works DW 2008):   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]})'   select   {[Week Count]} on columns from   [Adventure Works]     where   [Date].[Fiscal Weeks].[CM]   Here we are attempting to count the existing fiscal weeks in slicer.  This is useful to get a per-week average for another member. Many applications generate queries in this manner (such as Oracle OBIEE).  This query returns the correct result of (4) weeks. Now let's put a twist in it.  What if the querying application submits the query in the following manner:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Customer].[Customer Geography].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]})'   select   {[Week Count]} on columns from   [Adventure Works]     where   [Customer].[Customer Geography].[CM]   Here we are attempting to count the existing fiscal weeks in slicer.  However, the AGGREGATE member is built on a different dimension (in name) than the one EXISTING is trying to detect.  In this case the query returns (174) which is the total number of [Date].[Fiscal Weeks].[Fiscal Week].members defined in the dimension.   Now another twist, the AGGREGATE member will be named appropriately and contain the hierarchy we are trying to detect with EXISTING but it will be cross-joined with another hierarchy:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}*    {[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})'  select   {[Week Count]} on columns from   [Adventure Works]    where   [Date].[Fiscal Weeks].[CM]   Once again, we are attempting to count the existing fiscal weeks in slicer.  Again, in this case the query returns (174) which is the total number of [Date].[Fiscal Weeks].[Fiscal Week].members defined in the dimension. However, in 2008 R2 this query returns the correct result of 4 and additionally , the following will return the count of existing countries as well (2):   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'   member [Country Count] as 'count(existing([Customer].[Customer Geography].[Country].members))'  member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}*    {[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})'  select   {[Week Count]} on columns from   [Adventure Works]    where   [Date].[Fiscal Weeks].[CM]   2008 R2 seems to work as long as the AGGREGATE member is on at least one of the hierarchies attempting to be detected (i.e. [Date].[Fiscal Weeks] or [Customer].[Customer Geography]). If not, it seems that the engine cannot find a "point of entry" into the aggregate member and ignores it for calculated members.   One way around this would be to put the sets from the AGGREGATE member explicitly in the WHERE clause (slicer).  I realize this is only supported in SSAS 2005 and 2008.  However, after talking with Chris Webb (his blog is here and I highly recommend following his efforts and musings) it is a far more efficient way to filter/slice a query:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    select   {[Week Count]} on columns from   [Adventure Works]    where   ({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}   ,{[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})   This query returns the correct result of (4) weeks.  Additionally, we can count the cross-join members of the two hierarchies in the slicer:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members)*existing([Customer].[Customer Geography].[Country].members))'    select   {[Week Count]} on columns from   [Adventure Works]    where   ({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}   ,{[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})   We get the correct number of (8) here.

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• Agile team with no dedicated Tester members. Insane or efficient?

  - by MetaFight

  I'm a software developer. I've been thinking a lot about the efficiency of the Software Testers I've worked with so far in my career. In fact, I've been thinking a lot about the Software Testers role in general and have reached a potentially contentious conclusion: Non-developer Software Testers staff are less efficient at software testing than developers. Now, before everyone gets upset, hear me out. This isn't mere opinion: Software Testing and Software Development both require a lot of skills in common: Problem solving Thinking about corner cases Analytical skills The ability to define clear and concise step-by-step scenarios What developers have in addition to this is the ability to automate their tests. Yes, I know non-dev testers can automate their tests too, but that often then becomes a test maintenance issue. Because automating UI tests is essentially programming, non-dev members encounter all the same difficulties software developers encounter: Copy-pasta, lack of code reusibility/maintainability, etc. So, I was wondering. Why not replace all non-dev roles with developer roles? Developers have the skills required to perform Software Testing tasks, and they have the skills to automate tests and keep them maintainable. Would the following work: Hire a bunch of developers and split them into 2 roles: Software developers Software developers doing testing (some manual, mostly automated by writing integration tests, unit tests, etc) Software developers doing application support. (I've removed this as it is probably a separate question altogether) And, in our case since we're doing Agile development, rotate the roles every sprint or two. Also, if at all possible, try to have people spend their Developer stints and Testing stints on different projects. Ideally you would want to reduce the turnover rate per rotation. So maybe you could have 2 groups and make sure the rotation cycles of the groups are elided. So, for example, if each rotation was two sprints long, the two groups would have their rotations 1 sprint apart. That way there's only a 50% turn-over rate per sprint. Am I crazy, or could this work? (Obviously a key component to this working is that all devs want to be in the 3 roles. Let's assume I'm starting a new company and I can hire these ideal people) Edit I've removed the phrase "QA", as apparently we are using it incorrectly where I work.

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• PASS: Bylaw Change 2013

  - by Bill Graziano

  PASS launched a Global Growth Initiative in the Summer of 2011 with the appointment of three international Board advisors.  Since then we’ve thought and talked extensively about how we make PASS more relevant to our members outside the US and Canada.  We’ve collected much of that discussion in our Global Growth site.  You can find vision documents, plans, governance proposals, feedback sites, and transcripts of Twitter chats and town hall meetings.  We also address these plans at the Board Q&A during the 2012 Summit. One of the biggest changes coming out of this process is around how we elect Board members.  And that requires a change to the bylaws.  We published the proposed bylaw changes as a red-lined document so you can clearly see the changes.  Our goal in these bylaw changes was to address the changes required by the global growth initiatives, conduct a legal review of the document and address other minor issues in the document.  There are numerous small wording changes throughout the document.  For example, we replaced every reference of “The Corporation” with the word “PASS” so it now reads “PASS is organized…”. Board Composition The biggest change in these bylaw changes is how the Board is composed and elected.  This discussion starts in section VI.2.  This section now says that some elected directors will come from geographic regions.  I think this is the best way to make sure we give all of our members a voice in the leadership of the organization.  The key parts of this section are: The remaining Directors (i.e. the non-Officer Directors and non-Vendor Appointed Directors) shall be elected by the voting membership (“Elected Directors”). Elected Directors shall include representatives of defined PASS regions (“Regions”) as set forth below (“Regional Directors”) and at minimum one (1) additional Director-at-Large whose selection is not limited by region. Regional Directors shall include, but are not limited to, two (2) seats for the Region covering Canada and the United States of America. Additional Regions for the purpose of electing additional Regional Directors and additional Director-at-Large seats for the purpose of expanding the Board shall be defined by a majority vote of the current Board of Directors and must be established prior to the public call for nominations in the general election. Previously defined Regions and seats approved by the Board of Directors shall remain in effect and can only be modified by a 2/3 majority vote by the then current Board of Directors. Currently PASS has six At-Large Directors elected by the members.  These changes allow for a Regional Director position that is elected by the members but must come from a particular region.  It also stipulates that there must always be at least one Director-at-Large who can come from any region. We also understand that PASS is currently a very US-centric organization.  Our Summit is held in America, roughly half our chapters are in the US and Canada and most of the Board members over the last ten years have come from America.  We wanted to reflect that by making sure that our US and Canadian volunteers would continue to play a significant role by ensuring that two Regional seats are reserved specifically for Canada and the US. Other than that, the bylaws don’t create any specific regional seats.  These rules allow us to create Regional Director seats but don’t require it.  We haven’t fully discussed what the criteria will be in order for a region to have a seat designated for it or how many regions there will be.  In our discussions we’ve broadly discussed regions for United States and Canada Europe, Middle East, and Africa (EMEA) Australia, New Zealand and Asia (also known as Asia Pacific or APAC) Mexico, South America, and Central America (LATAM) As you can see, our thinking is that there will be a few large regions.  I’ve also considered a non-North America region that we can gradually split into the regions above as our membership grows in those areas.  The regions will be defined by a policy document that will be published prior to the elections. I’m hoping that over the next year we can begin to publish more of what we do as Board-approved policy documents. While the bylaws only require a single non-region specific At-large Director, I would expect we would always have two.  That way we can have one in each election.  I think it’s important that we always have one seat open that anyone who is eligible to run for the Board can contest.  The Board is required to have any regions defined prior to the start of the election process. Board Elections – Regional Seats We spent a lot of time discussing how the elections would work for these Regional Director seats.  Ultimately we decided that the simplest solution is that every PASS member should vote for every open seat.  Section VIII.3 reads: Candidates who are eligible (i.e. eligible to serve in such capacity subject to the criteria set forth herein or adopted by the Board of Directors) shall be designated to fill open Board seats in the following order of priority on the basis of total votes received: (i) full term Regional Director seats, (ii) full term Director-at-Large seats, (iii) not full term (vacated) Regional Director seats, (iv) not full term (vacated) Director-at-Large seats. For the purposes of clarity, because of eligibility requirements, it is contemplated that the candidates designated to the open Board seats may not receive more votes than certain other candidates who are not selected to the Board. We debated whether to have multiple ballots or one single ballot.  Multiple ballot elections get complicated quickly.  Let’s say we have a ballot for US/Canada and one for Region 2.  After that we’d need a mechanism to merge those two together and come up with the winner of the at-large seat or have another election for the at-large position.  We think the best way to do this is a single ballot and putting the highest vote getters into the most restrictive seats.  Let’s look at an example: There are seats open for Region 1, Region 2 and at-large.  The election results are as follows: Candidate A (eligible for Region 1) – 550 votes Candidate B (eligible for Region 1) – 525 votes Candidate C (eligible for Region 1) – 475 votes Candidate D (eligible for Region 2) – 125 votes Candidate E (eligible for Region 2) – 75 votes In this case, Candidate A is the winner for Region 1 and is assigned that seat.  Candidate D is the winner for Region 2 and is assigned that seat.  The at-large seat is filled by the high remaining vote getter which is Candidate B. The key point to understand is that we may have a situation where a person with a lower vote total is elected to a regional seat and a person with a higher vote total is excluded.  This will be true whether we had multiple ballots or a single ballot.  Board Elections – Vacant Seats The other change to the election process is for vacant Board seats.  The actual changes are sprinkled throughout the document. Previously we didn’t have a mechanism that allowed for an election of a Board seat that we knew would be vacant in the future.  The most common case is when a Board members moves to an Officer role in the middle of their term.  One of the key changes is to allow the number of votes members have to match the number of open seats.  This allows each voter to express their preference on all open seats.  This only applies when we know about the opening prior to the call for nominations.  This all means that if there’s a seat will be open at the start of the next Board term, and we know about it prior to the call for nominations, we can include that seat in the elections.  Ultimately, the aim is to have PASS members decide who sits on the Board in as many situations as possible. We discussed the option of changing the bylaws to just take next highest vote-getter in all other cases.  I think that’s wrong for the following reasons: All voters aren’t able to express an opinion on all candidates.  If there are five people running for three seats, you can only vote for three.  You have no way to express your preference between #4 and #5. Different candidates may have different information about the number of seats available.  A person may learn that a Board member plans to resign at the end of the year prior to that information being made public. They may understand that the top four vote getters will end up on the Board while the rest of the members believe there are only three openings.  This may affect someone’s decision to run.  I don’t think this creates a transparent, fair election. Board members may use their knowledge of the election results to decide whether to remain on the Board or not.  Admittedly this one is unlikely but I don’t want to create a situation where this accusation can be leveled. I think the majority of vacancies in the future will be handled through elections.  The bylaw section quoted above also indicates that partial term vacancies will be filled after the full term seats are filled. Removing Directors Section VI.7 on removing directors has always had a clause that allowed members to remove an elected director.  We also had a clause that allowed appointed directors to be removed.  We added a clause that allows the Board to remove for cause any director with a 2/3 majority vote.  The updated text reads: Any Director may be removed for cause by a 2/3 majority vote of the Board of Directors whenever in its judgment the best interests of PASS would be served thereby. Notwithstanding the foregoing, the authority of any Director to act as in an official capacity as a Director or Officer of PASS may be suspended by the Board of Directors for cause. Cause for suspension or removal of a Director shall include but not be limited to failure to meet any Board-approved performance expectations or the presence of a reason for suspension or dismissal as listed in Addendum B of these Bylaws. The first paragraph is updated and the second and third are unchanged (except cleaning up language).  If you scroll down and look at Addendum B of these bylaws you find the following: Cause for suspension or dismissal of a member of the Board of Directors may include: Inability to attend Board meetings on a regular basis. Inability or unwillingness to act in a capacity designated by the Board of Directors. Failure to fulfill the responsibilities of the office. Inability to represent the Region elected to represent Failure to act in a manner consistent with PASS's Bylaws and/or policies. Misrepresentation of responsibility and/or authority. Misrepresentation of PASS. Unresolved conflict of interests with Board responsibilities. Breach of confidentiality. The bold line about your inability to represent your region is what we added to the bylaws in this revision.  We also added a clause to section VII.3 allowing the Board to remove an officer.  That clause is much less restrictive.  It doesn’t require cause and only requires a simple majority. The Board of Directors may remove any Officer whenever in their judgment the best interests of PASS shall be served by such removal. Other There are numerous other small changes throughout the document. Proxy voting.  The laws around how members and Board members proxy votes are specific in Illinois law.  PASS is an Illinois corporation and is subject to Illinois laws.  We changed section IV.5 to come into compliance with those laws.  Specifically this says you can only vote through a proxy if you have a written proxy through your authorized attorney.  English language proficiency.  As we increase our global footprint we come across more members that aren’t native English speakers.  The business of PASS is conducted in English and it’s important that our Board members speak English.  If we get big enough to afford translators, we may be able to relax this but right now we need English language skills for effective Board members. Committees.  The language around committees in section IX is old and dated.  Our lawyers advised us to clean it up.  This section specifically applies to any committees that the Board may form outside of portfolios.  We removed the term limits, quorum and vacancies clause.  We don’t currently have any committees that this would apply to.  The Nominating Committee is covered elsewhere in the bylaws. Electronic Votes.  The change allows the Board to vote via email but the results must be unanimous.  This is to conform with Illinois state law. Immediate Past President.  There was no mechanism to fill the IPP role if an outgoing President chose not to participate.  We changed section VII.8 to allow the Board to invite any previous President to fill the role by majority vote. Nominations Committee.  We’ve opened the language to allow for the transparent election of the Nominations Committee as outlined by the 2011 Election Review Committee. Revocation of Charters. The language surrounding the revocation of charters for local groups was flagged by the lawyers. We have allowed for the local user group to make all necessary payment before considering returning of items to PASS if required. Bylaw notification. We’ve spent countless meetings working on these bylaws with the intent to not open them again any time in the near future. Should the bylaws be opened again, we have included a clause ensuring that the PASS membership is involved. I’m proud that the Board has remained committed to transparency and accountability to members. This clause will require that same level of commitment in the future even when all the current Board members have rolled off. I think that covers everything.  I’d encourage you to look through the red-line document and see the changes.  It’s helpful to look at the language that’s being removed and the language that’s being added.  I’m happy to answer any questions here or you can email them to [email protected].

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• django m2m how can i get m2m table elements in a view

  - by dana

  i have a model using m2m feature: class Classroom(models.Model): user = models.ForeignKey(User, related_name = 'classroom_creator') classname = models.CharField(max_length=140, unique = True) date = models.DateTimeField(auto_now=True) open_class = models.BooleanField(default=True) members = models.ManyToManyField(User,related_name="list of invited members", through = 'Membership') and i want to take all members of one class in a view and display them using the template system. In the view, i'm trying to take all the members from a classroom like that: def inside_classroom(request,classname): try: theclass = Classroom.objects.get(classname = classname) members = Members.objects.all() etc but it doesn't work,(though the db_table is named Classroom_Members) i guess i have to use another query for getting all the members from the classroom classname. also, i want to verify if the request.user is a member using (if request.user in members) how can i het those members? Thanks in advance!

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• What must be done to allow a development team to minimize difficulties as new team members are added?

  - by Travis

  I work at a small Web Dev firm, and have been handling all the PHP/MySQL/etc. for a while. I'm looking at improving our practices to allow for easier collaboration as we grow. Some things I have in mind are: Implementing a versioning system (source control) Coding standards for the team (unless mandated by a certain framework, etc.) Enforcing a common directory structure for our Desktops (for backup purposes, etc.) Web-based task/project/time/file/password/contact management and collaboration app(we've tried a bunch; I may just create one) What do more experienced developers view as necessary first steps in this area? Do you recommend any books? One thing to consider is that the bulk of our daily tasks involve maintenance and adding minor functionality rather than new projects, and the team size will be between 3 and 5. I just found a related question about teams that will be expanding from a solo developer.

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