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• Windows Phone 7 development: first impressions

  - by DigiMortal

  After hard week in work I got some free time to play with Windows Phone 7 CTP developer tools. Although my first test application is still unfinished I think it is good moment to share my first experiences to you. In this posting I will give you quick overview of Windows Phone 7 developer tools from developer perspective. If you are familiar with Visual Studio 2010 then you will feel comfortable because Windows Phone 7 CTP developer tools base on Visual Studio 2010 Express. Project templates There are five project templates available. Three of them are based on Silverlight and two on XNA Game Studio: Windows Phone Application (Silverlight) Windows Phone List Application (Silverlight) Windows Phone Class Library (Silverlight) Windows Phone Game (XNA Game Studio) Windows Phone Game Library (XNA Game Studio) Currently I am writing to test applications. One of them is based on Windows Phone Application and the other on Windows Phone List Application project template. After creating these projects you see the following views in Visual Studio. Windows Phone Application. Click on image to enlarge. Windows Phone List Application. Click on image to enlarge.  I suggest you to use some of these templates to get started more easily. Windows Phone 7 emulator You can run your Windows Phone 7 applications on Windows Phone 7 emulator that comes with developer tools CTP. If you run your application then emulator is started automatically and you can try out how your application works in phone-like emulator. You can see screenshot of emulator on right. Currently there is opened Windows Phone List Application as it is created by default. Click on image to enlarge it. Emulator is a little bit slow and uncomfortable but it works pretty well. This far I have caused only couple of crashes during my experiments. In these cases emulator works but Visual Studio gets stuck because it cannot communicate with emulator. One important note. Emulator is based on virtual machine although you can see only phone screen and options toolbar. If you want to run emulator you must close all virtual machines running on your machine and run Visual Studio 2010 as administrator. Once you run emulator you can keep it open because you can stop your application in Visual Studio, modify, compile and re-deploy it without restarting emulator. Designing user interfaces You can design user interface of your application in Visual Studio. When you open XAML-files it is displayed in window with two panels. Left panel shows you device screen and works as visual design environment while right panel shows you XAML mark-up and let’s you modify XML if you need it. As it is one of my very first Silverlight applications I felt more comfortable with XAML editor because property names in property boxes of visual designer confused me a little bit. Designer panel is not very good because it is visually hard to follow. It has black background that makes dark borders of controls very hard to see. If you have monitor with very high contrast then it is may be not a real problem. I have usual monitor and I have problem. :) Putting controls on design surface, dragging and resizing them is also pretty painful. Some controls are drawn correctly but for some controls you have to set width and height in XML so they can be resized. After some practicing it is not so annoying anymore. On the right you can see toolbox with some controllers. This is all you get out of the box. But it is sufficient to get started. After getting some experiences you can create your own controls or use existing ones from other vendors or developers. If it is your first time to do stuff with Silverlight then keep Google open – you need it hard. After getting over the first shock you get the point very quickly and start developing at normal speed. :) Writing source code Writing source code is the most familiar part of this action. Good old Visual Studio code editor with all nice features it has. But here you get also some surprises: The anatomy of Silverlight controls is a little bit different than the one of user controls in web and forms projects. Windows Phone 7 doesn’t run on full version of Windows (I bet it is some version of Windows CE or something like this) then there is less system classes you can use. Some familiar classes have less methods that in full version of .NET Framework and in these cases you have to write all the code by yourself or find libraries or source code from somewhere. These problems are really not so much problems than limitations and you get easily over them. Conclusion Windows Phone 7 CTP developer tools help you do a lot of things on Windows Phone 7. Although I expected better performance from tools I think that current performance is not a problem. This far my first test project is going very well and Google has answer for almost every question. Windows Phone 7 is mobile device and therefore it has less hardware resources than desktop computers. This is why toolset is so limited. The more you need memory the more slower is device and as you may guess it needs the more battery. If you are writing apps for mobile devices then make your best to get your application use as few resources as possible and act as fast as possible.

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• Using Oracle Proxy Authentication with JPA (eclipselink-Style)

  - by olaf.heimburger

  Security is a very intriguing topic. You will find it everywhere and you need to implement it everywhere. Yes, you need. Unfortunately, one can easily forget it while implementing the last mile. The Last Mile In a multi-tier application it is a common practice to use connection pools between the business layer and the database layer. Connection pools are quite useful to speed database connection creation and to split the load. Another very common practice is to use a specific, often called technical, user to connect to the database. This user has authentication and authorization rules that apply to all application users. Imagine you've put every effort to define roles for different types of users that use your application. These roles are necessary to differentiate between normal users, premium users, and administrators (I bet you will find or already have more roles in your application). While these user roles are pretty well used within your application, once the flow of execution enters the database everything is gone. Each and every user just has one role and is the same database user. Issues? What Issues? As long as things go well, this is not a real issue. However, things do not go well all the time. Once your application becomes famous performance decreases in certain situations or, more importantly, current and upcoming regulations and laws require that your application must be able to apply different security measures on a per user role basis at every stage of your application. If you only have a bunch of users with the same name and role you are not able to find the application usage profile that causes the performance issue, or which user has accessed data that he/she is not allowed to. Another thread to your role concept is that databases tend to be used by different applications and tools. These tools can be developer tools like SQL*Plus, SQL Developer, etc. or end user applications like BI Publisher, Oracle Forms and so on. These tools have no idea of your applications role concept and access the database the way they think is appropriate. A big oversight for your perfect role model and a big nightmare for your Chief Security Officer. Speaking of the CSO, brings up another issue: Password management. Once your technical user account is compromised, every user is able to do things that he/she is not expected to do from the design of your application. Counter Measures In the Oracle world a common counter measure is to use Virtual Private Database (VPD). This restricts the values a database user can see to the allowed minimum. However, it doesn't help in regard of a connection pool user, because this one is still not the real user. Oracle Proxy Authentication Another feature of the Oracle database is Proxy Authentication. First introduced with version 9i it is a quite useful feature for nearly every situation. The main idea behind Proxy Authentication is, to create a crippled database user who has only connect rights. Even if this user is compromised the risks are well understood and fairly limited. This user can be used in every situation in which you need to connect to the database, no matter which tool or application (see above) you use.The proxy user is perfect for multi-tier connection pools. CREATE USER app_user IDENTIFIED BY abcd1234; GRANT CREATE SESSION TO app_user; But what if you need to access real data? Well, this is the primary use case, isn't it? Now is the time to bring the application's role concept into play. You define database roles that define the grants for your identified user groups. Once you have these groups you grant access through the proxy user with the application role to the specific user. CREATE ROLE app_role_a; GRANT app_role_a TO scott; ALTER USER scott GRANT CONNECT THROUGH app_user WITH ROLE app_role_a; Now, hr has permission to connect to the database through the proxy user. Through the role you can restrict the hr's rights the are needed for the application only. If hr connects to the database directly all assigned role and permissions apply. Testing the Setup To test the setup you can use SQL*Plus and connect to your database: $ sqlplus app_user[hr]/abcd1234 Java Persistence API The Java Persistence API (JPA) is a fairly easy means to build applications that retrieve data from the database and put it into Java objects. You use plain old Java objects (POJOs) and mixin some Java annotations that define how the attributes of the object are used for storing data from the database into the Java object. Here is a sample for objects from the HR sample schema EMPLOYEES table. When using Java annotations you only specify what can not be deduced from the code. If your Java class name is Employee but the table name is EMPLOYEES, you need to specify the table name, otherwise it will fail. package demo.proxy.ejb; import java.io.Serializable; import java.sql.Timestamp; import java.util.List; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.NamedQueries; import javax.persistence.NamedQuery; import javax.persistence.OneToMany; import javax.persistence.Table; @Entity @NamedQueries({ @NamedQuery(name = "Employee.findAll", query = "select o from Employee o") }) @Table(name = "EMPLOYEES") public class Employee implements Serializable { @Column(name="COMMISSION_PCT") private Double commissionPct; @Column(name="DEPARTMENT_ID") private Long departmentId; @Column(nullable = false, unique = true, length = 25) private String email; @Id @Column(name="EMPLOYEE_ID", nullable = false) private Long employeeId; @Column(name="FIRST_NAME", length = 20) private String firstName; @Column(name="HIRE_DATE", nullable = false) private Timestamp hireDate; @Column(name="JOB_ID", nullable = false, length = 10) private String jobId; @Column(name="LAST_NAME", nullable = false, length = 25) private String lastName; @Column(name="PHONE_NUMBER", length = 20) private String phoneNumber; private Double salary; @ManyToOne @JoinColumn(name = "MANAGER_ID") private Employee employee; @OneToMany(mappedBy = "employee") private List employeeList; public Employee() { } public Employee(Double commissionPct, Long departmentId, String email, Long employeeId, String firstName, Timestamp hireDate, String jobId, String lastName, Employee employee, String phoneNumber, Double salary) { this.commissionPct = commissionPct; this.departmentId = departmentId; this.email = email; this.employeeId = employeeId; this.firstName = firstName; this.hireDate = hireDate; this.jobId = jobId; this.lastName = lastName; this.employee = employee; this.phoneNumber = phoneNumber; this.salary = salary; } public Double getCommissionPct() { return commissionPct; } public void setCommissionPct(Double commissionPct) { this.commissionPct = commissionPct; } public Long getDepartmentId() { return departmentId; } public void setDepartmentId(Long departmentId) { this.departmentId = departmentId; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public Long getEmployeeId() { return employeeId; } public void setEmployeeId(Long employeeId) { this.employeeId = employeeId; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public Timestamp getHireDate() { return hireDate; } public void setHireDate(Timestamp hireDate) { this.hireDate = hireDate; } public String getJobId() { return jobId; } public void setJobId(String jobId) { this.jobId = jobId; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getPhoneNumber() { return phoneNumber; } public void setPhoneNumber(String phoneNumber) { this.phoneNumber = phoneNumber; } public Double getSalary() { return salary; } public void setSalary(Double salary) { this.salary = salary; } public Employee getEmployee() { return employee; } public void setEmployee(Employee employee) { this.employee = employee; } public List getEmployeeList() { return employeeList; } public void setEmployeeList(List employeeList) { this.employeeList = employeeList; } public Employee addEmployee(Employee employee) { getEmployeeList().add(employee); employee.setEmployee(this); return employee; } public Employee removeEmployee(Employee employee) { getEmployeeList().remove(employee); employee.setEmployee(null); return employee; } } JPA could be used in standalone applications and Java EE containers. In both worlds you normally create a Facade to retrieve or store the values of the Entities to or from the database. The Facade does this via an EntityManager which will be injected by the Java EE container. Here is sample Facade Session Bean for a Java EE container. package demo.proxy.ejb; import java.util.HashMap; import java.util.List; import javax.ejb.Local; import javax.ejb.Remote; import javax.ejb.Stateless; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import javax.persistence.Query; import javax.interceptor.AroundInvoke; import javax.interceptor.InvocationContext; import oracle.jdbc.driver.OracleConnection; import org.eclipse.persistence.config.EntityManagerProperties; import org.eclipse.persistence.internal.jpa.EntityManagerImpl; @Stateless(name = "DataFacade", mappedName = "ProxyUser-TestEJB-DataFacade") @Remote @Local public class DataFacadeBean implements DataFacade, DataFacadeLocal { @PersistenceContext(unitName = "TestEJB") private EntityManager em; private String username; public Object queryByRange(String jpqlStmt, int firstResult, int maxResults) { // setSessionUser(); Query query = em.createQuery(jpqlStmt); if (firstResult 0) { query = query.setFirstResult(firstResult); } if (maxResults 0) { query = query.setMaxResults(maxResults); } return query.getResultList(); } public Employee persistEmployee(Employee employee) { // setSessionUser(); em.persist(employee); return employee; } public Employee mergeEmployee(Employee employee) { // setSessionUser(); return em.merge(employee); } public void removeEmployee(Employee employee) { // setSessionUser(); employee = em.find(Employee.class, employee.getEmployeeId()); em.remove(employee); } /** select o from Employee o */ public List getEmployeeFindAll() { Query q = em.createNamedQuery("Employee.findAll"); return q.getResultList(); } Putting Both Together To use Proxy Authentication with JPA and within a Java EE container you have to take care of the additional requirements: Use an OCI JDBC driver Provide the user name that connects through the proxy user Use an OCI JDBC driver To use the OCI JDBC driver you need to set up your JDBC data source file to use the correct JDBC URL. hr jdbc:oracle:oci8:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521))(CONNECT_DATA=(SID=XE))) oracle.jdbc.OracleDriver user app_user 62C32F70E98297522AD97E15439FAC0E SQL SELECT 1 FROM DUAL jdbc/hrDS Application Additionally you need to make sure that the version of the shared libraries of the OCI driver match the version of the JDBC driver in your Java EE container or Java application and are within your PATH (on Windows) or LD_LIBRARY_PATH (on most Unix-based systems). Installing the Oracle Database Instance Client software works perfectly. Provide the user name that connects through the proxy user This part needs some modification of your application software and session facade. Session Facade Changes In the Session Facade we must ensure that every call that goes through the EntityManager must be prepared correctly and uniquely assigned to this session. The second is really important, as the EntityManager works with a connection pool and can not guarantee that we set the proxy user on the connection that will be used for the database activities. To avoid changing every method call of the Session Facade we provide a method to set the username of the user that connects through the proxy user. This method needs to be called by the Facade client bfore doing anything else. public void setUsername(String name) { username = name; } Next we provide a means to instruct the TopLink EntityManager Delegate to use Oracle Proxy Authentication. (I love small helper methods to hide the nitty-gritty details and avoid repeating myself.) private void setSessionUser() { setSessionUser(username); } private void setSessionUser(String user) { if (user != null && !user.isEmpty()) { EntityManagerImpl emDelegate = ((EntityManagerImpl)em.getDelegate()); emDelegate.setProperty(EntityManagerProperties.ORACLE_PROXY_TYPE, OracleConnection.PROXYTYPE_USER_NAME); emDelegate.setProperty(OracleConnection.PROXY_USER_NAME, user); emDelegate.setProperty(EntityManagerProperties.EXCLUSIVE_CONNECTION_MODE, "Always"); } } The final step is use the EJB 3.0 AroundInvoke interceptor. This interceptor will be called around every method invocation. We therefore check whether the Facade methods will be called or not. If so, we set the user for proxy authentication and the normal method flow continues. @AroundInvoke public Object proxyInterceptor(InvocationContext invocationCtx) throws Exception { if (invocationCtx.getTarget() instanceof DataFacadeBean) { setSessionUser(); } return invocationCtx.proceed(); } Benefits Using Oracle Proxy Authentification has a number of additional benefits appart from implementing the role model of your application: Fine grained access control for temporary users of the account, without compromising the original password. Enabling database auditing and logging. Better identification of performance bottlenecks. References Effective Oracle Database 10g Security by Design, David Knox TopLink Developer's Guide, Chapter 98

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• OpenIndiana (illumos): vmxnet3 interface lost on reboot

  - by protomouse

  I want my VMware vmxnet3 interface to be brought up with DHCP on boot. I can manually configure the NIC with: # ifconfig vmxnet3s0 plumb # ipadm create-addr -T dhcp vmxnet3s0/v4dhcp But after creating /etc/dhcp.vmxnet3s0 and rebooting, the interface is down and the logs show: Aug 13 09:34:15 neumann vmxnet3s: [ID 654879 kern.notice] vmxnet3s:0: getcapab(0x200000) -> no Aug 13 09:34:15 neumann vmxnet3s: [ID 715698 kern.notice] vmxnet3s:0: stop() Aug 13 09:34:17 neumann vmxnet3s: [ID 654879 kern.notice] vmxnet3s:0: getcapab(0x200000) -> no Aug 13 09:34:17 neumann vmxnet3s: [ID 920500 kern.notice] vmxnet3s:0: start() Aug 13 09:34:17 neumann vmxnet3s: [ID 778983 kern.notice] vmxnet3s:0: getprop(TxRingSize) -> 256 Aug 13 09:34:17 neumann vmxnet3s: [ID 778983 kern.notice] vmxnet3s:0: getprop(RxRingSize) -> 256 Aug 13 09:34:17 neumann vmxnet3s: [ID 778983 kern.notice] vmxnet3s:0: getprop(RxBufPoolLimit) -> 512 Aug 13 09:34:17 neumann nwamd[491]: [ID 605049 daemon.error] 1: nwamd_set_unset_link_properties: dladm_set_linkprop failed: operation not supported Aug 13 09:34:17 neumann vmxnet3s: [ID 654879 kern.notice] vmxnet3s:0: getcapab(0x20000) -> no Aug 13 09:34:17 neumann nwamd[491]: [ID 751932 daemon.error] 1: nwamd_down_interface: ipadm_delete_addr failed on vmxnet3s0: Object not found Aug 13 09:34:17 neumann nwamd[491]: [ID 819019 daemon.error] 1: nwamd_plumb_unplumb_interface: plumb IPv4 failed for vmxnet3s0: Operation not supported on disabled object Aug 13 09:34:17 neumann nwamd[491]: [ID 160156 daemon.error] 1: nwamd_plumb_unplumb_interface: plumb IPv6 failed for vmxnet3s0: Operation not supported on disabled object Aug 13 09:34:17 neumann nwamd[491]: [ID 771489 daemon.error] 1: add_ip_address: ipadm_create_addr failed on vmxnet3s0: Operation not supported on disabled object Aug 13 09:34:17 neumann nwamd[491]: [ID 405346 daemon.error] 9: start_dhcp: ipadm_create_addr failed for vmxnet3s0: Operation not supported on disabled object I then tried disabling network/physical:nwam in favour of network/physical:default. This works, the interface is brought up but physical:default fails and my network services (e.g. NFS) refuse to start. # ifconfig -a lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 vmxnet3s0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:1: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:2: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:3: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:4: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:5: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:6: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:7: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 vmxnet3s0:8: flags=1004842<BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 9000 index 2 inet 192.168.178.248 netmask ffffff00 broadcast 192.168.178.255 lo0: flags=2002000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 8252 index 1 inet6 ::1/128 vmxnet3s0: flags=20002000840<RUNNING,MULTICAST,IPv6> mtu 9000 index 2 inet6 ::/0 # cat /var/svc/log/network-physical\:default.log [ Aug 16 09:46:39 Enabled. ] [ Aug 16 09:46:41 Executing start method ("/lib/svc/method/net-physical"). ] [ Aug 16 09:46:41 Timeout override by svc.startd. Using infinite timeout. ] starting DHCP on primary interface vmxnet3s0 ifconfig: vmxnet3s0: DHCP is already running [ Aug 16 09:46:43 Method "start" exited with status 96. ] NFS server not running: # svcs -xv network/nfs/server svc:/network/nfs/server:default (NFS server) State: offline since August 16, 2012 09:46:40 AM UTC Reason: Service svc:/network/physical:default is not running because a method failed. See: http://illumos.org/msg/SMF-8000-GE Path: svc:/network/nfs/server:default svc:/milestone/network:default svc:/network/physical:default Reason: Service svc:/network/physical:nwam is disabled. See: http://illumos.org/msg/SMF-8000-GE Path: svc:/network/nfs/server:default svc:/milestone/network:default svc:/network/physical:nwam Reason: Service svc:/network/nfs/nlockmgr:default is disabled. See: http://illumos.org/msg/SMF-8000-GE Path: svc:/network/nfs/server:default svc:/network/nfs/nlockmgr:default See: man -M /usr/share/man -s 1M nfsd Impact: This service is not running. I'm new to the world of Solaris, so any help solving would be much appreciated. Thanks!

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• All Xen domU LVM volumes corrupt after reboot

  - by zcs

  I'm running a Debian Squeeze dom0, and after rebooting it all 7 of my domUs have data corruption. Each is setup as ext3 partition directly on a separate lvm2 volume. None of the lvm volumes will mount; all have bad superblocks. I've tried e2fsck with each superblock to no avail. What else can I try? Each domU has two LVM volumes connected to it, one for the disk and one for swap. The disk is mounted at root, formatted as a normal ext3 partition as a xen-blk device. The volumes are never mounted outside of the guest OS. I'm running Ubuntu 11.04 using the instructions here. I'm not sure that they didn't shutdown properly, all I know is they were corrupt after I issues a clean 'reboot' on the dom0. Here's a sample Xen config file; the rest are the same except for name, vcpus, memory, vif and disk. name = 'load1' vcpus = 2 memory = 512 vif = ['bridge=prbr0', 'bridge=eth0'] disk = ['phy:/dev/VolGroup00/load1-disk,xvda,w','phy:/dev/VolGroup00/load1-swap,xvdb,w'] #============================================================================ # Debian Installer specific variables def check_bool(name, value): value = str(value).lower() if value in ('t', 'tr', 'tru', 'true'): return True return False global var_check_with_default def var_check_with_default(default, var, val): if val: return val return default xm_vars.var('install', use='Install Debian, default: false', check=check_bool) xm_vars.var("install-method", use='Installation method to use "cdrom" or "network" (default: network)', check=lambda var, val: var_check_with_default('network', var, val)) # install-method == "network" xm_vars.var("install-mirror", use='Debian mirror to install from (default: http://archive.ubuntu.com/ubuntu)', check=lambda var, val: var_check_with_default('http://archive.ubuntu.com/ubuntu', var, val)) xm_vars.var("install-suite", use='Debian suite to install (default: natty)', check=lambda var, val: var_check_with_default('natty', var, val)) # install-method == "cdrom" xm_vars.var("install-media", use='Installation media to use (default: None)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-cdrom-device", use='Installation media to use (default: xvdd)', check=lambda var, val: var_check_with_default('xvdd', var, val)) # Common options xm_vars.var("install-arch", use='Debian mirror to install from (default: amd64)', check=lambda var, val: var_check_with_default('amd64', var, val)) xm_vars.var("install-extra", use='Extra command line options (default: None)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-installer", use='Debian installer to use (default: network uses install-mirror; cdrom uses /install.ARCH)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-kernel", use='Debian installer kernel to use (default: uses install-installer)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-ramdisk", use='Debian installer ramdisk to use (default: uses install-installer)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.check() if not xm_vars.env.get('install'): bootloader="/usr/sbin/pygrub" elif xm_vars.env['install-method'] == "network": import os.path print "Install Mirror: %s" % xm_vars.env['install-mirror'] print "Install Suite: %s" % xm_vars.env['install-suite'] if xm_vars.env['install-installer']: installer = xm_vars.env['install-installer'] else: installer = xm_vars.env['install-mirror']+"/dists/"+xm_vars.env['install-suite'] + \ "/main/installer-"+xm_vars.env['install-arch']+"/current/images" print "Installer: %s" % installer print print "WARNING: Installer kernel and ramdisk are not authenticated." print if xm_vars.env.get('install-kernel'): kernelurl = xm_vars.env['install-kernel'] else: kernelurl = installer + "/netboot/xen/vmlinuz" if xm_vars.env.get('install-ramdisk'): ramdiskurl = xm_vars.env['install-ramdisk'] else: ramdiskurl = installer + "/netboot/xen/initrd.gz" import urllib class MyUrlOpener(urllib.FancyURLopener): def http_error_default(self, req, fp, code, msg, hdrs): raise IOError("%s %s" % (code, msg)) urlopener = MyUrlOpener() try: print "Fetching %s" % kernelurl kernel, _ = urlopener.retrieve(kernelurl) print "Fetching %s" % ramdiskurl ramdisk, _ = urlopener.retrieve(ramdiskurl) except IOError, _: raise elif xm_vars.env['install-method'] == "cdrom": arch_path = { 'i386': "/install.386", 'amd64': "/install.amd" } if xm_vars.env['install-media']: print "Install Media: %s" % xm_vars.env['install-media'] else: raise OptionError("No installation media given.") if xm_vars.env['install-installer']: installer = xm_vars.env['install-installer'] else: installer = arch_path[xm_vars.env['install-arch']] print "Installer: %s" % installer if xm_vars.env.get('install-kernel'): kernelpath = xm_vars.env['install-kernel'] else: kernelpath = installer + "/xen/vmlinuz" if xm_vars.env.get('install-ramdisk'): ramdiskpath = xm_vars.env['install-ramdisk'] else: ramdiskpath = installer + "/xen/initrd.gz" disk.insert(0, 'file:%s,%s:cdrom,r' % (xm_vars.env['install-media'], xm_vars.env['install-cdrom-device'])) bootloader="/usr/sbin/pygrub" bootargs="--kernel=%s --ramdisk=%s" % (kernelpath, ramdiskpath) print "From CD" else: print "WARNING: Unknown install-method: %s." % xm_vars.env['install-method'] if xm_vars.env.get('install'): # Figure out command line if xm_vars.env['install-extra']: extras=[xm_vars.env['install-extra']] else: extras=[] # Reboot will just restart the installer since this file is not # reparsed, so halt and restart that way. extras.append("debian-installer/exit/always_halt=true") extras.append("--") extras.append("quiet") console="hvc0" try: if len(vfb) >= 1: console="tty0" except NameError, e: pass extras.append("console="+ console) extra = str.join(" ", extras) print "command line is \"%s\"" % extra root There are two LVM logical volumes connected to each VM. Here's the fdisk -l output for the disk volume: Disk /dev/VolGroup00/VMNAME-disk: 8589 MB, 8589934592 bytes 255 heads, 63 sectors/track, 1044 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00029c01 Device Boot Start End Blocks Id System /dev/VolGroup00/VMNAME-disk1 1 1045 8386560 83 Linux And the swap volume: Disk /dev/VolGroup00/VMNAME-swap: 536 MB, 536870912 bytes 37 heads, 35 sectors/track, 809 cylinders Units = cylinders of 1295 * 512 = 663040 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0004faae Device Boot Start End Blocks Id System /dev/VolGroup00/VMNAME-swap1 2 809 522240 82 Linux swap / Solaris Partition 1 has different physical/logical beginnings (non-Linux?): phys=(0, 32, 33) logical=(1, 21, 19) Partition 1 has different physical/logical endings: phys=(65, 36, 35) logical=(808, 4, 28)

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• Scripting custom drawing in Delphi application with IF/THEN/ELSE statements?

  - by Jerry Dodge

  I'm building a Delphi application which displays a blueprint of a building, including doors, windows, wiring, lighting, outlets, switches, etc. I have implemented a very lightweight script of my own to call drawing commands to the canvas, which is loaded from a database. For example, one command is ELP 1110,1110,1290,1290,3,8388608 which draws an ellipse, parameters are 1110x1110 to 1290x1290 with pen width of 3 and the color 8388608 converted from an integer to a TColor. What I'm now doing is implementing objects with common drawing routines, and I'd like to use my scripting engine, but this calls for IF/THEN/ELSE statements and such. For example, when I'm drawing a light, if the light is turned on, I'd like to draw it yellow, but if it's off, I'd like to draw it gray. My current scripting engine has no recognition of such statements. It just accepts simple drawing commands which correspond with TCanvas methods. Here's the procedure I've developed (incomplete) for executing a drawing command on a canvas: function DrawCommand(const Cmd: String; var Canvas: TCanvas): Boolean; type TSingleArray = array of Single; var Br: TBrush; Pn: TPen; X: Integer; P: Integer; L: String; Inst: String; T: String; Nums: TSingleArray; begin Result:= False; Br:= Canvas.Brush; Pn:= Canvas.Pen; if Assigned(Canvas) then begin if Length(Cmd) > 5 then begin L:= UpperCase(Cmd); if Pos(' ', L)> 0 then begin Inst:= Copy(L, 1, Pos(' ', L) - 1); Delete(L, 1, Pos(' ', L)); L:= L + ','; SetLength(Nums, 0); X:= 0; while Pos(',', L) > 0 do begin P:= Pos(',', L); T:= Copy(L, 1, P - 1); Delete(L, 1, P); SetLength(Nums, X + 1); Nums[X]:= StrToFloatDef(T, 0); Inc(X); end; Br.Style:= bsClear; Pn.Style:= psSolid; Pn.Color:= clBlack; if Inst = 'LIN' then begin Pn.Width:= Trunc(Nums[4]); if Length(Nums) > 5 then begin Br.Style:= bsSolid; Br.Color:= Trunc(Nums[5]); end; Canvas.MoveTo(Trunc(Nums[0]), Trunc(Nums[1])); Canvas.LineTo(Trunc(Nums[2]), Trunc(Nums[3])); Result:= True; end else if Inst = 'ELP' then begin Pn.Width:= Trunc(Nums[4]); if Length(Nums) > 5 then begin Br.Style:= bsSolid; Br.Color:= Trunc(Nums[5]); end; Canvas.Ellipse(Trunc(Nums[0]),Trunc(Nums[1]),Trunc(Nums[2]),Trunc(Nums[3])); Result:= True; end else if Inst = 'ARC' then begin Pn.Width:= Trunc(Nums[8]); Canvas.Arc(Trunc(Nums[0]),Trunc(Nums[1]),Trunc(Nums[2]),Trunc(Nums[3]), Trunc(Nums[4]),Trunc(Nums[5]),Trunc(Nums[6]),Trunc(Nums[7])); Result:= True; end else if Inst = 'TXT' then begin Canvas.Font.Size:= Trunc(Nums[2]); Br.Style:= bsClear; Pn.Style:= psSolid; T:= Cmd; Delete(T, 1, Pos(' ', T)); Delete(T, 1, Pos(',', T)); Delete(T, 1, Pos(',', T)); Delete(T, 1, Pos(',', T)); Canvas.TextOut(Trunc(Nums[0]), Trunc(Nums[1]), T); Result:= True; end; end else begin //No space found, not a valid command end; end; end; end; What I'd like to know is what's a good lightweight third-party scripting engine I could use to accomplish this? I would hate to implement parsing of IF, THEN, ELSE, END, IFELSE, IFEND, and all those necessary commands. I need simply the ability to tell the scripting engine if certain properties meet certain conditions, it needs to draw the object a certain way. The light example above is only one scenario, but the same solution needs to also be applicable to other scenarios, such as a door being open or closed, locked or unlocked, and draw it a different way accordingly. This needs to be implemented in the object script drawing level. I can't hard-code any of these scripting/drawing rules, the drawing needs to be controlled based on the current state of the object, and I may also wish to draw a light a certain shade or darkness depending on how dimmed the light is.

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• Composing Silverlight Applications With MEF

  - by PeterTweed

  Anyone who has written an application with complexity enough to warrant multiple controls on multiple pages/forms should understand the benefit of composite application development.  That is defining your application architecture that can be separated into separate pieces each with it’s own distinct purpose that can then be “composed” together into the solution. Composition can be useful in any layer of the application, from the presentation layer, the business layer, common services or data access.  Historically people have had different options to achieve composing applications from distinct well known pieces – their own version of dependency injection, containers to aid with composition like Unity, the composite application guidance for WPF and Silverlight and before that the composite application block. Microsoft has been working on another mechanism to aid composition and extension of applications for some time now – the Managed Extensibility Framework or MEF for short.  With Silverlight 4 it is part of the Silverlight environment.  MEF allows a much simplified mechanism for composition and extensibility compared to other mechanisms – which has always been the primary issue for adoption of the earlier mechanisms/frameworks. This post will guide you through the simple use of MEF for the scenario of composition of an application – using exports, imports and composition.  Steps: 1.     Create a new Silverlight 4 application. 2.     Add references to the following assemblies: System.ComponentModel.Composition.dll System.ComponentModel.Composition.Initialization.dll 3.     Add a new user control called LeftControl. 4.     Replace the LayoutRoot Grid with the following xaml:     <Grid x:Name="LayoutRoot" Background="Beige" Margin="40" >         <Button Content="Left Content" Margin="30"></Button>     </Grid> 5.     Add the following statement to the top of the LeftControl.xaml.cs file using System.ComponentModel.Composition; 6.     Add the following attribute to the LeftControl class     [Export(typeof(LeftControl))]   This attribute tells MEF that the type LeftControl will be exported – i.e. made available for other applications to import and compose into the application. 7.     Add a new user control called RightControl. 8.     Replace the LayoutRoot Grid with the following xaml:     <Grid x:Name="LayoutRoot" Background="Green" Margin="40"  >         <TextBlock Margin="40" Foreground="White" Text="Right Control" FontSize="16" VerticalAlignment="Center" HorizontalAlignment="Center" ></TextBlock>     </Grid> 9.     Add the following statement to the top of the RightControl.xaml.cs file using System.ComponentModel.Composition; 10.   Add the following attribute to the RightControl class     [Export(typeof(RightControl))] 11.   Add the following xaml to the LayoutRoot Grid in MainPage.xaml:         <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">             <Border Name="LeftContent" Background="Red" BorderBrush="Gray" CornerRadius="20"></Border>             <Border Name="RightContent" Background="Red" BorderBrush="Gray" CornerRadius="20"></Border>         </StackPanel>   The borders will hold the controls that will be imported and composed via MEF. 12.   Add the following statement to the top of the MainPage.xaml.cs file using System.ComponentModel.Composition; 13.   Add the following properties to the MainPage class:         [Import(typeof(LeftControl))]         public LeftControl LeftUserControl { get; set; }         [Import(typeof(RightControl))]         public RightControl RightUserControl { get; set; }   This defines properties accepting LeftControl and RightControl types.  The attrributes are used to tell MEF the discovered type that should be applied to the property when composition occurs. 14.   Replace the MainPage constructore with the following code:         public MainPage()         {             InitializeComponent();             CompositionInitializer.SatisfyImports(this);             LeftContent.Child = LeftUserControl;             RightContent.Child = RightUserControl;         }   The CompositionInitializer.SatisfyImports(this) function call tells MEF to discover types related to the declared imports for this object (the MainPage object).  At that point, types matching those specified in the import defintions are discovered in the executing assembly location of the application and instantiated and assigned to the matching properties of the current object. 15.   Run the application and you will see the left control and right control types displayed in the MainPage:   Congratulations!  You have used MEF to dynamically compose user controls into a parent control in a composite application model. In the next post we will build on this topic to cover using MEF to compose Silverlight applications dynamically in download on demand scenarios – so .xap packages can be downloaded only when needed, avoiding large initial download for the main application xap. Take the Slalom Challenge at www.slalomchallenge.com!

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• Gathering statistics for an Oracle WebCenter Content Database

  - by Nicolas Montoya

  Have you ever heard: "My Oracle WebCenter Content instance is running slow. I checked the memory and CPU usage of the application server and it has plenty of resources. What could be going wrong?An Oracle WebCenter Content instance runs on an application server and relies on a database server on the back end. If your application server tier is running fine, chances are that your database server tier may host the root of the problem. While many things could cause performance problems, on active Enterprise Content Management systems, keeping database statistics updated is extremely important.The Oracle Database have a set of built-in optimizer utilities that can help make database queries more efficient. It is strongly recommended to update or re-create the statistics about the physical characteristics of a table and the associated indexes in order to maximize the efficiency of optimizers. These physical characteristics include: Number of records Number of pages Average record length The frequency with which you need to update statistics depends on how quickly the data is changing. Typically, statistics should be updated when the number of new items since the last update is greater than ten percent of the number of items when the statistics were last updated. If a large amount of documents are being added or removed from the system, the a post step should be added to gather statistics upon completion of this massive data change. In some cases, you may need to collect statistics in the middle of the data processing to expedite its execution. These proceses include but are not limited to: data migration, bootstrapping of a new system, records management disposition processing (typically at the end of the calendar year), etc. A DOCUMENTS table with a ten million rows will often generate a very different plan than a table with just a thousand.A quick check of the statistics for the WebCenter Content (WCC) Database could be performed via the below query:SELECT OWNER, TABLE_NAME, NUM_ROWS, BLOCKS, AVG_ROW_LEN,TO_CHAR(LAST_ANALYZED, 'MM/DD/YYYY HH24:MI:SS')FROM DBA_TABLESWHERE TABLE_NAME='DOCUMENTS';OWNER                          TABLE_NAME                       NUM_ROWS------------------------------ ------------------------------ ----------    BLOCKS AVG_ROW_LEN TO_CHAR(LAST_ANALYZ---------- ----------- -------------------ATEAM_OCS                      DOCUMENTS                            4172        46          61 04/06/2012 11:17:51This output will return not only the date when the WCC table DOCUMENTS was last analyzed, but also it will return the <DATABASE SCHEMA OWNER> for this table in the form of <PREFIX>_OCS.This database username could later on be used to check on other objects owned by the WCC <DATABASE SCHEMA OWNER> as shown below:SELECT OWNER, TABLE_NAME, NUM_ROWS, BLOCKS, AVG_ROW_LEN,TO_CHAR(LAST_ANALYZED, 'MM/DD/YYYY HH24:MI:SS')FROM DBA_TABLESWHERE OWNER='ATEAM_OCS'ORDER BY NUM_ROWS ASC;...OWNER                          TABLE_NAME                       NUM_ROWS------------------------------ ------------------------------ ----------    BLOCKS AVG_ROW_LEN TO_CHAR(LAST_ANALYZ---------- ----------- -------------------ATEAM_OCS                      REVISIONS                            2051        46         141 04/09/2012 22:00:22ATEAM_OCS                      DOCUMENTS                            4172        46          61 04/06/2012 11:17:51ATEAM_OCS                      ARCHIVEHISTORY                       4908       244         218 04/06/2012 11:17:49OWNER                          TABLE_NAME                       NUM_ROWS------------------------------ ------------------------------ ----------    BLOCKS AVG_ROW_LEN TO_CHAR(LAST_ANALYZ---------- ----------- -------------------ATEAM_OCS                      DOCUMENTHISTORY                      5865       110          72 04/06/2012 11:17:50ATEAM_OCS                      SCHEDULEDJOBSHISTORY                10131       244         131 04/06/2012 11:17:54ATEAM_OCS                      SCTACCESSLOG                        10204       496         268 04/06/2012 11:17:54...The Oracle Database allows to collect statistics of many different kinds as an aid to improving performance. The DBMS_STATS package is concerned with optimizer statistics only. The database sets automatic statistics collection of this kind on by default, DBMS_STATS package is intended for only specialized cases.The following subprograms gather certain classes of optimizer statistics:GATHER_DATABASE_STATS Procedures GATHER_DICTIONARY_STATS Procedure GATHER_FIXED_OBJECTS_STATS Procedure GATHER_INDEX_STATS Procedure GATHER_SCHEMA_STATS Procedures GATHER_SYSTEM_STATS Procedure GATHER_TABLE_STATS ProcedureThe DBMS_STATS.GATHER_SCHEMA_STATS PL/SQL Procedure gathers statistics for all objects in a schema.DBMS_STATS.GATHER_SCHEMA_STATS (    ownname          VARCHAR2,    estimate_percent NUMBER   DEFAULT to_estimate_percent_type                                                 (get_param('ESTIMATE_PERCENT')),    block_sample     BOOLEAN  DEFAULT FALSE,    method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')),    granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'),    cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')),    stattab          VARCHAR2 DEFAULT NULL,    statid           VARCHAR2 DEFAULT NULL,    options          VARCHAR2 DEFAULT 'GATHER',    objlist          OUT      ObjectTab,   statown          VARCHAR2 DEFAULT NULL,    no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (                                     get_param('NO_INVALIDATE')),  force             BOOLEAN DEFAULT FALSE);There are several values for the OPTIONS parameter that we need to know about: GATHER reanalyzes the whole schema     GATHER EMPTY only analyzes tables that have no existing statistics GATHER STALE only reanalyzes tables with more than 10 percent modifications (inserts, updates,   deletes) GATHER AUTO will reanalyze objects that currently have no statistics and objects with stale statistics. Using GATHER AUTO is like combining GATHER STALE and GATHER EMPTY. Example:exec dbms_stats.gather_schema_stats( -   ownname          => '<PREFIX>_OCS', -   options          => 'GATHER AUTO' -);

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• Access Control Service v2: Registering Web Identities in your Applications [concepts]

  - by Your DisplayName here!

  ACS v2 support two fundamental types of client identities– I like to call them “enterprise identities” (WS-*) and “web identities” (Google, LiveID, OpenId in general…). I also see two different “mind sets” when it comes to application design using the above identity types: Enterprise identities – often the fact that a client can present a token from a trusted identity provider means he is a legitimate user of the application. Trust relationships and authorization details have been negotiated out of band (often on paper). Web identities – the fact that a user can authenticate with Google et al does not necessarily mean he is a legitimate (or registered) user of an application. Typically additional steps are necessary (like filling out a form, email confirmation etc). Sometimes also a mixture of both approaches exist, for the sake of this post, I will focus on the web identity case. I got a number of questions how to implement the web identity scenario and after some conversations it turns out it is the old authentication vs. authorization problem that gets in the way. Many people use the IsAuthenticated property on IIdentity to make security decisions in their applications (or deny user=”?” in ASP.NET terms). That’s a very natural thing to do, because authentication was done inside the application and we knew exactly when the IsAuthenticated condition is true. Been there, done that. Guilty ;) The fundamental difference between these “old style” apps and federation is, that authentication is not done by the application anymore. It is done by a third party service, and in the case of web identity providers, in services that are not under our control (nor do we have a formal business relationship with these providers). Now the issue is, when you switch to ACS, and someone with a Google account authenticates, indeed IsAuthenticated is true – because that’s what he is! This does not mean, that he is also authorized to use the application. It just proves he was able to authenticate with Google. Now this obviously leads to confusion. How can we solve that? Easy answer: We have to deal with authentication and authorization separately. Job done ;) For many application types I see this general approach: Application uses ACS for authentication (maybe both enterprise and web identities, we focus on web identities but you could easily have a dual approach here) Application offers to authenticate (or sign in) via web identity accounts like LiveID, Google, Facebook etc. Application also maintains a database of its “own” users. Typically you want to store additional information about the user In such an application type it is important to have a unique identifier for your users (think the primary key of your user database). What would that be? Most web identity provider (and all the standard ACS v2 supported ones) emit a NameIdentifier claim. This is a stable ID for the client (scoped to the relying party – more on that later). Furthermore ACS emits a claims identifying the identity provider (like the original issuer concept in WIF). When you combine these two values together, you can be sure to have a unique identifier for the user, e.g.: Facebook-134952459903700\799880347 You can now check on incoming calls, if the user is already registered and if yes, swap the ACS claims with claims coming from your user database. One claims would maybe be a role like “Registered User” which can then be easily used to do authorization checks in the application. The WIF claims authentication manager is a perfect place to do the claims transformation. If the user is not registered, show a register form. Maybe you can use some claims from the identity provider to pre-fill form fields. (see here where I show how to use the Facebook API to fetch additional user properties). After successful registration (which may include other mechanisms like a confirmation email), flip the bit in your database to make the web identity a registered user. This is all very theoretical. In the next post I will show some code and provide a download link for the complete sample. More on NameIdentifier Identity providers “guarantee” that the name identifier for a given user in your application will always be the same. But different applications (in the case of ACS – different ACS namespaces) will see different name identifiers. This is by design to protect the privacy of users because identical name identifiers could be used to create “profiles” of some sort for that user. In technical terms they create the name identifier approximately like this: name identifier = Hash((Provider Internal User ID) + (Relying Party Address)) Why is this important to know? Well – when you change the name of your ACS namespace, the name identifiers will change as well and you will will lose your “connection” to your existing users. Oh an btw – never use any other claims (like email address or name) to form a unique ID – these can often be changed by users.

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• Coherence Data Guarantees for Data Reads - Basic Terminology

  - by jpurdy

  When integrating Coherence into applications, each application has its own set of requirements with respect to data integrity guarantees. Developers often describe these requirements using expressions like "avoiding dirty reads" or "making sure that updates are transactional", but we often find that even in a small group of people, there may be a wide range of opinions as to what these terms mean. This may simply be due to a lack of familiarity, but given that Coherence sits at an intersection of several (mostly) unrelated fields, it may be a matter of conflicting vocabularies (e.g. "consistency" is similar but different in transaction processing versus multi-threaded programming). Since almost all data read consistency issues are related to the concept of concurrency, it is helpful to start with a definition of that, or rather what it means for two operations to be concurrent. Rather than implying that they occur "at the same time", concurrency is a slightly weaker statement -- it simply means that it can't be proven that one event precedes (or follows) the other. As an example, in a Coherence application, if two client members mutate two different cache entries sitting on two different cache servers at roughly the same time, it is likely that one update will precede the other by a significant amount of time (say 0.1ms). However, since there is no guarantee that all four members have their clocks perfectly synchronized, and there is no way to precisely measure the time it takes to send a given message between any two members (that have differing clocks), we consider these to be concurrent operations since we can not (easily) prove otherwise. So this leads to a question that we hear quite frequently: "Are the contents of the near cache always synchronized with the underlying distributed cache?". It's easy to see that if an update on a cache server results in a message being sent to each near cache, and then that near cache being updated that there is a window where the contents are different. However, this is irrelevant, since even if the application reads directly from the distributed cache, another thread update the cache before the read is returned to the application. Even if no other member modifies a cache entry prior to the local near cache entry being updated (and subsequently read), the purpose of reading a cache entry is to do something with the result, usually either displaying for consumption by a human, or by updating the entry based on the current state of the entry. In the former case, it's clear that if the data is updated faster than a human can perceive, then there is no problem (and in many cases this can be relaxed even further). For the latter case, the application must assume that the value might potentially be updated before it has a chance to update it. This almost aways the case with read-only caches, and the solution is the traditional optimistic transaction pattern, which requires the application to explicitly state what assumptions it made about the old value of the cache entry. If the application doesn't want to bother stating those assumptions, it is free to lock the cache entry prior to reading it, ensuring that no other threads will mutate the entry, a pessimistic approach. The optimistic approach relies on what is sometimes called a "fuzzy read". In other words, the application assumes that the read should be correct, but it also acknowledges that it might not be. (I use the qualifier "sometimes" because in some writings, "fuzzy read" indicates the situation where the application actually sees an original value and then later sees an updated value within the same transaction -- however, both definitions are roughly equivalent from an application design perspective). If the read is not correct it is called a "stale read". Going back to the definition of concurrency, it may seem difficult to precisely define a stale read, but the practical way of detecting a stale read is that is will cause the encompassing transaction to roll back if it tries to update that value. The pessimistic approach relies on a "coherent read", a guarantee that the value returned is not only the same as the primary copy of that value, but also that it will remain that way. In most cases this can be used interchangeably with "repeatable read" (though that term has additional implications when used in the context of a database system). In none of cases above is it possible for the application to perform a "dirty read". A dirty read occurs when the application reads a piece of data that was never committed. In practice the only way this can occur is with multi-phase updates such as transactions, where a value may be temporarily update but then withdrawn when a transaction is rolled back. If another thread sees that value prior to the rollback, it is a dirty read. If an application uses optimistic transactions, dirty reads will merely result in a lack of forward progress (this is actually one of the main risks of dirty reads -- they can be chained and potentially cause cascading rollbacks). The concepts of dirty reads, fuzzy reads, stale reads and coherent reads are able to describe the vast majority of requirements that we see in the field. However, the important thing is to define the terms used to define requirements. A quick web search for each of the terms in this article will show multiple meanings, so I've selected what are generally the most common variations, but it never hurts to state each definition explicitly if they are critical to the success of a project (many applications have sufficiently loose requirements that precise terminology can be avoided).

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• unittest import error with virtualenv + google-app-engine-django

  - by Ray Yun

  I'm working with google-app-engine-django + zipped django. Just running "python manage.py test" succeeded without error. But with virtualenv, test was failed with "import unittest error". same error with Django 1.1. - OSX 10.5.6 - google-app-engine-django (r101 via svn) : r100 was failed with launcher 1.3.0 - GoogleAppLauncher 1.3.0 - Django 1.1 & 1.1.1 (zipped) : both failed - virtualenv 1.4.5 - virtualenvwrapper 1.24 Error Message: (django_appengine)Reiot:warclouds Reiot$ python manage.py test WARNING:root:Could not read datastore data from /var/folders/UZ/UZ1vQeLFH2ShHk4kIiLcFk+++TI/-Tmp-/django_google-app-engine-django.datastore INFO:root:zipimporter('/Volumes/data/Documents/warclouds/django.zip', 'django/core/serializers/') .WARNING:root:Can't open zipfile /Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg: IOError: [Errno 13] file not accessible: '/Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg' WARNING:root:Can't open zipfile /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg: IOError: [Errno 13] file not accessible: '/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg' ERROR:root:Exception encountered handling request Traceback (most recent call last): File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3177, in _HandleRequest self._Dispatch(dispatcher, self.rfile, outfile, env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3120, in _Dispatch base_env_dict=env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 515, in Dispatch base_env_dict=base_env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2379, in Dispatch self._module_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2289, in ExecuteCGI reset_modules = exec_script(handler_path, cgi_path, hook) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2185, in ExecuteOrImportScript exec module_code in script_module.__dict__ File "/Volumes/data/Documents/warclouds/main.py", line 28, in <module> from appengine_django import InstallAppengineHelperForDjango File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1914, in load_module return self.FindAndLoadModule(submodule, fullname, search_path) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1816, in FindAndLoadModule description) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1264, in Decorate return func(self, *args, **kwargs) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 1767, in LoadModuleRestricted description) File "/Volumes/data/Documents/warclouds/appengine_django/__init__.py", line 44, in <module> import unittest ImportError: No module named unittest INFO:root:"GET / HTTP/1.1" 500 - INFO:root:zipimporter('/Users/Reiot/.virtualenvs/django_appengine/lib/python2.5/site-packages/setuptools-0.6c11-py2.5.egg', '') INFO:root:zipimporter('/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg', '') F........................................................... ====================================================================== FAIL: a request to the default page works in the dev_appserver ---------------------------------------------------------------------- Traceback (most recent call last): File "/Volumes/data/Documents/warclouds/appengine_django/tests/integration_test.py", line 176, in testBasic self.assertEquals(rv.status_code, 200) AssertionError: 500 != 200 I also tried with console import but it was ok. > which python /Users/Reiot/.virtualenvs/django_appengine/bin/python > python >>> import unittest Here is my environments: $ mkvirtualenv --no-site-packages no-django $ mkvirtualenv --no-site-packages django-1.1 $ mkvirtualenv --no-site-packages django-1.1.1 (django-1.1)$ easy_install Django-1.1.tar (django-1.1.1)$ easy_install Django-1.1.1.tar $ mkdir google-app-engine-django-svn $ cp -r google-app-engine-django-svn google-app-engine-django-svn-django-1.1 // copy appropriate django.zip $ cp -r google-app-engine-django-svn google-app-engine-django-svn-django-1.1.1 // copy appropriate django.zip

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• How to remove default header from WCF REST Outgoing Response?

  - by bmsantos

  The following C# WCF based REST service gives me some undesired headers that I'm not sure if I can remove them trough the API. The interface: [ServiceContract] public interface IControlSystem { [OperationContract] [WebGet] System.IO.Stream About(); } The implementation: public class ControlSystem : IControlSystem { public System.IO.Stream About() { return new System.IO.MemoryStream(ASCIIEncoding.Default.GetBytes("Hello World")); } } Out of a raw socket connection it gives the following response: HTTP/1.1 200 OK Server: ASP.NET Development Server/9.0.0.0 Date: Tue, 15 Jun 2010 13:12:51 GMT X-AspNet-Version: 2.0.50727 Cache-Control: private Content-Type: application/octet-stream Content-Length: 39 Connection: Close Hello World Question is, is it possible to get the server to not report anything other than the actual message? Need it in some calls so due to some small embedded device clients that will try to connect to the server and I would like to minimize the amount of parsing. Thanks, B.

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• why gcc 4.x default reserve 8 bytes for stack on linux when calling a method?

  - by nikcname

  as a beginner of asm, I am checking gcc -S generated asm code to learn. why gcc 4.x default reserve 8 bytes for stack when calling a method? func18 is the empty function with no return no param no local var defined. I can't figure out why 8 bytes is reserved here (neither any forum/site mention for the reason, ppl seems take it for granted) is it for the %ebp just push? or return type?! many thx! .globl _func18 _func18: pushl %ebp movl %esp, %ebp subl $8, %esp .text

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• why gcc 4.x default reserve 8 bytes for stack on linux when calling a method?

  - by nikcname

  as a beginner of asm, I am checking gcc -S generated asm code to learn. why gcc 4.x default reserve 8 bytes for stack when calling a method? func18 is the empty function with no return no param no local var defined. I can't figure out why 8 bytes is reserved here (neither any forum/site mention for the reason, ppl seems take it for granted) is it for the %ebp just push? or return type?! many thx! .globl _func18 _func18: pushl %ebp movl %esp, %ebp subl $8, %esp .text

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• In Rails/ActiveRecord 3, how do I change the default primary key type for MySQL?

  - by jfarmer

  In Rails 3, how do you change the default primary key type to, say, BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY In my case I'm only interested in MySQL. For Rails 2, you can see the answer to "How do I use long IDs in Rails?"1 In Rails 3, however, this will throw an error. I'm not sure if that's because the class is no long used, or if the code needs to go in the same place. You can see in active_record/connection_adapters/mysql_adapter.rb that the NATIVE_DATABASE_TYPES constant is still defined. What's the correct way to achieve the same effect in Rails 3?

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• Is there a default buffer length for 'sprintf' method?

  - by Isuru

  Hi, I used sprintf method to format data to a string which I want to write to a file, in C++ console application using VS 2008. The Input is a particular message, which has various variables and values (ex: Type 'int' and Value '10' / Type string and value "abc", etc.) When I send a two messages it works perfectly. But When I send more than two messages it gives a runtime error saying 0xC0000005: Access violation reading location 0xabababab. Why is this happening? Is it because the method 'sprintf' has a default buffer length? How can I overcome this problem?

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• How can I put my own text hover into default Eclipse editor?

  - by vitivy

  I need to put some extra information into to the standard "javadoc" hover, that shows up when you go with mouse over some token. Or I need to create a new hover showing that information while pressing some key (like alt) and then hovering (I can see that this is done e.g. with the shift key, which enables us to see the hover with sourcecode, instead of javadoc). So far I found documentation on how to create hover in your own editors, but I need to extend the default java editor. Basically I am interested in showing some e-mail information related to the classname (token) over which user is hovering. Is there any extension point that could be used for this? Thanks for any help!

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• How to manipulate the default behaviour of jQuery Imageflow?

  - by Tim

  Some of you sure know the jQuery-Plugin Imageflow on hxxp://finnrudolph.de/ImageFlow/ (sorry for that, I definitely need to gain reputation, working on it ;)) The default behaviour is that the images within the image-container (which has 100% width in this case) will be resized according to the image-container. There's an option to declare the distance between every image and it would be much better, if this value would be encreased and decreased with the window-resize-event. Everything seems to happen in a function called "moveTo" which is unfortunately also responsible for the resizing when moving to another image. I tried it since hours now but I don't come to a solution. Find the source-code here, and the mentioned function "moveTo" on line 554. Thank your very much for any help! Tim

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• How can I enable Pascal casing by default when using Jackson JSON in Spring MVC?

  - by bhilstrom

  I have a project that uses Spring MVC to create and handle multiple REST endpoints. I'm currently working on using Jackson to automatically handle the seralization/deserialization of JSON using the @RequestBody and @ResponseBody annotations. I have gotten Jackson working, so I've got a starting point. My problem is that our old serialization was done manually and used Pascal casing instead of Camel casing ("MyVariable" instead of "myVariable"), and Jackson does Camel casing by default. I know that I can manually change the name for a variable using @JsonProperty. That being said, I do not consider adding "@JsonProperty" to all of my variables to be a viable long-term solution. Is there a way to make Jackson use Pascal casing when serializing and deserializing other than using the @JsonProperty annotation?

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• how to hook up default beforeunload event on an aspx page ?

  - by Nikhil Vaghela

  I have a custom web part placed on one of the application page in SharePoint. This page it seems already have a function which gets executed on windows beforeunload javascript event. My problem is that i too need to execute some client side code (to prompt user for any unsaved changes in my web part) on windows beforeunload event. How can i achieve this ? I mean let the default event be fired as well as call my function also ? Appreciate any help. Nikhil.

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• How set panel Default Button that is inside a details view in asp.net?

  - by Avinash

  <asp:panel ID="Panel1" runat="server"> <asp:DetailsView ID="DetailsView1" .... <asp:templatefield ShowHeader="False"> <insertitemtemplate> <asp:Button ID="btnAdd" runat="server" CausesValidation="True" CommandName="Insert" Text="Insert"></asp:Button> ... <asp:DetailsView> </asp:panel> and i write the code for setting the panels default button in details view's DataBound event Button btnAdd = new Button(); btnAdd = DetailsView1.Rows[indexNumber].FindControl("btnAdd") as Button; Panel1.DefaultButton = btnAdd.UniqueID; but I get the error : The DefaultButton of 'Panel1' must be the ID of a control of type IButtonControl.

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• Move constructor and assignment operator: why no default for derived classes?

  - by doublep

  Why there is default move constructor or assignment operator not created for derived classes? To demonstrate what I mean; having this setup code: #include <utility> struct A { A () { } A (A&&) { throw 0; } A& operator= (A&&) { throw 0; } }; struct B : A { }; either of the following lines throws: A x (std::move (A ()); A x; x = A (); but neither of the following does: B x (std::move (B ()); B x; x = B (); In case it matters, I tested with GCC 4.4.

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• Wpf- Is there any way to disable some of the default hotkeys in a RichTextBox?

  - by Justin

  I have several keybindings in my text editing application that no longer work now that I have switched from using a regular textbox to using a richtextbox. This is because the wpf richtextbox has several default hokeys such as "Ctrl+1", "Ctrl+2", and "Ctrl+5". My keybindings are defined in a view that contains the view that the richtextbox is in. I can't move the keybindings to the richtextbox; Is there any fix for this problem? Other than using a third-party control or creating my own richtextbox from textboxbase.

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• How to make IE 9 Standards Mode the default mode?

  - by Evik James

  I have a web site that works perfectly fine in IE9 when compatibility mode is turned OFF (the compatibility symbol is gray). When compatibility mode is turned on (blue), the jQuery doesn't work at all. I have added the following tag to the site to tell the browser that compatibility mode should NOT be used. <meta http-equiv="X-UA-Compatible" content="IE=Edge" > I have the doctype as this: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Still, the browser doesn't seem to default to standard mode and the user must manually ensure that they are NOT in compatibility mode. Can I disable IE 9 Compatibility Mode? Have I done what I need to do to disable IE 9 Compatibility Mode? Can the user always override IE 9 Standards Mode?

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• iphone: custom UITableViewCell taller than the default cell view.

  - by Luc

  Hello, I'm creating an application that consists of a ListView with 5 rows: - 1st one containing a graph - 2nd to 5th rows containing some data with the same formatting. I have created 2 classes: GraphCustomViewCell and DataCustomViewCell. Depending upon the position of the cell I load the correct CustomCell with: NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"GraphCustomViewCell" owner:nil options:nil]; for(id currentObject in topLevelObjects) { if([currentObject isKindOfClass:[GraphCustomViewCell class]]) { cell = (GraphCustomViewCell *)currentObject; break; } } That works fine except that the first row, the one corresponding to the graph, is bigger (in height) that the 4 other rows, and as a results it hides the 3 first other rows. Is there any option in the table view that enables the custom cell to expand the default cells ? I'd like that the 5 rows (graph + 4 data rows) to fit the entire screen (480 - tabbar's height). Thanks a lot for your help. Regards, Luc

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• Python: re-initialize a function's default value for subsequent calls to the function.

  - by Peter Stewart

  I have a function that calls itself to increment and decrement a stack. I need to call it a number of times, and I'd like it to work the same way in subsequent calls but, as expected, it doesn't re-use the default value. I've read that this is a newbie trap and I've seen suggested solutions, but I haven't been able to make any solution work. It would be nice to be able to "fun.reset" def a(x, stack = [None]): print x,' ', stack if x > 5: temp = stack.pop() if x <=5: stack.append(1) if stack == []: return a(x + 1) print a(0) print a(2) #second call print a(3) #third call I expected this to work, but it doesn't. print a(0, [None]) print a(2, [None]) #second call print a(3, [None]) #third call Can I reset the function to it's initial state? Any help would be appreciated.

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