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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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• What features are helpful when performing remote debugging / diagnostics?

  - by Pemdas

  Obviously, the easiest way to solve a bug is to be able to reproduce it in-house. However, sometimes that is not practical. For starters, users are often not very good at providing you with useful information. Customer Service: "what seems to be the issue?" User: "It crashed!" To further compound that, sometimes the bug only occurs under certain environmentally conditions that can not be adequately replicated in-house. With that in mind, it is important to build some sort of diagnostic framework into your product. What types of built-in diagnostic tools have you used or seen used? Logging seems to be the predominate method, which makes sense. We have a fairly sophisticated logging frame work in place with different levels of verbosity and the ability to filter on specific modules (actually we can filter down to the granularity of a single file). Error logs are placed strategically to manufacture a pretty good representation of a stack trace when an error occurs. We don't have the luxury of 10 million terabytes of disk space since I work on embedded platforms, so we have two ways of getting them off the system: a serial port and a syslog server. However, an issue we run into sometimes is actually getting the user to turn the logs on. Our current framework often requires some user interaction.

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• Example of persisting an inheritance relationship using ORM

  - by Schemer

  I have some experience with OOP and RDBs, but very little exposure to web programming. I am trying to understand what non-trivial types of problems are solved by ORM. Of course, I am familiar with the need for data persistence, but I have never encountered a need for persisting relationships between objects, a situation which is indicated in many online articles about ORM. I am not asking about the process of persisting a POJO to a database and restoring it later. Nor am I asking about why ORM frameworks are useful -- or a pain in the butt -- for doing so. I am particularly interested in how the need arises to persist and restore relationships between objects. In various documentation, I have seen many examples of persisting POJOs to a database, but the examples have all been for only very simple objects that are essentially nothing more than records anyway: a constructor, some private fields, and getter/setter methods. The motivation for persisting such an "object-record" seems obvious and trivial. This example: Hibernate ORM Tutorial offers such an example, but goes on to discuss mismatch issues of granularity, inheritance, identity, associations, and navigation that are not motivated by the example. If someone could offer a toy example of an instance where, say, the need arises to persist an inheritance relationship, I would be grateful. This might be blindingly obvious for anyone who has already encountered this situation but I have not and a great deal of searching and reading have not turned up any examples.

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• Data indexing frameworks fit for large E-Commerce applications

  - by Dabu

  we wrote and still maintain a large E-Commerce application. Our feature list resembles what you would expect from most shops. We'd like to improve some of our features, and now the search/suggestion list functionality (enter some letters, a JScripted suggestion list appears) has caught our eye. Currently, we use http://xapian.org/. It has some drawbacks. Firstly, it's not actually the right solution. It has been created to index documents, not ever-changing data in a granularity that an E-Commerce application would need. Secondly, the load on the database is significant when we reindex all data every night. We'd like a framework that has been designed for indexing database data, which can add to the index easily and without much load, which can supply data changes in the backoffice quickly to the frontend without much load and delay. I'm aware of the fact that Xapian is Open Source and even Free Software, so we could adapt it to our needs if we decided to invest the time and manpower. But taking a quick look around for a solution more suited seems fair, right? Oh, and commercial applications are fine, too. FOSS is not required. Thanks a bunch.

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• Remote Debugging

  - by Pemdas

  Obviously, the easiest way to solve a bug is to be able to reproduce it in house. However, sometimes that is not practical. For starters, users are often not very good at providing you with useful information. Costumer Service: "what seems to be the issue?" User: "It crashed!" To further compound that, sometimes the bug only occurs under certain environmentally conditions that can not be adequately replicated in house. With that in mind, it is important to build some sort of diagnostic framework into your product. What type of solutions have you seen or used in your experience? Logging seems to be the predominate method, which makes sense. We have a fairly sophisticated logging frame work in place with different levels of verbosity and the ability to filter on specific modules (actually we can filter down to the granularity of a single file). Error logs are placed strategically to manufacture a pretty good representation of a stack trace when an error occurs. We don't have the luxury of 10 million terabytes of disk space since I work on embedded platforms, so we have two ways of getting them off the system: a serial port and a syslog server. However, an issue we run into sometimes is actually getting the user to turn the logs on. Our current framework often requires some user interaction.

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• Dealing with Fine-Grained Cache Entries in Coherence

  - by jpurdy

  On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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• Impact of Server Failure on Coherence Request Processing

  - by jpurdy

  Requests against a given cache server may be temporarily blocked for several seconds following the failure of other cluster members. This may cause issues for applications that can not tolerate multi-second response times even during failover processing (ignoring for the moment that in practice there are a variety of issues that make such absolute guarantees challenging even when there are no server failures). In general, Coherence is designed around the principle that failures in one member should not affect the rest of the cluster if at all possible. However, it's obvious that if that failed member was managing a piece of state that another member depends on, the second member will need to wait until a new member assumes responsibility for managing that state. This transfer of responsibility is (as of Coherence 3.7) performed by the primary service thread for each cache service. The finest possible granularity for transferring responsibility is a single partition. So the question becomes how to minimize the time spent processing each partition. Here are some optimizations that may reduce this period: Reduce the size of each partition (by increasing the partition count) Increase the number of JVMs across the cluster (increasing the total number of primary service threads) Increase the number of CPUs across the cluster (making sure that each JVM has a CPU core when needed) Re-evaluate the set of configured indexes (as these will need to be rebuilt when a partition moves) Make sure that the backing map is as fast as possible (in most cases this means running on-heap) Make sure that the cluster is running on hardware with fast CPU cores (since the partition processing is single-threaded) As always, proper testing is required to make sure that configuration changes have the desired effect (and also to quantify that effect).

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• State Changes in a Component Based Architecture [closed]

  - by Maxem

  I'm currently working on a game and using the naive component based architecture thingie (Entities are a bag of components, entity.Update() calls Update on each updateable component), while the addition of new features is really simple, it makes a few things really difficult: a) multithreading / currency b) networking c) unit testing. Multithreading / Concurrency is difficult because I basically have to do poor mans concurrency (running the entity updates in separate threads while locking only stuff that crashes (like lists) and ignoring the staleness of read state (some states are already updated, others aren't)) Networking: There are no explicit state changes that I could efficiently push over the net. Unit testing: All updates may or may not conflict, so automated testing is at least awkward. I was thinking about these issues a bit and would like your input on these changes / idea: Switch from the naive cba to a cba with sub systems that work on lists of components Make all state changes explicit Combine 1 and 2 :p Example world update: statePostProcessing.Wait() // ensure that post processing has finished Apply(postProcessedState) state = new StateBag() Concurrently( () => LifeCycleSubSystem.Update(state), // populates the state bag () => MovementSubSystem.Update(state), // populates the state bag .... }) statePostProcessing = Future(() => PostProcess(state)) statePostProcessing.Start() // Tick is finished, the post processing happens in the background So basically the changes are (consistently) based on the data for the last tick; the post processing can a) generate network packages and b) fix conflicts / remove useless changes (example: entity has been destroyed - ignore movement etc.). EDIT: To clarify the granularity of the state changes: If I save these post processed state bags and apply them to an empty world, I see exactly what has happened in the game these state bags originated from - "Free" replay capability. EDIT2: I guess I should have used the term Event instead of State Change and point out that I kind of want to use the Event Sourcing pattern

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• Using the Coherence ConcurrentMap Interface (Locking API)

  - by jpurdy

  For many developers using Coherence, the first place they look for concurrency control is the com.tangosol.util.ConcurrentMap interface (part of the NamedCache interface). The ConcurrentMap interface includes methods for explicitly locking data. Despite the obvious appeal of a lock-based API, these methods should generally be avoided for a variety of reasons: They are very "chatty" in that they can't be bundled with other operations (such as get and put) and there are no collection-based versions of them. Locks do directly not impact mutating calls (including puts and entry processors), so all code must make explicit lock requests before modifying (or in some cases reading) cache entries. They require coordination of all code that may mutate the objects, including the need to lock at the same level of granularity (there is no built-in lock hierarchy and thus no concept of lock escalation). Even if all code is properly coordinated (or there's only one piece of code), failure during updates that may leave a collection of changes to a set of objects in a partially committed state. There is no concept of a read-only lock. In general, use of locking is highly discouraged for most applications. Instead, the use of entry processors provides a far more efficient approach, at the cost of some additional complexity.

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• IIS Strategies for Accessing Secured Network Resources

  - by ErikE

  Problem: A user connects to a service on a machine, such as an IIS web site or a SQL Server database. The site or the database need to gain access to network resources such as file shares (the most common) or a database on a different server. Permission is denied. This is because the user the service is running under doesn't have network permissions in the first place, or if it does, it doesn't have rights to access the remote resource. I keep running into this problem over and over again and am tired of not having a really solid way of handling it. Here are some workarounds I'm aware of: Run IIS as a custom-created domain user who is granted high permissions If permissions are granted one file share at a time, then every time I want to read from a new share, I would have to ask a network admin to add it for me. Eventually, with many web sites reading from many shares, it is going to get really complicated. If permissions are just opened up wide for the user to access any file shares in our domain, then this seems like an unnecessary security surface area to present. This also applies to all the sites running on IIS, rather than just the selected site or virtual directory that needs the access, a further surface area problem. Still use the IUSR account but give it network permissions and set up the same user name on the remote resource (not a domain user, a local user) This also has its problems. For example, there's a file share I am using that I have full rights to for sharing, but I can't log in to the machine. So I have to find the right admin and ask him to do it for me. Any time something has to change, it's another request to an admin. Allow IIS users to connect as anonymous, but set the account used for anonymous access to a high-privilege one This is even worse than giving the IIS IUSR full privileges, because it means my web site can't use any kind of security in the first place. Connect using Kerberos, then delegate This sounds good in principle but has all sorts of problems. First of all, if you're using virtual web sites where the domain name you connect to the site with is not the base machine name (as we do frequently), then you have to set up a Service Principal Name on the webserver using Microsoft's SetSPN utility. It's complicated and apparently prone to errors. Also, you have to ask your network/domain admin to change security policy for both the web server and the domain account so they are "trusted for delegation." If you don't get everything perfectly right, suddenly your intended Kerberos authentication is NTLM instead, and you can only impersonate rather than delegate, and thus no reaching out over the network as the user. Also, this method can be problematic because sometimes you need the web site or database to have permissions that the connecting user doesn't have. Create a service or COM+ application that fetches the resource for the web site Services and COM+ packages are run with their own set of credentials. Running as a high-privilege user is okay since they can do their own security and deny requests that are not legitimate, putting control in the hands of the application developer instead of the network admin. Problems: I am using a COM+ package that does exactly this on Windows Server 2000 to deliver highly sensitive images to a secured web application. I tried moving the web site to Windows Server 2003 and was suddenly denied permission to instantiate the COM+ object, very likely registry permissions. I trolled around quite a bit and did not solve the problem, partly because I was reluctant to give the IUSR account full registry permissions. That seems like the same bad practice as just running IIS as a high-privilege user. Note: This is actually really simple. In a programming language of your choice, you create a class with a function that returns an instance of the object you want (an ADODB.Connection, for example), and build a dll, which you register as a COM+ object. In your web server-side code, you create an instance of the class and use the function, and since it is running under a different security context, calls to network resources work. Map drive letters to shares This could theoretically work, but in my mind it's not really a good long-term strategy. Even though mappings can be created with specific credentials, and this can be done by others than a network admin, this also is going to mean that there are either way too many shared drives (small granularity) or too much permission is granted to entire file servers (large granularity). Also, I haven't figured out how to map a drive so that the IUSR gets the drives. Mapping a drive is for the current user, I don't know the IUSR account password to log in as it and create the mappings. Move the resources local to the web server/database There are times when I've done this, especially with Access databases. Does the database have to live out on the file share? Sometimes, it was just easiest to move the database to the web server or to the SQL database server (so the linked server to it would work). But I don't think this is a great all-around solution, either. And it won't work when the resource is a service rather than a file. Move the service to the final web server/database I suppose I could run a web server on my SQL Server database, so the web site can connect to it using impersonation and make me happy. But do we really want random extra web servers on our database servers just so this is possible? No. Virtual directories in IIS I know that virtual directories can help make remote resources look as though they are local, and this supports using custom credentials for each virtual directory. I haven't been able to come up with, yet, how this would solve the problem for system calls. Users could reach file shares directly, but this won't help, say, classic ASP code access resources. I could use a URL instead of a file path to read remote data files in a web page, but this isn't going to help me make a connection to an Access database, a SQL server database, or any other resource that uses a connection library rather than being able to just read all the bytes and work with them. I wish there was some kind of "service tunnel" that I could create. Think about how a VPN makes remote resources look like they are local. With a richer aliasing mechanism, perhaps code-based, why couldn't even database connections occur under a defined security context? Why not a special Windows component that lets you specify, per user, what resources are available and what alternate credentials are used for the connection? File shares, databases, web sites, you name it. I guess I'm almost talking about a specialized local proxy server. Anyway, so there's my list. I may update it if I think of more. Does anyone have any ideas for me? My current problem today is, yet again, I need a web site to connect to an Access database on a file share. Here we go again...

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• IIS Strategies for Accessing Secured Network Resources

  - by Emtucifor

  Problem: A user connects to a service on a machine, such as an IIS web site or a SQL Server database. The site or the database need to gain access to network resources such as file shares (the most common) or a database on a different server. Permission is denied. This is because the user the service is running as doesn't have network permissions in the first place, or if it does, it doesn't have rights to access the remote resource. I keep running into this problem over and over again and am tired of not having a really solid way of handling it. Here are some workarounds I'm aware of: Run IIS as a custom-created domain user who is granted high permissions If permissions are granted one file share at a time, then every time I want to read from a new share, I would have to ask a network admin to add it for me. Eventually, with many web sites reading from many shares, it is going to get really complicated. If permissions are just opened up wide for the user to access any file shares in our domain, then this seems like an unnecessary security surface area to present. This also applies to all the sites running on IIS, rather than just the selected site or virtual directory that needs the access, a further surface area problem. Still use the IUSR account but give it network permissions and set up the same user name on the remote resource (not a domain user, a local user) This also has its problems. For example, there's a file share I am using that I have full rights to for sharing, but I can't log in to the machine. So I have to find the right admin and ask him to do it for me. Any time something has to change, it's another request to an admin. Allow IIS users to connect as anonymous, but set the account used for anonymous access to a high-privilege one This is even worse than giving the IIS IUSR full privileges, because it means my web site can't use any kind of security in the first place. Connect using Kerberos, then delegate This sounds good in principle but has all sorts of problems. First of all, if you're using virtual web sites where the domain name you connect to the site with is not the base machine name (as we do frequently), then you have to set up a Service Principal Name on the webserver using Microsoft's SetSPN utility. It's complicated and apparently prone to errors. Also, you have to ask your network/domain admin to change security policy for the web server so it is "trusted for delegation." If you don't get everything perfectly right, suddenly your intended Kerberos authentication is NTLM instead, and you can only impersonate rather than delegate, and thus no reaching out over the network as the user. Also, this method can be problematic because sometimes you need the web site or database to have permissions that the connecting user doesn't have. Create a service or COM+ application that fetches the resource for the web site Services and COM+ packages are run with their own set of credentials. Running as a high-privilege user is okay since they can do their own security and deny requests that are not legitimate, putting control in the hands of the application developer instead of the network admin. Problems: I am using a COM+ package that does exactly this on Windows Server 2000 to deliver highly sensitive images to a secured web application. I tried moving the web site to Windows Server 2003 and was suddenly denied permission to instantiate the COM+ object, very likely registry permissions. I trolled around quite a bit and did not solve the problem, partly because I was reluctant to give the IUSR account full registry permissions. That seems like the same bad practice as just running IIS as a high-privilege user. Note: This is actually really simple. In a programming language of your choice, you create a class with a function that returns an instance of the object you want (an ADODB.Connection, for example), and build a dll, which you register as a COM+ object. In your web server-side code, you create an instance of the class and use the function, and since it is running under a different security context, calls to network resources work. Map drive letters to shares This could theoretically work, but in my mind it's not really a good long-term strategy. Even though mappings can be created with specific credentials, and this can be done by others than a network admin, this also is going to mean that there are either way too many shared drives (small granularity) or too much permission is granted to entire file servers (large granularity). Also, I haven't figured out how to map a drive so that the IUSR gets the drives. Mapping a drive is for the current user, I don't know the IUSR account password to log in as it and create the mappings. Move the resources local to the web server/database There are times when I've done this, especially with Access databases. Does the database have to live out on the file share? Sometimes, it was just easiest to move the database to the web server or to the SQL database server (so the linked server to it would work). But I don't think this is a great all-around solution, either. And it won't work when the resource is a service rather than a file. Move the service to the final web server/database I suppose I could run a web server on my SQL Server database, so the web site can connect to it using impersonation and make me happy. But do we really want random extra web servers on our database servers just so this is possible? No. Virtual directories in IIS I know that virtual directories can help make remote resources look as though they are local, and this supports using custom credentials for each virtual directory. I haven't been able to come up with, yet, how this would solve the problem for system calls. Users could reach file shares directly, but this won't help, say, classic ASP code access resources. I could use a URL instead of a file path to read remote data files in a web page, but this isn't going to help me make a connection to an Access database, a SQL server database, or any other resource that uses a connection library rather than being able to just read all the bytes and work with them. I wish there was some kind of "service tunnel" that I could create. Think about how a VPN makes remote resources look like they are local. With a richer aliasing mechanism, perhaps code-based, why couldn't even database connections occur under a defined security context? Why not a special Windows component that lets you specify, per user, what resources are available and what alternate credentials are used for the connection? File shares, databases, web sites, you name it. I guess I'm almost talking about a specialized local proxy server. Anyway, so there's my list. I may update it if I think of more. Does anyone have any ideas for me? My current problem today is, yet again, I need a web site to connect to an Access database on a file share. Here we go again...

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• Good way to capture/replay sessions from Apache Log?

  - by Mark Harrison

  For performance testing, I would like to capture some traffic from a production server and use that as a basis to replay the request to a test server in order to simulate a realistic load in our development environment. These are all stateless queries, so no issues regarding cookies, sessions, etc. The Apache log timestamps everything down to a 1 second resolution, but that's not fine enough granularity for our peak times. What's the best way to capture more fine-grained timestamps for replay? And is there some ab-like load generating program that can use this data to replicate load?

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• iPhone CoreData: How can I track/observe all changes within a subgraph?

  - by D Carney

  I have a NSManagedObjectContext in which I have a number of subclasses of NSManagedObjects such that some are containers for others. What I'd like to do is watch a top-level object to be notified of any changes to any of its properties, associations, or the properties/associations of any of the objects it contains. Using the context's 'hasChanges' doesn't give me enough granularity. The objects 'isUpdated' method only applies to the given object (and not anything in its associations). Is there a convenient (perhaps, KVO-based) was I can observe changes in a context that are limited to a subgraph?

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• java version of python-dateutil

  - by elhefe

  Python has a very handy package that can parse nearly any unambiguous date and provides helpful error messages on a parse failure, python-dateutil. Comparison to the SimpleDateFormat class is not favorable - AFAICT SimpleDateFormat can only handle one exact date format and the error messages have no granularity. I've looked through the Joda API but it appears Joda is the same way - only one explicit format can be parsed at a time. Is there any package or library that reproduces the python-dateutil behavior? Or am I missing something WRT Joda/SimpleDateFormat?

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• NSPredicateEditorRowTemplate for date comparison

  - by Dave DeLong

  I'm building an NSPredicateEditor, and I want the ability to do advanced date comparison. I realize that I can build an NSPredicateEditorRowTemplate with a rightExpressionType of NSDateAttributeType, but the predicates I want to build need to be much more advanced than that. For example, I need to basic comparison like: dateKeypath < aDate dateKeypath <= aDate dateKeypath = aDate dateKeypath != aDate dateKeypath > aDate dateKeypath >= aDate These basic comparisons are quite easy to achieve, and I have these working. However, I also need to do comparisons like: dateKeypath isInTheLast n days (or weeks, months, years) dateKeypath isNotInTheLast n days (or weeks, months, years) dateKeypath between aDate and anotherDate How can I achieve these sorts of comparisons? I understand that I'll need to create a custom NSPredicateEditorRowTemplate, but I haven't found any clear documentation on how to achieve something like this. EDIT Bonus points are available for also knowing how to make these comparisons a full date-time (year-month-day-hour-minute-second) comparison (as NSDateAttributeType only has year-month-day granularity).

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• Possible to InvalidateVisual() on a given region instead of entire WPF control?

  - by Scott Bilas

  I have a complex WPF control that draws a lot of primitives in its OnRender (it's sort of like a map). When a small portion of it changes, I'd only like to re-issue render commands for the affected elements, instead of running the entire OnRender over. While I'm fine with my OnRender function's performance on a resize or whatever, it's not fast enough for mouse hover-based highlighting of primitives. Currently the only way I know how to force a screen update is to call InvalidateVisual(). No way to send in a dirty rect region to invalidate. Is the lowest granularity of WPF screen composition the UI element? Will I need to do my renders of primitives into an intermediate target and then have that use InvalidateVisual() to update to the screen?

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• algorithm to find Best 8 minute window in a 1 hour run

  - by Arun

  I have a requirement like, an activity runs for about more than an hour. I need to get the best 8 minute window where some parameters are maximum. say a value x, which is dynamic for every second. if my activity runs for one hr,i get 3600 values for x. I need to find the best continuous 8 minute time interval where x value was the highest among all the others. if i capture say from 0th minute to 8th minute, there may be another time frame like 0.4 to 8.4 where it was maximum. the granularity is one second. every second we need to consider. basically the peak 8 minute window where x was maximum. please help me with the design

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• Display relative time in hour, day, month and year

  - by JohnJohnGa

  I wrote a function toBeautyString(epoch) : String which given a epoch, return a string which will display the relative time from now in hour and minute For instance: // epoch: 1346140800 -> Tue, 28 Aug 2012 05:00:00 GMT // and now: 1346313600 -> Thu, 30 Aug 2012 08:00:00 GMT toBeautyString(1346140800) -> "2 days and 3 hours ago" I want now to extend this function to month and year, so it will be able to print: 2 years, 1 month, 3 days and 1 hour ago Only with epoch without any external libraries. The purpose of this function is to give to the user a better way to visualize the time in the past. I found this: Calculating relative time but the granularity is not enough.

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• Performing time consuming operation on STL container within a lock

  - by Ashley

  I have an unordered_map of an unordered_map which stores a pointer of objects. The unordered map is being shared by multiple threads. I need to iterate through each object and perform some time consuming operation (like sending it through network etc) . How could I lock the multiple unordered_map so that it won't blocked for too long? typedef std::unordered_map<string, classA*>MAP1; typedef std::unordered_map<int, MAP1*>MAP2; MAP2 map2; pthread_mutex_lock(&mutexA) //how could I lock the maps? Could I reduce the lock granularity? for(MAP2::iterator it2 = map2.begin; it2 != map2.end; it2++) { for(MAP1::iterator it1 = *(it2->second).begin(); it1 != *(it2->second).end(); it1++) { //perform some time consuming operation on it1->second eg sendToNetwork(*(it1->second)); } } pthread_mutex_unlock(&mutexA)

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• Get/save parameters to an expected JMock method call?

  - by Tayeb

  Hi, I want to test an "Adapter" object that when it receives an xml message, it digest it to a Message object, puts message ID + CorrelationID both with timestamps and forwards it to a Client object.=20 A message can be correlated to a previous one (e.g. m2.correlationID =3D m1.ID). I mock the Client, and check that Adapter successfully calls "client.forwardMessage(m)" twice with first message with null correlationID, and a second with a not-null correlationID. However, I would like to precisely test that the correlationIDs are set correctly, by grabing the IDs (e.g. m1.ID). But I couldn't find anyway to do so. There is a jira about adding the feature, but no one commented and it is unassigned. Is this really unimplemented? I read about the alternative of redesigning the Adapter to use an IdGenerator object, which I can stub, but I think there will be too many objects.=20 Don't you think it adds unnecessary complexity to split objects to a so fine granularity? Thanks, and I appreciate any comments :-) Tayeb

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• Which is faster in memory, ints or chars? And file-mapping or chunk reading?

  - by Nick

  Okay, so I've written a (rather unoptimized) program before to encode images to JPEGs, however, now I am working with MPEG-2 transport streams and the H.264 encoded video within them. Before I dive into programming all of this, I am curious what the fastest way to deal with the actual file is. Currently I am file-mapping the .mts file into memory to work on it, although I am not sure if it would be faster to (for example) read 100 MB of the file into memory in chunks and deal with it that way. These files require a lot of bit-shifting and such to read flags, so I am wondering that when I reference some of the memory if it is faster to read 4 bytes at once as an integer or 1 byte as a character. I thought I read somewhere that x86 processors are optimized to a 4-byte granularity, but I'm not sure if this is true... Thanks!

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• Controlling read and write access width to memory mapped registers in C

  - by srking

  I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only generate full 32-bit wide reads and writes in all cases? For example, if I do a read-modify-write operation like this: volatile uint32_t* p_reg = 0xCAFE0000; *p_reg |= 0x01; I don't want the compiler to get smart about the fact that only the bottom byte changes and generate 8-bit wide read/writes. Since the machine code is often more dense for 8-bit operations on x86, I'm afraid of unwanted optimizations. Disabling optimizations in general is not an option.

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• Design report of 4-D data set

  - by phq

  I'm writing a report generator that will present data each being generated from 4 parameters. Time interval Group Measurement value(one of several to choose from) Device All these are orthogonal giving me a 4-D dataset to present. There are some simplifications where one parameter is the same for all and other parameters are merged. Still it appears as there are situations where all values are wanted on the report. In short the report should both be simple to overview and contain details. There will also be an interface where the user setup the range and granularity for each parameter. The most naive solution would be to have a 2D table where each cell contain another table with values of the remaining two dimensions. This is technically feasible but I'm worried that it would become hard to overview. Another approach is to present first two dimensions in a 2D table and the remaining parameters in groups Are there any good method to address this kind of issue?

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• Will Sytem.currentTimeMillis always return a value >= previous calls?

  - by 1984isnotamanual

  http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html#currentTimeMillis() says: Returns the current time in milliseconds. Note that while the unit of time of the return value is a millisecond, the granularity of the value depends on the underlying operating system and may be larger. For example, many operating systems measure time in units of tens of milliseconds. It is not clear to me if I am guaranteed that this code will always print ever increasing (or the same) numbers. while (1) { System.out.println(System.currentTimeMillis() ); }

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• How granular should a command be in a CQ[R]S model?

  - by Aaronaught

  I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?

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