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• Could SQL Server 2008 replication be used with NLB to allow unlimited scaling of reporting servers?

  - by John Keranos

  We are currently using transactional replication in SQL Server 2008 to keep a secondary reporting server synchronized with a primary database server. This has been working weel and keeps some of the load off the primary server. Would it be possible to scale this solution to multiple reporting servers? We're expecting an increased load of read-only queries and it would be nice to be able to add reporting servers as needed. The general idea was the following: Each reporting server would use a "pull" subscription to get the data from the primary database publication. These reporting databases could be a couple of minutes behind the primary server without it being an issue. The reporting servers would be NLB'd together. All read-only queries would be directed to the NLB which should spread the load across the servers.

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• Strange befaviour of spring transaction support for JPA + Hibernate +@Transactional annotation

  - by abovesun

  I found out really strange behavior on relatively simple use case, probably I can't understand it because of not deep knowledges of spring @Transactional nature, but this is quite interesting. I have simple User dao that extends spring JpaDaoSupport class and contains standard save method: @Transactional public User save(User user) { getJpaTemplate().persist(user); return user; } If was working fine until I've add new method to same class: User getSuperUser(), this method should return user with isAdmin == true, and if there is no super user in db, method should create one. Thats how it was looking like: public User createSuperUser() { User admin = null; try { admin = (User) getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { return em.createQuery("select u from UserImpl u where u.admin = true").getSingleResult(); } }); } catch (EmptyResultDataAccessException ex) { User admin = new User('login', 'password'); admin.setAdmin(true); save(admin); // THIS IS THE POINT WHERE STRANGE THING COMING OUT } return admin; } As you see code is strange forward and I was very confused when found out that no transaction was created and committed on invocation of save(admin) method and no new user wasn't actually created despite @Transactional annotation. In result we have situation: when save() method invokes from outside of UserDAO class - @Transactional annotation counted and user successfully created, but if save() invokes from inside of other method of the same dao class - @Transactional annotation ignored. Here how I was change save() method to force it always create transaction. public User save(User user) { getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { em.getTransaction().begin(); em.persist(user); em.getTransaction().commit(); return null; } }); return user; } As you see I manually invoke begin and commit. Any ideas?

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• Advanced MySQL Replication - Improving Performance

  MySQL Replication can be made quite reliable and robust if the right tools are used to keep it running smoothly--but what if enormous loads on the primary server are overloading the slave server. Are there ways to speed up performance, so the slave can keep up?

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• Berkeley DB Java Edition High Availability/Replication Whitepaper

  - by charles.lamb

  My colleague Sam Haradhvala has written a great whitepaper on BDB JE HA/Replication. It takes a high level look at what JE/HA is, when you might use it, and the key architectural tradeoffs you might consider.

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• How do I handle mysql replication in EC2 using private IPs?

  - by chris

  I am trying to set up a mysql master/slave configuration in two EC2 instances. However, every time I reboot an instance, the IP address (and hostname) changes. I could assign an Elastic IP address, but would prefer to use the internal IP address. I can't be the first person to do this, but I can't seem to find a solution. There are a lot of "getting started" guides, but none of them mention how to handle changing IP addresses. So what are the best practices to manage master/slave replication in EC2?

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• Implementing Cluster Continuous Replication, Part 3

  Cluster continuous replication (CCR) uses log shipping and failover to provide a more resilient email system with faster recovery. Once it is installed, a clustered server requires different management routines. These are done either with a GUI tool, The Failover Cluster Management Console, or the Exchange Management Shell. You can use Powershell as well for some tasks. Confused? Not for long, since Brien Posey is once more here to help.

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• A simple Volume Replication Tool for large data set?

  - by Jin

  I'm looking for a solution to the following: Server A (Site A) - Win 2008 R2 - approx 10TB (15TB max) of data - well over 8 million files Server B (Site B) - Win 2008 R2 I want to assynchronously replicate Server A's volume to a volume on Server B for data redundancy. Something that I can say to my users, "go here for data" when/if Server A goes belly up due to machine problems, disaster, etc. Windows 2008 R2 does have DFS, but microsoft does not apparently support this large of a dataset (or more accurately, more than 8 million files - according to the docs I could find). I also looked at Veritas Volume Replication, but this seems almost too much as I would also require Veritas Volume Manager. There are numerous "back-up" software which makes a 1-1 backup, which would be ok, but since it will be transfering over internet, I'd like something that has compression during transfer like DFS has. Does anyone have any suggestions regarding this?

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• SQL 2008 publisher -> SQL 2000 subscriber: Is a pull subscription possible for merge replication?

  - by Brian Dunzweiler

  I am trying to synchronize a SQL 2000 SP4 subscriber to a SQL 2008 publisher via a merge pull subscription. When the subscriber tries to run the merge agent, it fails the following error: The process could not connect to Distributor 'OH05DBS002\SAM_SSG_2008'. SQL Server does not exist or access denied. Has anyone had success with this setup? I was able to create and synchronize a push subscription so I know that communication works between the two, at least from 2008-2000. The lack of communication from 2000-2008 also affects the ability to create a linked server on the SQL 2000 subscriber. One other tidbit - I did install the SQL 2008 native client on the the 2000 box but it didn't help either. Before anyone asks, I can't upgrade the subscriber as it still needs to support replication between MS Access 2003. Yeah, I know. :) TIA, Brian

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• How to recover from failed Mysql schema update, with replication?

  - by OmerGertel

  I have two MySQL servers configured with master-slave replication. Before we deploy a new application version we: 1) STOP SLAVE 2) Take a MySQL dump of the slave. However, if a mistake is done during the deployment of the new schema version (a table is dropped by mistake, for example), having the slave intact doesn't help. Our service is write-intensive, so we can't turn it back up until we have a master working. If we now load the mysql dump back into the master, it will take a long time during which our service remains down. What is the best-practice to recover from such a mistake? How can I setup the system so I can easily promote the slave, turn on our service and only then tend to the broken database? Mainly, I'm worried with re-syncing the slave and the master after changes are done on the slave.

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• Replication Presentation at the Southampton User Group

  - by GavinPayneUK

  Last night I delivered a presentation about SQL Server’s replication services to Mark Pryce-Maher’s user group in Southampton. As those who were there saw this is a massive topic and to deliver anything but a high level overview in 45 minutes does an injustice to the subject.  Therefore, what I gave the Wednesday night audience was a deliberately high level introduction through my slides with an accompanying detailed commentary as well as answering questions as we went along. The great thing...(read more)

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• Transaction Replication Publisher failover to Mirror

  Transaction Replication Publisher failover/failback to mirror standby with automatic redirection of the subscriber and client application. Does your database ever get out of sync?SQL Connect is a Visual Studio add-in that brings your databases into your solution. It then makes it easy to keep your database in sync, and commit to your existing source control system. Find out more.

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• Setting up MySQL Replication for High Availability

  <b>PACKT Publishing: </b>"MySQL Replication has been supported in MySQL for a very long time and is an extremely flexible and powerful technology. Depending on the configuration, you can replicate all databases, selected databases, or even selected tables within a database."

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• Init Replication From Backup

  One of the great features with SQL Replication is the ability to initialize a subscription from backup instead of from a snapshot. The official use for this is to take a database backup and restore it to a subscriber then replicate any additional changes to the backup. New! SQL Monitor 3.0 Red Gate's multi-server performance monitoring and alerting tool gets results from Day One.Simple to install and easy to use – download a free trial today.

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• Monitoring Active Directory (AD) Replication in Windows Server 2008 R2

  - by Kyle Brandt

  With Active Directory, what is a good way to monitor replication? I have multiple sites and multiple locations, so ideally both replication between sites and within sites would be monitored. I'm not really sure if each DC needs to be monitored, each NTDS connection, or each DC * Each NTDS connection. For the purposes of fitting into a standard alerting methodology, perfmon counters that would allow me to alert if replication was behind X minutes seems like it might be ideal.

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• How do I fix issue causing "incomplete startup packet" log message trying to implement replication in Postgresql?

  - by colour me brad

  I've got two cloud servers running Ubuntu 13.04 and PostgreSQL 9.2. I've primarily used this blog post to aid me in setting things up. However, to do the initial database dump to the slave I'm using pg_start_backup/pg_stop_backup strategy used in this other blog post. I've read through the docs and postgres wikis as well. I ran into several problems I was able to solve, but I can't get past this wretched "the database is starting up" failure. I'm not sure if seeing "cp: cannot stat '/var/lib/postgresql/9.2/archive/00000001000000000000003A': No such file or directory" after "consistent recover state reached" is normal or the first sign of a problem. The searching I've done on "the database is starting up" and "incomplete startup packet" tells me that something is sending empty TCP packets to the slave. The only thing that even knows about the slave is the master, so I'm not sure why it's sending empty packets... Has anyone worked with this and have an idea what might be going wrong? The postgres log on the slave looks like so: 2013-08-26 13:01:38 CDT LOG: entering standby mode 2013-08-26 13:01:38 CDT LOG: restored log file "000000010000000000000039" from archive 2013-08-26 13:01:38 CDT LOG: incomplete startup packet 2013-08-26 13:01:39 CDT LOG: redo starts at 0/39000020 2013-08-26 13:01:39 CDT LOG: consistent recovery state reached at 0/390000E0 cp: cannot stat '/var/lib/postgresql/9.2/archive/00000001000000000000003A': No such file or directory 2013-08-26 13:01:39 CDT LOG: streaming replication successfully connected to primary 2013-08-26 13:01:39 CDT FATAL: the database system is starting up 2013-08-26 13:01:39 CDT FATAL: the database system is starting up 2013-08-26 13:01:40 CDT FATAL: the database system is starting up 2013-08-26 13:01:40 CDT FATAL: the database system is starting up 2013-08-26 13:01:41 CDT FATAL: the database system is starting up 2013-08-26 13:01:42 CDT FATAL: the database system is starting up 2013-08-26 13:01:42 CDT FATAL: the database system is starting up 2013-08-26 13:01:43 CDT FATAL: the database system is starting up 2013-08-26 13:01:43 CDT FATAL: the database system is starting up 2013-08-26 13:01:44 CDT FATAL: the database system is starting up 2013-08-26 13:01:44 CDT FATAL: the database system is starting up 2013-08-26 13:01:44 CDT LOG: incomplete startup packet 2013-08-26 13:03:27 CDT FATAL: the database system is starting up 2013-08-26 13:03:27 CDT FATAL: the database system is starting up 2013-08-26 13:03:30 CDT FATAL: the database system is starting up 2013-08-26 13:03:30 CDT FATAL: the database system is starting up thanks! brad

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• Large scale file replication with an option to "unsubscribe" from a replicated file on a given machine

  - by Alexander Gladysh

  I have a 100+ GB files per day incoming on one machine. (File size is arbitrary and can be adjusted as needed.) I have several other machines that do some work on these files. I need to reliably deliver each incoming file to the worker machines. A worker machine should be able to free its HDD from a file once it is done working with it. It is preferable that a file would be uploaded to the worker only once and then processed in place, and then deleted, without copying somewhere else — to minimize already high HDD load. (Worker itself requires quite a bit of bandwidth.) Please advise a solution that is not based on Java. None of existing replication solutions that I've seen can do the "free HDD from the file once processed" stuff — but maybe I'm missing something... A preferable solution should work with files (from the POV of our business logic code), not require the business logic to connect to some queue or other. (Internally the solution may use whatever technology it needs to — except Java.)

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• Dependency Replication with TFS 2010 Build

  - by Jakob Ehn

  Some time ago, I wrote a post about how to implement dependency replication using TFS 2008 Build. We use this for Library builds, where we set up a build definition for a common library, and have the build check the resulting assemblies back into source control. The folder is then branched to the applications that need to reference the common library. See the above post for more details. Of course, we have reimplemented this feature in TFS 2010 Build, which results in a much nicer experience for the developer who wants to setup a new library build. Here is how it looks: There is a separate build process template for library builds registered in all team projects The following properties are used to configure the library build: Deploy Folder in Source Control is the server path where the assemblies should be checked in DeploymentFiles is a list of files and/or extensions to what files to check in. Default here is *.dll;*.pdb which means that all assemblies and debug symbols will be checked in. We can also type for example CommonLibrary.*;SomeOtherAssembly.dll in order to exclude other assemblies You can also see that we are versioning the assemblies as part of the build. This is important, since the resulting assemblies will be deployed together with the referencing application.   When the build executes, it will see of the matching assemblies exist in source control, if not, it will add the files automatically:   After the build has finished, we can see in the history of the TestDeploy folder that the build service account has in fact checked in a new version: Nice!   The implementation of the library build process template is not very complicated, it is a combination of customization of the build process template and some custom activities. We use the generic TFActivity (http://geekswithblogs.net/jakob/archive/2010/11/03/performing-checkins-in-tfs-2010-build.aspx) to check in and out files, but for the part that checks if a file exists and adds it to source control, it was easier to do this in a custom activity:   public sealed class AddFilesToSourceControl : BaseCodeActivity { // Files to add to source control [RequiredArgument] public InArgument<IEnumerable<string>> Files { get; set; } [RequiredArgument] public InArgument<Workspace> Workspace { get; set; } // If your activity returns a value, derive from CodeActivity<TResult> // and return the value from the Execute method. protected override void Execute(CodeActivityContext context) { foreach (var file in Files.Get(context)) { if (!File.Exists(file)) { throw new ApplicationException("Could not locate " + file); } var ws = this.Workspace.Get(context); string serverPath = ws.TryGetServerItemForLocalItem(file); if( !String.IsNullOrEmpty(serverPath)) { if (!ws.VersionControlServer.ServerItemExists(serverPath, ItemType.File)) { TrackMessage(context, "Adding file " + file); ws.PendAdd(file); } else { TrackMessage(context, "File " + file + " already exists in source control"); } } else { TrackMessage(context, "No server path for " + file); } } } } This build template is a very nice tool that makes it easy to do dependency replication with TFS 2010. Next, I will add funtionality for automatically merging the assemblies (using ILMerge) as part of the build, we do this to keep the number of references to a minimum.

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• MySQL-Cluster or Multi-Master for production? Performance issues?

  - by Phillip Oldham

  We are expanding our network of webservers on EC2 to a number of different regions and currently use master/slave replication. We've found that over the past couple of months our slave has stopped replicating a number of times which required us to clear the db and initialise the replication again. As we're now looking to have servers in 3 different regions we're a little concerned about these MySQL replication errors. We believe they're due to auto_increment values, so we're considering a number of approaches to quell these errors and stabilise replication: Multi-Master replication; 3 masters (one in each region), with the relevant auto_increment offsets, regularly backing up to S3. Or, MySQL-Cluster; 3 nodes (one in each region) with a separate management node which will also aggregate logs and statistics. After investigating it seems they both have down-sides (replication errors for the former, performance issues for the latter). We believe the cluster approach would allow us to manage and add new nodes more easily than the Multi-Master route, and would reduce/eliminate the replication issues we're currently seeing. But performance is a priority. Are the performance issues of MySQL-Cluster as bad as people say?

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• Hibernate @Transactional not starting transaction

  - by rhinds

  I have a web app using Hibernate, and I am attempting to persist some data, but it is failing to persist within a Transaction despite using the @Transactional annotation. My service class is as follows: @Service("profileService") public class ProfileService { private EntityManager entityManager; @Autowired private AccountService accountService; @Autowired private ProfileDAOImpl profileDao; @PersistenceContext public void setEntityManager(EntityManager em) { this.entityManager = em; } @Transactional public void addConnectionToAccount(SocialConnection sc) { entityManager.persist(sc); } } The addConnectionToAccount() method is being called from another Spring bean in a normal method, and the ProfileService class is currently being injected there: public class HibernateConnectionRepository implements ConnectionRepository { @Inject private ProfileService profileService; @Override @Transactional public void addConnection(SocialConnection sc) { try { profileService.addConnectionToAccount(accountId, sc); } catch (Exception e) { e.printStackTrace(); } } I tried putting the @Transactional annotation on the calling method in the vain hope that it might make a difference but nothing. Previously I have experienced problems like this its been because the object being persisted does not satisfy table restrictions (such as non-nullable columns as null) or because the method is being called from within the same class and the calling method is not Transactional, but neither of those are the case here.. Any ideas? it just fails silently, the logs are as follows: 2012-03-26 22:25:04,702 [http-bio-8085-exec-9] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@1bc25c8 [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@e5b006) 2012-03-26 22:25:04,710 [http-bio-8085-exec-9] DEBUG org.hibernate.SQL - select SEQ_COUNT from SEQUENCE where SEQ_NAME = 'PO_SEQ' for update 2012-03-26 22:25:04,711 [http-bio-8085-exec-9] DEBUG org.hibernate.SQL - update SEQUENCE set SEQ_COUNT = ? where SEQ_COUNT = ? and SEQ_NAME = 'PO_SEQ' 2012-03-26 22:25:04,723 [http-bio-8085-exec-9] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@1bc25c8 [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@e5b006) 2012-03-26 22:25:04,723 [http-bio-8085-exec-9] DEBUG org.hibernate.event.internal.AbstractSaveEventListener - Generated identifier: 2200, using strategy: org.hibernate.id.MultipleHiLoPerTableGenerator UPDATE Also wanted to mention that the HibernateConnectionRepository bean is not annotated and is actually being configured in an @Configuration class (if this makes any difference? not used @Configuration classes much). The method to create the bean is as follows: @Bean @Scope(value = "request", proxyMode = ScopedProxyMode.INTERFACES) public ConnectionRepository connectionRepository() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); if (authentication == null) { throw new IllegalStateException("Unable to get a ConnectionRepository: no user signed in"); } ApplicationUser user = (ApplicationUser) authentication.getPrincipal(); return usersConnectionRepository().createConnectionRepository(String.valueOf(user.getAccountId())); } The bean is scoped to the logged in user, but may also be created multiple times for each user..

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• Hibernate Session flush behaviour [ and Spring @Transactional ]

  - by EugeneP

  I use Spring and Hibernate in a web-app, SessionFactory is injected into a DAO bean, and then this DAO is used in a Servlet through webservicecontext. DAO methods are transactional, inside one of the methods I use ... getCurrentSession().save(myObject); One servlet calls this method with an object passed. The update seems to not be flushed at once, it takes about 5 seconds to see the changes in the database. The servlet's method in which that DAO's update method is called, takes a fraction of second to complete. After the @Transactional method of DAO is completed, flushing may NOT happen ? It does not seem to be a rule [ I already see it ]. Then the question is this: what to do to force the session to flush after every DAO method? It may not be a good thing to do, but talking about a Service layer, some methods must end with immediate flush, and Hibernate Session behavior is not predictable. So what to do to guarantee that my @Transactional method persists all the changes after the last line of that method code? getCurrentSession().flush() is the only solution? p.s. I read somewhere that @Transactional IS ASSOCIATED with a DB Transaction. Method returns, transaction must be committed. I do not see this happens.

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• Is it safe to set MySQL isolation to "Read Uncommitted" (dirty reads) for typical Web usage? Even with replication?

  - by Continuation

  I'm working on a website with typical CRUD web usage pattern: similar to blogs or forums where users create/update contents and other users read the content. Seems like it's OK to set the database's isolation level to "Read Uncommitted" (dirty reads) in this case. My understanding of the general drawback of "Read Uncommitted" is that a reader may read uncommitted data that will later be rollbacked. In a CRUD blog/forum usage pattern, will there ever be any rollback? And even if there is, is there any major problem with reading uncommitted data? Right now I'm not using any replication, but in the future if I want to use replication (row-based, not statement-based) will a "Read Uncommitted" isolation level prevent me from doing so? What do you think? Has anyone tried using "Read Uncommitted" on their RDBMS?

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• MySQL documentation writer for MEM and Replication wanted!

  - by stefanhinz

  As MySQL is thriving and growing, we're looking for an experienced technical writer located in the UK or Ireland to join the MySQL documentation team. For this job, we need the best and most dedicated people around. You will be part of a geographically distributed documentation team responsible for the technical documentation of all MySQL products. Team members are expected to work independently, requiring discipline and excellent time-management skills as well as the technical facilities and experience to communicate across the Internet. Candidates should be prepared to work intensively with our engineers and support personnel. The overall team is highly distributed across different geographies and time zones. Our source format is DocBook XML. We're not just writing documentation, but also handling publication. This means you should be familiar with DocBook, and willing to learn our publication infrastructure. Your areas of responsibility would initially be MySQL Enterprise Monitor, and MySQL Replication. This means you should be familiar with MySQL in general, and preferably also with the MySQL Enterprise offerings. A MySQL certification will be considered an advantage. Other qualifications you should have: Native English speaker 5 or more years previous experience in writing software documentation Familiarity with distributed working environments and versioning systems such as SVN Comfortable with working on multiple operating systems, particularly Windows, Mac OS X, and Linux Ability to administer own workstations and test environment Excellent written and oral communication skills Ability to provide (online) samples of your work, e.g. books or articles If you're interested, contact me under [email protected]. For reference, the job offer can be viewed here.

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• Replication with AK8

  - by Steve Tunstall

  Hello folks, This came up today and I want to make sure it's clear. Remember the "deferred update" I spoke about in my "Upgrade to AK8" entry just a bit ago? It's important to understand that this deferred update changes the way replication works. It is necessary that systems with the deferred update applied only replicate with other systems that have also had this deferred update applied. So if you apply it, your system can NOT replicate with ANY other system that has NOT had it applied, even if that other system is running AK8!!! Got it??? Remember, we do have a new version of the 2011 code for the older systems that do not want to upgrade to AK8. This 2011.1.8 code ALSO HAS this same deferred update in it. So, if you upgrade your system to AK8, and then apply the deferred update, and you have another system running either 2011.1.8 or AK8, you can replicate with them again once they apply the deferred update for multiple initiator groups. Yes, even if you're not using LUNs. Here is what it looks like if you try. It will fail.

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• Make MySQL database replication always use the most free node?

  - by Chad Johnson

  We started using Multi-Master Replication Manager for MySQL, and I am wondering whether it is possible to to treat this setup like multi-symmetric processing: a process pops off the process queue, and the node (in this case a server) that is most free is selected for the job. It seems that what happens is, the service switches to a slave ONLY when it mysqld crashes or goes away. Is there a way to make database replication for MySQL act in more of a distributed manner? Maybe there is other software besides MMM that can do this? Is there a way to switch the reader role to another server whene mysqld slows down (rather than just when it fails)?

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• Using both RolesAllowed and Transactional in beans

  - by Laran Evans

  I have some beans which contain methods which are annotated with both @RolesAllowed and @Transactional. I have one Spring config file which utilizes a BeanNameAutoProxyCreator for Security related beans and another Spring config file which utilizes a BeanNameAutoProxyCreator for Transactional related beans. The problem is that some beans contain both security as well as transactional-related beans. So Spring creates proxies for one set of beans. It then tries to create proxies for the other set of beans. When it does, it tries to create proxies of the proxies and bombs out. Has anyone tried to configure both security and transactionality in the same beans via Spring? What's the trick? Thanks.

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