About concurrency

manual

Locking in JPA

Explains how to use optimistic locking and pessimistic locking in JPA. JPA 2 supports both optimistic locking and pessimistic locking . Locking is essential to avoid update collisions resulting from simultaneous updates to the same data by two concurrent users. Locking in ObjectDB (and in JPA) is always at the da ...

 
manual

JPA Entity Fields

Explains how to define and use primary keys in JPA, including composite and embedded primary keys. Fields of persistable user defined classes (entity classes, embeddable classes and mapped superclasses) can be classified into the following five groups: Transient fields Persistent fields Inverse (Mapped By ...

 
forum_thread

ArrayIndexOutOfBoundsException at com.objectdb.o.ALS.c(ALS.java:89)

Hi all, I have created a packet grabber using JNetPcap. It creates a scala actor (java thread) for every packet grabbed which connect to an OpenDB database to add or update relevant entry's. Everything works fine until packets arrive with a time difference in the order of microseconds. Every scala actor opens a connection to the database, does what it needs to do, and then closes the connection. Something like: #1 2011-05-11 08:24 Hi all, I have created a packet grabber using JNetPcap. It creates a scala actor (java thread) for every ...

 
forum_thread

Recommendation - concurrent access multiple class v

Hi! I've just started to architect a new system, stateless JSON API, which is expected to have very high load and to require more servers for parallel deployments (same app across multiple servers). I am considering using ObjectDB, because of its advantages and easy usage, but I'm afraid that it might get corrupted because the manual says that we must not access ObjectDB with different versions of a class. Let's take the following scenario: #1 2014-02-09 10:15 Hi! I've just started to architect a new system, stateless JSON API, which is expected to have very h ...

 
forum_thread

Optimistic locking failure

Optimistic locking failure: I am using a Semaphore to force this execution of concurrents transactions T1 and T2 that cause parallel updates to A/B but it does not throw an OptimisticLockException and roll back. #1 2012-04-30 16:02 Optimistic locking failure: I am using a Semaphore to force this execution of concurrents transactions T1 ...

 
forum_thread

Several parallel threads to speed up query on one DB

Hi, I have an application: producer (from a DB) to a consumer. The current bottleneck is the producer from DB (based on a query) and I would like to speed it up. I have tried using several entity managers (same DB instance) to benefit from the parallelisation - but it looks like I don't get much benefit from doing that.  #1 2015-01-25 13:57 Hi, I have an application: producer (from a DB) to a consumer. The current bottleneck is the prod ...

 
forum_thread

Where Does ObjectDB Block/Lock?

These are questions asked in the context of the proposed architecture described in the forum thread titled, "Sample JDO Architecture for Follow Up Questions".   Questions about blocking/locking.  With my PersistenceManager multiThreaded=true architecture, I desire to know where ObjectDB is actually blocking/locking so I might adapt to achieve better concurrency. 1) Where are locks when accessing PersistenceManager by multiple threads? 2) Does it lock at PersistenceManager.currentTransaction()? ... blocking/locking so I might adapt to achieve better concurrency. 1) Where are locks when accessing PersistenceManager by ... read, is desired, should I use optimistic=true to get more concurrency?   edit ...

 
forum_thread

Glassfish 3.1.2.1 and ObjectDB 2.4.3

Hello, I tried to get the Guestbook tutorial run with Glassfish (see above) but it's not working. When I try to add a guest I got a HTTP Status 404 Wich versions of ObjectDB should I use? Thanks #1 2012-09-04 16:26 Hello, I tried to get the Guestbook tutorial run with Glassfish (see above) but it's not working. Whe ...

 
issue

stress test -> com.objectdb.o.InternalException: null

I am running a stress test with 2 users, each making a request to the JSON API (which uses as storage ObjectDB) each 50 milliseconds. An API call might have between 1-4 db calls, but they are relatively light, and the db has just a few MB at the moment. After a few minutes I got this exception. If I decrease the load, it doesn't happen. If I increase it, I get it very often. Any solution/fix? A sample project is very hard, if not impossible, to create, because it uses all the system. Bug Version: 2.5.5 Priority: Critical Status: Fixed Replies: 19 Type:  Bug ...

 
forum_thread

How to open a running db in ObjectDB Explorer?

Hi! I've just discovered that I can't see the content of a database while it's in use. Is there any way in which I could do that? It's not nice at all to close the application, copy the db in another location, start the application then finally I could explore my data, but it will be just a copy of the data, not the live information. #1 2013-05-25 18:08 Hi! I've just discovered that I can't see the content of a database while it's in use. Is the ...