Re: [h2] Need advice with embedded H2 losing data due to "revert"

[Christian Dirks]

Thanks for the reply.

I do not believe that the application is used in a setup with cloud-share 
by our customer. The devices are used in an environemnt where it is not 
guaranteed to even have internet connectivity all the time. But I will ask 
them to make sure.

I do not believe that this can be caused by HA-JDBC choosing the wrong 
file. As touched on in the "Notes" section we have custom code that 
compares both databases' content before we start the cluster. This includes 
compariong the amount of rows in each table as well as equality of each 
individual row. If we would detect any difference in content we wouldn't 
add the mirror database to the cluster, running with only the master 
database.
A similar situation would require that HA-JDBC stopped writing to the 
master database midway during the last run of our application and only 
wrote to the mirror. But I would assume that a failed write operation would 
result in a database exception from either the cluster or H2. We have a 
listener attached to the cluster that should be informed about all 
exceptions. If an exception happens, this listener will remove the 
databases from the cluster, check them and only reattach them if they are 
successfully tested. We do not see such a behavior happening in the 
logfiles. So this scenario would only be possible if neither HA-JDBC nor H2 
realized that the write operation failed or if the exception was caught in 
a way that neither the transaction nor the listener knew about it.

Noel Grandin schrieb am Donnerstag, 4. Mai 2023 um 15:25:29 UTC+2:

>
>
> On 5/3/2023 3:10 PM, Christian Dirks wrote:
> > We are running a java application using embedded H2 databases and ran 
> into data loss situation that we can not explain. 
> > It appears as if the database reverted to a previous state - or that 
> data wasn't written to file for hours.
> > 
>
> Given the lengths of time involved, my first guess would be some kind of 
> cloud-sync service that is getting confused and 
> reverting parts of the filesystem to a prior state.
>
> My second guess would be that HA-JDBC is doing something weird like 
> directing writes to one file and not the other, and 
> then choosing the wrong file the next time the software starts up.
>
>

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Re: [h2] Need advice with embedded H2 losing data due to "revert"

[Noel Grandin]

On 5/3/2023 3:10 PM, Christian Dirks wrote:
We are running a java application using embedded H2 databases and ran into data loss situation that we can not explain. 
It appears as if the database reverted to a previous state - or that data wasn't written to file for hours.




Given the lengths of time involved, my first guess would be some kind of cloud-sync service that is getting confused and 
reverting parts of the filesystem to a prior state.


My second guess would be that HA-JDBC is doing something weird like directing writes to one file and not the other, and 
then choosing the wrong file the next time the software starts up.


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[h2] In-file H2 database in a Docker container

[Thomas Collignon]

Hello,

Is there an example somewhere of the code of a simple Java app (Spring Boot 
would be nice) running in a Docker container, and using an in-file (not 
in-memory) H2 database ?

Linked post on StackOverflow 


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