H2

Last modified 14 Dec 2021 10:55 +01:00
Deprecated
This functionality is deprecated since version 4.4. The functionality is still supported and maintained, but it will no longer be extended. The plan is to remove this functionality sooner or later. Users of this functionality are strongly encouraged to stop using this functionality and migrate to a newer equivalent.
Table of Contents

Usage

Database creation

MidPoint will create the database midpoint.mv.db automatically inside ${midpoint.home}. Optionally, fileName configuration option can be used to customize the base part of the file name (without .mv.db suffix). There is no necessity to precreate the database from h2 console. The database is accessible with username sa with no password.

Configuration sample

The minimal default configuration with the embedded H2 repository (this is the default configuration, nothing needs to be changed):

<configuration>
  <midpoint>
  <repository>
     <repositoryServiceFactoryClass>com.evolveum.midpoint.repo.sql.SqlRepositoryFactory</repositoryServiceFactoryClass>
     <baseDir>${midpoint.home}</baseDir>
  </repository>
  </midpoint>
</configuration>

Driver

Driver for this database is bundled as a part of MidPoint application.

Version notes

This are semi-internal notes that can be ignored if you just want to run with H2.

Remember that H2 is not supported as a production database - it is only used for testing or proof-of-concept experiments.

Since December 2016 we use H2 1.4.193 (released in October 2016). There are some issues with H2, especially when running multi-threaded transactions, but in general the version works fine.

Current Spring Boot BOM offers H2 in version 1.4.200. During experimental upgrades to this fresh version we discovered couple of issues.

Firstly, the following must be changed in the code to go above version 1.4.197, which was rather a disruptive version change:

  • MVCC option in JDBC URL is obsolete and its usage must be removed. Threading model of H2 was reworked in 1.4.198 - which seems to be version with multiple breaking changes. See also: http://www.h2database.com/html/changelog.html

    • This affects jdbcUrl if sqlConfig.isEmbedded() in TaskManagerConfiguration#setJdbcJobStoreInformation,

    • and getDefaultEmbeddedJdbcUrl() in SqlRepositoryConfiguration.

  • Some SQLs in OrgClosureManager, mainly strange usage of parenthesis around two columns in selects used in IN clause. All these isH2() branches can be unified with isPostgreSQL() branches safely.

  • In SqlRepositoryFactory.createArguments() versions 1.4.198 and higher require additional argument args.add("-ifNotExists"), because remote database is not created by default. In lower versions this can’t be used.

These changes are not an issue and can be done quickly. The real problem are other issues that seriously affect the midPoint experience:

  • MidPoint with H2 always suffered with multi-threading issues, but with versions >=1.4.198 we regularly hit https://github.com/h2database/h2database/issues/1808 (NPE in LobStorageMap.copyLob) during TestDummyParallelism, but also during normal user interaction (e.g. adding a working thread to an existing task).

  • With 1.4.200 TestObjectLifecycleApprovalGlobal failed consistently with some timeouts, 100% reproducible. This was OK with 1.4.199. No investigation was done to find out whether this requires a change or is a bug in H2 - mainly because of the show stopper above.

There was also an experimental upgrade to 1.4.197, which is the last version before the disruptive changes and could be done without code changes. However, we experienced self-corrupting behavior as described in MID-6510. This was a critical failure and we couldn’t continue using 1.4.197.

There was no will left to test other versions between 193 and 197, and there is also no reason. We’re standing by for some fresh development with versions above 1.4.200. SQL unification with PostgreSQL in OrgClosureManager would be actually nice and other changes are not a problem. But there must be some reliability, at least for a few weeks worth of tests.

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