This projects intends to test DB connection pooling and JDBC drivers with virtual threads.

How to run

./gradlew jmh -PtestedDb=<DB_NAME>

The currently supported databases are (DB_NAME is in bold):

• H2
• H2.NOSYNC: A modified version of H2 where intrinsic locks were replaced with jucl locks.
• HSQL
• MARIA: Maria DB.
• POSTGRES: Postgres with the new virtual thread aware JDBC driver.
• POSTGRES.OLD: Postgres with the old driver using synchronized blocks.
• DERBY: Derby aka. Java DB.
• MSSQL
• ORACLE
• ORACLE.OLD: Oracle with the old driver using synchronized blocks.

Optionally, all databases support a .SLEEP suffix where the EXECUTE_SCRIPT action just sleeps for 60 ms. For example, you use POSTGRES.SLEEP instead of POSTGRES as the DB_NAME.

Note: Databases that are not run within the JVM are assumed to run on the localhost having a user "loomdbtest" with password "loomdbtest", and full access to the "loomdbtest" database. Currently, these databases are the following: MariaDB. Postgres and MsSQL.

You may set additional parameters for the benchmark by passing the -Pbenchmark.<PARAMETER_NAME>=<PARAMETER_VALUE>, the supporter parameter names are:

• poolSize: The size of the connection pool. If non-positive, then it is relative to the number of threads. It can also be "*X", and in this case the pool size is the number of threads times X.
• connectionAction: The action to do with a connection retrieved from the pool. The possible values are:
  • EXECUTE_SCRIPT: Execute the benchmark.sql(.ftl) in the sql-scripts directory.
  • DO_NOTHING: Does nothing with the connection.
  • SLEEP: Sleeps for 60 ms.
  • PINNING_SLEEP: Sleeps for 60 ms, but pins the carrier thread while sleeping.
• dbPoolType: The type of the connection pool. The possible values are:
  • DBCP2: Uses BasicDataSource of DBCP2.
  • HIKARI: Uses HikariDataSource of HikariCP.
  • C3P0: Uses ComboPooledDataSource of C3P0.
  • VIBUR: Uses ViburDBCPDataSource of Vibur.
  • SEMAPHORE: Uses a semaphore to limit the number of connections.
• forkType: The way to fork new tasks. The possible values are:
  • VIRTUAL_THREADS: Uses Thread.startVirtualThread.
  • LIMITED_EXECUTOR: Uses an executor with as many threads as returned by Runtime.getRuntime().availableProcessors().
• cpuWork: The amount of CPU work to do in tasks not using a connection. The value is an integer as defined by the Blackhole.consumeCPU method.
• cpuSleepMs: The number of ms to sleep in tasks not using a connection.
• fullConcurrentTasks: Set it to false to run the tasks in a partially sequential manner. Otherwise all tasks will be just submitted to run concurrently. This is true by default.

If you want multiple values, then you can provide them as a comma separated list. For example:

./gradlew jmh -PtestedDb=POSTGRES -Pbenchmark.forkType=VIRTUAL_THREADS,LIMITED_EXECUTOR

Even more conveniently: You can just run the provided jmh.sh script, but instead of writing -Pbenchmark.<PARAMETER_NAME>=<PARAMETER_VALUE> you can just write --<PARAMETER_NAME>=<PARAMETER_VALUE>. Similarly for the -PtestedDb=<DB_NAME>, you can just write --testedDb=<DB_NAME>. Also, jmh.sh supports multiple comma separate values for the testedDb parameter (unlike the Gradle command). For example:

./jmh.sh --testedDb=POSTGRES,POSTGRES.OLD --forkType=VIRTUAL_THREADS,LIMITED_EXECUTOR

Custom scripts

The scripts run by the benchmark are in the sql-scripts directory. If you want to run a custom script, you can either overwrite them, or pass the -Ploomdbtest.sqlScriptDir=<REL_PATH> parameter to the build to replace its default value (which is "sql-scripts*). When calling jmh.sh, then the parameter is --sqlScriptDir=<REL_PATH>.

The script files are processed by Freemarker. See the examples for the parameters available to the template.