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https://github.com/chrisvest/stormpot

A fast object pool for the JVM
https://github.com/chrisvest/stormpot

concurrency connection-pool high-performance java performance pool tdd

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A fast object pool for the JVM

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README 

        
== Stormpot



Stormpot is an object pooling library for Java.

Use it to recycle objects that are expensive to create.

The library will take care of creating and destroying your objects in the

background.



image:https://github.com/chrisvest/stormpot/actions/workflows/maven.yml/badge.svg[Build status, link=https://github.com/chrisvest/stormpot/actions/workflows/maven.yml]

image:https://codecov.io/gh/chrisvest/stormpot/branch/master/graph/badge.svg[Code coverage, link=https://codecov.io/gh/chrisvest/stormpot]



Stormpot is very mature, is used in production, and has done hundreds of

trillions footnote:[Fermi estimate.] claim-release cycles in testing.

It is faster and scales better than any competing pool.



 * Home page: http://chrisvest.github.io/stormpot/

 * Source code: https://github.com/chrisvest/stormpot/

 * API docs: http://chrisvest.github.io/stormpot/site/apidocs/index.html

 * Mailing list: http://groups.google.com/d/forum/stormpot

 * License: http://www.apache.org/licenses/LICENSE-2.0.html[The Apache Software

   License 2.0]

 * Simple versioning: X.Y where Y{plus}{plus} is backwards compatible, and

   X{plus}{plus} is backwards incompatible.



=== Why choose Stormpot?



There are a number of options out there, when it comes to object pools on the

JVM. Stormpot has been carefully designed for high performance, and robust

operation. Some of the things that sets Stormpot apart include:



 * Business friendly http://www.apache.org/licenses/LICENSE-2.0.html[Apache 2

   license].

 * Very high http://chrisvest.github.io/stormpot/site/jacoco/index.html[test

   coverage].

 * The https://medium.com/@chrisvest/released-stormpot-2-1-c31509142757[highest

   throughput and lowest latency] in its class.

   (since 2.1)

 * https://medium.com/@chrisvest/released-stormpot-2-2-ccd1e8639f07[Automatic

   recovery] from sporadic backend (Allocator) failures.

   (since 2.2)

 * Precise object leak detection with virtually no overhead.

   (since 2.3)

 * Optional background object expiration checking.

   (since 2.3)

 * Explicit object expiration.

   (since 2.4)

 * Gradual back-off for prolonged allocation failures.

   (since 3.0)

 * Support for Java Platform Module system.

   (since 3.0)

 * Support for a directly-allocating thread-less mode, via `Pool.of(...)`.

   (since 3.0)

 * Convenient lambda-based API.

   (since 3.0)

 * Control over the thread-local caching mechanics, via ``PoolTap``s.

   (since 3.0)

 * Support for operating without a background thread, via `Pool.fromInline()`.

   (since 3.1)

 * Support for configuring zero-sized (dormant) pools.

   (since 3.1)

 * Support for virtual threads.

   (since 4.0)

 * Support for more than 2 billion objects in a pool.

   (since 4.0)

 * Support for changing the `Allocator` after the pool has been created.

   (since 4.0)

 * And other features that makes for a smooth runtime behaviour.



[NOTE]

--

Stormpot is an _object pool_; a homogeneous collection of objects, where it does not matter which particular instance is returned from `claim` since the objects are all similar.

If your objects instead are heterogeneous, with different attributes and identified by a _key_, then what you need is a _object cache_.

We recommend https://github.com/ben-manes/caffeine[Caffeine] for object caching.

--



=== Installing



Stormpot 4.0 only depends on Java 21 or newer.

If you need to use Java 11 or newer, use Stormpot 3.2.

Add it as a Maven dependency to your projects:



[source,xml]

----



  com.github.chrisvest

  stormpot

  4.0



----



You can also build the latest snapshot from source with `mvn clean install`.

Note that Stormpot 4 require Java 21 or newer.



=== Getting Started



Stormpot needs 3 things before it can pool objects for you:



 . A http://chrisvest.github.io/stormpot/site/apidocs/stormpot/stormpot/Poolable.html[Poolable] type of objects it can pool.

   You have to implement this yourself.

 . An http://chrisvest.github.io/stormpot/site/apidocs/stormpot/stormpot/Allocator.html[Allocator] to allocate and deallocate the Poolable objects.

   You have to implement this yourself.

 . And a place where it all comes together:



[source,java]

----

MyAllocator allocator = new MyAllocator();

Pool pool = Pool.from(allocator).build();

Timeout timeout = new Timeout(1, TimeUnit.SECONDS);



MyPoolable object = pool.claim(timeout);

try {

  // Do stuff with 'object'.

  // Note: 'claim' returns 'null' if it times out.

} finally {

  if (object != null) {

    object.release();

  }

}

----



=== Contributing



 * *Report bugs* preferably with a failing test. You can submit a pull-request

   that adds a failing test that demonstrates the behaviour you think is wrong

   or missing. Travis-CI will build it, report the failure and shorten the

   feedback cycle. If you don't know how to write a test for something, then

   that's fine too. Just open an issue describing your configuration and

   environment, what you observe, and what you think should happen instead.

 * *Improve the documentation* by all means! Just fork the project and start.

   If you have questions about implementation or behavioural details, then start

   a discussion about it by opening a pull-request or an issue. Documentation

   is formatted with http://asciidoctor.org/[AsciiDoctor].

   The website and javadocs can be generated with

   `./mvnw clean pre-site javadoc:javadoc`.

 * *Fix bugs or implement features* by forking the project, but please start an

   issue about the bug or feature you want to work on (or find the existing

   issue) and describe the approach and design you have in mind. Keep in mind

   that Stormpot is implemented with a very strict adherence to TDD.

   Finally, make sure to respect the existing indentation and formatting.

   Use `./mvnw checkstyle:check` to check your formatting.

   If you are writing a test that takes more than a few hundred milliseconds to

   run, then put it in the `stormpot.slow` test package; either in the existing

   `PoolIT` suite, or in a new `\*IT` suite.

   Use `mvn clean test` to run only the fast tests. Use `mvn clean verify` to

   also run the slow tests. Javadoc comments are formatted with

   http://asciidoctor.org/[AsciiDoctor].

   Get test coverage with `./mvnw clean test site` and

   `open target/site/jacoco/index.html`. Get mutation test coverage with

   `mvn clean test-compile org.pitest:pitest-maven:mutationCoverage` and

   `open target/pit-reports/*/index.html`.

 * *Update* Maven plugins with `./mvnw versions:display-plugin-updates`, or other

   dependencies with `versions:display-dependency-updates`.

 * *Add to the ecosystem* and make Stormpot more than just an object pool.

   This is a good thing to take on if you'd like to contribute code, but you

   find the Stormpot code base itself to be intimidating (which, by the way, I

   completely understand).

   ** There is a repository for

      https://github.com/chrisvest/object-pool-benchmarks[object pool benchmarks]

      that is being maintained along side Stormpot.

      Adding more benchmarks and cases; analysing results; trying out

      optimisations.

      These are all useful things to do.

   ** I started working on a

      https://github.com/chrisvest/stormpot-jdbc[JDBC connection pool]

      based on Stormpot, but the project has stagnated.

      It is no doubt a useful thing to have, though.

      If you want to take on that problem, either with offset in the existing

      code or by starting over from scratch, then please go ahead.

   ** I'm sure there are other interesting related problems out there to take on.

      There are many database drivers for various NoSQL databases, that have

      object pooling needs.

 * *Build benchmarks* with `./mvnw package -DskipTests -f modular-pom.xml`,

   and run them with `java -jar benchmarks/target/benchmarks.jar`.



Whatever you decide to do, don't hesitate to ask questions in the discussions

on github if you have doubts or get stuck.