== 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.
=== 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
PoolTaps.
(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.