https://github.com/ralscha/xodus-queue
Persistent java.util.Queue implementation with Xodus
https://github.com/ralscha/xodus-queue
blocking-queue java kryo persistent queue xodus
Last synced: 28 days ago
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Persistent java.util.Queue implementation with Xodus
- Host: GitHub
- URL: https://github.com/ralscha/xodus-queue
- Owner: ralscha
- License: apache-2.0
- Created: 2018-05-13T04:12:34.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2024-10-27T16:59:02.000Z (7 months ago)
- Last Synced: 2024-10-27T19:56:23.922Z (7 months ago)
- Topics: blocking-queue, java, kryo, persistent, queue, xodus
- Language: Java
- Size: 300 KB
- Stars: 6
- Watchers: 5
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
This project provides a persistent `java.util.Queue` and `java.util.concurrent.BlockingQueue` implementation. It is using [Xodus](https://github.com/JetBrains/xodus) as the underlying storage engine.
For persisting POJOs, it relies on [Kryo](https://github.com/EsotericSoftware/kryo).
xodus-queue is not a high-performance queue, and it only works within a single JVM. The primary motivation was to write a queue that survives a server restart and does not introduce a lot of external dependencies to my projects. Because I often use [Xodus](https://github.com/JetBrains/xodus) already in my projects, this library
only adds [Kryo](https://github.com/EsotericSoftware/kryo) as an additional dependency.
Any contributions are welcome if something is missing or could be implemented better, submit a pull request, or create an issue.
## Usage
Create an instance of `XodusQueue` or `XodusBlockingQueue` and specify the database directory and the class of the entries you want to put into the queue.
These can be either built-in Java types like String, Integer, Long, or a more complex POJO.
It is recommended to open the queue in an automatic resource management block because the underlying Xodus database should be closed when you no longer access the queue.
```
try (XodusQueue queue = new XodusQueue<>("./test", String.class)) {
}
```
After the instantiation, you can call any of the methods from the `java.util.Queue` and `java.util.concurrent.BlockingQueue` interface.
See the JavaDoc ([Queue](https://docs.oracle.com/javase/10/docs/api/java/util/Queue.html), [BlockingQueue](https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/BlockingQueue.html)) for a list of all available methods.
Currently [`iterator()`](https://docs.oracle.com/javase/10/docs/api/java/util/Collection.html#iterator()) is not implemented.
The underlying storage engine requires that read and write operations have to run inside transactions, and I don't know how
to implement that in an iterator.
```
try (XodusQueue queue = new XodusQueue<>("./queue", String.class)) {
queue.add("one");
String head = queue.poll(); // "one"
}
```
The blocking queue supports a capacity limit. The following example limits the number of elements in the queue to 3.
`put` blocks the current thread when the queue is full and `take` blocks when the queue is empty.
```
try (XodusBlockingQueue queue = new XodusBlockingQueue<>("./blocking_queue", String.class, 3)) {
queue.put("one");
queue.put("two");
String head = queue.take(); // "one"
}
```
## Maven
The library is hosted on the Central Maven Repository
```
ch.rasc
xodus-queue
1.0.1
```
## Changelog
### 1.0.1 - May 19, 2018
* Fix key management in XodusQueue
* Add `java.util.concurrent.BlockingQueue` implementation: XodusBlockingQueue
### 1.0.0 - May 15, 2018
* Initial release
## License
Code released under [the Apache license](http://www.apache.org/licenses/).