https://github.com/yandex-qatools/pessimistic-mongodb
A library, implementing MongoDB-based key-value storage with pessimistic locks.
https://github.com/yandex-qatools/pessimistic-mongodb
Last synced: 5 months ago
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A library, implementing MongoDB-based key-value storage with pessimistic locks.
- Host: GitHub
- URL: https://github.com/yandex-qatools/pessimistic-mongodb
- Owner: yandex-qatools
- Created: 2015-11-09T13:56:12.000Z (almost 10 years ago)
- Default Branch: master
- Last Pushed: 2016-02-19T23:18:53.000Z (over 9 years ago)
- Last Synced: 2025-04-08T15:49:34.865Z (6 months ago)
- Language: Java
- Size: 55.7 KB
- Stars: 3
- Watchers: 11
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Pessimistic MongoDB
[](https://maven-badges.herokuapp.com/maven-central/ru.qatools/pessimistic-mongodb)
[](http://ci.qatools.ru/job/pessimistic-mongodb_master-deploy/) [](http://sonar.qatools.ru/dashboard/index/2302)
Not a very new, and, probably completely useless approach to implement the distributed pessimistic locking on top of MongoDB.
Allows to use MongoDB as a key-value storage with the ability to read-write using pessimistic locks.
Additionally this library contains the simple queue implementation that uses tailing cursor.
### Maven
Add the following dependency to your pom.xml:
```xml
ru.qatools
pessimistic-mongodb
1.9
```
### Usage
To use locking as a named locks (by key):
```java
final PessimisticLockng locking = new MongoPessimisticLocking(
mongoClient, // an instance of MongoClient
"locks-database", // mongo database name
"locks-collection", // collection to use
30 // a maximum interval of polling the locks (ms)
);
locking.tryLock("some-key", 5000); // trying to lock the key "some-key" with 5s timeout
new Thread(() -> locking.tryLock("some-key", 5000) ).start(); // thread will wait for 5s
locking.unlock("some-key"); // after this the thread will obtain the lock forever
```
To use a pessimistic repository:
```java
final PessimisticRepository repo = new MongoPessimisticRepository( locking, String.class );
String value = repo.tryLockAndGet("key", 3000); // locking the 'key'
repo.putAndUnlock("key", "new value"); // releasing the 'key' and writing 'new value' to the repository
repo.removeAndUnlock("key"); // removing key from the repository
```
To obtain a new unique lock (implementing java.util.concurrent.Lock):
```java
final Lock lock = new MongoPessimisticLock( locking )
lock.tryLock(5, SECONDS); // lock the unique lock
lock.unlock();
```
To use the simple queue polling
```java
final TailableQueue queue = new MongoTailableQueue(
mongoClient, // instance of MongoClient
"databaseName", // mongo db name
"collectionName", // collection name to use (must be capped!)
10000 // max messages count within queue
);
new Thread(() -> queue.poll( m -> System.out.println(m))).start(); // launch polling thread
queue.add( "hello" ); // send some messages to the queue (will be displayed on console)
```