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The Persistence API provides an easy and fast way to store data. It supports two main storages, namely PersistentSequence and PersistentQueue.

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PersistentSequence provides functionality for storing sequential data (for example, logs). Each record should have a unique index. Indexer implementation is used to provide an index for a certain storing record. Also, PersistentSequence requires custom Serializer implementation to serialize objects to byte buffer and restore it back.

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In addition to storing data, PersistentSequence provides methods for retrieving records from the storage. It supports reading a single item by index or iterating through items:

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There is a possibility to review stored records and remove some of them from the storage:

sequence.cleanUp(new CleanupItemListener<MyRecord>() {
    @Override
    public boolean checkForClean(long id, MyRecord item) {
        //return true to removed this record from storage
        return false;
    }
});

Or remove all and reset the sequence:

//remove all items and reset index
sequence.reset();

The default PersistentSequence implementation is optimized for writing data and , so reading operations may take a bit more time.

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PersistentQueue works like a queue but persist persists all items to the disk. Thus, it can restore its state after application restart. PersistentQueue has methods similar to java.util.Queue methods:

final PersistentQueue<MyRecord> queue = factory.buildQueue("queue_sample", serializer);

//push item to the tail of queue
queue.add(record);

// read iem from head but doesn't remove
record = queue.peek();

// extract item from head and remove it from queue
record = queue.poll();

Also PersistentQueue allow to iterate allows iterating all its items:

queue.iterate(new RetrieveQueueItemsListener<MyRecord>() {
    @Override
    public void onItem(MyRecord record) {
        //....
    }
});

To remove all the items from the queue, you can use the clean method:

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