Hazelcast Ringbuffer is a replicated but not partitioned data structure that stores its data in a ring-like structure. You can think of it as a circular array with a given capacity. Each Ringbuffer has a tail and a head. The tail is where the items are added and the head is where the items are overwritten or expired. You can reach each element in a Ringbuffer using a sequence ID, which is mapped to the elements between the head and tail (inclusive) of the Ringbuffer.
By default, a Ringbuffer is configured with a capacity of 10000 items. This creates an array with a size of 10000. If a time-to-live is configured, then an array of longs is also created that stores the expiration time for every item. In a lot of cases, you may want to change this capacity number to something that better fits your needs.
You can configure Hazelcast Ringbuffer with a time-to-live in seconds. Using this setting, you can control how long the items remain in the Ringbuffer before they are expired. By default, the time-to-live is set to 0, meaning that unless the item is overwritten, it will remain in the Ringbuffer indefinitely. If you set a time-to-live and an item is added, then, depending on the Overflow Policy, either the oldest item is overwritten, or the call is rejected.
You can configure Hazelcast Ringbuffer with an in-memory format that controls the format of the Ringbuffer’s stored items. By default, BINARY in-memory format is used, meaning that the object is stored in a serialized form. You can select the OBJECT in-memory format, which is useful when filtering is applied or when the OBJECT in-memory format has a smaller memory footprint than BINARY.
The number of synchronous backups. For example, if it is set to 1, then the Ringbuffer items are copied to one other member for fail-safety. Its default value is 1.